Updated on 2022/07/02

写真a

 
KOBAYASHI Tatsuo
 
Organization
Faculty of Natural Science and Technology Professor
Position
Professor
External link

Degree

  • Doctor (Science) ( Osaka University )

Research Interests

  • High field

  • 極限物性

  • 超伝導

  • magnetism

  • High pressure

Research Areas

  • Natural Science / Magnetism, superconductivity and strongly correlated systems

Education

  • Osaka University   大学院基礎工学研究科  

    1986.4 - 1988.3

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    Country: Japan

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  • Kobe University   理学部   物理学科

    1981.4 - 1985.3

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    Country: Japan

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Research History

  • Graduate School of Natural Science and Technology, Okayama University   Professor

    2003.4

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    Country:Japan

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  • Research Center for Materials Science at Extreme Conditions   Associate Professor (as old post name)

    1996.5 - 2003.3

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  • Graduate School of Engineering Science, Osaka University   Research Assistant

    1990.10 - 1996.4

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  • School of Liberal Arts, Kobe University   Research Assistant

    1988.4 - 1990.9

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Professional Memberships

 

Papers

  • Magnetotransport studies of the Sb square-net compound LaAgSb2 under high pressure and rotating magnetic fields

    Kazuto Akiba, Nobuaki Umeshita, Tatsuo C. Kobayashi

    Physical Review B   105 ( 3 )   2022.1

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    Publishing type:Research paper (scientific journal)   Publisher:American Physical Society (APS)  

    DOI: 10.1103/physrevb.105.035108

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    Other Link: http://harvest.aps.org/v2/journals/articles/10.1103/PhysRevB.105.035108/fulltext

  • Physical properties of liquid oxygen under ultrahigh magnetic fields

    T. Nomura, A. Ikeda, M. Gen, A. Matsuo, K. Kindo, Y. Kohama, Y. H. Matsuda, S. Zherlitsyn, J. Wosnitza, H. Tsuda, T. C. Kobayashi

    Physical Review B   104 ( 22 )   2021.12

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    Publishing type:Research paper (scientific journal)   Publisher:American Physical Society (APS)  

    DOI: 10.1103/physrevb.104.224423

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    Other Link: http://harvest.aps.org/v2/journals/articles/10.1103/PhysRevB.104.224423/fulltext

  • Spin-gap formation due to spin-Peierls instability in π-orbital-ordered NaO2 Reviewed International journal

    Mizuki Miyajima, Fahmi Astuti, Takahito Fukuda, Masashi Kodani, Shinsuke Iida, Shinichiro Asai, Akira Matsuo, Takatsugu Masuda, Koichi Kindo, Takumi Hasegawa, Tatsuo C. Kobayashi, Takehito Nakano, Isao Watanabe, Takashi Kambe

    Physical Review B   104 ( 14 )   2021.10

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    Publishing type:Research paper (scientific journal)   Publisher:American Physical Society (APS)  

    DOI: 10.1103/physrevb.104.l140402

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    Other Link: http://harvest.aps.org/v2/journals/articles/10.1103/PhysRevB.104.L140402/fulltext

  • Successive destruction of charge density wave states by pressure in LaAgSb2 Reviewed

    Kazuto Akiba, Hiroaki Nishimori, Nobuaki Umeshita, Tatsuo C. Kobayashi

    Physical Review B   103 ( 8 )   2021.2

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    Publishing type:Research paper (scientific journal)   Publisher:American Physical Society (APS)  

    DOI: 10.1103/physrevb.103.085134

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    Other Link: http://harvest.aps.org/v2/journals/articles/10.1103/PhysRevB.103.085134/fulltext

  • Domain Control by Adjusting Anisotropic Stress in Pyrochlore Oxide Cd2Re2O7 Reviewed

    Satoshi Tajima, Daigorou Hirai, Yuto Kinoshita, Masashi Tokunaga, Kazuto Akiba, Tatsuo C. Kobayashi, Hishiro T. Hirose, Zenji Hiroi

    Journal of the Physical Society of Japan   89 ( 11 )   114711 - 114711   2020.11

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    Publishing type:Research paper (scientific journal)   Publisher:Physical Society of Japan  

    DOI: 10.7566/jpsj.89.114711

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  • Anomalous Hall effect triggered by pressure-induced magnetic phase transition in α -Mn Reviewed

    Kazuto Akiba, Kaisei Iwamoto, Takaaki Sato, Shingo Araki, Tatsuo C. Kobayashi

    Physical Review Research   2 ( 4 )   2020.10

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    Publishing type:Research paper (scientific journal)   Publisher:American Physical Society (APS)  

    DOI: 10.1103/physrevresearch.2.043090

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    Other Link: http://harvest.aps.org/v2/journals/articles/10.1103/PhysRevResearch.2.043090/fulltext

  • Two Qualitatively Different Superconducting Phases under High Pressure in Single-Crystalline CeNiGe3 Reviewed

    Shunsaku Kitagawa, Shingo Araki, Tatsuo C. Kobayashi, Yoichi Ikeda

    Journal of the Physical Society of Japan   89 ( 6 )   063702 - 063702   2020.6

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    Publishing type:Research paper (scientific journal)   Publisher:Japan Society of Applied Physics  

    DOI: 10.7566/jpsj.89.063702

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  • Magnetotransport properties of tellurium under extreme conditions Reviewed

    Kazuto Akiba, Kaya Kobayashi, Tatsuo C. Kobayashi, Ryo Koezuka, Atsushi Miyake, Jun Gouchi, Yoshiya Uwatoko, Masashi Tokunaga

    Physical Review B   101 ( 24 )   2020.6

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    Publishing type:Research paper (scientific journal)   Publisher:American Physical Society (APS)  

    DOI: 10.1103/physrevb.101.245111

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    Other Link: http://harvest.aps.org/v2/journals/articles/10.1103/PhysRevB.101.245111/fulltext

  • Variation in Superconducting Symmetry Against Pressure on Noncentrosymmetric Superconductor Cd2Re2O7 Revealed by 185/187Re Nuclear Quadrupole Resonance Reviewed

    Shunsaku Kitagawa, Kenji Ishida, Tatsuo C. Kobayashi, Yasuhito Matsubayashi, Daigorou Hirai, Zenji Hiroi

    Journal of the Physical Society of Japan   89 ( 5 )   053701 - 053701   2020.5

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    Publishing type:Research paper (scientific journal)   Publisher:Physical Society of Japan  

    DOI: 10.7566/jpsj.89.053701

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  • Pressure-Temperature Phase Diagram of alpha-Mn Reviewed International journal

    Takaaki Sato, Kazuto Akiba, Shingo Araki, Tatsuo C. Kobayashi

    Proceedings of the International Conference on Strongly Correlated Electron Systems (SCES2019)   30   011030-1 - 011030-6   2020.3

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    Language:English   Publishing type:Research paper (international conference proceedings)   Publisher:Journal of the Physical Society of Japan  

    DOI: 10.7566/jpscp.30.011030

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  • Helimagnetic Structure and Heavy-Fermion-Like Behavior in the Vicinity of the Quantum Critical Point in Mn3P Reviewed

    Hisashi Kotegawa, Masaaki Matsuda, Feng Ye, Yuki Tani, Kohei Uda, Yoshiki Kuwata, Hideki Tou, Eiichi Matsuoka, Hitoshi Sugawara, Takahiro Sakurai, Hitoshi Ohta, Hisatomo Harima, Keiki Takeda, Junichi Hayashi, Shingo Araki, Tatsuo C. Kobayashi

    Physical Review Letters   124 ( 8 )   2020.2

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    Publishing type:Research paper (scientific journal)   Publisher:American Physical Society (APS)  

    DOI: 10.1103/physrevlett.124.087202

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    Other Link: http://harvest.aps.org/v2/journals/articles/10.1103/PhysRevLett.124.087202/fulltext

  • High magnetic field x-ray diffraction study of the α phase of solid oxygen: Absence of giant magnetostriction Reviewed

    Yasuhiro H. Matsuda, Ayumi Shimizu, Akihiko Ikeda, Toshihiro Nomura, Takeshi Yajima, Toshiya Inami, Kohki Takahashi, Tatsuo C. Kobayashi

    Physical Review B   100 ( 21 )   2019.12

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    Publishing type:Research paper (scientific journal)   Publisher:American Physical Society (APS)  

    DOI: 10.1103/physrevb.100.214105

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    Other Link: http://harvest.aps.org/v2/journals/articles/10.1103/PhysRevB.100.214105/fulltext

  • Interplay between unconventional superconductivity and heavy-fermion quantum criticality: CeCu2Si2 versus YbRh2Si2 Reviewed

    M. Smidman, O. Stockert, J. Arndt, G. M. Pang, L. Jiao, H. Q. Yuan, H. A. Vieyra, S. Kitagawa, K. Ishida, K. Fujiwara, T. C. Kobayashi, E. Schuberth, M. Tippmann, L. Steinke, S. Lausberg, A. Steppke, M. Brando, H. Pfau, U. Stockert, P. Sun, S. Friedemann, S. Wirth, C. Krellner, S. Kirchner, E. M. Nica, R. Yu, Q. Si, F. Steglich

    Philosophical Magazine   98 ( 32 )   2930 - 2963   2018.11

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    Publishing type:Research paper (scientific journal)   Publisher:Informa UK Limited  

    DOI: 10.1080/14786435.2018.1511070

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  • Pyrochlore Oxide Superconductor Cd2Re2O7Revisited Reviewed

    Zenji Hiroi, Jun-ichi Yamaura, Tatsuo C. Kobayashi, Yasuhito Matsubayashi, Daigorou Hirai

    Journal of the Physical Society of Japan   87 ( 2 )   024702 - 024702   2018.2

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    Publishing type:Research paper (scientific journal)   Publisher:Physical Society of Japan  

    DOI: 10.7566/jpsj.87.024702

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  • Magnetostriction studies up to megagauss fields using fiber Bragg grating technique

    Akihiko Ikeda, Yasuhiro H. Matsuda, Daisuke Nakamura, Shojiro Takeyama, Hiroshi Tsuda, Kazuya Nomura, Ayumi Shimizu, Akira Matsuo, Toshihiro Nomura, Tatsuo C. Kobayashi, Takeshi Yajima, Hajime Ishikawa, Zenji Hiroi, Masahiko Isobe, Touru Yamauchi, Keisuke Sato

    2018 16TH INTERNATIONAL CONFERENCE ON MEGAGAUSS MAGNETIC FIELD GENERATION AND RELATED TOPICS (MEGAGAUSS)   98 - 106   2018

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    Language:English   Publishing type:Research paper (international conference proceedings)   Publisher:IEEE  

    We here report magnetostriction measurements under pulsed megagauss fields using a high-speed 100 MHz strain monitoring system devised using fiber Bragg grating (FBG) technique with optical filter method. The optical filter method is a detection scheme of the strain of FBG, where the changing Bragg wavelength of the FBG reflection is converted to the intensity of reflected light to enable the 100 MHz measurement. In order to show the usefulness and reliability of the method, we report the measurements for solid oxygen, spin-controlled crystal, and volborthite, a deformed Kagome quantum spin lattice, using static magnetic fields up to 7 T and non-destructive millisecond pulse magnets up to 50 T. Then, we show the application of the method for the magnetostriction measurements of CaV4O9, a two-dimensional antiferromagnet with spin-halves, and LaCoO3, an anomalous spin-crossover oxide, in the megagauss fields.

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  • Pressure-Induced Superconductivity from Doping-Induced Antiferromagnetic Phase of 112-type Ca1−xLaxFeAs2 Reviewed

    Shunsaku Kitagawa, Taishi Sekiya, Yo Fujiyoshi, Shingo Araki, Tatsuo C. Kobayashi, Naoki Nishimoto, Tasuku Mizukami, Satoshi Ioka, Kazunori Fujimura, Kazutaka Kudo, Minoru Nohara

    Journal of the Physical Society of Japan   86 ( 11 )   113705 - 113705   2017.11

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    The effects of pressure on antiferromagnetic (AFM) and superconducting phase transitions of 112-type Ca1-xLaxFeAs2 were studied, and the in-plane electrical resistivity rho(ab) was measured with an indenter-type pressure cell. The AFM phase transition temperatures of T-N = 47, 63, and 63 K at ambient pressure for x = 0.18, 0.21, and 0.26 was suppressed by applying pressure P, with superconductivity emerging at critical pressures of P-c similar or equal to 0, 1.5, and 3.4 GPa, respectively. Correspondingly, the slope of T-N against P decreased as dT(N)/P similar or equal to -15 and -2K/GPa for x = 0.21 and 0.26, respectively. Thus, although the AFM phase was stabilized with La doping x, the AFM phase was suppressed by pressure, and superconductivity eventually emerged.

    DOI: 10.7566/jpsj.86.113705

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  • H-T phase diagram of solid oxygen Reviewed

    T. Nomura, Y. H. Matsuda, T. C. Kobayashi

    PHYSICAL REVIEW B   96 ( 5 )   2017.8

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    The comprehensive magnetic field-temperature (H-T) phase diagram of solid oxygen including the theta phase is discussed in the context of the ultrahigh-field measurement and the magnetocaloric effect (MCE) measurement. The problems originating from the short duration of the pulse field, nonequilibrium conditions and MCEs, are pointed out and dealt with. The obtained phase diagram manifests the entropy relation between the phases as S-theta similar to S-alpha < S-beta << S-gamma

    DOI: 10.1103/PhysRevB.96.054439

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  • alpha-beta and beta-gamma phase boundaries of solid oxygen observed by adiabatic magnetocaloric effect Reviewed

    Toshihiro Nomura, Yoshimitsu Kohama, Yasuhiro H. Matsuda, Koichi Kindo, Tatsuo C. Kobayashi

    Phys Rev B   5   104420   2017.3

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  • Successive spatial symmetry breaking under high pressure in the spin-orbit-coupled metal Cd2Re2O7

    Jun-ichi Yamaura, Keiki Takeda, Yoichi Ikeda, Naohisa Hirao, Yasuo Ohishi, Tatsuo C. Kobayashi, Zenji Hiroi

    PHYSICAL REVIEW B   95 ( 2 )   163 - 170   2017.1

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    The 5d-transition-metal pyrochlore oxide Cd2Re2O7, which was recently suggested to be a prototype of the spin-orbit-coupled metal [Phys. Rev. Lett. 115, 026401 (2015)], exhibits an inversion-symmetry-breaking (ISB) transition at 200 K and a subsequent superconductivity below 1 K at ambient pressure. We study the crystal structure at high pressures up to 5 GPa by means of synchrotron x-ray powder diffraction. A rich structural phase diagram is obtained, which contains at least seven phases, and is almost consistent with the electronic phase diagram determined by previous resistivity measurements. Interestingly, the ISB transition vanishes at similar to 4 GPa where the enhancement of the upper critical field was observed in resistivity. Moreover, it is shown that the point groups at 8 K, probably kept in the superconducting phases, sequentially transform into piezoelectric, ferroelectric, and centrosymmetric structures on the application of pressure.

    DOI: 10.1103/PhysRevB.95.020102

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  • Chemical analysis of superconducting phase in K-doped picene

    Takashi Kambe, Saki Nishiyama, Huyen L. T. Nguyen, Takahiro Terao, Masanari Izumi, Yusuke Sakai, Lu Zheng, Hidenori Goto, Yugo Itoh, Taiki Onji, Tatsuo C. Kobayashi, Hisako Sugino, Shin Gohda, Hideki Okamoto, Yoshihiro Kubozono

    JOURNAL OF PHYSICS-CONDENSED MATTER   28 ( 44 )   2016.11

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    Language:English   Publishing type:Research paper (scientific journal)   Publisher:IOP PUBLISHING LTD  

    Potassium-doped picene (K(3.0)picene) with a superconducting transition temperature (TC) as high as 14 K at ambient pressure has been prepared using an annealing technique. The shielding fraction of this sample was 5.4% at 0 GPa. The TC showed a positive pressure-dependence and reached 19 K at 1.13 GPa. The shielding fraction also reached 18.5%. To investigate the chemical composition and the state of the picene skeleton in the superconducting sample, we used energy-dispersive x-ray (EDX) spectroscopy, MALDI-time-of-flight (MALDI-TOF) mass spectroscopy and x-ray diffraction (XRD). Both EDX and MALDI-TOF indicated no contamination with materials other than K-doped picene or K-doped picene fragments, and supported the preservation of the picene skeleton. However, it was also found that a magnetic K-doped picene sample consisted mainly of picene fragments or K-doped picene fragments. Thus, removal of the component contributing the magnetic quality to a superconducting sample should enhance the volume fraction.

    DOI: 10.1088/0953-8984/28/44/444001

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  • Irreversible Heating Measurement with Microsecond Pulse Magnet: Example of the alpha-theta Phase Transition of Solid Oxygen

    Toshihiro Nomura, Yasuhiro H. Matsuda, Shojiro Takeyama, Tatsuo C. Kobayashi

    JOURNAL OF THE PHYSICAL SOCIETY OF JAPAN   85 ( 9 )   2016.9

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    Dissipation inevitably occurs in first-order phase transitions, leading to irreversible heating. Conversely, the irreversible heating effect may indicate the occurrence of the first-order phase transition. We measured the temperature change at the magnetic-field-induced alpha-theta phase transition of solid oxygen. A significant temperature increase from 13 to 37 K, amounting to 700 J/mol, due to irreversible heating was observed at the first-order phase transition. We argue that the hysteresis loss of the magnetization curve and the dissipative structural transformation account for the irreversible heating. The measurement of irreversible heating can be utilized to detect the first-order phase transition in combination with an ultrahigh magnetic fields generated in a time of mu s order.

    DOI: 10.7566/JPSJ.85.094601

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  • Characteristic Fermi surfaces and charge density wave in SrAl4 and related compounds with the BaAl4-type tetragonal structure

    Ai Nakamura, Taro Uejo, Hisatomo Harima, Shingo Araki, Tatsuo C. Kobayashi, Miho Nakashima, Yasushi Amako, Masato Hedo, Takao Nakama, Yoshichika Onuki

    JOURNAL OF ALLOYS AND COMPOUNDS   654   290 - 299   2016.1

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    Language:English   Publishing type:Research paper (scientific journal)   Publisher:ELSEVIER SCIENCE SA  

    We succeeded in growing single crystals of SrAl4 and related compounds with the BaAl4-type tetragonal structure by the self-flux method, and measured the electrical resistivity, magnetic susceptibility, Hall coefficient, thermoelectric power, and de Haas-van Alphen (dHvA) effect. A plausible characteristic feature of the charge density wave (CDW) was observed below T-CDW = 243 K in SrAl4. We also studied an effect of pressure on the electronic state in SrAl4 by measuring the electrical resistivity and thermoelectric power. T-CDW is found to decrease with increasing pressure, with a rate of dT(CDW)/dP = -12.5 K/GPa. To clarify the Fermi surface nesting, we studied the Fermi surface in SrAl4, which is found to be different from the Fermi surfaces of the similar compounds SrGa4, BaGa4, and BaAl4 without CDW. The Fermi surfaces in these compounds were determined from the dHvA experiments, together with the energy band calculations. (C) 2015 Published by Elsevier B.V.

    DOI: 10.1016/j.jallcom.2015.08.193

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  • 21pBL-13 Superconductivity near antiferromagnetic quantum critical point in CeNiGe_3

    Kitagawa S., Araki S., Kobayashi T. C., Ikeda Y., Yoshizawa H.

    Meeting Abstracts of the Physical Society of Japan   71   2294 - 2294   2016

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    Language:Japanese   Publisher:The Physical Society of Japan (JPS)  

    DOI: 10.11316/jpsgaiyo.71.1.0_2294

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  • 22aPS-34 Crystal synthesis and high pressure effect on rare earth ferromagnetic Bi_3R_4 with noncentrosymmetric cubic structure.

    Sogabe Y., Furutani A., Araki S., Sekiya T., Kitagawa S., Kobayashi T. C., Inada Y.

    Meeting Abstracts of the Physical Society of Japan   71   2427 - 2427   2016

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    Language:Japanese   Publisher:The Physical Society of Japan (JPS)  

    DOI: 10.11316/jpsgaiyo.71.1.0_2427

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  • 20pPSB-21 Pressure Effect in Ferromagnetic CeNiSb_2

    Imai K., Sekiya T., Kitagawa S., Araki S., Kobayashi T. C., Onuki Y.

    Meeting Abstracts of the Physical Society of Japan   71   2125 - 2125   2016

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    Language:Japanese   Publisher:The Physical Society of Japan (JPS)  

    DOI: 10.11316/jpsgaiyo.71.1.0_2125

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  • 20pPSB-20 Magnetization measurement with Hall sensor under high pressure in CeAgSb_2

    Araki S., Mashiyama H., Fujiwara Y., Kitagawa S., Kobayashi T.C.

    Meeting Abstracts of the Physical Society of Japan   71   2124 - 2124   2016

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    Language:Japanese   Publisher:The Physical Society of Japan (JPS)  

    DOI: 10.11316/jpsgaiyo.71.1.0_2124

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  • Hall Effect in CeIn3 under High Pressure

    Shingo Araki, Taiki Onji, Shunsaku Kitagawa, Tatsuo C. Kobayashi, Takashi Kambe

    JOURNAL OF THE PHYSICAL SOCIETY OF JAPAN   84 ( 12 )   123702-1-123702-4   2015.12

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    The temperature dependence of the Hall coefficient of CeIn3 under high pressure has been investigated. The absolute value of the Hall coefficient shows an anomalous increase below T* similar to 80K at ambient pressure. The increase in T* with increasing pressure is similar to the pressure dependence of the characteristic temperature where the resistivity reaches its maximum. The temperature variations below T* at various pressures are well scaled on a single curve that is the formula based on the two-fluid model. No effect of the antiferromagnetic fluctuations observed in CeTIn5 (T = Co, Rh, and Ir) is observed above 2K even near the critical pressure where antiferromagnetic ordering disappears.

    DOI: 10.7566/JPSJ.84.123702

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  • Suppression of Nonmagnetic Insulating State by Application of Pressure in Mineral Tetrahedrite Cu12Sb4S13

    Shunsaku Kitagawa, Taishi Sekiya, Shingo Araki, Tatsuo C. Kobayashi, Kenji Ishida, Takashi Kambe, Takumi Kimura, Naoki Nishimoto, Kazutaka Kudo, Minoru Nohara

    JOURNAL OF THE PHYSICAL SOCIETY OF JAPAN   84 ( 9 )   093701-1-093701-4   2015.9

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    The mineral tetrahedrite Cu12Sb4S13 exhibits a first-order metal-insulator transition (MIT) at T-MI = 85K and ambient pressure. We measured the 63Cu-NMR at ambient pressure and the resistivity and magnetic susceptibility at high pressures. Cu-63-NMR results indicate a nonmagnetic insulating ground state in this compound. The MIT is monotonically suppressed by pressure and disappears at similar to 1.0 GPa. Two other anomalies are observed in the resistivity measurements, and the pressure-temperature phase diagram of Cu12Sb4S13 is constructed.

    DOI: 10.7566/JPSJ.84.093701

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  • Phase boundary of θ phase of solid oxygen in ultrahigh magnetic fields Reviewed

    T. Nomura, Y. H. Matsuda, S. Takeyama, A. Matsuo, K. Kindo, T. C. Kobayashi

    Physical Review B - Condensed Matter and Materials Physics   92 ( 6 )   2015.8

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    Language:English   Publishing type:Research paper (scientific journal)   Publisher:American Physical Society  

    The phase diagram of solid oxygen in the magnetic-field-temperature (B-T) plane is revealed by magnetization and magnetotransmission measurements. The high-field phase of solid oxygen, which we term the θ phase, is induced at the temperature below 42 K. The transition fields at the α-θ and β-θ transitions are almost temperature independent, with the phase boundary being very steep. This phase boundary indicates that the entropy change is very small at the α-θ and β-θ transitions, in contrast to the entropy-driven β-γ transition at zero field. We argue that the θ phase differs from the high-temperature γ phase in terms of entropy
    the molecular rotation is inhibited in the θ phase, whereas permitted in the γ phase. This finding consolidates the novelty of the θ phase.

    DOI: 10.1103/PhysRevB.92.064109

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  • Emergence of double-dome superconductivity in ammoniated metal-doped FeSe

    Masanari Izumi, Lu Zheng, Yusuke Sakai, Hidenori Goto, Masafumi Sakata, Yuki Nakamoto, Huyen L. T. Nguyen, Tomoko Kagayama, Katsuya Shimizu, Shingo Araki, Tatsuo C. Kobayashi, Takashi Kambe, Dachun Gu, Jing Guo, Jing Liu, Yanchun Li, Liling Sun, Kosmas Prassides, Yoshihiro Kubozono

    SCIENTIFIC REPORTS   5   9477-1-9477-7   2015.4

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    Language:English   Publishing type:Research paper (scientific journal)   Publisher:NATURE PUBLISHING GROUP  

    The pressure dependence of the superconducting transition temperature (T-c) and unit cell metrics of tetragonal (NH3)(y)Cs0.4FeSe were investigated in high pressures up to 41 GPa. The T-c decreases with increasing pressure up to 13 GPa, which can be clearly correlated with the pressure dependence of c (or FeSe layer spacing). The T-c vs. c plot is compared with those of various (NH3)(y)MxFeSe (M: metal atoms) materials exhibiting different T-c and c, showing that the T-c is universally related to c. This behaviour means that a decrease in two-dimensionality lowers the T-c. No superconductivity was observed down to 4.3 K in (NH3)(y)Cs0.4FeSe at 11 and 13 GPa. Surprisingly, superconductivity re-appeared rapidly above 13 GPa, with the T-c reaching 49 K at 21 GPa. The appearance of a new superconducting phase is not accompanied by a structural transition, as evidenced by pressure-dependent XRD. Furthermore, T-c slowly decreased with increasing pressure above 21 GPa, and at 41 GPa superconductivity disappeared entirely at temperatures above 4.9 K. The observation of a double-dome superconducting phase may provide a hint for pursuing the superconducting coupling-mechanism of ammoniated/non-ammoniated metal-doped FeSe.

    DOI: 10.1038/srep09477

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  • Pressure-Temperature-Field Phase Diagram in the Ferromagnet U3P4

    Shingo Araki, Minami Hayashida, Naoto Nishiumi, Hiroki Manabe, Yoichi Ikeda, Tatsuo C. Kobayashi, Keizo Murata, Yoshihiko Inada, Piotr Wisniewski, Dai Aoki, Yoshichika Onuki, Etsuji Yamamoto, Yoshinori Haga

    JOURNAL OF THE PHYSICAL SOCIETY OF JAPAN   84 ( 2 )   024705-1-024705-8   2015.2

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    The pressure-temperature-field phase diagram and quantum fluctuation effect were investigated in the itinerant ferromagnet U3P4 by resistivity, ac susceptibility, and Hall effect measurements under high pressure. The zero-temperature ferromagnetic-to-paramagnetic transition is located at P-c similar to 4.0 GPa. The tricritical point exists at P* = 3.8 GPa and T* = 32 K, where the ferromagnetic transition changes from second- to first-order. As a quantum fluctuation effect, the low-temperature resistivity at P-c follows T-5/3 dependence, which was theoretically described in the case of a three-dimensional ferromagnet. This result indicates that the ferromagnetic-to-paramagnetic transition at P-c may be considered as weakly first-order. Another critical behavior, the huge enhancement of rho(0) observed at P-c, cannot be interpreted as the ferromagnetic fluctuation effect. The Hall effect measurements suggest that the magnetic structure in the ordered state changes under high pressure.

    DOI: 10.7566/JPSJ.84.024705

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  • Resistance Anomalies Accompanying Crossover from Heavy-Fermion Regime to Intermediate-Valence Regime: A Study of Cu-Ni Substitution and Pressure Effects on CeCu2Si2

    Yoichi Ikeda, Yuzo Ito, Shingo Araki, Tatsuo C. Kobayashi, Hideki Yoshizawa

    JOURNAL OF THE PHYSICAL SOCIETY OF JAPAN   84 ( 2 )   024702-1-024702-9   2015.2

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    We present detailed investigations on the effects of Ni substitution (x) on Ce(Cu1-xNix)(2)Si-2 with x < 0.3, and a pressure (p) study for x = 0.04(2), 0.05(2), and 0.09(2) by resistivity measurements. The Cu-Ni substitution suppresses both antiferromagnetic fluctuations and superconductivity in CeCu2Si2, and leads to a dramatic crossover from the heavy-fermion (HF) regime to the intermediate-valence(IV) regime with progressive Ni doping. The crossover can be characterized by a marked increase in Kondo temperature evaluated from resistivity, specific heat, and susceptibility measurements. In high-pressure resistivity measurements, the Ni-doped system exhibits similar anomalies to those observed in CeCu2Si2, namely, T-linear dependence, an enhancement of residual resistivity, and a marked decrease in the A coefficient of the T-2-resistivity. Furthermore, we observed an unexpected upturn anomaly in resistivity in the Ni-doped system under high pressure. By constructing the x-p phase diagram of Ce(Cu1-xNix)(2)Si-2, we demonstrate that the crossover from the HF regime to the IV regime can be associated with these characteristic anomalies in resistivity.

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  • Characterization of Ferromagnetic Order in CePd2P2

    Y. Ikeda, H. Yoshizawa, S. Konishi, S. Araki, T. C. Kobayashi, T. Yokoo, S. Ito

    INTERNATIONAL CONFERENCE ON STRONGLY CORRELATED ELECTRON SYSTEMS 2014 (SCES2014)   592   012013-1-012013-6   2015

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    We examine magnetic ordering in CePd2P2 by neutron-scattering experiment and confirmed a ferromagnetic order at low temperatures. From the neutron-scattering data, the ordered moment is evaluated to be similar to 1.3(3) mu(B) per Ce ion at 3 K and is considered to be parallel to the c-axis. In addition, no evidence of the change in the magnetic structure was observed below T-C within the experimental accuracy. In DC magnetization measurement with an as-grown powder sample and a magnetically aligned sample, a clear magnetic anisotropy in CePd2P2 was observed in both ferromagnetic and paramagnetic phases. To obtain further insight to the large Curie temperature T-C of CePd2P2, we have examined the magnetic properties of GdPd2P2 as a reference material. In DC magnetization measurement, successive magnetic transitions at T-I = 10.6 K and T-II = 7.4 K were observed in GdPd2P2. By comparing the transition temperatures of the Ce and Gd compounds, we argue the origin of the large Curie temperature of CePd2P2.

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  • 17aDA-8 Pressure induced ferromagnetic quantum criticality on CeTiGe_3

    Kitagawa S., Kawashima G., Araki S., Kobayashi T. C., Inamdar M., Thamizhavel A., Dhar S. K.

    Meeting Abstracts of the Physical Society of Japan   70   1769 - 1769   2015

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    DOI: 10.11316/jpsgaiyo.70.2.0_1769

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  • 18aDB-3 P-T-x phase diagram in the iron - based superconductor Ca_<1-x>La_xFeAs_2

    Sekiya T., Kitagawa S., Araki S., Kobayashi T. C., Nishimoto N., Ioka S., Fujimura K., Mizukami T., Kudo K., Nohara M.

    Meeting Abstracts of the Physical Society of Japan   70   1989 - 1989   2015

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    DOI: 10.11316/jpsgaiyo.70.2.0_1989

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  • 17aPS-18 Hall effect in CeRh_2Si_2 under high pressure

    Araki S., Onji T., Kitagawa S., Kobayashi T. C., Miyazaki M., Settai R., Sakai H.

    Meeting Abstracts of the Physical Society of Japan   70   1814 - 1814   2015

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    DOI: 10.11316/jpsgaiyo.70.2.0_1814

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  • Simultaneous suppression of superconductivity and structural phase transition under pressure in Ca-10(Ir4As8)(Fe2-xIrxAs2)(5)

    Shunsaku Kitagawa, Shingo Araki, Tatsuo C. Kobayashi, Hiroyuki Ishii, Kazunori Fujimura, Daisuke Mitsuoka, Kazutaka Kudo, Minoru Nohara

    PHYSICAL REVIEW B   90 ( 22 )   224513-1-224513-4   2014.12

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    We measured the pressure dependence of in-plane resistivity rho(ab) in the recently discovered iron-based superconductor Ca-10(Ir4As8)(Fe2-xIrxAs2)(5), which shows a unique structural phase transition in the absence of magnetic ordering, with a superconducting transition temperature T-c = 16 K and a structural phase transition temperature T-s similar or equal to 100 K at ambient pressure. T-c and T-s are suppressed on applying pressure and disappear at approximately 0.5 GPa, suggesting a relationship between superconductivity and structure. Ca-10(Ir4As8)(Fe2-xIrxAs2)(5) is a rather rare example in which the superconductivity appears only in a low-temperature ordered phase. The fact that the change in the crystal structure is directly linked with superconductivity suggests that the crystal structure as well as magnetism are important factors governing superconductivity in iron pnictides.

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  • Role of Valence Fluctuations in the Superconductivity of Ce122 Compounds

    H. Yamaoka, Y. Ikeda, I. Jarrige, N. Tsujii, Y. Zekko, Y. Yamamoto, J. Mizuki, J. -F. Lin, N. Hiraoka, H. Ishii, K. -D. Tsuei, T. C. Kobayashi, F. Honda, Y. Onuki

    PHYSICAL REVIEW LETTERS   113 ( 8 )   86403-1-86403-6   2014.8

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    Pressure dependence of the Ce valence in CeCu2Ge2 has been measured up to 24 GPa at 300 K and to 17 GPa at 18-20Kusing x-ray absorption spectroscopy in the partial fluorescence yield. Asmooth increase of the Ce valence with pressure is observed across the two superconducting (SC) regions without any noticeable irregularity. The chemical pressure dependence of the Ce valence was also measured in Ce(Cu1-xNix)(2)Si-2 at 20 K. Avery weak, monotonic increase of the valence with x was observed, without any significant change in the two SC regions. Within experimental uncertainties, our results showno evidence for the valence transition with an abrupt change in the valence state near the SC II region, challenging the valence-fluctuation mediated superconductivity model in these compounds at high pressure and low temperature.

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  • Novel Phase of Solid Oxygen Induced by Ultrahigh Magnetic Fields

    T. Nomura, Y. H. Matsuda, S. Takeyama, A. Matsuo, K. Kindo, J. L. Her, T. C. Kobayashi

    PHYSICAL REVIEW LETTERS   112 ( 24 )   247201-1-247201-5   2014.6

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    Magnetization measurements and magnetotransmission spectroscopy of the solid oxygen alpha phase were performed in ultrahigh magnetic fields of up to 193 T. An abrupt increase in magnetization with large hysteresis was observed when pulsed magnetic fields greater than 120 T were applied. Moreover, the transmission of light significantly increased in the visible range. These experimental findings indicate that a first-order phase transition occurs in solid oxygen in ultrahigh magnetic fields, and that it is not just a magnetic transition. Considering the molecular rearrangement mechanism found in the O-2-O-2 dimer system, we conclude that the observed field-induced transition is caused by the antiferromagnetic phase collapsing and a change in the crystal structure.

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  • Superconducting phases in (NH3)(y)MxFeSe1-zTez (M = Li, Na, and Ca)

    Yusuke Sakai, Lu Zheng, Masanari Izumi, Kazuya Teranishi, Ritsuko Eguchi, Hidenori Goto, Taiki Onji, Shingo Araki, Tatsuo C. Kobayashi, Yoshihiro Kubozono

    PHYSICAL REVIEW B   89 ( 14 )   144509-1-144509-6   2014.4

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    Superconducting phases of (NH3)(y)MxFeSe1-z Te-z have been synthesized by the intercalation of metal atoms (M: Li, Na, Ca) into FeSe and FeSe0.5Te0.5 using a low-temperature liquid NH3 technique. The superconducting transition temperature (T-c) is 31.5 K for Na-doped FeSe, and for Li-, Na-, and Ca-doped FeSe0.5Te0.5 it is 26, 22, and 17 K, respectively. The 31.5 K superconducting is the superconducting phase in ammoniated Na-doped FeSe. The T-c is lower than that (onset T-c = 46 K) of the superconducting phase reported previously. The reason why the T-c of this phase is lower is discussed based on the structure. The pressure dependences of T-c in the (NH3)(y)Na0.5FeSe and (NH3)(y)Na0.4FeSe0.5Te0.5 samples have been measured and a negative pressure dependence is observed; i.e., a decrease in lattice constant c leads to a decrease in Tc, consistent with the behavior of (NH3)(y)Cs0.4FeSe reported previously by our group. Furthermore, the magnetic behavior of (NH3)(y)Na0.4FeSe0.5Te0.5 has been fully investigated at different applied magnetic fields (H) to determine the critical magnetic This is a successful metal intercalation into FeSe1-z Te-z (z not equal 0) and an observation of superconductivity.

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  • Charge Density Wave Transition in EuAl4

    Shingo Araki, Yoichi Ikeda, Tatsuo C. Kobayashi, Ai Nakamura, Yuichi Hiranaka, Masato Hedo, Takao Nakama, Yoshichika Onuki

    JOURNAL OF THE PHYSICAL SOCIETY OF JAPAN   83 ( 1 )   015001-1-015001-2   2014.1

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    DOI: 10.7566/JPSJ.83.015001

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  • Emergence of novel phase of solid oxygen in ultrahigh magnetic field

    T. C. Kobayashi, T. Nomura, Y. H. Matsuda, J. L. Her, S. Takeyama, A. Matsuo, K. Kindo

    27TH INTERNATIONAL CONFERENCE ON LOW TEMPERATURE PHYSICS (LT27), PTS 1-5   568   42018-1-42018-6   2014

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    Faraday discovered the magnetism of molecular oxygen in 1850, and since then, oxygen has attracted significant interests as a ubiquitous but exotic molecular magnet. In solid oxygen, the magnetic energy through the exchange interaction is comparable to the van der Waals cohesive energy, resulting in a strong spin-lattice correlation. We reported the discovery of a magnetic-field-induced phase transition of solid oxygen using ultrahigh magnetic fields up to 186 T. This is the first experiments demonstrating the phase control through the spin by applying a magnetic field. Magneto-optical absorption measurements of the a phase at low temperatures revealed that visible light absorption suddenly ceases and the background transparency dramatically improves above the critical field. The large hysteresis in these data indicates a first-order transition with a relaxation time on the order of microseconds. The results strongly suggest the reconstruction of the O-2 molecular geometry by the magnetic field, which causes that the antiferromagnetic phase collapses and the field-induced phase should have an isotropic crystal structure. Since all of the known phases of O-2 are induced in high pressure, the discovery of a field-induced phase is noteworthy in the long history of solid O-2 studies.

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  • Valence Crossover of Ce Ions in CeCu2Si2 under High Pressure - Pressure Dependence of the Unit Cell Volume and the NQR Frequency

    Tatsuo C. Kobayashi, Kenji Fujiwara, Keiki Takeda, Hisatomo Harima, Yoichi Ikeda, Takafumi Adachi, Yasuo Ohishi, Christoph Geibel, Frank Steglich

    JOURNAL OF THE PHYSICAL SOCIETY OF JAPAN   82 ( 11 )   114701-1-6   2013.11

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    The pressure dependence of the valence of Ce ions in CeCu2Si2 has been investigated by means of X-ray powder diffraction (XRPD) and nuclear quadrupole resonance (NQR) measurements. The high-pressure XRPD measurements were carried out at 12K for CeCu2Si2 and CeCu2Ge2. Precise measurements under smoothly-applied pressure were achieved through the selection of the gasket material of a diamond anvil cell. The jump of the unit cell volume, which was reported previously in CeCu2Ge2, was not observed within the experimental accuracy, indicating the absence of a first-order valance transition. The pressure dependence of Cu-63-NQR frequency nu(Q) measured in CeCu2Si2 was compared with that calculated from the measured lattice parameters. The nu(Q)'s were calculated for the two cases of LaCu2Si2 and CeCu2Si2, corresponding to localized and itinerant cases for 4f electrons, respectively. The measured and calculated slopes d nu(Q)/dP show good agreement. A small but significant deviation from the pressure-linear dependence in nu(Q) was observed in the narrow pressure range of 3.9-4.5 GPa, indicating a valence crossover adjacent to the critical end point.

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  • Superconductivity in (NH3)yCs0.4FeSe

    Lu Zheng, Masanari Izumi, Yusuke Sakai, Ritsuko Eguchi, Hidenori Goto, Yasuhiro Takabayashi, Takashi Kambe, Taiki Onji, Shingo Araki, Tatsuo C. Kobayashi, Jungeun Kim, Akihiko Fujiwara, Yoshihiro Kubozono

    Physical Review B - Condensed Matter and Materials Physics   88 ( 9 )   094521-094525   2013.9

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    Alkali-metal-intercalated FeSe materials, (NH3) yM0.4FeSe (M: K, Rb, and Cs), have been synthesized using the liquid NH3 technique. (NH3)yCs 0.4FeSe shows a superconducting transition temperature (T c) as high as 31.2 K, which is higher by 3.8 K than the Tc of nonammoniated Cs0.4FeSe. The Tcs of (NH 3)yK0.4FeSe and (NH3) yRb0.4FeSe are almost the same as those of nonammoniated K0.4FeSe and Rb0.4FeSe. The Tc of (NH 3)yCs0.4FeSe shows a negative pressure dependence. A clear correlation between Tc and lattice constant c is found for ammoniated metal-intercalated FeSe materials, suggesting a correlation between Fermi-surface nesting and superconductivity. © 2013 American Physical Society.

    DOI: 10.1103/PhysRevB.88.094521

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  • Longitudinal magnetoresistance of Ce(Cu1-xNix)2Si2

    Yoichi Ikeda, Shingo Araki, Tatsuo C. Kobayashi

    Journal of the Korean Physical Society   63 ( 3 )   766 - 767   2013.8

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    The longitudinal magnetoresistance (LMR) of polycrystalline Ce(Cu1-xNix)2Si2 samples is investigated between T = 2 and 15 K up to H = 80 kOe. The application of magnetic field induces anomalous temperature dependence of the resistivity with the power index n &lt
    2 for x = 0.12 and 0.14, in which ρ(T) obeys a T 2-law at H = 0 Oe. A sign-change of the LMR from positive (x &lt
    0.03) to negative (x &gt
    0.03) is observed at 2 K. The negative LMR at 80 kOe is maximized (∼ -4 % at T = 2 K) around x ∼ 0.10 and subsequently disappears at higher Ni concentrations. Disappearance of the positive LMR in lower x region and the negative LMR at higher Ni concentrations implies a collapse of a coherent Kondo lattice state, and a rapid enhancement of Kondo temperature, respectively. Anomalous quantum fluctuations are probably developed around x ∼ 0.10. © 2013 The Korean Physical Society.

    DOI: 10.3938/jkps.63.766

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  • Spin-Dependent Molecular Orientation of O-2-O-2 Dimer Formed in the Nanoporous Coordination Polymer

    Akihiro Hori, Tatsuo C. Kobayashi, Yoshiki Kubota, Akira Matsuo, Koichi Kindo, Jungeun Kim, Kenichi Kato, Masaki Takata, Hirotoshi Sakamoto, Ryotaro Matsuda, Susumu Kitagawa

    JOURNAL OF THE PHYSICAL SOCIETY OF JAPAN   82 ( 8 )   084703-1-6   2013.8

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    In a model system of an O-2-O-2 dimer confined in the nanopores of Cu-1,4-cyclohexanedicarboxylic acid, the molecular orientation associated with the spin state was observed by precise synchrotron radiation structure analysis. The obtained charge density level structures revealed that the molecular orientation varied with increasing temperature, coupling with the spin states of the O-2-O-2 dimer. The magnetic properties previously reported were consistently explained by the S = 1 dimer model taking into account the molecular arrangements. The obtained gap parameters are different from those of the O-2-O-2 dimer confined in the nanopores of Cu-2,3-pyrazinedicarboxylate-pyrazine, which is explained by the pore deformation due to the adsorption, depending on the pore size and/or flexibility of the coordination polymer.

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  • Pressure effects on rattling and superconductivity in the einstein solids

    Yoichi Ikeda, Yasuhiro Kawasaki, Takafumi Shinohara, Shingo Araki, Tatsuo C. Kobayashi, Atsushi Onosaka, Yoshihiko Okamoto, Jun-Ichi Yamaura, Zenji Hiroi

    Journal of the Physical Society of Japan   82 ( 6 )   063707-1-4   2013.6

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    Pressure effects on the rattling and superconductivity in the Einstein solids
    AxV2Al20 (Ax = Ga0:2, Al0:3, and Y) are investigated by means of electrical resistivity measurements under high pressure. We observed bumps in resistivity at low temperatures only for Ga0:2 and Al0:3, which can be explained by scattering of conduction electrons by local phonons with Einstein temperatures of 8.5 and 22 K, respectively. The bumps gradually fade out with increasing pressure, and the temperature variations of resistivity for Ga0:2 and Al0:3 approach those of Y. This indicates that the low-energy local phonons in the Ga and Al compounds disappear at high pressures. We also observed T2 behavior with large A coefficients in the low-temperature limit for Ga and Al compounds, but not for Y. With increasing pressure, the A coefficient is largely suppressed, while H' c2 ≡ jdHc2=dTj Tc that also reflects the density of states at Fermi energy decreases more slowly. The T2 behavior in Ga and Al compounds probably originates from el-ph scatterings enhanced by rattling of Ga and Al atoms rather than el-el scatterings. An enhancement in the superconducting transition temperatures by the rattling is also demonstrated by comparing the pressure responses of T c between the three compounds. The enhancements of Tc and el-ph interaction λ is relatively small for these Einstein solids in contrast to those of the β-pyrochlore oxides. © 2013 The Physical Society of Japan.

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  • Magneto-absorption in the α phase of solid oxygen at megagauss magnetic fields

    T. Nomura, Y. H. Matsuda, J. L. Her, S. Takeyama, A. Matsuo, K. Kindo, T. C. Kobayashi

    Journal of Low Temperature Physics   170 ( 5-6 )   372 - 376   2013.3

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    Optical absorption spectra of solid oxygen α phase and liquid oxygen were measured in high magnetic fields over 100 T using a single turn coil method. The absorption originates from the bimolecular transition was observed. The spectra strongly reflect the local magnetic interaction between two oxygen molecules. The shape of the absorption spectrum of the α oxygen changed dramatically with increasing magnetic fields, even though the absorption intensity of liquid oxygen simply declined. This difference cannot be explained by only the local magnetic interaction, and we speculate that the field induced lattice distortion plays an important role in the solid oxygen α phase. © 2012 Springer Science+Business Media, LLC.

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  • A Study of Ni-Substitution Effects on Heavy-Fermion CeCu2Si2 - Similarities between Ni Substitution and High-Pressure Effects -

    Yoichi Ikeda, Shingo Araki, Tatsuo C. Kobayashi, Yusei Shimizu, Tatsuya Yanagisawa, Hiroshi Amitsuka

    81 ( 8 )   083701-1-083701-4   2012.6

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    The effects of Ni substitution on Ce(Cu1-xNix)2Si2 have been studied by
    specific heat and electrical resistivity measurements. The specific heat
    measurement has revealed that the enhanced quantum fluctuations around an
    antiferromagnetic quantum critical point are markedly suppressed by Ni
    substitution, and that the Fermi liquid state recovers in the Nirich region (x
    > 0.12). The characteristic T-linear dependence of the resistivity has been
    observed at approximately x ~ 0.10 together with a sign of superconductivity.
    The variation of n in the form of rho - rho0 = aT^n against Tmax^1, at which
    the resistivity peaks, coincides with the case of high-pressure experiments on
    pure CeCu2Si2. The anomalous T-linear behavior appears to occur in the
    crossover region from the Kondo regime to the valence fluctuation regime rather
    than in the conventional antiferromagnetic quantum critical region.

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  • Iron-platinum-arsenide superconductors Ca10(PtnAs8)(Fe2−xPtxAs2)5 Reviewed

    Minoru,Nohara, Satomi Kakiya, Kazutaka Kudoa, Yoshihiro Oshiro, Shingo Araki, Tatsuo C. Kobayashi, Kenta Oku, Eiji Nishibori, Hi

    Solid State Communications.   152   635 - 639   2012.4

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  • Hall Effect in Single Crystal CeCu2Si2 under High Pressure Reviewed

    S. Araki, Y. Shiroyama, T. Shinohara, Y. Ikeda, T. C. Kobayashi, S. Seiro, C. Geibel, F. Steglich

    Journal of Physics: Conference Series   391   012005   2012

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    DOI: 10.1088/1742-6596/391/1/012005

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  • Cu-NQR of CeCu2Si2 under High Pressure Reviewed

    K. Fujiwara, Y. Okazaki, K. Miyoshi, J. Takeuchi, Y. Ikeda, T. C. Kobayashi, C. Geibel, F. Steglich

    Journal of Physics: Conference Series   391   012012   2012

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  • Interplay of Superconductivity and Fermi-Liquid Transport in Rh-Doped CaFe2As2 with Lattice-Collapse Transition

    Masataka Danura, Kazutaka Kudo, Yoshihiro Oshiro, Shingo Araki, Tatsuo C. Kobayashi, Minoru Nohara

    JOURNAL OF THE PHYSICAL SOCIETY OF JAPAN   80 ( 10 )   103701-1-103701-4   2011.10

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    Ca(Fe1-xRhx)(2)As-2 undergoes successive phase transitions with increasing Rh doping in the T = 0 limit. The antiferromagnetic-metal phase with orthorhombic structure at 0.00 &lt;= x &lt;= 0.020 is driven to a superconducting phase with uncollapsed-tetragonal (ucT) structure at 0.020 &lt;= x &lt;= 0.024; a non-superconducting collapsed-tetragonal (cT) phase takes over at x &gt;= 0.024. The breakdown of Fermi-liquid transport is observed in the ucT phase above T-c. In the adjacent cT phase, Fermi-liquid transport is restored along with a disappearance of superconductivity. This interplay of superconductivity and Fermi-liquid transport suggests the essential role of magnetic fluctuations in the emergence of superconductivity in doped CaFe2As2.

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  • Pressure-induced structural phase transitions in UIr

    H. Kotegawa, S. Araki, T. Akazawa, A. Hori, Y. Irie, S. Fukushima, H. Hidaka, T. C. Kobayashi, K. Takeda, Y. Ohishi, K. Murata, E. Yamamoto, S. Ikeda, Y. Haga, R. Settai, Y. Onuki

    PHYSICAL REVIEW B   84 ( 5 )   054524-1-054524-5   2011.8

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    Strain and resistivity measurements in UIr showed the occurrence of two structural phase transitions under high pressure, indicating the existence of three phases I-III, with slightly different crystal structures. It is suggested that ferromagnetic phases FM1-FM3 emerge in phases I-III, respectively. The pressure-temperature phase diagram was sensitive to the hydrostaticity of pressure. FM3 and superconductivity are observed in the measurements in which Daphne 7373 is used as a pressure-transmitting medium; however they are both absent in the case where petroleum ether is used as a pressure-transmitting medium. These results indicate a close relationship between ferromagnetism and superconductivity.

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  • Hall effect in CeCu2Si2 under pressure

    Shingo Araki, Yuki Shiroyama, Yoichi Ikeda, Tatsuo C. Kobayashi, Silvia Seiro, Christoph Geibel, Frank Steglich

    JOURNAL OF THE PHYSICAL SOCIETY OF JAPAN   80 ( Suppl. A )   SA034-1-SA034-3   2011.7

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    We report the results of Hall effect measurements on CeCu2Si2 under high pressures up to 4.8 GPa. The Hall coefficient at ambient pressure increases with decreasing temperature and exhibits maximum at 4 K. The Hall coefficient at temperature higher than the coherent temperature of 10 K is consistent with the anomalous Hall effect. The pressure effect on the temperature dependence of the Hall coefficient is not simple. The pressure dependence of the Hall coefficient shows anomaly from 3.1 to 4.8 GPa, where the superconductivity is enhanced. These results indicate the close relationship between the Hall coefficient and the superconductivity.

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  • Superconductivity of Heavy Carriers in the Pressure-Induced Phases of Cd2Re2O7

    Tatsuo C. Kobayashi, Yuta Irie, Jun-ichi Yamaura, Zenji Hiroi, Keizo Murata

    JOURNAL OF THE PHYSICAL SOCIETY OF JAPAN   80 ( 2 )   023715   2011.2

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    The superconductivity of Cd2Re2O7 is investigated under hydrostatic pressures up to 4.6 GPa by means of electrical resistivity. A rich phase diagram is obtained, which contains at least five new pressure-induced phases in addition to the three already present at ambient pressure, revealing inherent structural and electronic instabilities of the compound. We find large enhancements of more than one order of magnitude in the upper critical field as well as in the coefficient of the T-2 term in resistivity at around a critical pressure of 4.2 GPa, where an inversion-symmetry-breaking structural transition tends to disappear. Heavy fermion superconductivity is probably realized under high pressures in Cd2Re2O7, which is extraordinary for d-electron compounds.

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  • Incommensurate guest adsorption in bellows-shaped one-dimensional channels of porous coordination polymers Reviewed

    Ryotaro Matsuda, Ryo Kitaura, Yoshiki Kubota, Tatsuo C. Kobayashi, Masaki Takata, Susumu Kitagawa

    MICROPOROUS AND MESOPOROUS MATERIALS   129 ( 3 )   2010.4

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    DOI: 10.1016/j.micromeso.2009.06.023

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  • Magnetic Properties and the Arrangement of Molecular Oxygen Adsorbed in the Microporous Coordination Polymer Cd(bpndc)(bpy)

    A. Hori, T. Yamaguchi, T. C. Kobayashi, A. Matsuo, K. Kindo, D. Tanaka, S. Kitagawa

    Journal of Low Temperature Physics   159 ( 1-2 )   122 - 125   2010.4

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    DOI: 10.1007/s10909-009-0084-8

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  • NQR study of pressure induced superconductivity in CeCu2Si2 Reviewed

    K. Fujiware, Y. Okazaki, Y. Hata, K. Miyoshi, J. Takeuchi, T. C. Kobayashi, C. Geibel, F. Steglich

    PHYSICA STATUS SOLIDI B-BASIC SOLID STATE PHYSICS   247 ( 3 )   608 - 610   2010.3

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    We have measured nuclear quadrupole resonance (NQR) for Cu-63 nuclei under high pressure up to 4.8 GPa. A linear increase in NQR frequency (63)nu(Q) of Cu-63 nuclei was observed below 3 GPa. However, (63)nu(Q) deviates gradually from the linear relation above 3.5 GPa. The downward deviation is associated with a change of valence and consistent with the results of band calculations with the structural parameters under pressure. Antiferromagnetic (AFM) spin fluctuations are drastically suppressed with increasing pressure, whereas T-c increases from 0.7 K at ambient pressure to 1.64K at 4.2 GPa. We have found that bulk superconductivity suddenly disappears at 4.8 GPa accompanied with a rapid decrease in the density of states at the Fermi level.
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    These are indenter pressure cells for NQR measurements. (C) 2010 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim

    DOI: 10.1002/pssb.200983050

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  • High-field magnetization process of O<inf>2</inf> adsorbed in a microporous coordination polymer CPL-1 at various temperatures Reviewed

    A. Hori, T. C. Kobayashi, A. Matsuo, K. Kindo, R. Matsuda, S. Kitagawa

    Journal of Physics: Conference Series   200   2010.1

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    High-field magnetization measurements have been performed at various temperatures on the molecular oxygen adsorbed in a microporous coordination polymer CPL-1. Molecular oxygen with S = 1 forms O2-O2 dimer in the nanochannels of CPL-1. The magnetic properties can be explained by not the S = 1 Heisenberg antiferromagnetic dimer model but the O 2-O2 dimer model taking into account the spin-dependent intermolecular potential. This feature is attributed to the fact that the magnetic interaction between O2 is comparable to the van der Waals force. ? 2010 IOP Publishing Ltd.

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  • Pressure and magnetic field tuned quantum critical point in the Kondo antiferromagnet CePtZn

    S. K. Dhar, R. Kulkarni, H. Hidaka, Y. Toda, H. Kotegawa, T. C. Kobayashi, P. Manfrinetti, A. Provino

    JOURNAL OF PHYSICS-CONDENSED MATTER   21 ( 15 )   156001   2009.4

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    We report magnetization, heat capacity and electrical resistivity measurements on CePtZn, which crystallizes in the orthorhombic TiNiSi type structure. Magnetization and electrical resistivity on the iso-structural series of compounds Ce1-xLaxPtZn (x = 0.1, 0.2 0.5 and 1) were also carried out. The electrical resistivity of CePtZn was also measured in external magnetic fields up to 12 T and under pressures up to 2.66 GPa. We find that CePtZn is a dense Kondo lattice, ordering antiferromagnetically at T-N = 1.7 K, with a comparable Kondo temperature. The magnetic transition temperature, T-N, is continuously suppressed both by the magnetic field and pressure and T-N. 0 around 5-6 T and at 1.2 GPa, respectively. Non-Fermi liquid behavior of resistivity at 4 T and 1.2 GPa and logarithmic divergence of the heat capacity, C-4f/T, at 6 T in a limited temperature region strongly suggest the emergence of a quantum critical point as T-N -&gt; 0.

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  • Pressure Effect on Yb-Based Strongly Correlated Electron Systems

    T. Mito, M. Otani, M. Nakamura, T. Koyama, S. Wada, H. Kotegawa, T. C. Kobayashi, B. Idzikowski, M. Reiffers, J. L. Sarrao

    ACTA PHYSICA POLONICA A   115 ( 1 )   47 - 52   2009.1

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    We studied pressure effects on YbCu(5) and YbInCu(4), good examples of the Yb-based compounds to investigate the nonmagnetic-magnetic transition in Yb-based strongly correlated electron systems. With increasing pressure, the low-temperature Fermi liquid state of YbCu(5) is gradually suppressed, suggesting the second-order like nonmagnetic-magnetic transition around the pressure of 5-6 GPa. On the other hand, in YbInCu(4) which has a pressure-induced magnetic ordered ground state above P(C) = 2.45 GPa, both high-temperature paramagnetic and low-temperature intermediate valence phases are insensitive to pressure. Our results confirm the first-order nature of the transition between the intermediate valence and magnetic ordered phases with pressure.

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  • Hindered Rotation of Methane Molecules in the One-Dimensional Nanochannel of a Porous Coordination Polymer

    Yoshiki Kubota, Masaki Takata, Ryo Kitaura, Ryotaro Matsuda, Tatsuo C. Kobayashi, Susumu Kitagawa

    JOURNAL OF NANOSCIENCE AND NANOTECHNOLOGY   9 ( 1 )   69 - 76   2009.1

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    The crystal structure of a microporous coordination polymer with adsorbed methane gas was determined by in situ synchrotron powder diffraction of the gas adsorption and the MEM (maximum entropy method)/Rietveld method. Methane molecules were found to be adsorbed forming a one-dimensional array in the nanochannels of the polymer. The MEM charge density distribution of the adsorbed methane molecules indicated some protrusions which were not observed in that of a spherical atom of adsorbed argon. This was interpreted as a mixed distribution of two uniaxially rotating molecules with different pivotal axes. The methane molecules displayed hindered rotation depending on the shape of the nanopore surface. This result indicates the capability to control the molecular arrangement and orientation by the adsorption of gas molecules on the precisely designed nanopores of coordination polymers.

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  • High Pressure NQR Measurement in CeCu2Si2 up to Sudden Disappearance of Superconductivity

    Kenji Fujiwara, Yoshiki Hata, Keigo Kobayashi, Kiyotaka Miyoshi, Jun Takeuchi, Yoshiyuki Shimaoka, Hisashi Kotegawai, Tatsuo C. Kobayashi, Christoph Geibel, Frank Steglich

    JOURNAL OF THE PHYSICAL SOCIETY OF JAPAN   77 ( 12 )   123711   2008.12

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    We report the results of Cu-63 nuclear quadrupole resonance (NQR) measurements on CeCu2Si2 under high pressures up to 4.8GPa. Enhanced spin fluctuations due to quantum criticality at ambient pressure are drastically suppressed with increasing pressure, whereas T-c increases from 0.7 K at ambient pressure to 1.64K at 4.2GPa. We have found that bulk superconductivity suddenly disappears at 4.8GPa accompanied with a rapid decrease in the density of states at the Fermi level. The nuclear spin-lattice relaxation rate 1/T-1 at 4.2 GPa reveals that anisotropic superconductivity in the strong-coupling regime is realized even under high pressure far from the antiferromagnetic critical point. Superconductivity under high pressure is unconventional in origin, but the spin fluctuation scenario is not likely to be applicable.

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  • Unconventional superconductivity in f-electron systems

    Y. Onuki, R. Settai, T. Takeuchi, Y. Haga, E. Yamamoto, N. Tateiwa, M. Nakashima, H. Shishido, T. C. Kobayashi, D. Aoki

    JOURNAL OF THE KOREAN PHYSICAL SOCIETY   53 ( 2 )   1034 - 1040   2008.8

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    We report pressure-induced superconductivity in antiferromagnetic cerium compounds and a ferromagnetic uranium compound, focusing on the relation between the superconducting state and the Fermi surface instability in CeRhIn5 and the huge upper critical field H-c2 in CeIrSi3 without inversion symmetry in the crystal structure. The pairing interaction is well correlated with ferromagnetism, as well as antiferromagnetism or antiferromagnetic fluctuations. In the recently discovered superconductor NpPd5Al2, superconductivity is found to be located in the vicinity of an antiferromagnetically ordered state. The upper critical field H-c2 is strongly supressed by the large paramagneic effect, and the corresponding magnetization curve indicates a step-like increase at H-c2, producing a first-order phase transition.

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  • Dependence of pressure-induced phase transitions on pressure-transmitting media in the heavy-electron superconductor URu2Si2

    H. Amitsuka, K. Matsuda, M. Yokoyama, I. Kawasaki, S. Takayama, Y. Ishihara, K. Tenya, N. Tatelwa, T. C. Kobayashi, H. Yoshizawa

    PHYSICA B-CONDENSED MATTER   403 ( 5-9 )   925 - 927   2008.4

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    Elastic neutron-scattering and ac-susceptibility measurements have been performed on a 20 single crystal of URu2Si2 under hydrostatic pressure up to similar to 1.1 GPa using Fluorinert 70 & 77 and Daphne oil 7373 as pressure-transmitting media. Daphne oil produces better hydrostaticity of the applied pressure than Fluorinert, resulting in a slight shift of the phase boundary between hidden order and antiferromagnetic order to a lower pressure. The superconducting phase is also influenced, but never overlaps with the antiferromagnetic phase. (c) 2007 Elsevier B.V. All rights reserved.

    DOI: 10.1016/j.physb.2007.10.065

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  • Observation of charge fluctuations in skutterudite compounds through an Sb-NQR measurement

    H. Kotegawa, Y. Irie, H. Hidaka, T. C. Kobayashi, D. Kikuchi, H. Sugawara, H. Sato

    PHYSICA B-CONDENSED MATTER   403 ( 5-9 )   772 - 774   2008.4

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    We report that the nuclear spin-spin relaxation rate 1/T-2 shows characteristic peaks in the skutterudite compounds of ROs4Sb12 (R = La, Pr, Nd, and Sm) and PrRu4Sb12. The broadening of Sb-NQR spectrum accompanied with the peak in 1/T-2 suggests that some charge fluctuation exists in these systems and slows down around the peak in 1/T-2. The peaks in 1/T-2 appear around 120 K in all the systems we measured, while the other peaks around 20 K are observed in ROs4Sb12 (R = Pr, Nd, and Sm). The 12 Sb sites are not equivalent at low temperatures in these compounds. (C) 2007 Elsevier B.V. All rights reserved.

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  • Evolution of transport and low-energy spin fluctuations in YbXCu4(X = Au and Pd) with the application of magnetic field

    A. Yamamoto, T. Yokoyama, S. Wada, K. Tabira, H. Kotegawa, T. C. Kobayashi, J. L. Sarrao

    PHYSICA B-CONDENSED MATTER   403 ( 5-9 )   1205 - 1207   2008.4

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    We have investigated evolution of transport and low-energy spin fluctuation properties of heavy Fermi liquid compounds YbAuCu4 and YbPdCu4 with the application of magnetic field. YbAuCu4 is found to be driven from the originally antiferromagnetically (AFM) ordered ground state (T-N similar to 0.8K) to a nonmagnetic Fermi liquid (FL) one through the field-tuned quantum critical point (QCP) at H-cr similar or equal to 13 kOe (T-N -&gt; 0). In the vicinity of H-cr, the electrical resistivity measurement provides evidence for the increase in the inelastic scattering of heavy electrons, and the Cu-63 Spin-lattice relaxation rate measurement exhibits the occurrence of AFM spin order instability. Whilst, YbPdCu4 transforms from the originally ferromagnetically (FM) ordered ground state (T-C similar to 0.6K) into the nonmagnetic FL state, without any intermediate NFL phenomena. This result indicates that the competition of the field-stabilized FM correlation and field-destabilized AFM correlation plays an important role on the field-driven quantum critical phenomena. (C) 2007 Elsevier B.V. All rights reserved.

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  • de Haas-van Alphen study of the Pr-based filled skutterudite PrOs4P12

    Hitoshi Sugawara, Yoshinori Iwahashi, Ko-ichi Magishi, Takahito Saito, Kuniyuki Koyama, Hisatomo Harima, Daisuke Kikuchi, Hideyuki Sato, Toyoaki Endo, Rikio Settai, Yoshichika Onuki, Naoki Wada, Hisashi Kotegawa, Tatsuo C. Kobayashi

    JOURNAL OF THE PHYSICAL SOCIETY OF JAPAN   77 ( Suppl. A )   108 - 113   2008.1

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    We have succeeded in observing the de Haas-van Alphen effect in PrOs4P12 which shows no anomaly down to 50 mK in contrast to PrFe4P12 and PrRu4P12. The Fermi surface (FS) topology is reasonably explained by the energy band structure calculation based on a full potential linearized augmented-plane-wave method within the local-density-approximation. Whereas the localized nature of 4f-electrons, we have confirmed a highly enhanced cyclotron effective mass up to 18m(0) in PrOs4P12, which is enhanced 3.8 times compared to that of LaOs4P12. No nesting property with q = (1, 0, 0) in the FS of PrOs4P12 has been confirmed, which suggests both the 4f-electron's contribution and the FS nesting property play the role for the phase transitions in PrFe4P12 and PrRu4P12.

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  • Anomalous Kondo Effect and Ordered State in Heavy Fermion System SmOs4Sb12 : Resistivity, Sb-NQR, and Magnetization Measurements under High Pressure

    Hisashi Kotegawa, Keisuke Tabira, Yuta Irie, Hiroyuki Hidaka, Tatuo C. Kobayashi, Daisuke Kikuchi, Kenya Tanaka, Sho Tatsuoka, Hitoshi Sugawara, Hideyuki Sato

    JOURNAL OF THE PHYSICAL SOCIETY OF JAPAN   77 ( Suppl. A )   90 - 95   2008.1

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    We report resistivity, nuclear quadrupole resonance (NQR), and magnetization measurements under high pressures in a novel heavy fermion compounds SmOs4Sb12. The resistivity and nuclear spin-lattice relaxation rate 1/T-1 show the coherent behavior below a characteristic temperature T* = 20 - 25 K at ambient pressure. Nuclear spin-spin relaxation rate 1/T-2 was found to show a peak of electrical origin around T*. Some charge fluctuation is considered to play an important role in the Kondo effect of SmOs4Sb12. On the other hand, the magnetization at low temperature does not increase under pressures, although the transition temperature increases. The NQR signals are strongly suppressed around the transition temperature and vanishes at low temperatures. These suggest that the ordered state in SmOs4Sb12 is not simple ferromagnetism.

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  • Sb-NQR study of PrOs4Sb12 under high pressure

    Shinji Kawasaki, Kouta Katayama, Masahide Nishiyama, Hisashi Kotegawa, Tatsuo C. Kobayashi, Hitoshi Sugawara, Daisuke Kikuchi, Hideyuki Sato, Guo-qing Zheng

    JOURNAL OF THE PHYSICAL SOCIETY OF JAPAN   77 ( Suppl. A )   330 - 332   2008.1

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    We report Sb-123 nuclear quadrupole resonance (NQR) measurements of the filled skutterudite heavy-fermion superconductor PrOs4Sb12 under high pressure. The temperature dependence of NQR frequency and spin-lattice relaxation rate 1/T-1 indicate that the crystal electric field splitting Delta(CEF) between the ground state Gamma(1) singlet and the first excited state Gamma((2))(4) 4 triplet decreases with increasing pressure. However, it is found Delta(CEF) and T-c stay constant above P similar to 2 GPa revealed by Sb-NQR up to P = 3.82 GPa for the first time. Remarkably, the temperature dependence of 1/T1 below T-c = 1.55 K at P = 1.91 GPa shows no coherence peak just below Tc and power-law behavior well below Tc in contrast to the exponential decrease observed at P = 0. Present results indicate the superconductivity in PrOs4Sb12 under pressure has nodes in the superconducting gap function.

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  • Pressure-induced unconventional superconductivity in the heavy-fermion antiferromagnet CeIn3: An 115In-NQR study under pressure

    S. Kawasaki, M. Yashima, Y. Kitaoka, K. Takeda, K. Shimizu, Y. Oishi, M. Takata, T. C. Kobayashi, H. Harima, S. Araki, H. Shishido, R. Settai, Y. Onuki

    Phys. Rev. B   77 ( 6 )   064508-1-064508-12   2008

  • Appearance of the pressure-induced magnetic phase in alpha-manganese

    K. Takeda, A. Miyake, K. Shimizu, T. C. Kobayashi, K. Amaya

    J. Phys. Soc. Jpn.   77 ( 2 )   25001-1-25001-2   2008

  • Kinetic gate-opening process in a flexible porous coordination polymer

    Daisuke Tanaka, Keiji Nakagawa, Masakazu Higuchi, Satoshi Horike, Yoshiki Kubota, Latsuo C. Kobayashi, Masaki Takata, Susumu Kitagawa

    ANGEWANDTE CHEMIE-INTERNATIONAL EDITION   47 ( 21 )   3914 - 3918   2008

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    DOI: 10.1002/anie.200705822

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  • Observation of gas molecules adsorbed in the nanochannels of porous coordination polymers by the in situ synchrotron powder diffraction experiment and the MEM/Rietveld charge density analysis

    Yoshiki Kubota, Masaki Takata, Tatsuo C. Kobayashi, S. Kitagawa

    COORDINATION CHEMISTRY REVIEWS   251 ( 21-24 )   2510 - 2521   2007.11

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    Microporous coordination polymers have attracted attention for their numerous nanotechnology and engineering applications. Nano-coordination space provides some unique properties and functions that could never be realized in conventional porous materials. For the strategy of rational designs and the syntheses of novel porous coordination polymers, the structural information of adsorbed guest molecules inside the nanopores and the host framework is very important. In the present study, we describe the technique of the direct observation of gas molecules adsorbed in the nanochannels of porous coordination polymers by the in situ synchrotron powder diffraction measurement of gas adsorption and the maximum entropy method (MEM)/Rietveld charge density analysis. Specific alignment and properties of molecular oxygen obtained by gas adsorption in the nano-coordination space are revealed. (C) 2007 Elsevier B.V. All rights reserved.

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  • Connection between charge fluctuations and the coherent temperature in the heavy-fermion system SmOs4Sb12 :: A Sb-121,Sb-123 NQR study

    H. Kotegawa, H. Hidaka, T. C. Kobayashi, D. Kikuchi, H. Sugawara, H. Sato

    PHYSICAL REVIEW LETTERS   99 ( 15 )   156408-1-156408-4   2007.10

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    We report Sb-121,Sb- 123 nuclear quadrupole resonance measurements under pressure in a novel heavy fermion (HF) system SmOs4Sb12. The nuclear spin-spin relaxation rate 1/T-2 exhibits a distinct peak near the coherent temperature of the Kondo effect. The isotope effect of Sb-121 and Sb-123 indicates that the peak in 1/T-2 is electrical in origin. The connection between the peak in 1/T-2 and the development of coherency of the Kondo effect is robust even under pressure. It is conjectured that charge fluctuation plays an important role in forming the HF state in SmOs4Sb12.

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  • Pressure-temperature phase diagram and superconductivity in UIr

    Tatsuo C. Kobayashi, Akihiro Hori, Satoshi Fukushima, Hiroyuki Hidaka, Hisashi Kotegawa, Teruhiko Akazawa, Keiki Takeda, Yasuo Ohishi, Etsuji Yamamoto

    JOURNAL OF THE PHYSICAL SOCIETY OF JAPAN   76 ( 5 )   51007-1 -51007-11   2007.5

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    Pressure-induced superconductivity is found in UIr without inversion symmetry. The pressure-temperature phase diagram has been investigated by means of the electrical resistivity, ac-susceptibility and magnetization measurements under high pressure. The phase diagram consists of three magnetic phases FM1-3 and a superconducting phase. The huge enhancement of residual resistivity and the negative magnetoresistance are found in the intermediate pressure region. These behavior may be induced by the pressure-induced structural phase transition and the accompanied phase separation in this pressure range. The superconducting phase with narrow pressure range is embedded in the FM3 phase, adjacent to zero-temperature FM3-to-nonmagnetic transition. The temperature dependence of resistivity above T-SC follows non-Fermi liquid form of T-1.6. From these experimental facts, superconductivity is considered to be associated with the ferromagnetic fluctuation.

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  • Pressure-temperature phase diagrams of some heavy fermion systems

    T. C. Kobayashi, H. Hidaka, T. Fujiwara, M. Tanaka, K. Takeda, T. Akazawa, K. Shimizu, S. Kirita, R. Asai, H. Nakawaki, M. Nakashima, R. Settai, E. Yamamoto, Y. Haga, Y. Onuki

    JOURNAL OF PHYSICS-CONDENSED MATTER   19 ( 12 )   125205-1-125205-9   2007.3

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    We have studied the pressure-temperature phase diagrams in UIr, U3P4, UP2, CeAgSb2 and CeMg2Cu9 by means of the electrical resistivity. Application of pressure suppresses the magnetic ordering shown at ambient pressure in all compounds. In UIr, the pressure-induced superconductivity is observed in the vicinity of the magnetic-nonmagnetic transition. In this article, we review the pressure-temperature phase diagram and the properties of the magnetic nonmagnetic transition in these compounds.

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  • Drastic change of the electronic states at the quantum critical point in heavy fermions

    R. Settai, H. Shishido, T. Kubo, S. Araki, T. C. Kobayashi, H. Harima, Y. Onuki

    JOURNAL OF MAGNETISM AND MAGNETIC MATERIALS   310 ( 2 )   541 - 547   2007.3

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    We studied the change of the Fermi surface properties in antiferromagnets CeIn3 and CeRhIn5 via the dHvA experiments under pressure. We found the abrupt change of the Fermi surface at the critical pressure P-c, where the magnetic ordering state changes to the paramagnetic one. The change of the Fermi surface indicates that the 4f-electron character is changed from localized to itinerant in CeIn3 and CeRhIn5 at P-c. Namely, the 4f-electron contributes to the volume of the Fermi surface above P-c. Interestingly, the pressure-induced heavy fermion state with large effective mass was observed around P-c, where the pressure-induced superconductivity appears. We also discuss the Fermi surface properties in the system without inversion symmetry in the crystal structure as in CePt3Si and CeTX3 (T:Co, Ir, Rh, X: Si, Ge). The spin-orbit interaction due to the lack of inversion symmetry brings about a splitting of the Fermi surface, which is important for considering the formation of Cooper pair. (c) 2006 Elsevier B.V. All rights reserved.

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  • Ge-73-NQR study of heavy-fermion compound CeNi2Ge2

    S. Kawasaki, T. Sada, T. Miyoshi, H. Kotegawa, H. Mukuda, Y. Kitaoka, T. C. Kobayashi, T. Fukuhara, K. Maezawa, K. M. Itoh, E. E. Haller

    JOURNAL OF MAGNETISM AND MAGNETIC MATERIALS   310 ( 2 )   590 - 592   2007.3

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    We report 73 Ge-nuclear-quadrupole resonance (NQR) study of heavy-fermion compound CeNi2Ge2. The temperature dependence of the 73 Ge nuclear-spin-lattice-relaxation rate 1/T-1 indicates the development of magnetic correlations and the formation of a Fermi-liquid state at temperatures lower than T-FL 0.4K, where 1/T1T is constant. The 1/T1T decrease below T(NQR)c 0.1K, whereas resistance decreases below T (onset)c = 0.2K and does not become zero. These results indicate CeNi2Ge2 closely locates to a superconducting quantum critical point. (c) 2006 Elsevier B. V. All rights reserved.

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  • High-quality single crystal growth and physical properties in a ferromagnet UIr

    E. Yamamoto, Y. Haga, S. Ikeda, T. D. Matsuda, T. Akazawa, H. Kotegawa, T. C. Kobayashi, Y. Onuki

    JOURNAL OF MAGNETISM AND MAGNETIC MATERIALS   310 ( 2 )   E123 - E125   2007.3

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    UIr crystallizes in the monoclinic crystal structure without inversion symmetry. The magnetization measurement indicated that UIr is an Ising-type ferromagnet with the Curie temperature T-C1 = 46K at ambient pressure. We grew a high-quality single crystal by the Czochralski method in a tetra-arc furnace. The ingot was annealed under high vacuum by the solid state electrotransport method. Superconductivity with a transition temperature T-sc = 0.14 K was found under pressure. (c) 2006 Elsevier B.V. All rights reserved.

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  • Effect of uniaxial stress on pressure-induced metal-insulator transition in PrFe4P12

    Hiroyuki Hidaka, Naoki Wada, Hisashi Kotegawa, Tatsuo C. Kobayashi, Daisuke Kikuchi, Hideyuki Sato, Hitoshi Sugawara

    JOURNAL OF MAGNETISM AND MAGNETIC MATERIALS   310 ( 2 )   E228 - E230   2007.3

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    We have carried out electrical resistivity measurements on PrFe4P12 under high pressure using some kinds of pressure-transmitting mediums in order to investigate the effect of uniaxial stress on a pressure-induced metal-insulator (M-I) transition. In the measurement under uniaxial stress, the M-I transition appears at a lower pressure than in the case of quasi-hydrostatic pressure, indicating that the uniaxial stress is favorable to the insulating phase. On the other hand, the M-I transition appears suddenly with finite M-I transition temperature between 2.55 and 2.66 GPa in the measurement under hydrostatic pressure. This fact suggests that the transition from the antiferroquadrupolar metallic phase to the insulating phase is of first order. (c) 2006 Elsevier B.V. All rights reserved.

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  • Nonmagnetic indenter-type high-pressure cell for magnetic measurements

    T. C. Kobayashi, H. Hidaka, H. Kotegawa, K. Fujiwara, M. I. Eremets

    REVIEW OF SCIENTIFIC INSTRUMENTS   78 ( 2 )   23909-1-23909-5   2007.2

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    An indenter-type high-pressure cell has been developed for electric and magnetic measurements in low-temperature and high-magnetic-field environments. The maximum pressure achieved at low temperatures is more than 4.5 GPa, which is higher than that of a conventional piston-cylinder cell. The typical sample space at maximum pressure is 1.6 mm in diameter and approximately 0.7 mm in depth, and magnetic measurements such as ac-susceptibility and nuclear magnetic resonance can be performed using a miniature coil. All the components of the indenter cell are made of nonmagnetic materials that have enough thermal conductivity for low-temperature experiments using a He-3/He-4 dilution refrigerator. Another indenter-type cell designed for a commercial superconducting quantum interference device magnetometer is also reported. (c) 2007 American Institute of Physics.

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  • Transport and magnetic properties of pressure-induced insulating phase in PrFe4P12

    Hiroyuki Hidaka, Hisashi Kotegawa, Satoshi Fukushima, Naoki Wada, Tatsuo C. Kobayashi, Hisatomo Harima, Kenji Fujiwara, Daisuke Kikuchi, Hideyuki Sato, Hitoshi Sugawara

    JOURNAL OF THE PHYSICAL SOCIETY OF JAPAN   75 ( 9 )   2006.9

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    We have studied the physical properties of a pressure-induced insulating phase in PrFe4P12 via Hall effect, P-31-NMR and magnetization measurements under quasi-hydrostatic pressure. In the Hall effect measurement, a decrease in the number of hole carriers due to the metal-insulator (M-I) transition is confirmed, indicating a band insulating state. The P-31-NMR spectrum exhibits abrupt broadening and the susceptibility is suppressed markedly owing to the M-I transition, suggesting that an antiferromagnetic ordering occurs in the insulating phase and the M-I transition is of first order. Both spectra corresponding to the metallic and insulating phases are observed simultaneously in a wide temperature range near the M-I transition. This fact reflects the sensitivity of the M-I transition to uniaxial stress, which is confirmed in the resistivity measurement under uniaxial stress.

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  • Pressure-induced superconductivity in CeNiGe3

    H Kotegawa, T Miyoshi, K Takeda, S Fukushima, H Hidaka, K Tabata, TC Kobayashi, M Nakashima, A Thamizhavel, R Settai, Y Onuki

    PHYSICA B-CONDENSED MATTER   378-80   419 - 420   2006.5

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    An antiferromagnet CeNiGe3, which exhibits a quantum critical point at P-C-6-7 GPa, shows the superconductivity in wide pressure range of 1.7-9.3 GPa. In addition to the superconductivity around P-C, the sharp Superconducting transition can be observed by both the resistivity and the susceptibility measurements at lower pressure region far apart from P-C, where 4f-localized Picture seems to be still dominant. Such a superconductivity is a first example in the f-electron systems. (c) 2006 Elsevier B.V. All rights reserved.

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  • Pressure-induced superconductivity in ferromagnet UIr without inversion symmetry

    TC Kobayashi, S Fukushima, H Hidaka, H Kotegawa, T Akazawa, E Yamamoto, Y Haga, R Settai, Y Onuki

    PHYSICA B-CONDENSED MATTER   378-80   355 - 358   2006.5

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    High-pressure AC-susceptibility measurement has been carried out in UIr. Three series of peaks corresponding to the successive ferromagnetic transitions indicate the existence of three ferromagnetic phases FM 1-3. The phase boundary between FM2 and FM3 was not realized in the resistivity measurement. The Meissner effect is observed successfully in the pressure range of 2.63-2.74 GPa where the peak of AC-susceptibility survives. This result indicates that the superconducting phase is embedded in the FM3 phase with the ordered moment less than 0.051 mu(B)/U and adjoins the quantum critical point. (c) 2006 Elsevier B.V. All rights reserved.

    DOI: 10.1016/j.physb.2006.01.26

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  • Anisotropic behavior in resistivity of RAgSb2 (R = Ce, La)

    Y Watanabe, Y Inada, H Hidaka, H Kotegawa, TC Kobayashi, TD Matsuda, D Aoki

    PHYSICA B-CONDENSED MATTER   378-80   827 - 828   2006.5

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    CeAgSb2 crystallizes in the tetragonal ZrCuSi2 type structure (P4/nmm), which consists of Sb-Ce, Sb-Ag-Ce, Sb-Sb layers. It shows the peculiar anisotropic ferromagnetic ordering below 9.7 K with a small ordered moment of 0.33 mu B. Its residual resistivity steeply increases above p(c) congruent to 3.3 GPa where the magnetic order disappears. It is expected that the p-f mixing on the peculiar hollow square pillar-like Fermi surface plays an important role in CeAgSb2, while similar Fermi surfaces were not observed in LaAgSb,. We have measured the anisotropy in the electrical resistivity of CexLa1-xAgSb2 to study the p-f mixing effect. Small humps were observed in the temperature dependence of the resistivity in (CeLa1-xAgSb2)-La-x. We expected them the CDW transition. The CDW state coexisted with the ferromagnetic state around x = 0.2. (c) 2006 Elsevier B.V. All rights reserved.

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  • Evidence for unconventional superconducting fluctuations in heavy-fermion compound CeNi2Ge2

    S Kawasaki, T Sada, T Miyoshi, H Kotegawa, H Mukuda, TC Kobayashi, T Fukuhara, K Maezawa, KM Itoh, EE Haller

    JOURNAL OF THE PHYSICAL SOCIETY OF JAPAN   75 ( 4 )   2006.4

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    We present evidence for unconventional superconducting fluctuations in a heavy-fermion compound CeNi2Ge2. The temperature dependence of the Ge-73 nuclear-spin-lattice-relaxation rate 1/T-1 indicates the development of magnetic correlations and the formation of a Fermi-liquid state at temperatures lower than T-FL = 0.4 K, where 1/T1T is constant. The resistance and 1/T1T measured on an as-grown sample decrease below 7(c)(onset) = 0.2 K and T-c(NQR) = 0.1 K, respectively: these are indicative of the onset of superconductivity. However, after annealing the sample to improve its quality. these superconducting signatures disappear. These results are consistent with the emergence of unconventional superconducting fluctuations in close proximity to a quantum critical point from the superconducting to the normal phase in CeNi2Ge2.

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  • Electronic states in a semimetal Ce3Sn7

    Y Okuda, MT Suzuki, H Harima, M Nakashima, S Kirita, TC Kobayashi, R Settai, Y Onuki

    JOURNAL OF THE PHYSICAL SOCIETY OF JAPAN   75 ( 4 )   2006.4

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    We carried out the de Haas-van Alphen (dHvA) measurement and the pressure experiment of the electrical resistivity for an antiferromagnet Ce3Sn7 with the orthorhombic crystal structure. The detected dHvA branches are many in number and their dHvA frequencies are extremely small in magnitude, indicating that Ce3Sn7 is a semimetal. This is consistent with the result of the energy band calculations under the assumption that the 4f electrons of two Ce atoms in the 2(a) site are localized and the 4f electron of one Ce atom in the 4(i) site is itinerant. In the pressure experiment, the Neel temperature of T-N = 5.3 K is found to slightly increase with increasing pressure, becomes maximum around 1 GPa, then decreases steeply with further increasing pressure and most likely becomes zero between 3 and 4GPa. The anti ferromagnetic state is changed into the non-magnetic state under pressure.

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  • Tomonaga-Luttinger liquid in a quasi-one-dimensional S=1 antiferromagnet observed by specific heat measurements

    M Hagiwara, H Tsujii, CR Rotundu, B Andraka, Y Takano, N Tateiwa, TC Kobayashi, T Suzuki, S Suga

    PHYSICAL REVIEW LETTERS   96 ( 14 )   2006.4

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    Specific-heat experiments on single crystals of the S=1 quasi-one-dimensional bond-alternating antiferromagnet Ni(C9H24N4)(NO2)ClO4 (NTENP) have been performed in magnetic fields applied both parallel and perpendicular to the spin chains. We have found for the parallel field configuration that the magnetic specific heat (C-mag) is proportional to temperature (T) above a critical field H-c, at which the energy gap vanishes, in a temperature region above that of the long-range ordered state. The ratio C-mag/T increases as the magnetic field approaches H-c from above. The data are in good quantitative agreement with the prediction of the c=1 conformal field theory in conjunction with the velocity of the excitations calculated by a numerical diagonalization, providing conclusive evidence for a Tomonaga-Luttinger liquid.

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  • Pressure-induced superconductivity emerging from antiferromagnetic phase in CeNiGe3

    H Kotegawa, K Takeda, T Miyoshi, S Fukushima, H Hidaka, TC Kobayashi, T Akazawa, Y Ohishi, M Nakashima, A Thamizhavel, R Settai, Y Onuki

    JOURNAL OF THE PHYSICAL SOCIETY OF JAPAN   75 ( 4 )   044713-1-6   2006.4

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    The antiferromagnet CeNiGe3 exhibits superconductivity under pressure. The Neel temperature initially increases with increasing pressure up to 3GPa and then becomes zero at a critical pressure (P-C) that is located at approximately 7GPa. We found that superconductivity emerges from 1.7 GPa in the antiferromagnetic (AF) phase removed from P-C. The superconductivity is realized in a wide pressure region including P-C. The coefficient A in the resistivity and the upper critical field (H,2) significantly change against pressure. A feature of CeNiGe3 is that the moderate heavy fermion state in the AF phase induces superconductivity.

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  • Anisotropic residual resistivity under high pressure in UIr

    Akihiro Hori, Hiroyuki Hidaka, Hisashi Kotegawa, Tatsuo C. Kobayashi, Teruhiko Akazawa, Syugo Ikeda, Etsuji Yamamoto, Yoshinori Haga, Rikio Settai, Yoshichika Onuki

    JOURNAL OF THE PHYSICAL SOCIETY OF JAPAN   75   82 - 84   2006.1

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    Anisotropic resistivity in UIr has been investigated under high pressure. A huge enhancement of residual resistivity was found under high pressure for the measuring current parallel to the [0 1 0] direction while any anomalies were not observed in the resistivity for [1 0 (1) over bar]. The residual resistivity for [0 1 0] reduced to the original value in the pressure range where superconductivity appears. This anomalous behavior indicates that the ground state in the high-rho(0) state is not simple ferromagnet and the application of pressure induces the first-order transition to slightly different electronic state.

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  • Metastable sorption state of a metal-organic porous material determined by in situ synchrotron powder diffraction

    Yoshiki Kubota, Masaki Takata, Ryotaro Matsuda, Ryo Kitaura, Susumu Kitagawa, Tatsuo C. Kobayashi

    ANGEWANDTE CHEMIE-INTERNATIONAL EDITION   45 ( 30 )   4932 - 4936   2006

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    DOI: 10.1002/anie.200600976

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  • Formation and characterization of crystalline molecular arrays of gas molecules in a 1-dimensional ultramicropore of a porous copper coordination polymer

    R Kitaura, R Matsuda, Y Kubota, S Kitagawa, M Takata, TC Kobayashi, M Suzuki

    JOURNAL OF PHYSICAL CHEMISTRY B   109 ( 49 )   23378 - 23385   2005.12

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    Molecules and atoms confined in a nanospace may have properties distinctly different from those of the bulk fluid, owing to the formation of a specific molecular array characteristic of nanospace. In situ synchrotron powder X-ray diffraction measurements have been used to observe confined guest molecules such as N(2), O(2), Ar, and CH(4) in the well-regulated ultramicropore of a copper coordination polymer, 1 ([Cu(2),(pzdc)(2)pyz]: pzdc = 2,3-pyrazinedicarboxylate and pyz = pyrazine). The obtained crystal structures indicate that guest molecules are confined in a linear fashion to form crystal ine-like regular ordered arrays, in contrast to the situation in the gas and liquid state, even at temperatures above the boiling point, and the ordered arrays are characteristic of the kind of gas molecule and the geometrical and potential properties of the ultramicropore of 1.

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  • Change of the Fermi surface across the critical pressure in CeIn3: The de Haas-van Alphen study under pressure

    R Settai, T Kubo, T Shiromoto, D Honda, H Shishido, K Sugiyama, Y Haga, TD Matsuda, K Betsuyaku, H Harima, TC Kobayashi, Y Onuki

    JOURNAL OF THE PHYSICAL SOCIETY OF JAPAN   74 ( 11 )   3016 - 3026   2005.11

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    We have studied a change of the Fermi surface in an antiferromagnet CeIn3 via the de Haas-van Alphen experiment under pressure up to 3 GPa. With increasing pressure P, the Neel temperature T-N = 10 K decreases and becomes zero at a critical pressure P-c similar or equal to 2.6 GPa. In the pressure region P &gt; P,, we have observed a large main Fermi surface named a, which indicates that the electronic state of 4f electron in CeIn3 changes from localized to itinerant at P-c, as observed in the similar antiferromagnets CeRh2Si2 and CeRhIn5. The cyclotron effective mass m(c)(*) of this main Fermi surface is extremely enhanced around P-c: m(c)(*) similar or equal to 60m(0) at 2.7 GPa for the magnetic field along the (100) direction.

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  • Single crystal growth and fermi surface properties of an antiferromagnet UPdGa5

    S Ikeda, TD Matsuda, Y Haga, E Yamamoto, M Nakashima, S Kirita, TC Kobayashi, M Hedo, Y Uwatoko, H Yamagami, H Shishido, T Ueda, R Settai, Y Onuki

    JOURNAL OF THE PHYSICAL SOCIETY OF JAPAN   74 ( 8 )   2277 - 2281   2005.8

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    We have succeeded in growing a high-quality single crystal of an antiferromagnet UPdGa5 by the Ga-flux method with the off-stoichiometric composition of U : Pd : Ga = 1 : 2 : 7.3. The Neel temperature T-N = 30.5 K is found to increase with increasing the residual resistivity ratio (RRR) and becomes constant for a high-quality single crystal sample whose RRR is larger than 50. The electronic state has been investigated by the de Haas-van Alphen experiment, indicating the similar cylindrical Fermi surfaces as in an antiferromagnet UPtGa5. We have also studied the pressure effect by measuring the electrical resistivity. The Neel temperature decreases with increasing pressure and becomes zero at 3.1 GPa. The antiferromagnetic state is changed into the paramagnetic state above 3.1 GPa.

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  • Heavy fermion compound SmOs4Sb12 in vicinity of ferromagnetic critical point

    H Kotegawa, H Hidaka, Y Shimaoka, T Miki, TC Kobayashi, D Kikuchi, H Sugawara, H Sato

    JOURNAL OF THE PHYSICAL SOCIETY OF JAPAN   74 ( 8 )   2173 - 2176   2005.8

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    We report nuclear quadrupole resonance (NQR) measurement at ambient pressure and resistivity measurement under high pressure in the new heavy fermion (HF) compound SmOs4Sb12. The NQR spectrum and the nuclear spin-lattice relaxation rate (1/T-1) clearly demonstrate the bulk nature of ferromagnetic ordering below T-C similar to 2 K. The temperature dependence of 1/T-1 exhibits the characteristic behaviors of a Kondo lattice. The application of pressure decreases Kondo temperature and stabilizes the magnetic ordering, which is the same tendency as that found in some Yb-based compounds. The obtained phase diagram indicates SmOs4Sb12 to be in the vicinity of its ferromagnetic critical point.

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  • Highly controlled acetylene accommodation in a metal-organic microporous material

    R Matsuda, R Kitaura, S Kitagawa, Y Kubota, RV Belosludov, TC Kobayashi, H Sakamoto, T Chiba, M Takata, Y Kawazoe, Y Mita

    NATURE   436 ( 7048 )   238 - 241   2005.7

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    Metal - organic microporous materials(1-4) (MOMs) have attracted wide scientific attention owing to their unusual structure and properties, as well as commercial interest due to their potential applications in storage(5-9), separation(10,11) and heterogeneous catalysis(12,13). One of the advantages of MOMs compared to other microporous materials, such as activated carbons, is their ability to exhibit a variety of pore surface properties such as hydrophilicity and chirality, as a result of the controlled incorporation of organic functional groups into the pore walls(11,13-15). This capability means that the pore surfaces of MOMs could be designed to adsorb specific molecules; but few design strategies for the adsorption of small molecules have been established so far. Here we report high levels of selective sorption of acetylene molecules as compared to a very similar molecule, carbon dioxide, onto the functionalized surface of a MOM. The acetylene molecules are held at a periodic distance from one another by hydrogen bonding between two non-coordinated oxygen atoms in the nanoscale pore wall of the MOM and the two hydrogen atoms of the acetylene molecule. This permits the stable storage of acetylene at a density 200 times the safe compression limit of free acetylene at room temperature.

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  • De Haas-van Alphen effect in CeIn3 under pressure

    Rikio Settai, Tetsuo Kubo, Hiroaki Shishido, Tatsuo C. Kobayashi, Yoshichika Onuki

    Physica B: Condensed Matter   359-361   317 - 319   2005.4

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    We have investigated a change of the electronic state in CeIn3 via de Haas-van Alphen (dHvA) experiments under pressure up to 2.72 GPa for the magnetic field along 〈110〉. A main Fermi surface with the dHvA frequency F=9.4×107 Oe and a large cyclotron mass mc*=53m0 was observed at 2.72 GPa in the vicinity of the critical pressure where the Néel temperature is suppressed to zero. © 2005 Elsevier B.V. All rights reserved.

    DOI: 10.1016/j.physb.2005.01.119

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  • Magnetization study of heavy Fermion superconductor URu2Si2 under high pressures

    K Tenya, Kawasaki, I, K Tameyasu, S Yasuda, M Yokoyama, H Amitsuka, N Tateiwa, TC Kobayashi

    PHYSICA B-CONDENSED MATTER   359   1135 - 1137   2005.4

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    Magnetization measurements of URu2Si2 have been performed under hydrostatic pressures. The superconducting transition temperature decreases linearly with pressure up to 1.1 GPa and disappears above 1.5 GPa. The hysteretic magnetization shows characteristic behaviors at high pressures, suggesting that the pinning properties are changed due to the switch of the normal state to the antiferromagnetic state. (c) 2005 Elsevier B.V. All rights reserved.

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  • Metal-insulator transition under high pressure in PrFe4P12

    H Hidaka, Ando, I, H Kotegawa, TC Kobayashi, H Harima, M Kobayashi, H Sugawara, H Sato

    PHYSICA B-CONDENSED MATTER   359   886 - 888   2005.4

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    We have studied the electrical resistivity in a skutterudite compound PrFe4P12 under high pressure. An antiferroquadrupolar ordering temperature T-Q decreases monotonously with increasing pressure up to 2.4 GPa. Above 2.4 GPa, the metal-insulator (M-I) transition appears. By applying magnetic field, this M-I transition is suppressed easily and heavy-fermion state is realized. The observed Kondo effect and the field-induced heavy-fermion state at high pressure suggest that the quadrupolar interactions of the f electrons of Pr3+ survive even in the insulator phase. (c) 2005 Elsevier B.V. All rights reserved.

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  • High-pressure effect on the electrical resistivity in CeNiGe3 and CeNi2Al5

    M Nakashima, K Tabata, A Thamizhavel, TC Kobayashi, M Hedo, Y Uwatoko, K Shimizu, R Settai, Y Onuki

    PHYSICA B-CONDENSED MATTER   359   266 - 268   2005.4

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    We have measured the electrical resistivity of antiferromagnetic Kondo compounds CeNiGe3 and CeNi2Al5 under pressure. In CeNiGe3, Neel temperature T-N initially increases with increasing pressure P up to 3 GPa, then decreases rather steeply with further increasing pressure, and becomes zero at a critical pressure P-c similar or equal to 5.5 GPa. The A and rho(0) values of the resistivity rho = rho(0) + AT(2) in the Fermi liquid relation become maximum around P-c. Superconductivity is found below 0.48 K in a wide pressure region from 4 to 10 GPa. In CeNi2Al5, the similar pressure dependence of TN is found, has a maximum at 3.9 GPa, and becomes zero around 6 GPa. (c) 2005 Elsevier B.V. All rights reserved.

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  • Pressure-induced charge ordering of LiV2O4

    K Takeda, H Hidaka, H Kotegawa, TC Kobayashi, K Shimizu, H Harima, K Fujiwara, K Miyoshi, J Takeuchi, Y Ohishi, T Adachi, M Takata, E Nishibori, M Sakata, T Watanuki, O Shimomura

    PHYSICA B-CONDENSED MATTER   359   1312 - 1314   2005.4

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    The powder X-ray diffraction experiments of LiV2O4 have been performed at low temperature and high pressure using synchrotron radiation. In the isothermal experiment at 10 K, the cubic-rhombohedral phase transition corresponding to the metal-insulator transition is found at around 13 GPa. This transition seems to be due to charge ordering of V ions on the analogy of the metal-insulator transition in AlV2O4. (c) 2005 Elsevier B.V. All rights reserved.

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  • Pressure-induced superconductivity in UIr without inversion symmetry

    T Akazawa, H Hidaka, H Kotegawa, TC Kobayashi, T Fujiwara, E Yamamoto, Y Haga, R Settai, Y Onuki

    PHYSICA B-CONDENSED MATTER   359   1138 - 1140   2005.4

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    Pressure-induced superconductivity is found in UIr without inversion symmetry. The pressure-temperature phase diagram has been investigated by means of electrical resistivity and magnetization. The phase diagram consists of two ferromagnetic phases. The ferromagnetic phase FM1 with T-Cl similar to 46 K at ambient pressure disappears around 1.7 GPa. With further increase of pressure, the phase (FM2) with small ferromagnetic moment appears in the pressure range of P-Cl &lt; P &lt; 2.6 GPa. The superconducting phase exists near the disappearance point of the FM2 phase, indicating that the superconductivity is associated with the ferromagnetic critical fluctuation around P-C2. (c) 2005 Elsevier B.V. All rights reserved.

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  • Pressure-induced metal-insulator transition in the filled skutterudite PrFe4P12

    H Hidaka, Ando, I, H Kotegawa, TC Kobayashi, H Harima, M Kobayashi, H Sugawara, H Sato

    PHYSICAL REVIEW B   71 ( 7 )   2005.2

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    We have studied the electrical resistivity of the filled skutterudite compound PrFe4P12 under high pressure. The antiferroquadrupolar ordering temperature T-Q decreases monotonically with increasing pressure up to 2.4 GPa. Above 2.4 GPa, we have found that a metal-insulator (M-I) transition appears. The insulating state is easily suppressed by a magnetic field. The observed Kondo effect and a field-induced heavy-fermion state at high pressure suggest that the quadrupolar interactions survive in the insulating region. The quadrupolar interactions might play an essential role in the M-I transition. PrFe4P12 is an unusual compound in that it shows a pressure-induced transition from a metal to an insulator.

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  • Direct observation of hydrogen molecules adsorbed in a microporous coordination polymer

    Y. Kubota, M. Takata, R. Matsuda, R. Kitaura, S. Kitagawa, K. Kato, M. Sakata, T. C. Kobayashi

    Angew. Chem. Int. Ed.   2005

  • Magnetic properties of molecular oxygen adsorbed in micro-porous metal-organic solids

    TC Kobayashi, A Matsuo, M Suzuki, K Kindo, R Kitaura, R Matsuda, S Kitagawa

    PROGRESS OF THEORETICAL PHYSICS SUPPLEMENT   ( 159 )   271 - 279   2005

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    The magnetic properties of O-2 adsorbed in nanochannels of porous metal-organic solids CPL-1 and CPL-p1 have been investigated by means of high-field magnetization process measurement. The contribution from adsorbed 02 shows the metamagnetic-like behavior in both compounds. We propose "the field-induced rearrangement mechanism" as the explanation for the metamagnetic-like behavior. It is known for the O-2-O-2 dimer that the magnetic interaction depends strongly on the intermolecular distance and the orientation of molecular axes. It is considered naturally that the stable arrangement with saturated magnetic moment in the sufficient high field is different from the H-structure which is stable at zero field.

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  • Guest shape-responsive fitting of porous coordination polymer with shrinkable framework

    R Matsuda, R Kitaura, S Kitagawa, Y Kubota, TC Kobayashi, S Horike, M Takata

    JOURNAL OF THE AMERICAN CHEMICAL SOCIETY   126 ( 43 )   14063 - 14070   2004.11

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    In situ synchrotron X-ray powder diffraction patterns of porous coordination polymers {[Cu-2-(pzdc)(2)(bpy)](.)G} have been measured (pzdc = pyrazine-2,3-dicarboxylate, bpy = 4,4'-bipyridine) (where G = H2O for CPL-2 superset of H2O, G = benzene for CPL-2 superset of benzene, and G = void for the apohost). The structures of apohost and CPL-2 superset of benzene were determined from Rietveld analysis. Adsorption of benzene in the channels induced a remarkable contraction in the crystal (b axis; 6.8%, volume; 4.9%), although the channels were occupied by the benzene molecules. This crystal transformation provides a new pore structure that is well suited for benzene molecules, and we denote it as a "shape-responsive fitting" transformation. This type of pore gives rise to a new guideline: frameworks can be composed of flexible motifs that are linked via strong bond and/or stiff motifs that are connected via weaker bonds.

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  • Pressure-induced superconductivity in UIr

    T Akazawa, H Hidaka, H Kotegawa, TC Kobayashi, T Fujiwara, E Yamamoto, Y Haga, R Settai, Y Onuki

    JOURNAL OF THE PHYSICAL SOCIETY OF JAPAN   73 ( 11 )   3129 - 3134   2004.11

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    Pressure-induced superconductivity is found in UIr without inversion symmetry. The pressure-temperature phase diagram has been investigated by means of the electrical resistivity and magnetization measurements under high pressure. The phase diagram consists of two magnetic phases, the Ising-like ferromagnetic phase (FM1) at low pressures and another magnetic phase (FM2) with the small ferromagnetic component along the [101] direction at high pressures. Superconductivity is observed in the narrow pressure range near the disappearance point of the FM2 phase, where the temperature dependence of resistivity follows the non-Fermi liquid form of T-1.6. From these experimental facts, the superconductivity is considered to be associated with the critical fluctuation with the disappearance of FM2 phase.

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  • Rational design and crystal structure determination of a 3-D metal-organic jungle-gym-like open framework

    R Kitaura, F Iwahori, R Matsuda, S Kitagawa, Y Kubota, M Takata, TC Kobayashi

    INORGANIC CHEMISTRY   43 ( 21 )   6522 - 6524   2004.10

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    A new three-dimensional (3-D) jungle-gym-like open metal-organic framework has been synthesized from a two-dimensional (2-D) layer compound using a heterogeneous pillar insertion reaction. Both the starting 2-D layer and the resulting 3-D open compounds have been characterized using X-ray crystallography.

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  • Heat-capacity anomalies at T-sc and T-* in the ferromagnetic superconductor UGe2

    N Tateiwa, TC Kobayashi, K Amaya, Y Haga, R Settai, Y Onuki

    PHYSICAL REVIEW B   69 ( 18 )   2004.5

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    The heat-capacity and magnetization measurements under high pressure have been carried out in a ferromagnetic superconductor UGe2. Both measurements were done using a same pressure cell in order to obtain both data for one pressure. Contrary to the heat capacity at ambient pressure, an anomaly is found in the heat capacity at the characteristic temperature T-* where the magnetization shows an anomalous enhancement under high pressure where the superconductivity appears. This suggests that a thermodynamic phase transition takes place at T-* at least under high pressure slightly below P-c(*) where T-* becomes zero. The heat-capacity anomaly associated with the superconducting transition is also investigated, where a clear peak of C/T is observed in a narrow pressure region (DeltaPsimilar to0.1 GPa) around P-c(*) contrary to the previous results of the resistivity measurement. Present results suggest the importance of the thermodynamic critical point P-c(*) for the appearance of the superconductivity.

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  • Heat-capacity anomalies at Tsc and T* in the ferromagnetic superconductor UGe2 Reviewed

    N. Tateiwa, T. C. Kobayashi, K. Amaya, Y. Haga, R. Settai, Y. Onuki

    Physical Review B - Condensed Matter and Materials Physics   69 ( 18 )   1 - 180513   2004.5

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    The heat-capacity and magnetization measurements under high pressure have been carried out in a ferromagnetic superconductor UGe2. Both measurements were done using a same pressure cell in order to obtain both data for one pressure. Contrary to the heat capacity at ambient pressure, an anomaly is found in the heat capacity at the characteristic temperature T* where the magnetization shows an anomalous enhancement under high pressure where the superconductivity appears. This suggests that a thermodynamic phase transition takes place at T* at least under high pressure slightly below P*c where T* becomes zero. The heat-capacity anomaly associated with the superconducting transition is also investigated, where a clear peak of C/T is observed in a narrow pressure region (ΔP∼0.1 GPa) around P* contrary to the previous results of the resistivity measurement. Present results suggest the importance of the thermodynamic critical point P*c for the appearance of the superconductivity.

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  • A change of the Fermi surface in CeIn3 under pressure

    R Settai, T Kubo, H Shishido, TC Kobayashi, Y Onuki

    JOURNAL OF MAGNETISM AND MAGNETIC MATERIALS   272   223 - 224   2004.5

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    We have investigated a change of the electronic state in CeIn3 via de Haas-van Alphen (dHvA) experiments under pressure up to 2.7 GPa. The shape of a spherical Fermi surface with humps along &lt;111&gt; changes slightly at 2.5 GPa. (C) 2003 Elsevier B.V. All rights reserved.

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  • Magnetism of uranium dioxide UO2 under high pressure

    H. Sakai, H. Kato, Y. Tokunaga, S. Kambe, R. E. Walstedt, A. Nakamura, N. Tateiwa, C. Kobayashi

    JOURNAL OF MAGNETISM AND MAGNETIC MATERIALS   272   E413 - E414   2004.5

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    The DC magnetization of insulating UO2 under high pressure up to similar to 1 GPa has been measured using a piston-cylinder cell. Pressure-induced weak ferromagnetism was found to appear at low pressure (similar to 0.2 GPa). Both the remanent magnetization and the coercive force increase as pressure increases. This weak ferromagnetism may come from spin canting or from uncompensated moments around grain boundaries. (C) 2003 Elsevier B.V. All rights reserved.

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  • Magnetism of a one-dimensional array of oxygen in a micro-porous metal-organic solid

    A. Matsuo, T. C. Kobayashi, M. Suzuki, K. Kindo, R. Kitaura, R. Matsuda, H. -C. Chang, S. Kitagawa

    JOURNAL OF MAGNETISM AND MAGNETIC MATERIALS   272   E643 - E645   2004.5

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    The magnetic properties of molecular oxygen adsorbed in the micro-porous metal-organic solids have been investigated. Adsorbed O-2 molecules form a ladder structure in the nanochannels of CPL-1. The temperature dependence of susceptibility and the high-field magnetization process indicate the nonmagnetic ground state of the adsorbed O-2 at low temperatures. (C) 2003 Elsevier B. V. All rights reserved.

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  • Evidence for the pressure induced magnetic ordering in YbInCu4

    Takeshi Mito, Takehide Koyama, Shinji Wada, Takaki Muramatsu, Tatsuo C. Kobayashi, John L. Sarrao

    JOURNAL OF MAGNETISM AND MAGNETIC MATERIALS   272   E47 - E48   2004.5

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    We have carried out electrical resistivity rho and AC-susceptibility chi(AC) measurements on YbInCu4 under pressure. For pressures above 2.49 GPa, the first-order valence transition is completely suppressed and a clear peak appears in chi(AC) with a small kink in rho at T-M = 2.4 K. The chi(AC) peak is easily diminished by applying low magnetic fields and disappears above similar to 500 Oe. The characteristic behavior of chi(AC) at T-M can generally be ascribed to the onset of long-range ferromagnetic ordering and, therefore, the ground state of the pressure-stabilized phase of YbInCu4 is most probably a ferromagnetically ordered state. (C) 2003 Elsevier B.V. All rights reserved.

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  • Recent advances in the magnetism and superconductivity of heavy fermion systems

    Y Onuki, R Settai, K Sugiyama, T Takeuchi, TC Kobayashi, Y Haga, E Yamamoto

    JOURNAL OF THE PHYSICAL SOCIETY OF JAPAN   73 ( 4 )   769 - 787   2004.4

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    We present recent advances in the magnetism and superconductivity of rare earth and uranium compounds. Heavy fermions are formed on the basis of the competition between the RKKY interaction and the Kondo effect in these compounds. The application of pressure to these compounds is useful to control the electronic states in the antiferromagnets CeRh2Si2 and CeRhIn5, and the ferromagnet UGe2. The quadrupole interaction or the quadrupole Kondo effect is found to be responsible for heavy fermions in PrFe4P12. A rich variety of superconducting properties are demonstrated: superconductivity of CeCoIn5 and CeRhIn5 in the vicinity of a quantum critical point, coexistence of ferromagnetism and superconductivity in UGe2, and superconductivity based on the quadrupole fluctuations in PrOs4Sb12, together with the relation between the superconducting transition temperature and the quasi-two dimensionality of the electronic states.

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  • LiNMR in LiV2O4 under high pressure

    K Fujiwara, K Miyoshi, J Takeuchi, Y Shimaoka, T Kobayashi

    JOURNAL OF PHYSICS-CONDENSED MATTER   16 ( 11 )   S615 - S619   2004.3

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    The Knight shift K and the nuclear spin-lattice relaxation time T-1 of Li-7 have been measured under high pressure up to 4.74 GPa. 1/T1T becomes larger on applying higher pressure below 10 K and does not obey the T1T = constant relation down to 1 K. Meanwhile, K is independent of pressure above 2 GPa, indicating that the uniform component of the susceptibility does not change under high pressure. These results indicate that some antiferromagnetic fluctuations with wavevector q not equal 0 dominate the relaxation rate in LiV2O4 near the boundary of the pressure induced insulating phase. It is noted that the pressure dependence of T-1 for LiV2O4 is opposite to that of typical Ce HF compounds, such as CeCu5.9Au0.1 and CeCu2Si2. At the highest pressure of 4.74 GPa, we found that 1/T-1 obeys a power law dependence of T-2/3 over the wide T range between 60 mK and 10 K. The spin dynamics under high pressure will be discussed.

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  • Observation of a transient magnetization plateau in a quantum antiferromagnet on the Kagome lattice

    Y Narumi, K Katsumata, Z Honda, JC Domenge, P Sindzingre, C Lhuillier, Y Shimaoka, TC Kobayashi, K Kindo

    EUROPHYSICS LETTERS   65 ( 5 )   705 - 711   2004.3

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    The magnetization process of an S = 1/2 antiferromagnet on the Kagome lattice, [Cu-3(titmb)(2)(OCOCH3)(6)] . H2O{titmb = 1, 3, 5-tris(imidazol-1-ylmethyl)-2.4.6 trimethyl-benzene}, has been measured at very low temperature's in both pulsed and steady fields. We have found a new dynamical behavior in the magnetization process. A plateau at one third of the saturation magnetization M-s appears in the pulsed-field experiments for intermediate sweep rates of the magnetic field and disappears in the steady-field experiment's. A theoretical analysis using exact diagonalization yields J(1) = 19+/-2 K and J(2) = 6+/-2 K. for the nearest-neighbor and second-nearest-neighbor interactions. respectively. This set of exchange parameters explains the very low saturation field and the absence of the plateau in the thermodynamic equilibrium as well as the two-peak feature in the magnetic heat. capacity observed by Honda et. al. (Z. Honda et al., J. Phys. Condens. Matter. 14 (2002) L625). Supported by numerical results we argue that a dynamical order by disorder phenomenon could explain the transient appearance of the M-s/3 plateau in pulsed-field experiments.

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  • Pressure-induced superconductivity in ferromagnetic UIr without inversion symmetry

    T Akazawa, H Hidaka, T Fujiwara, TC Kobayashi, E Yamamoto, Y Haga, R Settai, Y Onuki

    JOURNAL OF PHYSICS-CONDENSED MATTER   16 ( 4 )   L29 - L32   2004.2

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    We report the discovery of pressure-induced superconductivity in ferromagnetic UIr, which lacks inversion symmetry in the crystal structure. The Curie temperature T-CI = 46 K at ambient pressure decreases with increasing pressure, reaching a value of 11 K at 1.5 GPa. It presumably decreases further up to about P-cl = 1.7 GPa. The ferromagnetic region named 'Fl' exists up to P-cl. A second magnetic phase named 'F2' with a low ferromagnetic moment appears in the pressure range frorn 1.9 to 2.4 GPa. In the 'F2' phase, the magnetic transition temperature T-C2 decreases with pressure, from 18 K at 1.9 GPa to approximately zero at P-C2 = 2.6-2.7 GPa. In this critical pressure region, superconductivity appears below T-sc = 0.14 K.

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  • High-pressure effect on the electronic state in CeNiGe3: Pressure-induced superconductivity

    M. Nakashima, K. Tabata, A. Thamizhavel, T. C. Kobayashi, M. Hedo, Y. Uwatoko, K. Shimizu, R. Settai, Y. Onuki

    J. Phys.: Condens. Matter   2004

  • Dissimilarity between metallic-like transport in the dielectric spin density wave and field-induced spin density wave states in (TMTSF) <inf>2</inf>PF<inf>6</inf>

    A. V. Kornilov, V. M. Pudalov, Y. Kitaoka, K. Ishida, T. Mito, N. Tateiwa, T. C. Kobayashi, J. S. Qualls

    JETP Letters   80 ( 11 )   707 - 710   2004

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    We report similarities and differences of the transport features in the spin density wave (SDW) and in the field-induced SDW (FISDW) phases of the quasi-one-dimensional compound (TMTSF)"2PF"6. As temperature decreases below ≈2 K, the resistance in both phases exhibits a maximum and a subsequent strong drop. However, the characteristic temperature of the R(T) maximum and its scaling behavior in different magnetic fields B are evidence that the nonmonotonic R(T) dependences have different origin in SDW and FISDW regions of the phase diagram. We also found that the borderline T"0(B, P) which divides the FISDW region of the P-B-T phase diagram into the hysteresis and nonhysteresis domains terminates in the N = 1 subphase; the borderline thus has no extension to the SDW N = 0 phase. © 2004 MAIK "Nauka/Interperiodica".

    DOI: 10.1134/1.1862799

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  • Low temperature magnetic properties of CeTBi2 (T : Ni, Cu and Ag) single crystals

    A Thamizhavel, A Galatanu, E Yamamoto, T Okubo, M Yamada, K Tabata, TC Kobayashi, N Nakamura, K Sugiyama, K Kindo, T Takeuchi, R Settai, Y Onuki

    JOURNAL OF THE PHYSICAL SOCIETY OF JAPAN   72 ( 10 )   2632 - 2639   2003.10

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    A series of the ternary compounds CeTBi2 (T: Ni, Cu and Ag) have been grown in the single crystalline form by means of the flux method. These compounds crystallize in the tetragonal crystal structure. Measurements of the electrical resistivity, magnetic susceptibility, magnetization, low temperature specific heat and de Haas-van Alphen effect are reported. These compounds order antiferromagnetically with an easy-axis of magnetization along the [001] direction(c-axis). The electrical resistivity and magnetic susceptibility are highly anisotropic, reflecting the quasi-two dimensional crystal structure.

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  • Magnetic properties and a change of the electrical resistivity under pressure in CePtGe2

    S Kirita, A Thamizhavel, T Takeuchi, K Tabata, TC Kobayashi, A Galatanu, E Yamamoto, R Settai, S Ramakrishnan, Y Onuki

    JOURNAL OF THE PHYSICAL SOCIETY OF JAPAN   72 ( 9 )   2338 - 2343   2003.9

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    We have succeeded in growing a single crystal of CePtGe2 with the orthorhombic crystal structure by the Bi-flux method. In order to investigate the anisotropic properties, the magnetic susceptibility, magnetization and electrical resistivity measurements have been performed along the principal axes. From these measurements, it is found that CePtGe2 orders ferromagnetically below T-C = 5.1 K, and the magnetic easy-axis corresponds to the a-axis. The anisotropic properties have been analyzed on the basis of the crystalline electric field model. We have also studied the pressure effect on the ferromagnetic ordering, and T-C is found to increase with increasing pressure. However, T-C smears out around 3.5 GPa and a new phase appears at higher pressures, where the transition temperature of the new phase also increases with increasing pressure.

    DOI: 10.1143/JPSJ.72.2338

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  • Pressure-induced weak ferromagnetism in uranium dioxide, UO2

    H Sakai, H Kato, Y Tokunaga, S Kambe, RE Walstedt, A Nakamura, N Tateiwa, TC Kobayashi

    JOURNAL OF PHYSICS-CONDENSED MATTER   15 ( 28 )   S2035 - S2037   2003.7

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    The do magnetization of insulating UO2 under high pressure up to similar to 1 GPa has been measured using a piston-cylinder cell. Pressure-induced weak ferromagnetism appeared at low pressure (similar to0.2 GPa). Both the remanent magnetization and the coercive force increase as pressure increases. This weak ferromagnetism may come from spin canting or from uncompensated moments around grain boundaries.

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  • An anomalously huge resistivity peak under pressure in CeRhGe

    R Asai, A Thamizhavel, H Shishido, T Ueda, Y Inada, R Settai, C Kobayashi, Y Onuki

    JOURNAL OF PHYSICS-CONDENSED MATTER   15 ( 29 )   L463 - L468   2003.7

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    We have measured the electrical resistivity under pressure up to 2 GPa for an antiferromagnet, CeRhGe. The resistivity at ambient pressure decreases monotonically below a Neel temperature T-N = 10 K. With increasing pressure P, the resistivity has a peak around 10 K, which is anomalously enhanced up to 1.2 GPa. With further increasing pressure, the resistivity peak is diminished; the Neel temperature becomes zero at a critical pressure P-c = 9 GPa. The A-value of the resistivity rho in the Fermi liquid relation rho = rho(0) +AT(2) is also found to increase with increasing pressure and has a maximum at Pc which corresponds to the value for the heavy-fermion superconductor CeCu2Si2.

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  • Magnetic properties of a S = 1/2 zigzag spin chain compound (N2H5)CuCl3

    N Maeshima, M Hagiwara, Y Narumi, K Kindo, TC Kobayashi, K Okunishi

    JOURNAL OF PHYSICS-CONDENSED MATTER   15 ( 21 )   3607 - 3618   2003.6

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    We present a theoretical and experimental study of a quasi-one-dimensional zigzag antiferromagnet (N2H5)CuCl3, which can be viewed as weakly coupled Heisenberg chains with a frustrated interaction. We first discuss generic features of the magnetic properties of the zigzag spin chain between the nearly single chain case and the nearly double chain case, on the basis of the finite temperature density-matrix renormalization group (DMRG) calculations. We next show the experimental results for the magnetic susceptibility and the high-field magnetization of a single crystal of (N2H5)CuCl3 above the Neel temperature T-N = 1.55 K. By comparing the experimental data with the DMRG results carefully, we finally obtain the ratio of the nearest and next-nearest exchange couplings as J(1)/J(2) = 0.25 with J(2)/k(B) = 16.3 K. We also investigate the three-dimensional (3D) coupling J' effect by using mean-field theory combined with the DMRG calculations. The estimated value J' similar to 0.04J(2) supports the one-dimensionality of (N2H5)CuCl3 above T-N.

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  • De Haas-Van Alphen experiments under extreme conditions of low temperature, high field and high pressure, for high-quality cerium and uranium compounds

    R Settai, S Araki, H Shishido, Y Inada, Y Haga, E Yamamoto, TC Kobayashi, N Tateiwa, Y Onuki

    JOURNAL OF MAGNETISM AND MAGNETIC MATERIALS   262 ( 3 )   399 - 406   2003.6

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    When pressure is applied to cerium and uranium compounds, the magnetic ordering temperature is suppressed and becomes zero at a critical pressure P-c. Around P-c, non-Fermi liquid and/or superconductivity are observed. We clarified a change of the electronic state via a de Haas-van Alphen (dHvA) experiment when pressure crosses P-c. The dHvA experiment under pressure was done for the antiferromagnets CeRh2Si2 and CeRhIn5, and for a ferromagnet UGe2. We found an abrupt change of the Fermi surface for CeRh2Si2 and UGe2 when crossing P-c, indicating a first-order like phase transition. For CeRhIn5, the topology of the Fermi surface was unchanged, but the cyclotron mass increased steeply above 1.6 Gpa, where superconductivity sets in. (C) 2003 Elsevier Science B.V. All rights reserved.

    DOI: 10.1016/S0304-8853(03)00070-2

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  • Magnetic ordering in the pressure-stabilized high-temperature phase of YbInCu4

    T Mito, T Koyama, M Shimoide, S Wada, T Muramatsu, TC Kobayashi, JL Sarrao

    PHYSICAL REVIEW B   67 ( 22 )   2003.6

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    To elucidate the ground state of the pressure-stabilized high-temperature (HT) phase of YbInCu4, we have carried out electrical resistivity rho and ac-susceptibility chi(ac) measurements at high pressures. For pressures above 2.49 GPa, the first-order valence transition is completely suppressed (below similar to80 mK). Separately, above 2.39 GPa, a clear peak appears in chi(ac) with a small kink in rho at around T-M=2.4 K. The chi(ac) peak is easily diminished by applying low magnetic fields and disappears above similar to500 Oe. The characteristic behavior of chi(ac) at T-M can generally be ascribed to the onset of long-range ferromagnetic ordering and, therefore, the ground state of the pressure-stabilized HT phase is most probably a ferromagnetically ordered state. This result is compatible with the occurrence of weak ferromagnetism recently reported for the Y-substituted compound Yb0.8Y0.2InCu4 under pressure of 1.2 GPa.

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  • A heat capacity anomaly of the superconducting transition in a ferromagnetic superconductor UGe2

    N Tateiwa, TC Kobayashi, K Amaya, Y Haga, R Settai, Y Onuki

    PHYSICA C-SUPERCONDUCTIVITY AND ITS APPLICATIONS   388   527 - 528   2003.5

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    We performed the heat capacity, C(T), measurement under high pressure on a ferromagnetic superconductor UGe2, in order to study the pressure dependence of the anomaly in C(T) associated with the superconducting transition. A clear peak appears only around a critical pressure P-c(*) where an another transition temperature T* becomes 0 K. This result suggests that a bulk superconducting phase exists in the narrower pressure region around P-c(*), than those clarified by previous studies. (C) 2002 Elsevier Science B.V. All rights reserved.

    DOI: 10.1016/S0921-4534(02)02650-3

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  • De Haas-van Alphen experiments in the quantum critical region of cerium and uranium compounds

    Y Onuki, R Settai, S Araki, M Nakashima, H Ohkuni, H Shishido, A Thamizhavel, Y Inada, Y Haga, E Yamamoto, TC Kobayashi

    ACTA PHYSICA POLONICA B   34 ( 2 )   667 - 678   2003.2

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    When pressure is applied to the cerium and uranium compounds, their magnetic ordering temperatures are suppressed and become zero at a critical pressure P-c. Around P-c non-Fermi liquid and/or superconductivity are observed. We clarified a change of the electronic state via the de Haas-van Alphen (dHvA) experiment when pressure crosses P-c. The dHvA experiment under pressure was done for antiferromagnets CeRh2Si2, CeRhIn5 and URu2Si2, and a ferromagnet UGe2. We find an abrupt change of the Fermi surface for CeRh2Si2 and UGe2 when crossing P-c, indicating a first-order like phase transition. For CeRhIn5 and URu2Si2, a change of the cyclotron mass is clearly observed.

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  • Huge residual resistivity in the quantum critical region of CeAgSb2

    M Nakashima, S Kirita, R Asai, TC Kobayashi, T Okubo, M Yamada, A Thamizhavel, Y Inada, R Settai, A Galatanu, E Yamamoto, T Ebihara, Y Onuki

    JOURNAL OF PHYSICS-CONDENSED MATTER   15 ( 4 )   L111 - L117   2003.2

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    We have studied the effect of pressure on the electrical resistivity of a high-quality single crystal CeAgSb2 which has a small net ferromagnetic moment of 0.4 mu(B)/Ce. The magnetic ordering temperature. T-ord = 9.7 K decreases with increasing pressure p and disappears at a critical pressure p(c) similar or equal to 3.3 GPa. The residual resistivity, which is close to zero up to 3 GPa, increases steeply above 3 GPa, reaching 55 muOmega cm at p(c). A huge residual resistivity is found to appear when the magnetic order disappears.

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  • A heat capacity anomaly at T* in a ferromagnetic superconductor UGe2

    N Tateiwa, TC Kobayashi, K Amaya, Y Haga, R Settai, Y Onuki

    ACTA PHYSICA POLONICA B   34 ( 2 )   515 - 518   2003.2

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    We performed the heat capacity, C(T), measurement under high pressure for a ferromagnetic superconductor UGe2. At 1.15 GPa, we found a peak in C/T at a characteristic temperature, T-* = 6 K where the magnetization showed anomalous increase. At 1.28 GPa, above the critical pressure P-c(*) where T-* becomes 0 K, C/T does not show notable anomaly at zero magnetic field, but the application of the external field above 2.5 T induces the peak again at T-* &gt; 0 K. It corresponds to the induction of T-* by the magnetic field. Our experimental result suggests that a second order phase transition takes place at T-* and thus a disappearance of the phase transition at T-* is of second order.

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  • Electrical resistivity of CeTIn5 (T=Rh, Ir) under high pressure

    T. Muramatsu, T. C. Kobayashi, K. Shimizu, K. Amaya, D. Aoki, Y. Haga, Y. Onuki

    Physica C   2003

  • Evolution of pressure-induced heavy fermion state and superconductivity in CeRhIn5: A high-pressure Fermi surface study

    H Shishido, R Settai, S Araki, T Ueda, Y Inada, TC Kobayashi, T Muramatsu, Y Haga, Y Onuki

    PHYSICAL REVIEW B   66 ( 21 )   2002.12

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    Evolution of the pressure-induced heavy fermion state and superconductivity in CeRhIn5 have been established by high-pressure Fermi surface studies using dHvA technique. The effective mass of the conduction electrons named branch beta(2) increases from 5.5 m(0) at ambient pressure to 20 m(0) at 1.6 GPa where superconductivity sets in. This heavy electron mass continues to increase steeply up to 2.1 GPa, 45 m(0) at 2.1 GPa, with a concomitant increase of the superconducting transition temperature. However, the underlying Fermi surface remains approximately same even at 2.1 GPa, strongly suggesting that antiferromagnetic fluctuations of Ce moments do not contribute to the volume of the Fermi surface, but enhance the cyclotron mass of the conduction electrons.

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  • Formation of a one-dimensional array of oxygen in a microporous metal-organic solid

    R Kitaura, S Kitagawa, Y Kubota, TC Kobayashi, K Kindo, Y Mita, A Matsuo, M Kobayashi, HC Chang, TC Ozawa, M Suzuki, M Sakata, M Takata

    SCIENCE   298 ( 5602 )   2358 - 2361   2002.12

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    We report the direct observation of dioxygen molecules physisorbed in the nanochannels of a microporous copper coordination polymer by the MEM (maximum entropy method)/Rietveld method, using in situ high-resolution synchrotron x-ray powder diffraction measurements. The obtained MEM electron density revealed that van der Waals dimers of physisorbed O(2) locate in the middle of nanochannels and form a one-dimensional ladder structure aligned to the host channel structure. The observed O-O stretching Raman band and magnetic susceptibilities are characteristic of the confined O(2) molecules in one-dimensional nanochannels of CPL-1 (coordination polymer 1 with pillared layer structure).

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  • Pressure-induced superconductivity in a ferromagnet, UGe2: resistivity measurements in a magnetic field

    TC Kobayashi, K Hanazono, N Tateiwa, K Amaya, Y Haga, R Settai, Y Onuki

    JOURNAL OF PHYSICS-CONDENSED MATTER   14 ( 44 )   10779 - 10782   2002.11

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    Electrical resistivity measurements in a magnetic field are carried out on UGe2 which exhibits pressure-induced superconductivity. The superconductivity is observed from 1.06 to 1.44 GPa. In the temperature and field dependences of the resistivity at P &gt; PC where the ferromagnetic ordering disappears, it is observed that the application of an external field along the a-axis increases the coefficient A of the Fermi-liquid behaviour (alphaAT(2)) abruptly-corresponding to the metamagnetic transition. The characteristic enhancement of H-C2 is reconfirmed for H parallel to a-axis. The upper critical field of H-C2 is anisotropic: H-C2(T) exhibits positive curvature for H parallel to b-axis and H parallel to c-axis.

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  • Heavy fermions in cerium and uranium compounds studied by the de Haas-van Alphen experiment

    S Araki, R Settai, M Nakashima, H Shishido, S Ikeda, H Nakawaki, Y Haga, N Tateiwa, TC Kobayashi, H Harima, H Yamagami, Y Aoki, T Namiki, H Sato, Y Onuki

    JOURNAL OF PHYSICS AND CHEMISTRY OF SOLIDS   63 ( 6-8 )   1133 - 1139   2002.6

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    We carried out the de Haas-van Alphen (dHvA) experiment under pressure to clarify the nature of f-electron compounds of CeRh2Si2, UGe2 and CeCoIn5. With increasing pressure, the Neel temperature T-N = 36 K in CeRh2Si2 and the Curie temperature T-C = 52 K in UGe2 decrease, and a quantum critical point corresponding to the extrapolation T-N or T-C --&gt; 0 is reached at the critical pressure p(c) similar or equal to 1.06 and 1.52 GPa, respectively. Experimental results indicate a discontinuous change of the Fermi surface in CeRh2Si2 and UGe2 when the pressure crosses pc. A heavy fermion superconductor CeCoIn5 with a quasi-two dimensional Fermi surface was found to be located in the vicinity of the quantum critical point. (C) 2002 Elsevier Science Ltd. All rights reserved.

    DOI: 10.1016/S0022-3697(02)00156-7

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  • Pressure-induced superconductivity in an antiferromagnet CeRh2Si2

    S Araki, M Nakashima, R Settai, TC Kobayashi, Y Onuki

    JOURNAL OF PHYSICS-CONDENSED MATTER   14 ( 21 )   L377 - L383   2002.6

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    We studied the pressure effect by measuring the electrical resistivity for a high-quality single crystal of an antiferromagnet CeRh2Si2 with the tetragonal structure. The Neel temperature becomes zero around I GPa. An onset of superconductivity appears below 0.5 K in a relatively wide pressure region from 0.97 to 1.20 GPa, while the resistivity zero, which appears below 0.4 K, is found to be located in an extremely narrow region from 1.03 to 1.08 GPa. Correspondingly the A value of the Fermi liquid relation in the electrical resistivity (rho = rho(0) + AT(2)) becomes maximum around I GPa. Superconductivity is realized in a heavy fermion state.

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  • Pressure study of an antiferromagnet, CeMg2Cu9

    H Nakawaki, Y Inada, R Asai, M Yamada, T Okubo, S Ikeda, A Thamizhavel, TC Kobayashi, R Settai, E Yamamoto, Y Onuki

    JOURNAL OF PHYSICS-CONDENSED MATTER   14 ( 14 )   L305 - L311   2002.4

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    We have studied the effect of pressure on the electrical resistivity of the antiferrornagnet CeMg2Cu9 which crystallizes in the hexagonal structure. The structure is built up of alternating MgCu2 Laves-type and CeCu5-type layers along the [0001] direction. The Neel temperature T-N = 2.7 K at ambient pressure decreases with increasing pressure p and disappears at a critical pressure p(e) similar or equal to 2.5 GPa. Correspondingly, the residual resistivity rho(0) and the coefficient A in a Fermi-liquid relation rho = rho(0) + AT(2) are found to have maximum values around p(e).

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  • Heat capacity of the pressure-induced superconductivity in itinerant ferromagnet UGe2

    N Tateiwa, TC Kobayashi, K Amaya, Y Haga, R Settai, Y Onuki

    PHYSICA B-CONDENSED MATTER   312   109 - 111   2002.3

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    Recently, co-existence of the ferromagnetism and superconductivity was reported in the high-pressure region (1.0-1.6 GPa) in UGe2. We performed the heat capacity measurement on UGe2 under high pressure. At 1.15 GPa, we found a peak corresponding to the superconducting transition. The superconducting temperature T-sc and DeltaC/(gammaTSC) are 0.6 K and 0.25, respectively. The superconducting transition was also confirmed by the appearance of the Meissner effect in the AC susceptibility. From these results, we confirm a bulk nature of the superconductivity in UGe2. The value of C/T (similar to 95 mJ/molK(2)) just above Tsc at 1.15 GPa is as much as 3 times larger than that at ambient pressure, which indicates a large mass enhancement of quasiparticles under high pressure. (C) 2002 Elsevier Science B.V. All rights reserved.

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  • Transport properties of CeRhIn5 under high pressures up to 8.5 GPa

    T Muramatsu, N Tateiwa, TC Kobayashi, K Shimizu, K Amaya, D Aoki, H Shishido, Y Haga, Y Onuki

    PHYSICA B-CONDENSED MATTER   312   140 - 141   2002.3

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    Transport properties of a pressure-induced superconductor CeRhIn5 were investigated under high pressures up to 8.5 GPa by using a diamond-anvil cell. Superconductivity was observed in a wide pressure range from 1.5 to 7.6 GPa.We also investigated the transport properties in the external magnetic field in order to study a characteristic temperature dependence of the resistivity in the normal state. (C) 2002 Published by Elsevier Science B.V.

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  • Spin dynamics of heavy fermion system LiV2O4 under high pressure

    K Fujiwara, H Yoshioka, K Miyoshi, J Takeuchi, TC Kobayashi, K Amaya

    PHYSICA B-CONDENSED MATTER   312   913 - 915   2002.3

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    The nuclear spin lattice relaxation time (T-1) Li-7 in the heavy fermion system LiV2O4 has been measured under high pressure up to 3.7 GPa. At ambient pressure, 1/T-1 shows broad maximum around 50K and is proportional to the temperature below 8 K. This is apparently quite similar to the relaxation behavior in f-electron systems. However, 1/T-1 becomes larger with applying higher pressure below 10 K and does not obey T1T =constant relation down to I K. This pressure dependence of T, is opposite to that of Cc compounds, such as CeCu5.9Au0.1 and CeCu2Si2. Spin dynamics of LiV2O4 under pressure is discussed. (C) 2002 Elsevier Science B.V. All rights reserved.

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  • Novel phases in the field-induced spin-density-wave state in (TMTSF)<inf>2</inf>PF<inf>6</inf>

    A. V. Kornilov, V. M. Pudalov, Y. Kitaoka, K. Ishida, T. Mito, J. S. Brooks, J. S. Qualls, J. A. Perenboom, N. Tateiwa, T. C. Kobayashi

    Physical Review B - Condensed Matter and Materials Physics   65 ( 6 )   604041 - 604044   2002.2

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    Magnetoresistance measurements on the quasi-one-dimensional organic conductor (TMTSF)2PF6 performed in magnetic fields B up to 16 T, temperatures T down to 0.12 K and under pressures P up to 14 kbar have revealed new phases on its P-B-T phase diagram. We found a new boundary which subdivides the field induced spin density wave (FISDW) phase diagram into two regions. Whereas a low-temperature region of the FISDW diagram is characterized by a hysteresis behavior typical for the first-order transitions, in a hightemperature region of the FISDW phase diagram, the hysteresis was found to disappear. We also found that the temperature dependence of the resistance (at a constant B) changes sign at about the same boundary. We compare these results with recent theoretical models.

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  • A change of the Fermi surface across the metamagnetic transition under pressure in UGe2

    Y Haga, M Nakashima, R Settai, S Ikeda, T Okubo, S Araki, TC Kobayashi, N Tateiwa, Y Onuki

    JOURNAL OF PHYSICS-CONDENSED MATTER   14 ( 5 )   L125 - L135   2002.2

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    We have performed the de Haas-van Alphen (dHvA) and ac-susceptibility experiments on a ferromagnet UGe2 under pressure for the field along the easy a-axis. The p-H phase diagram was determined, indicating three kinds of phase: paramagnetic and weakly and strongly polarized phases. The detected dHvA frequencies as well as the cyclotron masses are found to be very different between the weakly and strongly polarized states. A change of the Fermi surface occurs when the weakly polarized phase is changed into the strongly polarized phase with increasing magnetic field.

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  • Novel phases in the field-induced spin-density-wave state in (TMTSF)(2)PF6

    AV Kornilov, VM Pudalov, Y Kitaoka, K Ishida, T Mito, JS Brooks, JS Qualls, JAAJ Perenboom, N Tateiwa, TC Kobayashi

    PHYSICAL REVIEW B   65 ( 6 )   2002.2

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    Magnetoresistance measurements on the quasi-one-dimensional organic conductor (TMTSF)(2)PF6 performed in magnetic fields B up to 16 T, temperatures T down to 0.12 K and under pressures P up to 14 kbar have revealed new phases on its P-B-T phase diagram. We found a new boundary which subdivides the field induced spin density wave (FISDW) phase diagram into two regions. Whereas a low-temperature region of the FISDW diagram is characterized by a hysteresis behavior typical for the first-order transitions, in a high-temperature region of the FISDW phase diagram, the hysteresis was found to disappear. We also found that the temperature dependence of the resistance (at a constant B) changes sign at about the same boundary, We compare these results with recent theoretical models.

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  • A change of the Fermi surface in UGe2 across the critical pressure

    R Settai, M Nakashima, S Araki, Y Haga, TC Kobayashi, N Tateiwa, H Yamagami, Y Onuki

    JOURNAL OF PHYSICS-CONDENSED MATTER   14 ( 1 )   L29 - L36   2002.1

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    We carried out the de Haas-van Alphen (dHvA) experiment under pressure for a ferromagnet UGe2. The dHvA frequency of a main dHvA branch named a, that corresponds to a majority up-spin band 40-hole Fermi surface, decreases monotonously with increasing pressure, but in the pressure range from p(c)* (similar or equal to1.2 GPa) to p(c) (similar or equal to1.5 GPa) the dHvA signal disappears completely, where p(c) and p(c)* correspond to critical pressures for a Curie temperature T-C and the C second phase transition temperature T* (&lt;T-C), respectively. For p &gt; p(c) we observed new dHvA branches with large cyclotron masses of 19-64m(0), which correspond to main Fermi surfaces in the paramagnetic state.

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  • Fermi surface, magnetic and superconducting properties of LaRhIn5 and CeTIn5 (T : Co, Rh and Ir)

    H Shishido, R Settai, D Aoki, S Ikeda, H Nakawaki, N Nakamura, T Iizuka, Y Inada, K Sugiyama, T Takeuchi, K Kindo, TC Kobayashi, Y Haga, H Harima, Y Aoki, T Namiki, H Sato, Y Onuki

    JOURNAL OF THE PHYSICAL SOCIETY OF JAPAN   71 ( 1 )   162 - 173   2002.1

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    We have studied Fermi surface properties of LaRhIn5 and CeTIa(5) (T: Co, Rh and Ir) via the de Haasvan Alphen (dHvA) experiment. The Fermi surface of a non-4f reference compound LaRhIn5 is quasi-two dimensional, reflecting the unique tetragonal crystal structure, which is consistent with the result of FLAWP energy band calculations. The Fermi surface of an antiferromagnet CeRhIn5 is similar to that of LaRhIn5 although the cyclotron mass in CeRhIn5 is roughly by one order larger than that in LaRhIn5. Both Fermi surfaces are. however, different from those of CeCoIn5 and CcIrIn(5) which are well explained by the 4f-itinerant band model. The 4f electrons in CeRhIn5 thus do not contribute to the volume of ate Fermi surface. We have also studied magnetic and superconducting properties of CeCoIn5 and CeIrIn5.

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  • Thermal Property of Heavy Fermion Compound YbP Reviewed

    N. Tateiwa, T. Kobayashi, K. Amaya, D. X. Li, Y. Shiokawa, T. Suzuki

    J. Phys. Soc. Jpn.   71   1365 - 1369   2002

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    DOI: 10.1143/JPSJ.71.1365

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  • Thermal properties of a ferromagnetic superconductor UGe2

    Naoyuki Tateiwa, Tatsuo C. Kobayashi, Kichi Amaya, Yoshinori Haga, Rikio Settai, Yoshichika Onuki

    Journal of Nuclear Science and Technology   39   195 - 198   2002

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    Thermal properties of a ferromagnetic superconductor UGe2 were investigated by the heat capacity measurements. The bulk nature of the superconductivity was confimied by the observation of a peak in the heat capacity at the superconducting transition temperature T SC, From the pressure dependence of the linear heat capacity coefficient γ, it is suggested that the low energy magnetic excitation near the critical point Pc*, where T* becomes OK, might play an important role on the superconductivity. The pressure dependence of the superconducting peak and the temperature dependence of CIT above T SC suggest that the order parameter of the superconducting state might be different between the phases below and above PC *. © 2002 Atomic Energy Society of Japan. All rights reserved.

    DOI: 10.1080/00223131.2002.10875442

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  • Magnetic - nonmagnetic transition of U3P4 at high pressures

    Keiki Takeda, Masashi Tanaka, Tatsuo C. Kobayashi, Teruhiko Akazawa, Katsuya Shimizu, Kiichi Amaya, Yoshihiko Inada, Piotr Wiśniewski, Dai Aoki, Etsuji Yamamoto, Yoshinori Haga, Yoshichika Ōnuki

    Journal of Nuclear Science and Technology   39   191 - 194   2002

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    The transport properties of the itinerant ferromagnet U3P4 have been studied at high pressures up to 6.0 GPa using a diamond anvil cell. The Curie temperature TC decreases with increasing pressure, but then TC cannot be assigned above 4.0 GPa. The coefficient A, assuming the Fermi liquid behavior (p(T) = p0 + AT2) at low temperatures, shows a maximum at 5.3 GPa. The temperature dependence of the resistivity at 5.0 GPa follows T 5/3 which is expected in the SCR theory of a three dimensional ferromagnet. From these results, it is concluded that the ferromagnetic-nonmagnetic transition exists at around 5.0 GPa. © 2002 Atomic Energy Society of Japan. All rights reserved.

    DOI: 10.1080/00223131.2002.10875441

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  • Slow magnetization reversal in [Ni-4(OMe)(4)(sal(4)(MeOH)(4)]

    M Nakano, GE Matsubayashi, T Muramatsu, TC Kobayashi, K Amaya, J Yoo, G Christou, DN Hendrickson

    MOLECULAR CRYSTALS AND LIQUID CRYSTALS   376   405 - 410   2002

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    The magnetic behavior of the nickel cubane complex [Ni-4(OMe)(4)(sal)(4)(MeOH)(4)] (Hsal = salicylaldehyde) was studied by using a Hartshorn bridge equipped with a He-3/He-4 dilution refrigerator. This complex has long been known to have a well-isolated high-spin ground state with S = 4 and it was suggested to have an easy-axis type anisotropy. AC magnetic susceptibility data clearly show a slow magnetization reversal below 0.3 K, characteristic of single-molecule magnets. The Arrhenius plot of the relaxation rate provides the activation energy of about 5 K.

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  • Thermal properties of a low carrier concentration compound YbP

    N. Tateiwa, T. C. Kobayashi, K. Amaya, D. Li, Y. Shiokawa, T. Suzuki

    J. Phys. Soc. Jpn.   2002

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  • Evolution of pressure-induced heavy fermion state and superconductivity in (formula presented) A high-pressure Fermi surface study Reviewed

    H. Shishido, R. Settai, S. Araki, T. Ueda, Y. Inada, T. C. Kobayashi, T. Muramatsu, Y. Haga, Y. Ōnuki

    Physical Review B - Condensed Matter and Materials Physics   66 ( 21 )   1 - 5   2002

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    Evolution of the pressure-induced heavy fermion state and superconductivity in (formula presented) have been established by high-pressure Fermi surface studies using dHvA technique. The effective mass of the conduction electrons named branch (formula presented) increases from 5.5 (formula presented) at ambient pressure to 20 (formula presented) at 1.6 GPa where superconductivity sets in. This heavy electron mass continues to increase steeply up to 2.1 GPa, 45 (formula presented) at 2.1 GPa, with a concomitant increase of the superconducting transition temperature. However, the underlying Fermi surface remains approximately same even at 2.1 GPa, strongly suggesting that antiferromagnetic fluctuations of Ce moments do not contribute to the volume of the Fermi surface, but enhance the cyclotron mass of the conduction electrons. © 2002 The American Physical Society.

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  • Fermi surface instability in CeRh2Si2 under pressure

    S Araki, R Settai, TC Kobayashi, H Harima, Y Onuki

    PHYSICAL REVIEW B   64 ( 22 )   2001.12

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    That the 4f electrons in the rare-earth antiferromagnetic compound CeRh2Si2 should be considered as localized electrons at cerium sites has been confirmed by comparing a de Haas-van Alphen experiment to the result of energy band calculations for LaRh2Si2. When pressure p is applied to the compound, the Neel temperature T-N1 = 36 K decreases and finally becomes zero at p(c)similar or equal to1.0-1.1 GPa. The topology of the Fermi surface is found to be almost unchanged up to 1.0 GPa, but the cyclotron effective mass increases with increasing pressure. Above 1.1 GPa, the topology of the Fermi surface changes abruptly. A new Fermi surface is explained by the 4f-itinerant-band model. The corresponding cyclotron mass is large, being about 22m(o).

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  • Superconductivity of CeRhIn5 under high pressure

    T Muramatsu, N Tateiwa, TC Kobayashi, K Shimizu, K Amaya, D Aoki, H Shishido, Y Haga, Y Onuki

    JOURNAL OF THE PHYSICAL SOCIETY OF JAPAN   70 ( 11 )   3362 - 3367   2001.11

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    The pressure dependence of transport properties in CeRhIn5 was studied up to 8.5 GPa by using a diamond-anvil cell. The electrical resistivity does not follow the T-2-dependecne of a Fermi liquid nature under any pressure. In this non-Fermi liquid state, superconductivity was observed in a wide pressure range of 1.5 GPa &lt; P &lt; 7.6 GPa. The superconducting temperature TC has a double-maximum structure with a minimum at 5.2 GPa. A maximum of T-C = 2.2 K was observed at P = 2.5 GPa, where the corresponding electrical resistivity just above TC has the maximum. The upper critical field H-C2 and the magnetoresistances were also investigated under pressure.

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  • Magnetic properties of a pressure-induced superconductor UGe2

    N Tateiwa, K Hanazono, TC Kobayashi, K Amaya, T Inoue, K Kindo, Y Koike, N Metoki, Y Haga, R Settai, Y Onuki

    JOURNAL OF THE PHYSICAL SOCIETY OF JAPAN   70 ( 10 )   2876 - 2879   2001.10

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    We performed DC-magnetization and neutron scattering experiments under pressure P for a pressure-induced superconductor UGe2. We found that the magnetic moment is enhanced at a characteristic temperature T* in the ferromagnetic state, where T* is smaller than a Curie temperature T-C. This enhancement becomes remarkable in the vicinity of P-C* = 1.20 GPa, where T* becomes 0 K and the superconducting transition temperature T-SC shows a maximum. The characteristic temperature T*, which decreases with increasing pressure, also depends on the magnetic field.

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  • Pressure-induced superconductivity in a ferromagnet UGe2 (vol 13, pg L17, 2001)

    N Tateiwa, TC Kobayashi, K Hanazono, K Amaya, Y Haga, R Settai, Y Onuki

    JOURNAL OF PHYSICS-CONDENSED MATTER   13 ( 29 )   6443 - 6443   2001.7

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  • Neutron scattering study of linear-chain Haldane compounds NDMAZ and NDMAP

    N Metoki, Y Koike, Y Matsuoka, T Kobayashi, M Yamashita

    JOURNAL OF MAGNETISM AND MAGNETIC MATERIALS   226   414 - 416   2001.5

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    Neutron scattering experiments were carried out for the new Haldane compounds Ni(C5H14N2)(2)N-3(ClO4) (NDMAZ) and Ni(C5H14N2)(2)N-3(PF6) (NDMAP) in the magnetic field up to 10 T in order to investigate the field-induced long-range ordering and the spin excitation. For NDMAZ. the triplet excited state (1.61, 1.76, and 3.2 meV) and field dependence of these levels were observed at Q = (000.5). From these data. the intra-chain coupling constant approximate to 4.3 meV and the anisotropic parameters D approximate to 0.76 meV and /E/ approximate to 0.038 meV were estimated. For NDMAP the gap was observed at about 0.48 and 0.64 meV at Q (000.5). By applying the field of 5 T, the first excited state shifted below the resolution less than 0.13 meV. Above the critical field H-C, the intensities of singlet-triplet excitation becomes very weak. This work is the first neutron scattering study on a Haldane system above the critical fields. (C) 2001 Elsevier Science B.V. All rights reserved.

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  • Proton NMR study of the field-induced long-range ordering in Haldane gap system NDMAP

    TC Kobayashi, K Tanaka, K Fujiwara, K Amaya, N Aizawa, T Ishii, M Yamashita

    JOURNAL OF MAGNETISM AND MAGNETIC MATERIALS   226   423 - 424   2001.5

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    Appearance of the field-induced long-range ordering was observed directly by a proton NMR measurement in Haldane gap system, Ni(C5H14N2)(2)N-3(PF6) (NDMAP). A sudden splitting of the spectrum due to the appearance of the transverse staggered moment was observed just below T-N. The transverse staggered moment is estimated as 1.1 mu (B) in the external field of 10.9 T parallel to the ab-plane. (C) 2001 Elsevier Science B.V. All rights reserved.

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  • Field-induced long-range ordering in Haldane gap system NDMAZ

    TC Kobayashi, H Tatewaki, A Koda, K Amaya, Y Narumi, K Kindo, N Aizawa, T Ishii, M Yamashita

    JOURNAL OF THE PHYSICAL SOCIETY OF JAPAN   70 ( 3 )   813 - 817   2001.3

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    Field-induced long-range ordering is investigated by heat capacity and high-field magnetization measurements in Haldane gap system Ni(C5H14N2)(2)N-3(ClO4) (NDMAZ). In the high-field magnetization measurement along the crystal c-axis, the differential magnetization is found to reveal the characteristic peak corresponding to the phase transition to the ordered state. The magnetization increases as (H - H-C)(0.6) at the lowest temperature. The phase boundary determined down to 44 mK by the peak of the differential magnetization obeys T-N similar to (H - H-C)(0.45). Anisotropic phase diagram is similar to that of Ni(C5H14N2)(2)N-3(PF6) (NDMAP).

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  • High-field magnetization of URu2Si2 under high pressure

    T Inoue, K Kindo, H Okuni, K Sugiyama, Y Haga, E Yamamoto, TC Kobayashi, Y Uwatoko, Y Onuki

    PHYSICA B   294   271 - 275   2001.1

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    The temperature dependence of the magnetic susceptibility and the high-field magnetization up to 55T are measured for URu2Si2 under high pressures up to 1 GPa. Both T-chi max and T-N in the susceptibility increase with increasing pressure. The Value of the susceptibility below T-chi max decreases with increasing pressure. The three high-held metamagnetic transitions at H-c1 = 35.1T, H-c2 = 36.5 T and H-c3 = 39.6 T at ambient pressure, show different pressure-dependent behaviors. The metamagnetic transition at H-c1 broadens but survives and its transition field increases with increasing pressure. However, the transition at H-c2 is smeared out and disappears above 0.4 GPa. The transition at H-c3 broadens more clearly than the transition at H-c1. The fact that both T-chi max and the metamagnetic transition fields increase suggests that the interaction between the f-electrons and the conduction electrons is enhanced by pressure. (C) 2001 Elsevier Science B.V. All rights reserved.

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  • High-quality single-crystal growth and a change of the electronic states under pressure in CeRh2Si2

    S. Araki, R. Settai, T. C. Kobayashi, Y. Onuki

    Journal of Magnetism and Magnetic Materials   226-230 ( I )   80 - 82   2001

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    We succeeded in growing a high-quality single crystal of CeRh2Si2 with a residual resistivity ratio of 110. Under a pressure of 1.1 GPa, superconductivity is found below Tc = 0.38 K, where a Néel temperature of TN = 36K is suppressed down to almost zero. © 2001 Elsevier Science B.V. All rights reserved.

    DOI: 10.1016/S0304-8853(00)00785-X

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  • Pressure-temperature phase diagram of antiferromagnetism and superconductivity in CeRhIn5 and CeIn3: 115In-NQR study under pressure

    S. Kawasaki, T. Mito, C. Thessieu, Y. Kawasaki, G.-q.Zheng, K. Ishida, Y. Kitaoka, T. Muramatsu, T. C. Kobayashi, D. Aoki, S. Araki, Y. Haga, R. Settai, Y. Onuki

    Phys. Rev. B   2001

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  • Neutron scattering studies in the linear-chain Haldane materials, NDMAZ and NDMAP

    Y Koike, N Metoki, Y Morii, T Kobayashi, T Ishii, M Yamashita

    JOURNAL OF THE PHYSICAL SOCIETY OF JAPAN   69 ( 12 )   4034 - 4042   2000.12

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    Neutron scattering experiments were carried out in order to investigate the field-induced. antiferromagnetic long-range order and spin dynamics for the new Haldane compounds Ni(C5H14N2)(2)N-3 (ClO4) (NDMAZ) and Ni(C5H14N2)(2)N-3 (PF6) (NDMAP). We observed the energy gaps corresponding to the excited triplet, Delta (chi) = 1.61 meV, Delta (gamma) = 1.76 meV, Delta (z) = 3.2 meV for NDMAZ and Delta (chi), = 0.48 meV, Delta (gamma), = 0.64 meV for NDMAP. The dispersion in NDMAZ was well explained by the theoretical curve with the intra-chain interaction J = 50 K. The field dependence of the gap energy below critical field (H-c), was observed for NDMAZ and NDMAP as applying the field perpendicular to the chain direction. The field dependence of the excitation levels in NDMAZ was well explained by the fermionic field-theory treatment of the one-dimensional Heisenberg antiferromagnetic Hamiltonian with these gap energies and g-value, 2.3. In NDMAP, we found that the excitation peaks at Q = (0 0 0.5) became unobservably weak above H-c. This result would indicate a level crossing between the ground and the excited level at H-c and the change of the ground state above H-c. No trace of the magnetic Bragg peak due to the field induced ordering could be observed in the present study with our non-deuterated single crystal sample.

    DOI: 10.1143/JPSJ.69.4034

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  • Specific heat and effect of pressure on the electrical resistivity of CePtGa single crystal Reviewed

    Y Uwatoko, M Kosaka, M Shirakawa, G Oomi, N Mori, T Kobayashi, H Tatewaki, K Shimizu, K Amaya

    PHYSICA B   284   1321 - 1322   2000.7

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    Specific heat and effect of pressure on the electrical resistivity of CePtGa single crystal have been measured upto 30 kbar. A sharp peak in the ratio of specific heat to temperature and in electrical resistivity is observed at 33 and 3.5 K, respectively, which is ascribed to an antiferromagnetic transition. The results reveal that T-N decreases linearly with increasing pressure upto 30 kbar. (C) 2000 Elsevier Science B.V. All rights reserved.

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  • Pressure dependence of quadrupole ordering temperature T-Q in CeB6

    TC Kobayashi, K Hashimoto, S Eda, K Shimizu, K Amaya, Y Onuki

    PHYSICA B   281   553 - 554   2000.6

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    Pressure dependence of electrical resistance in CeB6 is investigated up to 13 GPa. A maximum in temperature dependence of the resistance shifts to higher temperature by the application of pressure. The quadrupole ordering temperature T-Q shows no obvious pressure dependence at zero field, while the field dependence of T-Q is enhanced slightly under high pressure. (C) 2000 Elsevier Science B.V. All rights reserved.

    DOI: 10.1016/S0921-4526(99)00947-3

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  • Metamagnetic transition of CeRh2Si2 under high fields and high pressures at various temperatures

    T Hamamoto, K Kindo, TC Kobayashi, Y Uwatoko, S Araki, R Settai, Y Onuki

    PHYSICA B   281   64 - 65   2000.6

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    High-field magnetization measurements in a heavy fermion antiferromagnet CeRh2Si2 were performed under high pressures at various temperatures to study the nature of the metamagnetism. Metamagnetic transitions were observed not only in the antiferromagnetic state but also in the paramagnetic stale at various pressures, The metamagnetism in CeRh2Si2 does not originate from the rearrangement of antiferromagnetic moments but from the recovery of the local moment from the Kondo singlet state by applying high magnetic fields. (C) 2000 Published by Elsevier Science B.V. All rights reserved.

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  • Pressure-dependence of superconducting behavior in CeRh2Si2

    TC Kobayashi, T Muramatsu, M Takimoto, K Hanazono, K Shimizu, K Amaya, S Araki, R Settai, Y Onuki

    PHYSICA B   281   7 - 8   2000.6

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    Electrical resistance has been investigated in a high-quality polycrystal of CeRh2Si2 under high pressures of up to 5.4 GPa. We found a resistance drop corresponding to superconductivity in the pressure range from 0.7 to 2.9 GPa. The relative decrease of the resistance shows a maximum in the vicinity of a critical pressure Pc. An onset temperature of superconductivity is about 0.6 K. (C) 2000 Elsevier Science B.V. All rights reserved.

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  • Electrical studies in DAC

    K. Shimizu, M. I. Eremets, T. C. Kobayashi, K. Amaya

    Sci. & Tech. of High Pressure   2000

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  • Electrical resistance measurement in hydrostatic pressure up to 10 GPa using a diamond anvil cell

    K. Shimizu, T. C. Kobayashi, T. Muramatsu, K. Takeda, K. Hashimoto, K. Amaya

    Sci. & Tech. of High Pressure   2000

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  • Two gaps in (VO)(2)P2O7: Observation using high-field magnetization and NMR

    T Yamauchi, Y Narumi, J Kikuchi, Y Ueda, K Tatani, TC Kobayashi, K Kindo, K Motoya

    PHYSICAL REVIEW LETTERS   83 ( 18 )   3729 - 3732   1999.11

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    The alternating one-dimensional Heisenberg S = 1/2 chain compound with spin gap, (VO)(2)P2O7, has been studied by the high-field magnetization and P-31 NMR measurements. Two critical phenomena at 25 +/- 1 and 46 +/- 2 T are observed in the magnetization curve, which are considered to be a crossover between the ground state and the excited state in two kinds of gap systems. P-31 NMR also revealed the coexistence of two magnetic systems with independent spin gaps. Results obtained from the present and previous studies are well explained by the model in which two kinds of magnetic chains along the b axis behave as alternating spin chains with independent gap energies.

    DOI: 10.1103/PhysRevLett.83.3729

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  • Field-induced 3D-LRO of Haldane-gap antiferromagnet NDMAZ

    A Koda, TC Kobayashi, K Amaya, H Yamashita

    JOURNAL OF MAGNETISM AND MAGNETIC MATERIALS   196   443 - 445   1999.5

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    The heat capacity and magnetization measurements of the single crystal of Haldane-gap antiferromagnet NDMAZ were carried out at low temperatures down to 0.1 K and under magnetic fields up to 14 T. We have observed three-dimensional long-range ordering of NDMAZ at around T similar or equal to 0.3 K above H similar or equal to 13 T (H parallel to c), which is ascribed to both the field-induced gap quenching and the existence of finite interchain interaction. Applying the higher external held, the transition temperature reaches up to 0.6 K at H = 14 T, showing a negative curvature with respect to the external field. (C) 1999 Elsevier Science B.V. All rights reserved.

    DOI: 10.1016/S0304-8853(98)00804-X

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  • Magnetic and transport properties of CeRh2Si2 under high pressures

    T Muramatsu, S Eda, TC Kobayashi, MI Eremets, K Amaya, S Araki, R Settai, Y Onuki

    PHYSICA B-CONDENSED MATTER   259-61   61 - 62   1999.1

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    Magnetic and transport properties have been investigated in the single crystal of CeRh2Si2 under high pressures. We found that the magnetic susceptibility under high pressure shows a broad maximum like CeRu2Si2. In the present pressure range up to 13 kbar where the ordered state is suppressed, no obvious evidence of the superconducting transition is observed down to 50 mK. (C) 1999 Elsevier Science B.V. All rights reserved.

    DOI: 10.1016/S0921-4526(98)00909-0

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  • Metallization and superconductivity in CsI at pressures up to 220 GPa Reviewed

    M. I. Eremets, K. Shimizu, T. C. Kobayashi, K. Amaya

    Journal of Physics Condensed Matter   10 ( 49 )   11519 - 11523   1998.12

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    The pressure range for electrical transport measurements has been dramatically increased up to 220 GPa in the 0.05-300 K temperature region and at magnetic fields of up to 10 T. Metallization of caesium iodide was found at a pressure of 115 GPa. A superconducting transition with T c = 2 K was observed above 180 GPa. T c decreases with increasing pressure. The superconducting transition shifts to lower temperatures and disappears under magnetic field above 0.3 Tesla.

    DOI: 10.1088/0953-8984/10/49/037

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  • Observation of pressure-induced superconductivity in the megabar region Reviewed

    K. Amaya, K. Shimizu, M. I. Eremets, T. C. Kobayashi, S. Endo

    Journal of Physics Condensed Matter   10 ( 49 )   11179 - 11190   1998.12

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    A review of recent developments in high-pressure techniques and their application in the search for superconductivity at low temperature is presented. We have focused the discussion mainly on the experimental results obtained by our group for simple molecular systems.

    DOI: 10.1088/0953-8984/10/49/008

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  • Metallic CsI at Pressure of up to 220 Gigapascals Reviewed

    M. I. Eremets, K. Shimizu, T. C. Kobayashi, K. Amaya

    Science   1998.4

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    DOI: 10.1126/science.281.5381.1333

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  • Enhancement of superconducting transition temperature in CeCu2Ge2 under high pressures Reviewed

    T. C. Kobayashi, T. Miyazu, N. Takeshita, K. Shimizu, K. Amaya, Y. Kitaoka, Y. Onuki

    J. Phys. Soc. Jpn.   1998.4

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    DOI: 10.1143/JPSJ.67.996

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  • Magnetic-to-nonmagnetic transition in the ferromagnetic heavy-fermion compound CeRu2Ge2 at high pressures Reviewed

    T. C. Kobayashi, T. Miyazu, K. Shimizu, K. Amaya, Y. Kitaoka, Y. Onuki, M. Shirase, T. Takabatake

    Phys. Rev. B   57 ( 9 )   5025 - 5028   1998.4

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    DOI: 10.1103/PhysRevB.57.5025

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  • Phase diagram of a new spin-Peierls compound: p-CyDOV

    T. Hamamoto, Y. Narumi, K. Kindo, K. Mukai, Y. Shimobe, T. C. Kobayashi, T. Muramatsu, K. Amaya

    Physica B   246   36 - 39   1998

  • Magnetic Properties of One-Dimensional Heisenberg Chains with Ferromagnetic-Antiferromagnetic Bond Alternation Reviewed

    M. Hagiwara, Y. Narumi, K. Kindo, T. C. Kobayashi, H. Yamakage, K. Amaya, G. Schmauch

    J. Phys. Soc. Jpn.   66 ( 6 )   361 - 364   1997.6

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    DOI: 10.1143/JPSJ.66.1792

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  • High Pressure Methods at Low Temperatures and High Magnetic Field Reviewed

    M. I. Eremets, K. Amaya, K. Shimizu, T. C. Kobayashi

    Rev. High Pressure Sci. Technol.   1997.4

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    DOI: 10.4131/jshpreview.7.469

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  • Pressure Induced Superconductivity in Some Simple Systems Reviewed

    K. Amaya, K. Shimizu, N. Takeshita, S. Kometani, M. I. Eremets, A. Onodera, T. C. Kobayashi, T. Mizutani, M. Ishizuka, S. Endo, M. Takai, N. Hamaya, I. Shirotani

    Rev. High Pressure Sci. Technol.   1997.4

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    DOI: 10.4131/jshpreview.7.688

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  • Magnetic properties of 1,5-dimethyl-6-oxoverdazyl radical crystal. Observation of a spin-Peierls transition in 3-(4-cyanophenyl)-1,5-dimethyl-6-oxoverdazyl radical, p-CyDOV

    Kazuo Mukai, Naoki Wada, Javad, B. Jamali, Norio Achiwa, Yasuo Narumi, Koichi Kindo, Tatsuo Kobayashi, Kiichi Amaya

    Molecular Crystals and Liquid Crystals   305   499 - 508   1997

  • Magnetic properties of 1,5-dimethyl-6-oxoverdazyl radical crystals. Observation of a spin-Peierls transition in 3-(4-cyanophenyl)-1,5-dimethyl-6-oxoverdazyl radical, p-CyDOV

    K Mukai, N Wada, JB Jamali, N Achiwa, Y Narumi, K Kindo, T Kobayashi, K Amaya

    CHEMICAL PHYSICS LETTERS   257 ( 5-6 )   538 - 544   1996.8

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    Magnetic susceptibilities of 5 kinds of 3-(4-R-phenyl)-1,5-dimethyl-6-oxoverdazyl radicals (PDOV (R=H), p-MDOV (R-CH3O), p-MeDOV (R=CH3), p-CyDOV (R=CN), and p-NDOV (R=NO2)) have been measured in the temperature range of 4.2-300 K. The susceptibilities of PDOV, p-MDOV, and p-MeDOV can be explained by an antiferromagnetic Heisenberg alternating chain model. The susceptibility of p-CyDOV shows a broad maximum at 54 K, and decreases abruptly at 15 K, suggesting a spin-Peierls transition, High-field magnetization data (H=0-35 T) which provide a clear evidence for a spin-Peierls transition were reported.

    DOI: 10.1016/0009-2614(96)00577-5

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  • Superconductivity of Calcium under High Pressures Reviewed

    S. Okada, K. Shimizu, T. C. Kobayashi, K. Amaya, S. Endo

    J. Phys. Soc. Jpn   65 ( 7 )   1924 - 1926   1996.4

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    DOI: 10.1143/JPSJ.65.1924

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  • NMR study of strongly correlated electron systems Reviewed

    Y. Kitaoka, H. Tou, G. -q. Zheng, K. Ishida, K. Asayama, T. C. Kobayashi, A. Kohda, N. Takeshita, K. Amaya, Y. Onuki, G. Geibel, C. Schank, F. Steglich

    PHYSICA B-CONDENSED MATTER   206 ( 1-4 )   55 - 61   1995.2

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    Various types of ground states in strongly correlated electron systems have been systematically investigated by means of NMR/NQR at low temperatures under high magnetic field and pressure. We focus on two well-known heavy-electron families, CeCu2X2 (X = Si and Ge) (Ce(122)) and UM2Al3 (M = Ni and Pd) (U(123)). The Cu NQR experiments on CeCu2X2 under high pressure indicate that the physical property of CeCu2Ge2 at high pressure, i.e. above the transition at 7.6GPa from antiferromagnetic (AF) to superconductivity, are clearly related to that of CeCu2Si2 at ambient pressure. In addition to the H-T phase diagram established below 7 T, NMR and specific heat experiments on polycrystal CeCu2.05Si2 have revealed the presence of a new phase above 7 T. In a high-quality polycrystal of UPd2Al3 with a record high-T-c of 2 K at ambient pressure and the narrowest AI NQR line width, the nuclear-spin lattice relaxation rate, (27)(1/T-1) measured in zero field has been found to obey the T-3 law down to 0.13 K, giving strong evidence that the energy gap vanishes along lines on the Fermi surface. Thus it seems that all heavy-electron superconductors exhibit lines of zero gap, regardless of their different magnetic properties.

    DOI: 10.1016/0921-4526(94)00365-3

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    Other Link: http://orcid.org/0000-0001-5081-2777

  • Heat capacity anomaly of CeCu2.05Si2 under magnetic fields Reviewed

    T. C. Kobayashi, A. Koda, H. Honda, K. Amaya, Y. Kitaoka, K. Asayama, C. Geibel, F. Steglich

    PHYSICA B-CONDENSED MATTER   206   600 - 602   1995.2

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    Heat capacity measurements of CeCu2.05Si2 have been carried out at temperatures down to 0.1 K under magnetic field up to 13 T. The heat capacity divided by temperature C/T has revealed as a characteristic feature that the peak of C/T shifts down to around 0.5 K with increasing field up to 7 T, whereafter it shifts up again to around 0.6 K at 13 T. In the first case, a peak appears around the phase boundary (labeled A) first found in NMR and magnetoresistance. Most remarkably, in the latter case, the peak coincides with the new phase boundary (labeled B) identified recently by elastic constant and thermal expansion measurements.

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Books

  • 配位空間の化学 ―最新技術と応用―

    シーエムシー出版  2009 

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  • 静水圧性が向上して明らかになった相転移

    小林達生, 荒木新吾

    高圧力の科学と技術   26 ( 1 )   21 - 26   2016

  • 21aPS-56 Hall effect under pressure on CeCu_2Si_2

    Shiroyama Y., Araki S., Kobayashi T. C., Seiro S., Geibel C., Steglich F.

    Meeting abstracts of the Physical Society of Japan   65 ( 1 )   614 - 614   2010.3

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  • 22pPSA-36 The molecular arrangement of O_2 absorbed in MFI zeolite

    Wanikawa Y., Kubota Y., Hori A., Kuwana K., Kobayashi T. C., Hakuman M., Nakai K., Kim J., Kato K., Takata M., Matsuda R., Kitagawa S.

    Meeting abstracts of the Physical Society of Japan   65 ( 1 )   506 - 506   2010.3

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  • 重い電子系超伝導体CeCu2Si2の価数ゆらぎ機構の検証―Cu-NQRからのアプローチ―

    藤原賢二, 小林達生

    固体物理   44   393 - 398   2009

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  • 23pPSB-38 Crystalline structure and electrical resistivity in UIr under Pressure

    Akazawa T., Hori A., Tabira K., Irie Y., Kotegawa H., Kobayashi T.C., Takeda K., Ohishi Y., Yamamoto E., Ikeda S., Haga Y., Settai R., Onuki Y.

    Meeting abstracts of the Physical Society of Japan   63 ( 1 )   555 - 555   2008.2

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  • 21aXA-1 Electrical resistivity and AC-susceptibility measurements on Pr(Fe_<0.95>Ru_<0.05>)_4P_<12> under high pressure

    Hidaka H., Toda Y., Kotegawa H., Kobayashi T. C., Motomura Y., Aoki Y., Kikuchi D., Sato H.

    Meeting abstracts of the Physical Society of Japan   62 ( 2 )   513 - 513   2007.8

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  • 22pXA-14 Relationship between pressure-induced 1st order phase transition and superconductivity

    Kotegawa E., Hori A., Irie Y., Hidaka H., Kobayashi T. C., Akazawa T., Yamamoto E., Ikeda S., Haga Y., Onuki Y.

    Meeting abstracts of the Physical Society of Japan   62 ( 2 )   617 - 617   2007.8

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  • 18pWK-6 Cu-NQR/NMR Study in CeCu_2Si_2 under high pressure

    Fujiwara K., Tatsumi T., Kotegawa H., Kobayashi T. C., Kitaoka Y., Geibel C., Steglioh F.

    Meeting abstracts of the Physical Society of Japan   62 ( 1 )   505 - 505   2007.2

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  • 18pPSB-5 Pressure dependence of Electrical Resistivity in UIr

    Akazawa T., Hidaka H., Kotegawa H., Fukushima S., Hori A., Kobayashi T. C., Yamamoto E., Haga Y., Settai R., Onuki Y.

    Meeting abstracts of the Physical Society of Japan   62 ( 1 )   528 - 528   2007.2

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  • 18pPSB-7 Coexistence of ferromagnetism and superconductivity in UIr : AC-susceptibility measurement under high pressure

    Fukushima S., Kotegawa H., Hidaka H., Kobayashi T.C., Akazawa T., Yamamoto E., Ikeda S., Haga Y., Onuki Y.

    Meeting abstracts of the Physical Society of Japan   62 ( 1 )   529 - 529   2007.2

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  • 18pPSB-6 Anomalous enhancement of residual resistivity in pressure-induced superconductor UIr

    Hori A., Hidaka H., Kotegawa H., Kobayashi T. C., Akazawa T., Ikeda S., Haga Y., Yamamoto E., Onuki Y.

    Meeting abstracts of the Physical Society of Japan   62 ( 1 )   529 - 529   2007.2

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  • 24pYA-3 Pressure-induced superconductivity in a ferromagnet UIr

    Kobayashi T.C., Hori A., Fukushima S., Hidaka H., Kotegawa H., Akazawa T., Settai R., Ikeda S., Yamamoto E., Haga Y., Onuki Y.

    Meeting abstracts of the Physical Society of Japan   61 ( 2 )   465 - 465   2006.8

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  • 27aPS-7 Coexistence of ferromagnetism and superconductivity in UIr : AC-susceptibility measurement under high pressure

    Fukushima S., Kotegawa H., Hidaka H., Kobayashi T.C., Akazawa T., Ikeda S., Yamamoto E., Haga Y., Onuki Y.

    Meeting abstracts of the Physical Society of Japan   61 ( 1 )   521 - 521   2006.3

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  • 27aUF-9 Cu-NQR Study in CeCu_2Si_2 under high pressure

    Fujiwara K., Tatsumi T., Kotegawa H., Kobayashi T.C., Kitaoka Y., Geibel C., Steglich F.

    Meeting abstracts of the Physical Society of Japan   61 ( 1 )   519 - 519   2006.3

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  • UIrの圧力誘起超伝導

    小林達生, 日高宏之, 福島賢, 小手川恒, 赤澤輝彦, 摂待力生, 大貫惇睦, 山本悦嗣, 芳賀芳範

    固体物理   40, 415-420   2005

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  • UGe2の強磁性と超伝導の共存

    小林達生, 芳賀芳範, 立岩尚之, 山上浩志, 摂待力生, 大貫惇睦

    固体物理   36 ( 11 )   43(803) - 48(808)   2001.11

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Presentations

  • α-Mnの高圧物性

    小林達生

    JPhysics+イン淡路  2020.12.4 

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    Event date: 2020.12.3 - 2020.12.5

    Language:Japanese   Presentation type:Oral presentation (general)  

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  • Quantum Transport Properties on Chemically Etched (0001) Surface of Tellurium International conference

    K. Akiba, S. Asada, K. Kobayashi, T. C. Kobayashi, R. Koezuka, M. Tokunaga

    International Conference on Strongly Correlated Electron Systems 2019 (SCES2019)  2019.9 

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    Event date: 2019.9.23 - 2019.9.28

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    Venue:Okayama Convention Center  

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  • Pressure-Temperature Phase Diagram of alpha-Mn International conference

    T. Sato, K. Akiba, S. Araki, T. C. Kobayashi

    International Conference on Strongly Correlated Electron Systems 2019 (SCES2019)  2019.9 

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    Event date: 2019.9.23 - 2019.9.28

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    Venue:Okayama Convention Center  

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  • Fluctuation Effect of the Parity-Breaking Order in the Hall Effect of Cd2Re2O7 International conference

    T. C. Kobayashi, Y. Ikeyama, R. Mitsui, K. Akiba, S. Araki, J. Yamaura, Y. Matsubayashi, Z. Hiroi

    International Conference on Strongly Correlated Electron Systems 2019 (SCES2019)  2019.9 

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    Event date: 2019.9.23 - 2019.9.28

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    Venue:Okayama Convention Center  

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  • Magnetism of Alkali Superoxide NaO2 under Pressure International conference

    M. Miyajima, F. Astuti, T. Fukuda, M. Kodani, T. Nakano, A. Matsuo, K. Kindo, I. Watanabe, T. C. Kobayashi, T. Kambe

    International Conference on Strongly Correlated Electron Systems 2019 (SCES2019)  2019.9 

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    Event date: 2019.9.23 - 2019.9.28

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    Venue:Okayama Convention Center  

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  • Antiferromagnetic quantum criticality in CeRh2Si2 International coauthorship International conference

    S. Araki, R. Mitsui, T. C. Kobayashi, W. Imai, M. Miyazaki, R. Settai, D. Braithwaite, D. Aoki

    International Conference on Strongly Correlated Electron Systems 2019 (SCES2019)  2019.9 

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    Event date: 2019.9.23 - 2019.9.28

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  • Hall effect in Cd2Re2O7 under high pressure

    J-Physics 2019 International Conference  2019.9 

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    Event date: 2019.9.18 - 2019.9.21

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  • Cd2Re2O7における高圧下ホール効果

    小林達生, 池山由十, 三井理功, 秋葉和人, 荒木新吾, 山浦淳一, 松林康仁, 廣井善二

    日本物理学会2019年秋季大会  2019.9 

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    Event date: 2019.9.10 - 2019.9.13

    Language:Japanese  

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  • Cd2Re2O7のホール効果

    小林達生

    J-Physics地域研究会 - 北九州  2019.6 

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    Event date: 2019.6.7 - 2019.6.8

    Language:Japanese  

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  • Cd2Re2O7の高圧物性

    小林達生

    第1回ETQ研究会  2018.8 

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    Event date: 2018.8.8 - 2018.8.9

    Language:Japanese   Presentation type:Oral presentation (general)  

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  • Cd2Re2O7の高圧下における奇パリティ多極子秩序とパリティゆらぎ超伝導

    小林達生

    J-Physics:多極子伝導系の物理 平成30年度領域全体会議  2018.5 

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    Event date: 2018.5.24 - 2018.5.26

    Language:Japanese   Presentation type:Oral presentation (general)  

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  • Cd2Re2O7における圧力 温度相図とホール効果の圧力効果

    小林達生, 三井理功, 安部大貴, 荒木新吾, 町田洋, 井澤公一, 山浦淳一, 松林康仁, 広井善二

    日本物理学会第73回年次大会  2018.3 

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    Event date: 2018.3.22 - 2018.3.25

    Language:Japanese   Presentation type:Oral presentation (general)  

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  • Hall effect in Cd2Re2O7 under high pressure

    T. C. Kobayashi, R. Mitsui, S. Araki, J. Yamaura, Y. Matsubayashi, Z. Hiroi

    J-Physics Annual Meeting FY2017  2018.3 

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    Event date: 2018.3.15 - 2018.3.17

    Language:English   Presentation type:Poster presentation  

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  • Superconductivity in Cd2Re2O7 under high pressure International conference

    T. C. Kobayashi

    Meeting on physics and chemistry of emerging superconductors and thermoelectric materials  2017.9 

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    Event date: 2017.9.13 - 2017.9.15

    Language:English   Presentation type:Oral presentation (general)  

    Venue:Sapienza University  

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  • Cd2Re2O7の圧力-温度相図と超伝導

    小林達生, 安部大貴, 荒木新吾, 町田洋, 井澤公一, 山浦淳一, 松林康仁, 廣井善二

    日本物理学会第72回年次大会  2017.3 

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    Event date: 2017.3.17 - 2017.3.20

    Language:Japanese   Presentation type:Oral presentation (general)  

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  • Cd2Re2O7の圧力-温度相図

    小林達生, 安部大貴, 荒木新吾, 山浦淳一, 松林康仁, 広井善二

    日本物理学会2016年秋季大会  2016.9 

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    Event date: 2016.9.13 - 2016.9.16

    Language:Japanese   Presentation type:Oral presentation (general)  

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  • 固体酸素の磁場誘起相転移

    小林達生

    日本物理学会第70回年次大会  2015.3 

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    Event date: 2015.3.21 - 2015.3.24

    Language:Japanese   Presentation type:Symposium, workshop panel (public)  

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  • 静水圧性が向上して明らかになった相転移

    小林達生

    未来を拓く高圧力科学技術セミナーシリーズ(40)「良質高圧力に支えられた物理学」  2015.2.10 

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    Event date: 2015.2.10

    Language:Japanese   Presentation type:Oral presentation (general)  

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  • 酸素分子の分子間相互作用と磁場誘起構造相転移

    小林達生

    第1回九工大物性ワークショップ  2014.11 

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    Event date: 2014.11.21 - 2014.11.22

    Language:Japanese   Presentation type:Oral presentation (general)  

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  • Novel Phase of Solid Oxygen Induced by Ultrahigh Magnetic Fields International conference

    T. C. Kobayashi

    2014.11 

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    Event date: 2014.11.8 - 2014.11.10

    Language:English   Presentation type:Oral presentation (general)  

    Venue:Hotel Limani (Okayama)  

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  • Emergence of ferromagnetic oxygen in ultrahigh magnetic field International conference

    T. C. Kobayashi, T. Nomura, Y. H. Matsuda, J. L. Her, S. Takeyama, A. Matsuo, K. Kindo

    27th International Conference on Low Temperature Physics  2014.8 

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    Event date: 2014.8.6 - 2014.8.13

    Language:English   Presentation type:Oral presentation (general)  

    Venue:Palais Rouge, Buenos Aires  

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  • 酸素分子間の磁気的相互作用と分子配列

    小林達生

    日本物理学会2013年秋季大会  2013.9 

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    Event date: 2013.9.25 - 2013.9.28

    Language:Japanese   Presentation type:Symposium, workshop panel (public)  

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  • 価数クロスオーバーと異常金属:CeCu2Si2の圧力効果

    小林達生

    日本物理学会2013年秋季大会  2013.9 

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    Event date: 2013.9.25 - 2013.9.28

    Language:Japanese   Presentation type:Symposium, workshop panel (public)  

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  • Pressure-induced magnetic transition and disappearance of superconductivity in CeNiGe3

    T. C. Kobayashi, Y. Ikeda, T. Tomijima, S. Araki, K. Murata

    SCES2013  2013.8 

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    Event date: 2013.8.5 - 2013.8.9

    Language:English   Presentation type:Poster presentation  

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  • 固体酸素の磁場誘起構造相転移

    小林達生

    パイロクロアワークショップ「高対称性格子上の変幻自在電子」  2013 

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    Event date: 2013.7.5 - 2013.7.7

    Language:Japanese   Presentation type:Oral presentation (general)  

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  • Localized to itinerant crossover of 4f electrons in CeCu2Si2 under high pressure Invited International coauthorship International conference

    T. C. Kobayashi

    SMEC2013  2013.3 

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    Event date: 2013.3.23 - 2013.3.30

    Language:English   Presentation type:Oral presentation (general)  

    Venue:Miami & East Caribbean  

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  • AxV2Al20 (A = Ga, Al) におけるラットリングと超伝導の圧力効果

    小林達生

    第3回パイロクロア研究会  2012.12 

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    Event date: 2012.12.25 - 2012.12.27

    Language:Japanese   Presentation type:Oral presentation (general)  

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  • AxV2Al20 (A = Ga, Al) におけるラットリングと超伝導の圧力効果

    小林達生

    新学術領域研究「重い電子系の形成と秩序化」ワークショップ ~カゴ状構造に宿る強相関物性~  2012.9 

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    Event date: 2012.9.26 - 2012.9.28

    Language:Japanese  

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  • Spin-dependent molecular arrangement of O2-O2 dimer in nanoporous metal-organic solids International conference

    T. C. Kobayashi, A. Hori, Y. Kubota, A. Matsuo, K. Kindo, J. Kim, K. Kato, M. Takata, H. Sakamoto, R. Matsuda, S. Kitagawa

    ICM19  2012.7 

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    Event date: 2012.7.8 - 2012.7.13

    Language:English   Presentation type:Oral presentation (general)  

    Venue:Busan  

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  • Arrangement and magnetism of O2-O2 dimer adsorbed in microporous coordination polymers Invited International conference

    T. C. Kobayashi

    The 11th Tamura Memorial Symposium -Frontiers in Nanoscience-  2011.12 

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    Event date: 2011.12.3 - 2011.12.5

    Language:English   Presentation type:Oral presentation (invited, special)  

    Venue:Osaka Prefecture University  

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  • Pressure-induced Structural Phase Transitions in UIr

    T. C. Kobayashi, H. Kotegawa, S. Araki, T. Akazawa, A. Hori, Y. Irie, S. Fukushima, H. Hidaka, K. Takeda, Y. Ohishi, K. Murata, E. Yamamoto, S. Ikeda, Y. Haga, Y. Onuki

    TOKIMEKI 2011, International workshop on heavy fermions  2011.11 

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    Event date: 2011.11.23 - 2011.11.26

    Language:Japanese  

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  • Cd2Re2O7の圧力誘起相図と超伝導

    小林達生, 入江祐太, 山浦淳一, 廣井善二, 村田恵三

    日本物理学会2011年秋季大会  2011.9 

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    Event date: 2011.9.21 - 2011.9.24

    Language:Japanese   Presentation type:Oral presentation (general)  

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  • Heat capacity of SmOs4Sb12 under high pressure International conference

    T. C. Kobayashi, K. Miyazawa, Y. Ikeda, S. Araki, H. Kotegawa, H. Sugawara, D. Kikuchi, H. Sato

    From Blue Pigment to Green Energy - Cobalt mines - Skutterudites - Thermoelectrics-  2011.9 

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    Event date: 2011.9.5 - 2011.9.8

    Language:English   Presentation type:Poster presentation  

    Venue:Vikersund  

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  • Hall effect in single crystal CeCu2Si2 under high pressure International conference

    S. Araki, Y. Shiroyama, T. Shinohara, Y. Ikeda, T. C. Kobayashi, S. Seiro, C. Geibel, F. Steglich

    SCES2011  2011.8 

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    Event date: 2011.8.29 - 2011.9.3

    Language:English   Presentation type:Poster presentation  

    Venue:Cambridge  

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  • Cd2Re2O7における高圧下で誘起される重い電子の超伝導

    小林達生, 入江祐太, 山浦淳一, 廣井善二, 村田惠三

    日本物理学会第66回年次大会  2011.3 

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    Event date: 2011.3.25 - 2011.3.28

    Language:Japanese   Presentation type:Oral presentation (general)  

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  • Cd2Re2O7の圧力―温度相図

    小林達生

    第2回パイロクロア研究会  2010.12 

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    Event date: 2010.12.25 - 2010.12.27

    Language:Japanese   Presentation type:Oral presentation (general)  

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  • Heat capacity measurement of SmOs4Sb12 under high pressure

    T.C. Kobayashi, Y. Kawasaki, K. Miyazawa, Y. Ikeda, S. Araki, H. Kotegawa, H. Sugawara, D. Kikuchi, H. Sato

    International Conference on Heavy Electrons 2010  2010.9 

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    Event date: 2010.9.17 - 2010.9.20

    Language:Japanese  

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  • 高圧下精密物性測定によるf 電子系化合物の量子相転移と超伝導の研究

    小林達生

    新学術領域研究「重い電子系の形成と秩序化」第2回研究会  2009.8 

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    Event date: 2009.8.18 - 2009.8.20

    Language:Japanese  

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  • 強磁性体U3P4 の圧力誘起強磁性-非磁性転移

    小林達生

    新学術領域研究「重い電子系の形成と秩序化」第1回研究会  2009.3 

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    Event date: 2009.3.9 - 2009.3.11

    Language:Japanese   Presentation type:Oral presentation (general)  

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  • PrFe4P12の圧力誘起金属-絶縁体転移

    小林達生

    特定領域研究「充填スクッテルダイト構造に創出する新しい量子多電子状態」第6回研究会  2008.7 

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    Event date: 2008.7.11 - 2008.7.13

    Language:Japanese  

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  • Magnetic properties of molecular oxygen adsorbed in the coordination space International conference

    T. C. Kobayashi

    Third International Symposium on Chemistry of Coordination Space -ISCCS 2007-  2007.12 

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    Event date: 2007.12.9 - 2007.12.12

    Language:English   Presentation type:Poster presentation  

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  • UIrの圧力誘起相と超伝導

    小林達生

    超伝導が拓く物性科学の最前線4 特定領域合同研究会  2007.12 

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    Event date: 2007.12.7 - 2007.12.9

    Language:Japanese   Presentation type:Oral presentation (general)  

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  • ミクロ孔をもつ配位高分子に吸着した酸素分子の磁性

    小林達生, 堀彰宏, 山口毅典, 松尾晶, 金道浩一, 久保田佳基, 高田昌樹, 北川進

    日本物理学会第62回年次大会  2007.9 

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    Event date: 2007.9.21 - 2007.9.24

    Language:Japanese   Presentation type:Oral presentation (general)  

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  • 配位空間に吸着した酸素分子の磁性

    小林達生

    特定領域「配位空間の化学」平成19年度全体会議  2007.5 

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    Event date: 2007.5.22 - 2007.5.23

    Language:Japanese   Presentation type:Oral presentation (general)  

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  • 配位空間に吸着した酸素分子の磁性

    小林達生

    特定領域「配位空間の化学」第三回公開講演会・成果報告会  2007.1 

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    Event date: 2007.1.12 - 2007.1.13

    Language:Japanese   Presentation type:Oral presentation (general)  

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  • Magnetic properties of molecular oxygen adsorbed in the coordination space

    T. C. Kobayashi

    Second International Symposium on Chemistry of Coordination Space -ISCCS 2006-  2006.12 

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    Event date: 2006.12.15 - 2006.12.16

    Language:English  

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  • 強磁性体UIrの圧力下の超伝導

    小林達生

    日本物理学会2006年秋季大会  2006.9 

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    Event date: 2006.9.23 - 2006.9.26

    Language:Japanese   Presentation type:Symposium, workshop panel (public)  

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  • Pressure-temperature phase diagram of UIr Invited

    T. C. Kobayashi

    Novel pressure-induced phenomena in condensed matter systems  2006.8.26 

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    Event date: 2006.8.26 - 2006.8.29

    Language:English   Presentation type:Oral presentation (invited, special)  

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  • 配位空間に吸着した酸素分子の磁性

    小林達生

    特定領域「配位空間の化学」平成18年度全体会議  2006.6 

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    Event date: 2006.6.23 - 2006.6.24

    Language:Japanese   Presentation type:Oral presentation (general)  

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  • 配位空間に吸着した酸素分子の異常磁性の解明

    小林達生

    特定領域「配位空間の化学」第2回公開講演会・成果報告会  2006.1 

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    Event date: 2006.1.27 - 2006.1.28

    Language:Japanese   Presentation type:Oral presentation (general)  

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  • Anisotropic residual resistivity under high pressure in UIr

    T. C. Kobayashi, A. Hori, H. Hidaka, H. Kotegawa, T. Akazawa, S. Ikeda, E. Yamamoto, Y. Haga, R. Settai, Y. Onuki

    The 5th International Symposium on Advanced Science Research in Celebration of the World Year of Physics 2005 -Advances in the Physics and Chemistry of Actinide Compounds-  2005.9 

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    Event date: 2005.9.27 - 2005.9.29

    Language:English  

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  • 一次元細孔内酸素分子ダイマーの異常磁性

    小林達生

    日本物理学会2005年秋季大会  2005.9 

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    Event date: 2005.9.19 - 2005.9.22

    Language:Japanese   Presentation type:Symposium, workshop panel (public)  

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  • Pressure-induced superconductivity in ferromagnet UIr without inversion symmetry Invited

    T. C. Kobayashi

    International Conference on Strongly Correlated Electron systems (SCES’05)  2005.7 

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    Event date: 2005.7.26 - 2005.7.30

    Language:English   Presentation type:Oral presentation (invited, special)  

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  • Pressure induced superconductivity in UIr and CeNiGe3 Invited International conference

    T. C. Kobayashi

    International Workshop on Materials Science and Nano-Engineering  2004.12 

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    Event date: 2004.12.11 - 2004.12.14

    Language:English   Presentation type:Oral presentation (invited, special)  

    Venue:Osaka  

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  • Magnetic properties of molecular oxygen adsorbed in micro-porous metal-organic solids Invited International conference

    T. C. Kobayashi

    International Conference on Quantum Spin Systems (QSS04)  2004.11 

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    Event date: 2004.11.30 - 2004.12.3

    Language:English   Presentation type:Oral presentation (invited, special)  

    Venue:Hayama, Kanagawa  

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  • Pressure induced superconductivity in UIr and CeNiGe3 Invited International conference

    T. C. Kobayashi

    Japan-French Colloquium “Quantum complex systems”  2004.7 

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    Event date: 2004.7.21 - 2004.7.24

    Language:English   Presentation type:Oral presentation (invited, special)  

    Venue:Grenoble  

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  • CeCu2Ge2の低温における体積の圧力依存性

    日本物理学会第60回年次大会  2005 

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  • YbXCu4 (X = In, Cu) の高圧物性の研究

    日本物理学会2005年秋季大会  2005 

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  • 配位空間に吸着した酸素分子の磁性

    特定領域「配位空間の化学」A01班会議  2005 

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  • ナノ細孔中に閉じ込められた酸素分子鎖の強磁場磁化

    日本物理学会2005年秋季大会  2005 

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  • RAgSb2(R=Ce,La)の電気伝導の異常とフェルミ面の研究

    日本物理学会2005年秋季大会  2005 

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  • PrFe4P12における圧力誘起絶縁相の研究

    日本物理学会2005年秋季大会  2005 

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  • CeCu2Si2の高圧下Cu-NQRの研究

    日本物理学会2005年秋季大会  2005 

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  • 73Ge-NQRによるCeNi2Ge2の研究

    日本物理学会2005年秋季大会  2005 

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  • CeNiGe3の反強磁性状態における超伝導

    日本物理学会2005年秋季大会  2005 

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  • UIrにおける交流帯磁率測定から見た強磁性と超伝導の共存

    日本物理学会2005年秋季大会  2005 

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  • Yb系化合物YbPd2Si2とYbCu5の圧力効果

    日本物理学会2005年秋季大会  2005 

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  • UIrにおける多重強磁性相の異方的電気伝導

    日本物理学会2005年秋季大会  2005 

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  • CeNiGe3の圧力誘起超伝導

    日本物理学会第60回年次大会  2005 

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  • UIrの高圧下での構造解析

    日本物理学会第60回年次大会  2005 

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  • 反転対称性を持たない強磁性超伝導体UIrの交流帯磁率測定II

    日本物理学会第60回年次大会  2005 

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  • 高圧下におけるUIrの電気伝導の異方性

    日本物理学会第60回年次大会  2005 

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  • CeCu2Si2の高圧下におけるCu-NQR III

    日本物理学会第60回年次大会  2005 

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  • 配位空間に吸着した酸素分子の磁性

    特定領域「配位空間の化学」平成17年度第一回全体会議  2005 

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  • PrFe4P12の圧力誘起絶縁体状態におけるホール効果

    日本物理学会第60回年次大会  2005 

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  • PrFe4P12の圧力誘起絶縁体状態における31P-NMR

    日本物理学会第60回年次大会  2005 

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  • URu2Si2の高圧下極低温磁化測定IV

    日本物理学会第60回年次大会  2005 

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  • 多孔性配位高分子に吸着した水素分子の直接観測

    日本物理学会第60回年次大会  2005 

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  • 配位空間に吸着した酸素分子の磁性

    特定領域「配位空間の化学」平成16年度成果報告会  2005 

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  • Pressure-induced charge ordering of LiV2O4

    The International Conference on Strongly Correlated Electron Systems  2004 

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  • 細孔をもつ銅錯体に吸着させた酸素の磁性

    日本物理学会 第59回年次大会  2004 

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  • CeNiGe3の圧力-温度相図

    日本物理学会 第59回年次大会  2004 

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  • スピン多面体Mo72Fe30の1/3磁化異常:非平衡性の検証

    日本物理学会 2004年秋季大会  2004 

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  • ナノ空間に閉じ込められた酸素の強磁場磁化

    日本物理学会 2004年秋季大会  2004 

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  • CeCu2Si2の高圧下におけるCu-NQR

    日本物理学会 2004年秋季大会  2004 

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  • 反転対称性を持たない強磁性超伝導体UIrの交流帯磁率測定

    日本物理学会 2004年秋季大会  2004 

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  • 充填スクッテルダイトPrFe4P12の圧力誘起金属絶縁体転移II

    日本物理学会 2004年秋季大会  2004 

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  • SmOs4Sb12の圧力効果

    日本物理学会 2004年秋季大会  2004 

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  • 反転対称をもたないUIrにおける強磁性量子臨界点近傍の超伝導

    日本物理学会 2004年秋季大会  2004 

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  • 遍歴強磁性体UIrの高圧下磁化測定II

    日本物理学会 2004年秋季大会  2004 

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  • CeCu2Si2の高圧下におけるCu-NQR

    日本物理学会 第59回年次大会  2004 

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  • 遍歴強磁性体UIrの圧力下磁化測定

    日本物理学会 第59回年次大会  2004 

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  • 反転対称性を持たない強磁性体UIrの圧力誘起超伝導

    日本物理学会 第59回年次大会  2004 

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  • NQR study of CeCu2Si2 up to 5 GPa

    The International Conference on Strongly Correlated Electron Systems  2004 

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  • Pressure-induced superconductivity in UIr without inversion symmetry

    The International Conference on Strongly Correlated Electron Systems  2004 

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  • Pressure-induced metal-insulator transition in the filled skutterudite PrFe4P12

    The International Conference on Strongly Correlated Electron Systems  2004 

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  • 充填スクッテルダイトPrFe4P12の圧力誘起金属絶縁体転移

    日本物理学会 第59回年次大会  2004 

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  • High-pressure effect on the electrical resistivity in CeNiGe3 and CeNi2Al5

    The International Conference on Strongly Correlated Electron Systems  2004 

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  • de Haas-van Alphen effect in CeIn3 under pressure

    The International Conference on Strongly Correlated Electron Systems  2004 

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  • Magnetism of a one-dimensional array of oxygen in a micro-porous metal-organic solid International conference

    T. C. Kobayashi, M. Suzuki, A. Matsuo, K. Kindo, R. Kitaura, R. Matsuda, H-C. Chang, S. Kitagawa

    International Conference on Magnetism (ICM 2003)  2003.7 

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    Language:English   Presentation type:Oral presentation (general)  

    Venue:Roma  

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  • 酸素分子ラダーⅡ-電子密度解析による吸着分子の直接観察-

    日本物理学会第58回年次大会  2003 

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  • CeNi2Al5とCeNiGe3の圧力下電気抵抗

    日本物理学会2003年秋季大会  2003 

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  • CeRhGeの加圧下抵抗異常

    日本物理学会2003年秋季大会  2003 

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  • LiV2O4の圧力誘起電荷整列II

    日本物理学会2003年秋季大会  2003 

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  • ウラン酸化物UO2における高圧下NMR測定III

    日本物理学会2003年秋季大会  2003 

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  • URu2Si2の高圧下極低温磁化測定Ⅱ

    日本物理学会2003年秋季大会  2003 

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  • 圧力誘起超伝導体UGe2の加圧下のdHvA効果III

    日本物理学会2003年秋季大会  2003 

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  • 細孔をもつ銅錯体に吸着させた酸素分子の磁性

    日本物理学会2003年秋季大会  2003 

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  • 圧力下でのUIrの磁気相図

    日本物理学会2003年秋季大会  2003 

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  • CePtGe2,Ce3RhGa10の高圧下での電気抵抗

    日本物理学会2003年秋季大会  2003 

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  • UP2の磁性-非磁性転移

    日本物理学会第58回年次大会  2003 

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  • Magnetism of uranium dioxide UO2 under high pressure

    International Conference on Magnetism (ICM 2003)  2003 

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  • A change of the Fermi surface in CeIn3 across the critical pressure

    International Conference on Magnetism (ICM 2003)  2003 

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  • PrFe4P12の圧力下電気抵抗率測定

    日本物理学会2003年秋季大会  2003 

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  • PrFe4P12の高圧下磁化測定

    日本物理学会2003年秋季大会  2003 

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  • 遍歴強磁性体UIrの高圧下磁化測定

    日本物理学会第58回年次大会  2003 

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  • YbInCu4の圧力誘起磁気秩序

    日本物理学会第58回年次大会  2003 

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  • Evidence for the pressure-induced magnetic ordering in YbInCu4

    International Conference on Magnetism (ICM 2003)  2003 

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  • Ce系圧力誘起超伝導体の低温高圧下粉末X線回折

    日本物理学会第58回年次大会  2003 

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  • URu2Si2の高圧下極低温磁化測定

    日本物理学会第58回年次大会  2003 

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  • 酸素分子ラダーⅢ-磁性

    日本物理学会第58回年次大会  2003 

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  • 酸素分子ラダーⅣ-吸着酸素分子のラマン散乱-

    日本物理学会第58回年次大会  2003 

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  • ウラン酸化物UO2における高圧下NMR測定II

    日本物理学会第58回年次大会  2003 

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  • 銅錯体に吸着させた酸素分子の磁気的性質

    日本物理学会第58回年次大会  2003 

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  • CeIn3の加圧下dHvA効果

    日本物理学会第58回年次大会  2003 

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  • 酸素分子ラダーI-ボトムアップ構築のための集積型細孔銅錯体の合成と酸素吸着-

    日本物理学会第58回年次大会  2003 

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  • 高圧下におけるUIrの磁性-非磁性転移

    日本物理学会第57回年次大会  2002 

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  • S=1反強磁性ボンド交替鎖における磁場誘起長距離秩序の観測II

    日本物理学会2002年秋季大会  2002 

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  • 金属絶縁体転移物質BaVS3の高圧下電気抵抗測定

    日本物理学会2002年秋季大会  2002 

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  • ウラン酸化物UO2における高圧下NMR測定

    日本物理学会2002年秋季大会  2002 

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  • 強磁性超伝導物質UGe2の高圧下比熱測定-T *における比熱異常-

    日本物理学会2002年秋季大会  2002 

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  • Superconductivity under high pressure

    The 23rd International Conference on Low Temperature Physics  2002 

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  • A heat capacity anomaly of the superconducting transition in a ferromagnetic superconductor UGe2

    The 23rd International Conference on Low Temperature Physics  2002 

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  • Specific heat of an S = 1 quasi-1D bond alternating antiferromagnet in a magnetic field

    The 23rd International Conference on Low Temperature Physics  2002 

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  • CeAgSb2の量子臨界点近傍での電気抵抗

    日本物理学会2002年秋季大会  2002 

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  • Heat capacity of the Ferromagnetic Superconductor UGe2

    International Conference on Strongly Correlated Electron Systems  2002 

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  • Superconductivity in CeRh2Si2 under pressure

    International Conference on Strongly Correlated Electron Systems  2002 

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  • de Haas-van Alphen experiments in the quantum critical region of cerium and uranium compounds

    International Conference on Strongly Correlated Electron Systems  2002 

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  • 高圧下におけるLiV2O4のスピンダイナミクス

    日本物理学会第57回年次大会  2002 

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  • 圧力下でのU3P4の強磁性―常磁性転移

    日本物理学会第57回年次大会  2002 

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  • 圧力誘起超伝導物質UGe2の高圧下比熱測定

    日本物理学会第57回年次大会  2002 

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  • 圧力誘起超伝導体UGe2の加圧下のdHvA効果II

    日本物理学会第57回年次大会  2002 

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  • α-Mnの磁性-非磁性転移

    日本物理学会第57回年次大会  2002 

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  • 高圧下におけるCeTIn5(T=Rh,Ir)の電気抵抗

    日本物理学会第57回年次大会  2002 

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  • CeMg2Cu9の圧力下での電気抵抗

    日本物理学会第57回年次大会  2002 

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  • LiV2O4の圧力誘起電荷整列

    日本物理学会第57回年次大会  2002 

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  • CeRh2Si2の圧力誘起超伝導

    日本物理学会第57回年次大会  2002 

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  • Pressure-induced superconductivity in a ferromagnet UGe2

    International Conference on High Pressure Science and Technology (AIRAPT-18)  2001 

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  • Magnetic-nonmagnetic transition of U3P4 at high pressures

    Actinides-2001 International Conference  2001 

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  • 圧力誘起超伝導体UGe2の加圧下のdHvA効果

    日本物理学会2001年秋季大会  2001 

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  • 圧力誘起超伝導物質UGe2の高圧下比熱・磁化測定

    日本物理学会2001年秋季大会  2001 

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  • 高圧下におけるU3P4の磁性―非磁性転移II

    日本物理学会2001年秋季大会  2001 

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  • Thermal properties of a ferromagnetic superconductor UGe2

    Actinides-2001 International Conference  2001 

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  • Heat capacity of pressure-induced superconductivity in itinerant ferromagnet UGe2

    International Conference on Strongly Correlated Electron Systems (SCES 2001)  2001 

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  • Spin dynamics of heavy fermion system LiV2O4 under pressure

    International Conference on Strongly Correlated Electron Systems (SCES 2001)  2001 

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  • 高圧下におけるLiV2O4のLi-NMR

    日本物理学会2001年秋季大会  2001 

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  • 高圧下におけるUIrの磁性―非磁性転移

    日本物理学会2001年秋季大会  2001 

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  • Transport properties of CeRhIn5 under high pressures up to 8.5 GPa

    International Conference on Strongly Correlated Electron Systems (SCES 2001)  2001 

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  • UGe2の圧力誘起超伝導I-高圧下の電気抵抗・磁化測定

    日本物理学会第56回年次大会  2001 

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  • 高圧下におけるUIrの電気抵抗測定

    日本物理学会第56回年次大会  2001 

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  • 高圧下におけるU3P4の磁性―非磁性転移

    日本物理学会第56回年次大会  2001 

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  • CeRhIn5の圧力誘起超伝導

    日本物理学会第56回年次大会  2001 

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  • 磁性と超伝導の圧力誘起相図

    日本物理学会第56回年次大会  2001 

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  • UGe2の圧力誘起超伝導II-高圧下比熱測定

    日本物理学会第56回年次大会  2001 

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  • スピネル化合物LiV2O4の5GPa級Li-NMR測定

    日本物理学会第56回年次大会  2001 

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  • CeRh2Si2の圧力下でのdHvA効果II

    日本物理学会第56回年次大会  2001 

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  • YbPの極低温比熱測定

    日本物理学会第55回年次大会  2000 

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  • 低温高圧下におけるα-Mnの電気伝導と粉末X線回折

    高圧討論会  2000 

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  • ハルデン物質NDMAPのプロトンNMR

    日本物理学会第55回年次大会  2000 

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  • ウラン化合物UGe2,UIrの加圧下の物性

    日本物理学会第55回年次大会  2000 

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  • Pressure-induced superconductivity

    International Symposium on New Developments in Strongly Correlated Electron Phase under Multiple Environment  2000 

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  • Fermi surface instability in CeRh2Si2 and UGe2

    International Symposium on New Developments in Strongly Correlated Electron Phase under Multiple Environment  2000 

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  • 高圧下におけるU3P4とU3As4の電気抵抗測定

    日本物理学会第55回年次大会  2000 

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  • UGe2の圧力誘起超伝導

    日本物理学会第55回年次大会  2000 

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  • Pressure dependence of the transport properties in CeRhIn5

    International Symposium on New Developments in Strongly Correlated Electron Phase under Multiple Environment  2000 

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  • Resistance measurement in UGe2 under high pressure

    International Symposium on New Developments in Strongly Correlated Electron Phase under Multiple Environment  2000 

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  • Heat capacity of the pressure-induced superconductivity in itinerant ferromagnet UGe2

    International Symposium on New Developments in Strongly Correlated Electron Phase under Multiple Environment  2000 

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  • Electrical resistivity of U3P4 at high pressures

    International Symposium on New Developments in Strongly Correlated Electron Phase under Multiple Environment  2000 

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  • CeIn3の圧力誘起超伝導

    日本物理学会2000年春の分科会  2000 

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  • ハルデン系NDMAPのプロトンNMR

    日本物理学会2000年春の分科会  2000 

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  • NDMAZの磁場誘起長距離秩序

    日本物理学会2000年春の分科会  2000 

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  • CeAl2の電気抵抗の圧力依存性

    日本物理学会2000年春の分科会  2000 

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  • 圧力誘起超伝導物質UGe2の高圧下比熱測定

    日本物理学会第55回年次大会  2000 

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  • High-quality single crystal growth and a change of the electronic states under pressure in CeRh2Si2

    International Conference on Magnetism 2000 (ICM-2000)  2000 

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  • Proton NMR study of the field-induced long-range ordering in Haldane gap system NDMAP

    International Conference on Magnetism 2000 (ICM-2000)  2000 

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  • 二次元スピンギャップ系SrCu2(BO3)2の極低温・高磁場中比熱測定

    日本物理学会第55回年次大会  2000 

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  • a-Mnの圧力下電気抵抗測定

    日本物理学会第54回年会  1999 

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  • α-Mnの圧力下電気抵抗測定Ⅱ

    高圧学会  1999 

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  • Dielectric to metal transformations at magabar pressures: Electrical conductivity measurements

    International Conference on High Pressure Science and Technology (AIRAPT-17)  1999 

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  • Pressure dependence of quadrupole ordering temperature TQ in CeB6

    International Conference on Strongly Correlated Electron System (SCES99)  1999 

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  • Pressure-dependence of superconducting behavior in CeRh2Si2

    International Conference on Strongly Correlated Electron System (SCES99)  1999 

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  • Metamagnetic transition of CeRh2Si2 under high fields and high pressures at various temperatures

    International Conference on Strongly Correlated Electron System (SCES99)  1999 

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  • α-Mnの圧力下電気抵抗測定Ⅱ

    日本物理学会1999年秋の分科会  1999 

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  • CeRh2Si2の圧力誘起超伝導

    日本物理学会1999年秋の分科会  1999 

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  • NDMAZの磁場誘起長距離秩序の比熱

    日本物理学会1999年秋の分科会  1999 

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  • ハルデン系NDMAPのプロトンNMR

    日本物理学会1999年秋の分科会  1999 

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  • 高圧下におけるCeIn3の電気抵抗

    日本物理学会1999年秋の分科会  1999 

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  • CeB6の四重極秩序の圧力効果

    日本物理学会1999年秋の分科会  1999 

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  • 高圧下でのCeRh2Si2の電気抵抗測定

    日本物理学会第54回年会  1999 

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  • 細孔中に吸着した酸素分子の磁性

    日本物理学会第54回年会  1999 

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  • Electrical Resistance Measurement in Hydrostatic Pressure up to 10 GPa using a Diamond Anvil Cell

    International Conference on High Pressure Science and Technology (AIRAPT-17)  1999 

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  • Electrical Studies in DAC

    International Conference on High Pressure Science and Technology (AIRAPT-17)  1999 

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  • CeCu6の圧力下における電気抵抗測定

    日本物理学会第54回年会  1999 

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  • CeIn3の圧力下比熱測定

    日本物理学会第54回年会  1999 

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  • 高圧下におけるCeIn3の交流帯磁率

    日本物理学会第54回年会  1999 

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Awards

  • JPSJ Papers of Editors' Choice

    2008  

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    Country:Japan

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  • Physics of Materials under Extreme Conditions (2021academic year) Late  - 金3,金4

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  • Seminar in Materials Physics in Extreme Environments (2021academic year) Year-round  - その他

  • Exercise of Electromagnetism 1 (2021academic year) 1st and 2nd semester  - 月3,月4

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  • Physics of Materials under Extreme Conditions (2020academic year) Late  - 金2,金3

  • Physics under Extreme Environment (2020academic year) Late  - その他

  • Seminar in Materials Physics in Extreme Environments (2020academic year) Year-round  - その他

  • Exercise of Electromagnetism 1 (2020academic year) 1st and 2nd semester  - 水3,水4

  • Exercise of Electromagnetism 1A (2020academic year) 1st semester  - 水3,水4

  • Exercise of Electromagnetism 1B (2020academic year) Second semester  - 水3,水4

  • Exercise of Electromagnetism 2 (2020academic year) 3rd and 4th semester  - 水3,水4

  • Exercise of Electromagnetism 2A (2020academic year) Third semester  - 水3,水4

  • Exercise of Electromagnetism 2B (2020academic year) Fourth semester  - 水3,水4

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