研究者詳細 - 小林　達生

論文 - 小林　達生

分割表示 217 件中 121 - 140 件目／全件表示 >>

Magnetization and Magnetoresistance measurements up to 60 T at 70 mK 査読

Y. Narumi, N. Takamoto, K. Kindo, T. C. Kobayashi, N. Shimizu, F. Iga, S. Hiura, T. Takabatake, M. Vendaguer

World Scientific Publishing Co. Pre. Ltd. 2004年11月

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

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

INORGANIC CHEMISTRY 43 ( 21 ) 6522 - 6524 2004年10月

記述言語：英語掲載種別：研究論文（学術雑誌）出版者・発行元：AMER CHEMICAL SOC

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.

DOI： 10.1021/ic049005d

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

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

PHYSICAL REVIEW B 69 ( 18 ) 2004年5月

記述言語：英語掲載種別：研究論文（学術雑誌）出版者・発行元：AMER PHYSICAL SOC

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.

DOI： 10.1103/PhysRevB.69.180513

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

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年5月

記述言語：英語掲載種別：研究論文（学術雑誌）

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.

DOI： 10.1103/PhysRevB.69.180513

A change of the Fermi surface in CeIn3 under pressure 査読

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

JOURNAL OF MAGNETISM AND MAGNETIC MATERIALS 272 223 - 224 2004年5月

記述言語：英語掲載種別：研究論文（学術雑誌）出版者・発行元：ELSEVIER SCIENCE BV

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 <111> changes slightly at 2.5 GPa. (C) 2003 Elsevier B.V. All rights reserved.

DOI： 10.1016/j.jmmm.2003.11.200

Magnetism of uranium dioxide UO2 under high pressure 査読

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年5月

記述言語：英語掲載種別：研究論文（学術雑誌）出版者・発行元：ELSEVIER SCIENCE BV

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.

DOI： 10.1016/j.jmmm.2003.11.307

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

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年5月

記述言語：英語掲載種別：研究論文（学術雑誌）出版者・発行元：ELSEVIER SCIENCE BV

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.

DOI： 10.1016/j.jmmm.2003.11.327

Evidence for the pressure induced magnetic ordering in YbInCu4 査読

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

JOURNAL OF MAGNETISM AND MAGNETIC MATERIALS 272 E47 - E48 2004年5月

記述言語：英語掲載種別：研究論文（学術雑誌）出版者・発行元：ELSEVIER SCIENCE BV

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.

DOI： 10.1016/j.jmmm.2003.11.146

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

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年4月

記述言語：英語出版者・発行元：PHYSICAL SOC JAPAN

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.

DOI： 10.1143/JPSJ.73.769

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

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年3月

記述言語：英語掲載種別：研究論文（学術雑誌）出版者・発行元：E D P SCIENCES

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.

DOI： 10.1209/epl/i2003-10164-5

LiNMR in LiV2O4 under high pressure 査読

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

JOURNAL OF PHYSICS-CONDENSED MATTER 16 ( 11 ) S615 - S619 2004年3月

記述言語：英語掲載種別：研究論文（学術雑誌）出版者・発行元：IOP PUBLISHING LTD

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.

DOI： 10.1088/0953-8984/16/11/007

Electrical, Thermal and Magnetic Properties of CeNiIn4 査読

Hiroaki Shishido, Noriko Nakamura, Taiki Ueda, Rihito Asai, Andrei Galatanu, Etsuji Yamamoto, Yoshinori Haga, Tetsuya Takeuchi, Yasuo Narumi, Tatsuo C Kobayashi, Koichi Kindo, Kiyohiro Sugiyama, Takahiro Namiki, Yuji Aoki, Hideyuki Sato, Yoshichika Ōnuki

Journal of the Physical Society of Japan 73 ( 3 ) 664 - 668 2004年3月

Pressure-induced superconductivity in ferromagnetic UIr without inversion symmetry 査読

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年2月

記述言語：英語出版者・発行元：IOP PUBLISHING LTD

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.

DOI： 10.1088/0953-8984/16/4/L02

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> 査読

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年

掲載種別：研究論文（学術雑誌）

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

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

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

J. Phys.: Condens. Matter 16 ( 20 ) 2004年

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

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年10月

記述言語：英語掲載種別：研究論文（学術雑誌）出版者・発行元：PHYSICAL SOC JAPAN

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.

DOI： 10.1143/JPSJ.72.2632

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

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年9月

記述言語：英語掲載種別：研究論文（学術雑誌）出版者・発行元：PHYSICAL SOC JAPAN

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

Pressure-induced weak ferromagnetism in uranium dioxide, UO2 査読

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年7月

記述言語：英語掲載種別：研究論文（学術雑誌）出版者・発行元：IOP PUBLISHING LTD

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.

DOI： 10.1088/0953-8984/15/28/321

An anomalously huge resistivity peak under pressure in CeRhGe 査読

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年7月

記述言語：英語出版者・発行元：IOP PUBLISHING LTD

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.

DOI： 10.1088/0953-8984/15/29/102

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

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

JOURNAL OF PHYSICS-CONDENSED MATTER 15 ( 21 ) 3607 - 3618 2003年6月

記述言語：英語掲載種別：研究論文（学術雑誌）出版者・発行元：IOP PUBLISHING LTD

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.

DOI： 10.1088/0953-8984/15/21/309

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