2021/07/12 更新

写真a

ムラオカ ユウジ
村岡 祐治
MURAOKA Yuji
所属
異分野基礎科学研究所 准教授
職名
准教授
外部リンク

学位

  • 博士(理学)

研究キーワード

  • 固体化学

  • 材料科学

  • 薄膜・界面

  • Solid State Chemistry

研究分野

  • ナノテク・材料 / 機能物性化学

  • ナノテク・材料 / 薄膜、表面界面物性  / 酸化物、炭素系材料

学歴

  • 東北大学   大学院理学研究科   化学専攻

    1993年4月 - 1996年3月

      詳細を見る

    国名: 日本国

    備考: 博士後期課程

    researchmap

  • 東北大学   大学院理学研究科   化学専攻

    1991年4月 - 1993年3月

      詳細を見る

    国名: 日本国

    備考: 博士前期課程

    researchmap

  • 東北大学   理学部   化学科

    1987年4月 - 1991年3月

      詳細を見る

    国名: 日本国

    researchmap

経歴

  • 岡山大学   異分野基礎科学研究所   准教授

    2016年4月 - 現在

      詳細を見る

  • 岡山大学   大学院自然科学研究科   准教授

    2007年4月 - 2016年3月

      詳細を見る

  • 岡山大学   大学院自然科学研究科   助教授

    2006年4月 - 2007年3月

      詳細を見る

  • 東京大学物性研究所   物質設計評価施設   助手

    2000年3月 - 2006年3月

      詳細を見る

所属学協会

委員歴

  • 応用物理学会   代議員  

    2020年2月 - 2022年1月   

      詳細を見る

    団体区分:学協会

    researchmap

  • 応用物理学会 中国四国支部   幹事  

    2011年4月 - 現在   

      詳細を見る

    団体区分:学協会

    researchmap

  • 東京大学物性研究所物質設計評価施設 外部評価委員   外部評価委員  

    2009年4月 - 2010年3月   

      詳細を見る

    団体区分:その他

    researchmap

 

論文

  • Soft x-ray irradiation induced metallization of layered TiNCl 査読

    Noriyuki Kataoka, Masashi Tanaka, Wataru Hosoda, Takumi Taniguchi, Shin-ichi Fujimori, Takanori Wakita, Yuji Muraoka, Takayoshi Yokoya

    Journal of Physics: Condensed Matter   33 ( 3 )   035501 - 035501   2021年1月

     詳細を見る

    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  

    DOI: 10.1088/1361-648x/abbbc3

    researchmap

    その他リンク: https://iopscience.iop.org/article/10.1088/1361-648X/abbbc3/pdf

  • Magnetic-field-induced insulator–metal transition in W-doped VO2 at 500 T 査読

    Yasuhiro H. Matsuda, Daisuke Nakamura, Akihiko Ikeda, Shojiro Takeyama, Yuki Suga, Hayato Nakahara, Yuji Muraoka

    Nature Communications   11 ( 1 )   3591   2020年12月

     詳細を見る

    担当区分:最終著者   記述言語:英語   掲載種別:研究論文(学術雑誌)   出版者・発行元:Springer Science and Business Media LLC  

    DOI: 10.1038/s41467-020-17416-w

    researchmap

    その他リンク: http://www.nature.com/articles/s41467-020-17416-w

  • Formation of Q-carbon by adjusting sp3 content in diamond-like carbon films and laser energy density of pulsed laser annealing 査読

    Hiroki Yoshinaka, Seiko Inubushi, Takanori Wakita, Takayoshi Yokoya, Yuji Muraoka

    Carbon   167   504 - 511   2020年10月

     詳細を見る

    担当区分:責任著者   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 BV  

    DOI: 10.1016/j.carbon.2020.06.025

    researchmap

  • Change in the electronic structure of the bismuth chalcogenide superconductor CsBi4-xPbxTe6 by dissociation of the bismuth dimers 査読

    Hiroyuki Okazaki, Kensei Terashima, David Billington, Keiji Iwata, Takanori Wakita, Masashi Tanaka, Yoshihiko Takano, Yuji Muraoka, Takayoshi Yokoya

    JOURNAL OF PHYSICS-CONDENSED MATTER   32 ( 14 )   145501-1 - 145501-7   2020年4月

     詳細を見る

    記述言語:英語   掲載種別:研究論文(学術雑誌)  

    researchmap

  • Strain effects on spinodal decomposition in TiO2-VO2 films on TiO2(100) substrates 査読

    Yuji Muraoka, Fumiya Yoshii, Takahiro Fukuda, Yuji Manabe, Mikiko Yasuno, Yoshito Takemoto, Kensei Terashima, Takanori Wakita, Takayoshi Yokoya

    Thin Solid Films   698   137854   2020年2月

     詳細を見る

    担当区分:筆頭著者   記述言語:英語   掲載種別:研究論文(学術雑誌)  

    researchmap

  • Electronic structure changed by Bi dimer in bismuth chalcogenide superconductor CsBi4-xPbxTe6 査読

    Hiroyuki Okazaki, Kensei Terashima, David Billington, Keiji Iwata, Takanori Wakita, Masashi Tanaka, Yoshihiko Takano, Yuji Muraoka, Takayoshi Yokoya

    J. Phys.:Condens. Matter   32 ( 12 )   145501   2020年1月

     詳細を見る

    記述言語:英語   掲載種別:研究論文(学術雑誌)  

    researchmap

  • Asymmetric Phosphorus Incorporation in Homoepitaxial P-Doped (111) Diamond Revealed by Photoelectron Holography 査読

    Nano Lett.   19   5915 - 5919   2019年

     詳細を見る

    記述言語:英語   掲載種別:研究論文(学術雑誌)  

    DOI: 10.1021/acs.nanolett.9b01481

    researchmap

  • Enhanced thermoelectricity by controlled local structure in bismuth-chalcogenides 査読

    J. Appl. Phys.   125   145105   2019年

     詳細を見る

    記述言語:英語   掲載種別:研究論文(学術雑誌)  

    DOI: 10.1063/1.5087096

    researchmap

  • µ-PES Studies on TiNCl and Quasi-two-dimensional Superconductor Na-intercalated TiNCl 査読

    88   104709   2019年

     詳細を見る

    記述言語:英語   掲載種別:研究論文(学術雑誌)  

    DOI: 10.7566/JPSJ.88.104709

    researchmap

  • Direct observation of double valence-band extrema and anisotropic effective masses of the thermoelectric material SnSe 査読

    Takanobu Nagayama, Kensei Terashima, Takanori Wakita, Hirokazu Fujiwara, Tetsushi Fukura, Yuko Yano, Kanta Ono, Hiroshi Kumigashira, Osamu Ogiso, Aichi Yamashita, Yoshihiko Takano, Hitoshi Mori, Hidetomo Usui, Masayuki Ochi, Kazuhiko Kuroki, Yuji Muraoka, Takayoshi Yokoya

    JAPANESE JOURNAL OF APPLIED PHYSICS   57 ( 1 )   010301   2018年1月

     詳細を見る

    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  

    Synchrotron-based angle-resolved photoemission spectroscopy is used to determine the electronic structure of layered SnSe, which was recently turned out to be a potential thermoelectric material. We observe that the top of the valence band consists of two nearly independent hole bands, whose tops differ by similar to 20meV in energy, indicating the necessity of a multivalley model to describe the thermoelectric properties. The estimated effective masses are anisotropic, with in-plane values of 0.16-0.39 m(0) and an out-of-plane value of 0.71 m(0), where m(0) is the rest electron mass. Information of the electronic structure is essential to further enhance the thermoelectric performance of hole-doped SnSe. (C) 2018 The Japan Society of Applied Physics

    DOI: 10.7567/JJAP.57.010301

    Web of Science

    researchmap

  • Martensitic transformation induced in Ti-15V-7Al alloy at low and high temperatures 査読

    Mater. Trans.   59   1560 - 1566   2018年

     詳細を見る

    記述言語:英語   掲載種別:研究論文(学術雑誌)  

    DOI: 10.2320/matertrans.M2018185

    researchmap

  • Fermi surface topology in a metallic phase of VO2 thin films grown on TiO2(001) substrates 査読

    Sci. Rep.   8   17906   2018年

     詳細を見る

    記述言語:英語   掲載種別:研究論文(学術雑誌)  

    DOI: 10.1038/s41598-018-36281-8

    researchmap

  • Origins of thermal spin depolarization in half-metallic ferromagnet CrO2 査読

    121   257201   2018年

     詳細を見る

    記述言語:英語   掲載種別:研究論文(学術雑誌)  

    DOI: 10.1103/PhysRevLett.121.257201

    researchmap

  • Multilayer formation via spinodal decomposition in TiO2-VO2 epitaxial films on sapphire substrates 査読

    J. Eur. Ceram. Soc.   38   5043 - 5050   2018年

     詳細を見る

    記述言語:英語   掲載種別:研究論文(学術雑誌)  

    DOI: 10.1016/j.jeurceramsoc.2018.07.035

    researchmap

  • Determination of the local structure of Sr2-xMxIrO4 (M = K, La) as a function of doping and temperature 査読

    Phys.Chem.Chem.Phys.   20   23783 - 23788   2018年

     詳細を見る

    記述言語:英語   掲載種別:研究論文(学術雑誌)  

    DOI: 10.1039/c8cp03756f

    researchmap

  • Temperature-dependent local structure and superconductivity of BaPd2As2 and SrPd2As2 査読

    Phys. Rev. B   98   09425   2018年

     詳細を見る

    記述言語:英語   掲載種別:研究論文(学術雑誌)  

    DOI: 10.1103/PhysRevB.98.094525

    researchmap

  • Observation of intrinsic half-metallic behavior of CrO2 (100) epitaxial films by bulk-sensitive spin-resolved PES 査読

    Hirokazu Fujiwara, Masanori Sunagawa, Kensei Terashima, Tomoko Kittaka, Takanori Wakita, Yuji Muraoka, Takayoshi Yokoya

    JOURNAL OF ELECTRON SPECTROSCOPY AND RELATED PHENOMENA   220   46 - 49   2017年10月

     詳細を見る

    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 the electronic states and spin polarization of half-metallic ferromagnet CrO2 (100) epitaxial films by bulk-sensitive spin-resolved photoemission spectroscopy with a focus on non-quasiparticle (NQP) states derived from electron-magnon interactions. We found that the averaged values of the spin polarization are approximately 100% and 40% at 40 K and 300 K, respectively. This is consistent with the previously reported result [H. Fujiwara et al., Appl. Phys. Lett. 106, 202404 (2015).]. At 100 K, peculiar spin depolarization was observed at the Fermi level (E-F), which is supported by theoretical calculations predicting NQP states. This suggests the possible appearance of NQP states in CrO2. We also compare the temperature dependence of our spin polarizations with that of the magnetization. (C) 2017 Elsevier B.V. All rights reserved.

    DOI: 10.1016/j.elspec.2017.02.003

    Web of Science

    researchmap

  • The electronic structure of Ag1-xSn1+xSe2 (x=0.0, 0.1, 0.2, 0.25 and 1.0) 査読

    Takanori Wakita, Eugenio Paris, Kaya Kobayashi, Kensei Terashima, Muammer Yasin Hacisalihoglu, Teppei Ueno, Federica Bondino, Elena Magnano, Igor Pis, Luca Olivi, Jun Akimitsu, Yuji Muraoka, Takayoshi Yokoya, Naurang L. Saini

    PHYSICAL CHEMISTRY CHEMICAL PHYSICS   19 ( 39 )   26672 - 26678   2017年10月

     詳細を見る

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

    We have studied the valence electronic structure of Ag1-xSn1+xSe2 (x = 0.0, 0.1, 0.2, 0.25) and SnSe (x = 1.0) by a combined analysis of X-ray absorption spectroscopy (XAS) and X-ray photoemission spectroscopy (XPS) measurements. Both XAS and XPS reveal an increase in electron carriers in the system with x (i.e. excess Sn concentration) for 0 <= x <= 0.25. The core-level spectra (Sn 3d, Ag 3d and Se 3d) show that the charge state of Ag is almost 1+, while that of of Sn splits into Sn2+ and Sn4+ (providing clear evidence of valence skipping for the first time) with a concomitant splitting of Se into Se2- and Se2-delta states. The x dependence of the split components in Sn and Se together with the Se-K edge XAS reveals that the Se valence state may have an essential role in the transport properties of this system.

    DOI: 10.1039/c7cp05369j

    Web of Science

    researchmap

  • Effect of aliovalent dopants on the kinetics of spinodal decomposition in rutile-type TiO2-VO2 査読

    Makoto Ogata, Kenji Kadowaki, Masataka Ijiri, Yoshito Takemoto, Kensei Terashima, Takanori Wakita, Takayoshi Yokoya, Yuji Muraoka

    JOURNAL OF THE EUROPEAN CERAMIC SOCIETY   37 ( 9 )   3177 - 3183   2017年8月

     詳細を見る

    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 SCI LTD  

    The effects of aliovalent dopants on the kinetics of spinodal decomposition in a rutile-type TiO2-VO2 system were studied by means of x-ray diffraction and transmission electron microscopy. In this study, as prepared polycrystalline samples were annealed at 673 k inside the spinodal. For undoped samples, phase decomposition occurred along the [001] direction, and a lamellar structure formed on the nanometer length scale. The phase decomposition kinetics in this system were sensitive to the type of aliovalent dopant; the decomposition rate in a sample doped with Al2O3 was more than one order of magnitude higher than a sample doped with . These observations could be explained on the basis of the premise that cation interstitial mobility is greater than cation vacancy mobility. The obtained results are consistent with those for a TiO2-SnO2 system, indicating that phase separation in both rutile-type oxide systems can be interpreted through a common framework. (C) 2017 Elsevier Ltd. All rights reserved.

    DOI: 10.1016/j.jeurceramsoc.2017.03.039

    Web of Science

    researchmap

  • Evolution of the remnant Fermi-surface state in the lightly doped correlated spin-orbit insulator Sr2−xLaxIrO4 査読

    Phys. Rev. B   96 ( 4 )   041106(R)   2017年7月

     詳細を見る

    記述言語:英語   掲載種別:研究論文(学術雑誌)  

    DOI: 10.1103/PhysRevB.96.041106

    Web of Science

    researchmap

  • Electronic structure of K-doped picene film on HOPG 査読

    T. Wakita, H. Okazaki, T. Jabuchi, H. Hamada, Y. Muraoka, T. Yokoya

    JOURNAL OF PHYSICS-CONDENSED MATTER   29 ( 6 )   26672 - 26678   2017年2月

     詳細を見る

    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 have performed potassium (K)-doping dependent photoemission (PES) measurements of picene film on highly oriented pyrolytic graphite (HOPG). K-doping dependent valence band PES data exhibits a shift of the valence band to a higher binding energy, indicative of the charge transfer from the K atoms to the picene film. K-doping dependent PES spectra near the Fermi level (EF) show the appearance and disappearance of a Fermi edge, indicating the metallic properties of the film at certain K concentrations. High-resolution PES spectrum at the lowest measured temperature does not show an opening of the superconducting gap, requesting further studies to explore the superconducting properties of the K-doped picene film. The results will be discussed by comparison with previous and recent spectroscopic studies.

    DOI: 10.1088/1361-648X/29/6/064001

    Web of Science

    researchmap

  • Ce 4f electronic states of CeO1-xFxBiS2 studied by soft x-ray photoemission spectroscopy 査読

    Wakita, Takanori, Terashima, Kensei, Hamada, Takahiro, Fujiwara, Hirokazu, Minohara, Makoto, Kobayashi, Masaki, Horiba, Koji, Kumigashira, Hiroshi, Kutluk, Galif, Nagao, Masanori, Watauchi, Satoshi, Tanaka, Isao, Demura, Satoshi, Okazaki, Hiroyuki, Takano, Yoshihiko, Mizuguchi, Yoshikazu, Miura, Osuke, Okada, Kozo, Muraoka, Yuji, Yokoya, Takayoshi

    Physical Review B   95 ( 8 )   085109   2017年

     詳細を見る

    記述言語:英語   掲載種別:研究論文(学術雑誌)  

    DOI: 10.1103/PhysRevB.95.085109

    Web of Science

    researchmap

  • Determination of the local structure of CsBi4-xPbxTe6 (x=0, 0.5) by X-ray absorption spectroscopy 査読

    Takanori Wakita, Eugenio Paris, Takashi Mizokawa, Muammer Yasin Hacisalihoglu, Kensei Terashima, Hiroyuki Okazaki, Olivier Proux, Isabelle Kieffer, Eric Lahera, William Del Net, Luca Olivi, Yoshihiko Takano, Yuji Muraoka, Takayoshi Yokoya, Naurang L. Saini

    PHYSICAL CHEMISTRY CHEMICAL PHYSICS   18 ( 36 )   25136 - 25142   2016年9月

     詳細を見る

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

    We have studied the local structure and valence electronic unoccupied states of thermoelectric CsBi4Te6 and superconducting CsBi3.5Pb0.5Te6 (T-c similar to 3 K) by extended X-ray absorption fine structure (EXAFS) and X-ray absorption near edge structure (XANES) measurements. The Bi-L-3 edge EXAFS reveals wide Bi-Te distance distribution for both compounds indicating complex atomic arrangements in the studied system. The mean square relative displacements (MSRDs) of the Bi-Te bond distances appear largely increased in Pb substituted system due to larger overall local disorder, however, one of the Bi-Te bonds shows a reduced disorder. On the other hand, the Bi-L-3 edge XANES is hardly affected by Pb substitution while the Te-L-1 edge XANES reveals increased density of unoccupied Te 5p states. This suggests that the carriers introduced by the Pb substitution in CsBi4-xPbxTe6 preferentially goes on Te sites. Similarly, the Cs-L-3 edge XANES also shows small changes due to Pb-substitution and reduced local disorder indicated by the reduced width of the Cs-L3 edge white line. We have also shown that the X-ray photoemission spectroscopy (XPS) measurements on various electronic core levels are in a qualitative agreement with the XANES results. These findings are consistent with carrier doping and a reduced disorder in one direction to be likely factors to drive the thermoelectric CsBi4Te6 into a bulk superconductor by Pb-substitution in CsBi4-xPbxTe6.

    DOI: 10.1039/c6cp04949d

    Web of Science

    researchmap

  • Observation of a Hidden Hole-Like Band Approaching the Fermi Level in K-Doped Iron Selenide Superconductor 査読

    Masanori Sunagawa, Kensei Terashima, Takahiro Hamada, Hirokazu Fujiwara, Tetsushi Fukura, Aya Takeda, Masashi Tanaka, Hiroyuki Takeya, Yoshihiko Takano, Masashi Arita, Kenya Shimada, Hirofumi Namatame, Masaki Taniguchi, Katsuhiro Suzuki, Hidetomo Usui, Kazuhiko Kuroki, Takanori Wakita, Yuji Muraoka, Takayoshi Yokoya

    JOURNAL OF THE PHYSICAL SOCIETY OF JAPAN   85 ( 7 )   073704   2016年7月

     詳細を見る

    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  

    One of the ultimate goals of the study of iron-based superconductors is to identify the common feature that produces the high critical temperature (T-c). In the early days, based on a weak-coupling viewpoint, the nesting between hole-and electron-like Fermi surfaces (FSs) leading to the so-called s +/- state was considered to be one such key feature. However, this theory has faced a serious challenge ever since the discovery of alkali-metal-doped FeSe (AFS) superconductors, in which only electron-like FSs with a nodeless superconducting gap are observed. Several theories have been proposed, but a consistent understanding is yet to be achieved. Here we show experimentally that a hole-like band exists in KxFe2-ySe2, which presumably forms a hole-like Fermi surface. The present study suggests that AFS can be categorized in the same group as iron arsenides with both hole- and electron-like FSs present. This result provides a foundation for a comprehensive understanding of the superconductivity in iron-based superconductors.

    DOI: 10.7566/JPSJ.85.073704

    Web of Science

    researchmap

  • Local electronic state in the half-metallic ferromagnet CrO2 investigated by site-selective Cr-53 NMR measurements 査読

    Hikaru Takeda, Yasuhiro Shimizu, Yoshiaki Kobayashi, Masayuki Itoh, Takaaki Jin-no, Masahiko Isobe, Yutaka Ueda, Sho Yoshida, Yuji Muraoka, Takayoshi Yokoya

    PHYSICAL REVIEW B   93 ( 23 )   235129   2016年6月

     詳細を見る

    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  

    We have made Cr-53 NMR measurements on polycrystalline and single-crystalline film samples to study the local electronic state of a half-metallic ferromagnet CrO2 which has the rutile structure with one crystallographically equivalent Cr site. We observe two kinds of Cr-53 NMR spectra in the ferromagnetic state of both the samples. An analysis on the hyperfine field shows the presence of two Cr sites with different orbital occupancies, suggesting that a local orbital order takes place with breaking the local symmetry in the rutile structure. This may be ascribed to the negative charge transfer between chromium and oxygen ions.

    DOI: 10.1103/PhysRevB.93.235129

    Web of Science

    researchmap

  • Preparation of TaO2 thin films using NbO2 template layers by a pulsed laser deposition technique 査読

    Y. Muraoka, Y. Fujimoto, M. Kameoka, Y. Matsuura, M. Sunagawa, K. Terashima, T. Wakita, T. Yokoya

    THIN SOLID FILMS   599   125 - 132   2016年1月

     詳細を見る

    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 SA  

    TaO2 thin films were prepared using rutile-type NbO2 template layers on Al2O3 (0001) substrates by a pulsed laser deposition technique. The structural and electronic properties of the films were characterized by performing four-circle X-ray diffraction (XRD) and X-ray photoemission spectroscopy (XPS) measurements. Four-circle XRD measurements revealed the formation and epitaxial growth of (100)-oriented tetragonal TaO2 on the NbO2 template layers. On the other hand, XPS measurements showed two kinds of valence states, namely Ta4+ and Ta5+ in the surface region of the film. The results from the XRD and XPS measurements suggest that the film is composed of epitaxially grown TaO2 with an amorphous Ta2O5 surface layer. It is found from control experiments that the NbO2 template layers play an important role in inducing the crystallization of the TaO2 films and promoting the formation of Ta4+ in the films deposited thereon. The results indicate the effectiveness of the NbO2 template layers for the formation of TaO2 thin films. Our work presents a promising method for the preparation of TaO2 thin films and provides a starting point for further research on TaO2. (C) 2015 Elsevier B.V. All rights reserved.

    DOI: 10.1016/j.tsf.2015.12.066

    Web of Science

    researchmap

  • Bulk sensitive angle-resolved photoelectron spectroscopy on Nd(O,F)BiS2 査読

    K. Terashima, J. Sonoyama, M. Sunagawa, H. Fujiwara, T. Nagayama, T. Muro, M. Nagao, S. Watauchi, I. Tanaka, H. Okazaki, Y. Takano, Y. Mizuguchi, H. Usui, K. Suzuki, K. Kuroki, T. Wakita, Y. Muraoka, T. Yokoya

    TMU INTERNATIONAL SYMPOSIUM ON NEW QUANTUM PHASES EMERGING FROM NOVEL CRYSTAL STRUCTURE   683   0012003   2016年

     詳細を見る

    記述言語:英語   掲載種別:研究論文(国際会議プロシーディングス)   出版者・発行元:IOP PUBLISHING LTD  

    Bulk electronic structure of novel layered superconductor Nd(O,F)BiS2 was studied by using soft x-ray angle-resolved photoelectron spectroscopy (ARPES). Electron-like Fermi surface centered at the X(R) point was observed, consistent with earlier ARPES reports on surface-sensitive VUV light source. Based on the comparison of the electronic structure between Nd(O,F)BiS2 and La(O,F)BiS2, we discuss possible important factors for the superconductivity in this series of material.

    DOI: 10.1088/1742-6596/683/1/012003

    Web of Science

    researchmap

  • Comparative ARPES studies of LaOxF1−xBiS2 (x = 0.23 and 0.46) 査読

    J. Phys.: Conf. Ser.   683   012002   2016年

     詳細を見る

    記述言語:英語   掲載種別:研究論文(国際会議プロシーディングス)  

    DOI: 10.1088/1742-6596/683/1/012002

    Web of Science

    researchmap

  • Intrinsic spin polarized electronic structure of CrO2 epitaxial film revealed by bulk-sensitive spin-resolved photoemission spectroscopy 査読

    Hirokazu Fujiwara, Masanori Sunagawa, Kensei Terashima, Tomoko Kittaka, Takanori Wakita, Yuji Muraoka, Takayoshi Yokoya

    APPLIED PHYSICS LETTERS   106 ( 20 )   202404   2015年5月

     詳細を見る

    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 INST PHYSICS  

    We have performed bulk-sensitive spin-resolved photoemission spectroscopy in order to clarify the intrinsic spin-resolved electronic states of half-metallic ferromagnet CrO2. We used CrO2 epitaxial films on TiO2(100), which shows a peak at 1 eV with a clear Fermi edge, consistent with the bulk-sensitive PES spectrum for CrO2. In spin-resolved spectra at 40 K, while the Fermi edge was observed in the spin up (majority spin) state, no states at the Fermi level (EF) with an energy gap of 0.5 eV below EF were observed in the spin down (minority spin) state. At 300 K, the gap in the spin down state closes. These results are consistent with resistivity measurements and magnetic hysteresis curves of the fabricated CrO2 film, constituting spectroscopic evidence for the half-metallicity of CrO2 at low temperature and reducing the spin polarization at room temperature. We also discuss the electron correlation effects of Cr 3d. (C) 2015 AIP Publishing LLC.

    DOI: 10.1063/1.4921629

    Web of Science

    researchmap

  • Comparative ARPES Study on Iron–Platinum–Arsenide Superconductor Ca10(Pt4As8)(Fe2−xPtxAs2)5 (x = 0.25 and 0.42) 査読

    J. Phys. Soc. Jpn.   84 ( 5 )   055001   2015年5月

     詳細を見る

    記述言語:英語   掲載種別:研究論文(学術雑誌)  

    DOI: 10.7566/JPSJ.84.055001

    Web of Science

    researchmap

  • Signature of high T-c above 25 K in high quality superconducting diamond 査読

    Hiroyuki Okazaki, Takanori Wakita, Takayuki Muro, Tetsuya Nakamura, Yuji Muraoka, Takayoshi Yokoya, Shin-ichiro Kurihara, Hiroshi Kawarada, Tamio Oguchi, Yoshihiko Takano

    APPLIED PHYSICS LETTERS   106 ( 5 )   052601   2015年2月

     詳細を見る

    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 INST PHYSICS  

    We have observed zero resistivity above 10K and an onset of resistivity reduction at 25.2K in a heavily B-doped diamond film. However, the effective carrier concentration is similar to that of superconducting diamond with a lower T-c. We found that the carrier has a longer mean free path and lifetime than in the previous report, indicating that this highest T-c diamond has better crystallinity compared to that of other superconducting diamond films. In addition, the susceptibility shows a small transition above 20K in the high quality diamond, suggesting a signature of superconductivity above 20 K. These results strongly suggest that heavier carrier doped defect-free crystalline diamond could give rise to high T-c diamond. (C) 2015 AIP Publishing LLC.

    DOI: 10.1063/1.4907411

    Web of Science

    researchmap

  • Signature of high $T_c$ around 25K in higher quality heavily boron-doped diamond 査読

    H. Okazaki, T. Wakita, T. Muro, T. Nakamura, Y. Muraoka, T. Yokoya, S. Kurihara, H. Kawarada, T. Oguchi, Y. Takano

    Appl. Phys. Lett.   2015年2月

     詳細を見る

    記述言語:英語   掲載種別:研究論文(学術雑誌)  

    researchmap

  • Proximity to Fermi-surface topological change in superconducting LaO0.54F0.46BiS2 査読

    Terashima Kensei, Sonoyama Junki, Wakita Takanori, Sunagawa Masanori, Ono Kanta, Kumigashira Hiroshi, Muro Takayuki, Nagao Masanori, Watauchi Satoshi, Tanaka Isao, Okazaki Hiroyuki, Takano Yoshihiko, Miura Osuke, Mizuguchi Yoshikazu, Usui Hidetomo, Suzuki Katsuhiro, Kuroki Kazuhiko, Muraoka Yuji, Yokoya Takayoshi

    PHYSICAL REVIEW B   90 ( 22 )   2014年12月

  • Proximity to Fermi-surface topological change in superconducting LaO0.54F0.46BiS2 査読

    Kensei Terashima, Junki Sonoyama, Takanori Wakita, Masanori Sunagawa, Kanta Ono, Hiroshi Kumigashira, Takayuki Muro, Masanori Nagao, Satoshi Watauchi, Isao Tanaka, Hiroyuki Okazaki, Yoshihiko Takano, Osuke Miura, Yoshikazu Mizuguchi, Hidetomo Usui, Katsuhiro Suzuki, Kazuhiko Kuroki, Yuji Muraoka, Takayoshi Yokoya

    PHYSICAL REVIEW B   90 ( 22 )   220512(R)   2014年12月

     詳細を見る

    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 electronic structure of nearly optimally doped novel superconductor LaO1-xFxBiS2(x = 0.46) was investigated using angle-resolved photoemission spectroscopy (ARPES). We clearly observed band dispersions from 2 to 6 eV binding energy and near the Fermi level (E-F), which are well reproduced by first-principles calculations when the spin-orbit coupling is taken into account. The ARPES intensity map near E-F shows a squarelike distribution around the Gamma(Z) point in addition to electronlike Fermi-surface (FS) sheets around the X(R) point, indicating that FS of LaO0.54F0.46BiS2 is in close proximity to the theoretically predicted topological change.

    DOI: 10.1103/PhysRevB.90.220512

    Web of Science

    researchmap

  • Electronic Structures of CeM2Al10 (M = Fe, Ru, and Os) Studied by Soft X-ray Resonant and High-Resolution Photoemission Spectroscopies 査読

    Toshihiko Ishiga, Takanori Wakita, Rikiya Yoshida, Hiroyuki Okazaki, Koji Tsubota, Masanori Sunagawa, Kanta Uenaka, Kozo Okada, Hiroshi Kumigashira, Masaharu Oshima, Keisuke Yutani, Yuji Muro, Toshiro Takabatake, Yuji Muraoka, Takayoshi Yokoya

    JOURNAL OF THE PHYSICAL SOCIETY OF JAPAN   83 ( 9 )   094717   2014年9月

     詳細を見る

    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 performed a photoemission spectroscopy (PES) study of CeM2Al10 (M = Fe, Ru, and Os) to directly observe the electronic structure involved in the unusual magnetic ordering. Soft X-ray resonant (SXR) PES provides spectroscopic evidence of the hybridization between conduction and Ce 4f electrons (c-f hybridization) and the order of the hybridization strength (Ru < Os < Fe). High-resolution (HR) PES of CeRu2Al10 and CeOs2Al10, as compared with that of CeFe2Al10, identifies two structures that can be ascribed to structures induced by the c-f hybridization and the antiferromagnetic ordering, respectively. Although the c-f hybridization-induced structure is a depletion of the spectral intensity (pseudogap) around the Fermi level (E-F) with an energy scale of 20-30 meV, the structure related to the antiferromagnetic ordering is observed as a shoulder at approximately 10-11 meV within the pseudogap. The energies of the shoulder structures of CeRu2Al10 and CeOs2Al10 are approximately half of the optical gap (20 meV), indicating that E-F is located at the midpoint of the gap.

    DOI: 10.7566/JPSJ.83.094717

    Web of Science

    researchmap

  • Current-Induced Enhancement of Magnetic Anisotropy in Spin-Charge-Coupled Multiferroic YbFe2O4 査読

    Kenji Yoshii, Daiju Matsumura, Hiroyuki Saitoh, Takashi Kambe, Mamoru Fukunaga, Yuji Muraoka, Naoshi Ikeda, Shigeo Mori

    JOURNAL OF THE PHYSICAL SOCIETY OF JAPAN   83 ( 6 )   063708   2014年6月

     詳細を見る

    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 report the change in the magnetic properties of multiferroic YbFe2O4 caused by cooling in the presence of an electrical current. The magnetization measured after the cooling is similar to 10-20% smaller than that after cooling without a current. The current also affects the magnetic anisotropy below similar to 100 K; the magnetic coercivity is increased by similar to 10-20%. These phenomena may arise from the coexistence of ferromagnetic and antiferromagnetic domains or a disturbance in the formation of charge-ordered domains. From the viewpoint of application, the enhancement of anisotropy by an electrical current provides a method for stabilizing magnetization other than the well-known method of exchange bias.

    DOI: 10.7566/JPSJ.83.063708

    Web of Science

    researchmap

  • Persistent insulator-to-metal transition of a VO2 thin film induced by soft X-ray irradiation 査読

    Yuji Muraoka, Hiroki Nagao, Shinsuke Katayama, Takanori Wakita, Masaaki Hirai, Takayoshi Yokoya, Hiroshi Kumigashira, Masaharu Oshima

    JAPANESE JOURNAL OF APPLIED PHYSICS   53 ( 5 )   05FB09   2014年5月

     詳細を見る

    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 persistent soft-X-ray-induced insulator-to-metal transition at room temperature for VO2 thin films. Continuous soft X-ray irradiation renders the insulating electronic state metallic in the VO2 thin films, which has been found by photoemission spectroscopy measurement. The observed transition is irreversible and the metallic state persists when soft X-ray irradiation is stopped. The analysis of valence band spectra reveals that the density of states (DOS) of the V 3d band increases with irradiation time, while the DOS of the O 2p band decreases. We propose a simple model where the persistent insulator-to-metal transition is driven by oxygen desorption from VO2 thin films under soft X-ray irradiation. The present results will help in developing a new route for controlling the phase transition of VO2 by light. (C) 2014 The Japan Society of Applied Physics

    DOI: 10.7567/JJAP.53.05FB09

    Web of Science

    researchmap

  • Ultrafast photoinduced transition of an insulating VO2 thin film into a nonrutile metallic state 査読

    Rikiya Yoshida, Takashi Yamamoto, Yukiaki Ishida, Hiroki Nagao, Tsubasa Otsuka, Kuninari Saeki, Yuji Muraoka, Ritsuko Eguchi, Kyoko Ishizaka, Takayuki Kiss, Shuntaro Watanabe, Teruto Kanai, Jiro Itatani, Shik Shin

    PHYSICAL REVIEW B   89 ( 20 )   205114   2014年5月

     詳細を見る

    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  

    Using time-resolved photoemission spectroscopy, we have investigated the nonequilibrium electronic structures of a VO2 thin film upon photoexcitation. We employed the high-harmonic generation method, which was crucial in obtaining the results. Irradiation by a 170-fs optical pulse at a fluence above similar to 6 mJ/cm(2) rapidly converts the insulating VO2 thin film into a metallic state, and we show that the transition is accompanied by a spectral-weight redistribution over a 1-eV scale. This observation provides direct spectroscopic evidence of an ultrafast insulator-to-metal transition. The transient metallic state has a unique spectrum that deviates from the static spectrum of the rutile metal phase. We also observe an anomalous spreading of spectral weight up to similar to 0.4 eV above the Fermi level as soon as the transient metallic state emerges. The temporal evolution of the spectral weight near the Fermi level exhibits an ultrafast increase and a subsequent slower increase over similar to 3 ps. We suggest that a broadening mechanism related to the excitation of phonon modes is responsible for the spreading of the spectral weight and that the slower increase of the spectral weight is associated with the expansion of the metallic region after photoinduced nucleation. In addition, the initial nucleation of the metallic state appears to be spatially inhomogeneous even near the surface. The results of this study highlight the uniqueness of the nonequilibrium metallic state in comparison to the equilibrium rutile metallic state from an electronic-state perspective.

    DOI: 10.1103/PhysRevB.89.205114

    Web of Science

    researchmap

  • Characteristic two-dimensional Fermi surface topology of high-T-c iron-based superconductors 査読

    Masanori Sunagawa, Toshihiko Ishiga, Koji Tsubota, Taihei Jabuchi, Junki Sonoyama, Keita Iba, Kazutaka Kudo, Minoru Nohara, Kanta Ono, Hiroshi Kumigashira, Tomohiro Matsushita, Masashi Arita, Kenya Shimada, Hirofumi Namatame, Masaki Taniguchi, Takanori Wakita, Yuji Muraoka, Takayoshi Yokoya

    SCIENTIFIC REPORTS   4   4381   2014年3月

     詳細を見る

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

    Unconventional Cooper pairing originating from spin or orbital fluctuations has been proposed for iron-based superconductors. Such pairing may be enhanced by quasi-nesting of two-dimensional electron and hole-like Fermi surfaces (FS), which is considered an important ingredient for superconductivity at high critical temperatures (high-T-c). However, the dimensionality of the FS varies for hole and electron-doped systems, so the precise importance of this feature for high-T-c materials remains unclear. Here we demonstrate a phase of electron-doped CaFe2As2 (La and P co-doped CaFe2As2) with T-c = 45 K, which is the highest T-c found for the AEFe(2)As(2) bulk superconductors (122-type; AE = Alkaline Earth), possesses only cylindrical hole-and electron-like FSs. This result indicates that FS topology consisting only of two-dimensional sheets is characteristic of both hole-and electron-doped 122-type high-T-c superconductors.

    DOI: 10.1038/srep04381

    Web of Science

    researchmap

  • Soft X-ray Photoemission Study of New BiS2-Layered Superconductor LaO1-xFxBiS2 査読

    Shinsuke Nagira, Junki Sonoyama, Takanori Wakita, Masanori Sunagawa, Yudai Izumi, Takayuki Muro, Hiroshi Kumigashira, Masaharu Oshima, Keita Deguchi, Hiroyuki Okazaki, Yoshihiko Takano, Osuke Miura, Yoshikazu Mizuguchi, Katsuhiro Suzuki, Hidetomo Usui, Kazuhiko Kuroki, Kozo Okada, Yuji Muraoka, Takayoshi Yokoya

    JOURNAL OF THE PHYSICAL SOCIETY OF JAPAN   83 ( 3 )   033703   2014年3月

     詳細を見る

    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 use core level and valence band soft X-ray photoemission spectroscopy (SXPES) to investigate the electronic structure of new BiS2 layered superconductor LaO1-xFxBiS2. The core level spectra of doped samples show a new spectral feature on the lower binding energy side of the Bi 4 f main peak, which may be explained by core-hole screening with metallic states near the Fermi level (E-F). The experimental electronic structure and its x dependence (a higher binding energy shift of the valence band as well as appearance of new states near E-F having the dominant Bi 6p character) were found to be consistent with the predictions of band structure calculations in general. Noticeable deviation of the spectral shape of the states near EF from that of calculations might provide insight into interesting physical properties. This study provides the first experimental electronic structure of the new BiS2 layered superconductors.

    DOI: 10.7566/JPSJ.83.033703

    Web of Science

    researchmap

  • Evidence for metallic states in potassium-intercalated picene film on graphite 査読

    Hiroyuki Okazaki, Taihei Jabuchi, Takanori Wakita, Takashi Kato, Yuji Muraoka, Takayoshi Yokoya

    PHYSICAL REVIEW B   88 ( 24 )   245414   2013年12月

     詳細を見る

    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  

    We report the results of photoemission spectroscopy on the potassium concentration (x) dependence of K-x picene films on graphite. The results show a systematic shift of a whole valence band and the appearance of a clear Fermi edge for a certain value of x, with additional structures at higher binding energies. Observed spectral evolutions are reminiscent to those of doped C-60, implying that the K-x picene film has multiple phases depending on the K concentration. Appearance of a clear Fermi edge, in contrast to multilayer K-x picene films on Au, SiO2, and Ag(111) substrates, where no clear Fermi edges are observed, suggests that the emergence of the metallic states for K-x picene films depends on the specific molecular orientations in the films on different substrates.

    DOI: 10.1103/PhysRevB.88.245414

    Web of Science

    researchmap

  • Collapsed Tetragonal Phase Transition of Ca(Fe1-xRhx)(2)As-2 Studied by Photoemission Spectroscopy 査読

    Koji Tsubota, Takanori Wakita, Hiroki Nagao, Chiaki Hiramatsu, Toshihiko Ishiga, Masanori Sunagawa, Kanta Ono, Hiroshi Kumigashira, Masataka Danura, Kazutaka Kudo, Minoru Nohara, Yuji Muraoka, Takayoshi Yokoya

    JOURNAL OF THE PHYSICAL SOCIETY OF JAPAN   82 ( 7 )   073705   2013年7月

     詳細を見る

    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 investigated the changes in the band structure and core-level energy of Ca(Fe1-xRhx)(2)As-2 across the tetragonal-collapsed tetragonal (T-cT) phase transition using photoemission spectroscopy. Angle-resolved photoemission spectroscopy clearly demonstrates that, at the Gamma point in the Brillouin zone, a hole-like band that crosses the Fermi level in the T phase lowers its energy position and is completely filled in the cT phase. This indicates the disappearance of a hole-like Fermi surface around the zone center in the cT phase, which gives rise to the extinction of nesting. The relationship of the present results with the results of previous transport and magnetic studies is discussed. The temperature dependences of the As 3d and Ca 2p core levels show energy shifts toward higher and lower binding energies, respectively. These data constitute the first direct experimental results on electronic structure and chemical states across the T-cT transition.

    DOI: 10.7566/JPSJ.82.073705

    Web of Science

    researchmap

  • Spinodal Decomposition in the TiO2-VO2 System 査読

    Zenji Hiroi, Hiroaki Hayamizu, Toni Yoshida, Yuji Muraoka, Yoshihiko Okamoto, Jun-ichi Yamaura, Yutaka Ueda

    CHEMISTRY OF MATERIALS   25 ( 11 )   2202 - 2210   2013年6月

     詳細を見る

    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  

    Spinodal decomposition is a ubiquitous phenomenon leading to phase separation from a uniform solution. We show that a spinodal decomposition occurs in a unique combination of two rutile compounds of TiO2 and VO2, which are chemically and physically distinguished from each other: TiO2 is a wide-gap insulator with photocatalytic activities, and VO2 is assumed to be a strongly correlated electron system which exhibits a dramatic metal insulator transition at 342 K. The spinodal decomposition takes place below 830 K at a critical composition of 34 mol % Ti, generates a unidirectional composition modulation along the c axis with a wavelength of approximately 6 nm, and finally results in the formation of self-assembled lamella structures made up of Ti-rich and V-rich layers stacked alternately with 30-50 nm wavelengths. A metal insulator transition is not observed in quenched solid solutions with intermediate compositions but emerges in the thin V-rich layers as the result of phase separation. Interestingly, the metal insulator transition remains as sharp as in pure VO2 even in such thin layers and takes place at significantly reduced temperatures of 310-340 K, which is probably due to a large misfit strain induced by lattice matching at the coherent interface.

    DOI: 10.1021/cm400236p

    Web of Science

    researchmap

  • Translational Symmetry Breaking and Gapping of Heavy-Quasiparticle Pocket in URu 2 Si 2 査読

    Rikiya Yoshida, Koji Tsubota, Toshihiko Ishiga, Masanori Sunagawa, Jyunki Sonoyama, Dai Aoki, Jacques Flouquet, Takanori Wakita, Yuji Muraoka, Takayoshi Yokoya

    Scientific Reports   3   2750   2013年

     詳細を見る

    記述言語:英語   掲載種別:研究論文(学術雑誌)  

    URu 2 Si 2 is a uranium compound that exhibits a so-called 'hidden-order' transition at ∼17.5â€...K. However, the order parameter of this second-order transition as well as many of its microscopic properties remain unclarified despite considerable research. One of the key questions in this regard concerns the type of spontaneous symmetry breaking occurring at the transition
    although rotational symmetry breaking has been detected, it is not clear whether another type of symmetry breaking also occurs. Another key question concerns the property of Fermi-surface gapping in the momentum space. Here we address these key questions by a momentum-dependent observation of electronic states at the transition employing ultrahigh-resolution three-dimensional angle-resolved photoemission spectroscopy. Our results provide compelling evidence of the spontaneous breaking of the lattice's translational symmetry and particle-hole asymmetric gapping of a heavy quasiparticle pocket at the transition.

    DOI: 10.1038/srep02750

    Scopus

    researchmap

  • Te concentration dependent photoemission and inverse-photoemission study of FeSe1-xTex 査読

    Takayoshi Yokoya, Rikiya Yoshida, Yuki Utsumi, Koji Tsubota, Hiroyuki Okazaki, Takanori Wakita, Yoshikazu Mizuguchi, Yoshihiko Takano, Takayuki Muro, Yukako Kato, Hiroshi Kumigashira, Masaharu Oshima, Hisatomo Harima, Yoshihiro Aiura, Hitoshi Sato, Akihiro Ino, Hirofumi Namatame, Masaki Taniguchi, Masaaki Hirai, Yuji Muraoka

    SCIENCE AND TECHNOLOGY OF ADVANCED MATERIALS   13 ( 5 )   054403   2012年10月

     詳細を見る

    記述言語:英語   掲載種別:研究論文(学術雑誌)   出版者・発行元:NATL INST MATERIALS SCIENCE  

    We have characterized the electronic structure of FeSe1-xTex for various x values using soft x-ray photoemission spectroscopy (SXPES), high-resolution photoemission spectroscopy (HRPES) and inverse photoemission spectroscopy (IPES). The SXPES valence band spectral shape shows that the 2 eV feature in FeSe, which was ascribed to the lower Hubbard band in previous theoretical studies, becomes less prominent with increasing x. HRPES exhibits systematic x dependence of the structure near the Fermi level (E-F): its splitting near EF and filling of the pseudogap in FeSe. IPES shows two features, near E-F and approximately 6 eV above E-F; the former may be related to the Fe 3d states hybridized with chalcogenide p states, while the latter may consist of plane-wave-like and Se d components. In the incident electron energy dependence of IPES, the density of states near E-F for FeSe and FeTe has the Fano lineshape characteristic of resonant behavior. These compounds exhibit different resonance profiles, which may reflect the differences in their electronic structures. By combining the PES and IPES data the on-site Coulomb energy was estimated at 3.5 eV for FeSe.

    DOI: 10.1088/1468-6996/13/5/054403

    Web of Science

    researchmap

  • Comparative photoemission studies on the superconducting gap of the filled skutterudite superconductors LaPt4Ge12 and PrPt4Ge12 査読

    Yoshiaki Nakamura, Hiroyuki Okazaki, Rikiya Yoshida, Takanori Wakita, Hiroyuki Takeya, Kazuto Hirata, Masaaki Hirai, Yuji Muraoka, Takayoshi Yokoya

    PHYSICAL REVIEW B   86 ( 1 )   014521   2012年7月

     詳細を見る

    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  

    We performed a comparative study of the superconducting gap in the new filled skutterudite superconductors LaPt4Ge12 and PrPt4Ge12 using high-resolution photoemission spectroscopy. We succeeded in observing spectral changes across T-c that reflect the opening of the superconducting gap in both compounds and also in observing a noticeable difference in their respective superconducting spectral shapes near the Fermi level, pointing toward a more complex superconducting gap structure in PrPt4Ge12. In addition, we found that the two-gap model is more suitable for describing the superconducting-state spectrum of PrPt4Ge12 than the single-isotropic-gap and single-anisotropic-gap models, which suggests an explanation that multiband effects may possibly induce the anomalous superconducting properties of PrPt4Ge12.

    DOI: 10.1103/PhysRevB.86.014521

    Web of Science

    researchmap

  • Observation of two fine structures related to the hidden order in the spectral functions of URu 2Si 2 査読

    Rikiya Yoshida, Masaki Fukui, Yoshinori Haga, Etsuji Yamamoto, Yoshichika Onuki, Mario Okawa, Walid Malaeb, Shik Shin, Yuji Muraoka, Takayoshi Yokoya

    Physical Review B - Condensed Matter and Materials Physics   85 ( 24 )   241102   2012年6月

     詳細を見る

    記述言語:英語   掲載種別:研究論文(学術雑誌)  

    We studied the spectral functions of URu 2Si 2 in the hidden-order state by means of ultrahigh-resolution angle-resolved photoemission spectroscopy. High signal-to-noise ratio data uncover the existence of two anomalous fine structures, namely a "splitting" in the previously reported narrow dispersive band, and a small, dispersionless "satellite" structure. These structures can be explained by neither ordinary bands nor the development of a hybridization of two states
    thus our observation should evoke the consideration of complicated many-body effects. As a possible origin, we suggest the existence of electron-mode coupling in the ordered state. © 2012 American Physical Society.

    DOI: 10.1103/PhysRevB.85.241102

    Scopus

    researchmap

  • Observation of two fine structures related to the hidden order in the spectral functions of URu2Si2 査読

    Rikiya Yoshida, Masaki Fukui, Yoshinori Haga, Etsuji Yamamoto, Yoshichika Onuki, Mario Okawa, Walid Malaeb, Shik Shin, Yuji Muraoka, Takayoshi Yokoya

    PHYSICAL REVIEW B   85 ( 24 )   241102(R)   2012年6月

     詳細を見る

    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  

    We studied the spectral functions of URu2Si2 in the hidden-order state by means of ultrahigh-resolution angle-resolved photoemission spectroscopy. High signal-to-noise ratio data uncover the existence of two anomalous fine structures, namely a "splitting" in the previously reported narrow dispersive band, and a small, dispersionless "satellite" structure. These structures can be explained by neither ordinary bands nor the development of a hybridization of two states; thus our observation should evoke the consideration of complicated many-body effects. As a possible origin, we suggest the existence of electron-mode coupling in the ordered state.

    DOI: 10.1103/PhysRevB.85.241102

    Web of Science

    researchmap

  • Effectiveness of a hot-filament chemical vapor deposition method for preparation of a boron-doped superconducting diamond film with higher superconducting transition temperature 査読

    T. Doi, T. Fukaishi, C. Hiramatsu, T. Wakita, M. Hirai, Y. Muraoka, T. Yokoya, Y. Kato, Y. Izumi, T. Muro, Y. Tamenori

    DIAMOND AND RELATED MATERIALS   25   5 - 7   2012年5月

     詳細を見る

    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 SA  

    We have investigated the effectiveness of a hot-filament chemical vapor deposition (HFCVD) method for preparation of a boron-doped superconducting diamond film with higher superconducting transition temperature (T-c). A boron-doped superconducting diamond film has been fabricated on a diamond (111) substrate using the HFCVD method, and studied by means of scanning electron microscopy. X-ray photoelectron spectroscopy (XPS), and resistivity. The film consists of grains with an average size of 200 mm. Analyses of valence band and boron Is core-level XPS spectra indicate the formation of boron-doped diamond film on the substrate. From the resistivity measurements, the film is found to be a superconductor with onset T-c of 7.1 K. Carrier concentration determined by Hall conductivity measurements is 1.1 x 10(21) cm(-3). The value of T-c is higher compared with that in boron-doped superconducting diamond films prepared by a commonly used microwave plasma-assisted chemical vapor deposition (MPCVD) method, at the same carrier concentration [A. Kawano et al., Phys. Rev. B 82 (2010) 085318]. The result of higher T-c in the film by the HFCVD method is consistent with the previous one [Wang et al., Diamond Relat. Mater. 15 (2006) 659], suggesting that the HFCVD method is effective for preparation of boron-doped superconducting diamond films showing higher T-c. (C) 2012 Elsevier B.V. All rights reserved.

    DOI: 10.1016/j.diamond.2012.02.008

    Web of Science

    researchmap

  • Photoemission Study of Rh17S15 Superconductor 査読

    Masaki Fukui, Rikiya Yoshida, Yoshiaki Nakamura, Yukako Kato, Takayuki Muro, Rikio Settai, Yoshichika Onuki, Hisatomo Harima, Masaaki Hirai, Yuji Muraoka, Takayoshi Yokoya

    JOURNAL OF THE PHYSICAL SOCIETY OF JAPAN   80   SA111   2011年7月

     詳細を見る

    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 investigated the electronic structures of Rh17S15 by using soft x-ray photoemission spectroscopy and first principle band structure calculations. While S 2p core level spectra are explained by symmetric components, Rh 3d core level exhibits asymmetric line shape, suggesting a dominant Rh 4d character at the states near the Fermi level. The binding energy of Rh 4d in Rh17S15 is similar to the one in Rh metal, and this observation implies metallic Rh-Rh bonding. Many features in experimental valence spectra are reasonably described by the calculations, indicating that one particle approximation is a good starting point to understand the electronic properties of Rh17S15. The comparison between the experiment and the calculation suggests that Rh 4d character at the states near the Fermi level is essential for the correlated superconductivity in Rh17S15. However, some deviation between the experiment and the calculation as well as a finite mass enhancement are found, indicating some corrections on the treatment of electron-phonon coupling and/or electron correlations are necessary.

    DOI: 10.1143/JPSJS.80SA.SA111

    Web of Science

    researchmap

  • Photoemission study of electronic structure evolution across the metal-insulator transition of heavily B-doped diamond 査読

    H. Okazaki, T. Arakane, K. Sugawara, T. Sato, T. Takahashi, T. Wakita, M. Hirai, Y. Muraoka, Y. Takano, S. Ishii, S. Iriyama, H. Kawarada, T. Yokoya

    JOURNAL OF PHYSICS AND CHEMISTRY OF SOLIDS   72 ( 5 )   582 - 584   2011年5月

     詳細を見る

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

    We studied the electronic structure evolution of heavily B-doped diamond films across the metal-insulator transition (MIT) using ultraviolet photoemission spectroscopy (UPS). From high-temperature UPS, through which electronic states near the Fermi level (E(F)) up to similar to 5k(B)T can be observed (k(B) is the Boltzmann constant and T the temperature), we observed the carrier concentration dependence of spectral shapes near E(F). Using another carrier concentration dependent UPS, we found that the change in energy position of sp-band of the diamond valence band, which corresponds to the shift of E(F), can be explained by the degenerate semiconductor model, indicating that the diamond valence band is responsible for the metallic states for samples with concentrations above MIT. We discuss a possible electronic structure evolution across MIT. (C) 2010 Elsevier Ltd. All rights reserved.

    DOI: 10.1016/j.jpcs.2010.10.052

    Web of Science

    researchmap

  • Ultrahigh-resolution laser photoemission study of URu2Si2 across the hidden-order transition 査読

    Rikiya Yoshida, Yoshiaki Nakamura, Masaki Fukui, Yoshinori Haga, Etsuji Yamamoto, Yoshichika Onuki, Mario Okawa, Shik Shin, Masaaki Hirai, Yuji Muraoka, Takayoshi Yokoya

    JOURNAL OF PHYSICS AND CHEMISTRY OF SOLIDS   72 ( 5 )   580 - 581   2011年5月

     詳細を見る

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

    We have studied the electronic structures of URu2Si2 employing ultrahigh-resolution laser angle-resolved photoemission spectroscopy. The change of photoemission spectra is investigated across the hidden-order transition, and the emergence of a narrow band is clearly observed near the Fermi level for both (pi,0) and (pi,pi) directions. In addition, it is shown that tuning of light's polarization allows the signal of a hole-like dispersive feature to enhance. These observations prove that laser angle-resolved photoemission spectroscopy is an effective tool for studying the evolution of electronic structures across the hidden-order transition in URu2Si2. (C) 2010 Elsevier Ltd. All rights reserved.

    DOI: 10.1016/j.jpcs.2010.10.048

    Web of Science

    researchmap

  • Multiple phosphorus chemical sites in heavily phosphorus-doped diamond 査読

    Hiroyuki Okazaki, Rikiya Yoshida, Takayuki Muro, Tetsuya Nakamura, Takanori Wakita, Yuji Muraoka, Masaaki Hirai, Hiromitsu Kato, Satoshi Yamasaki, Yoshihiko Takano, Satoshi Ishii, Tamio Oguchi, Takayoshi Yokoya

    APPLIED PHYSICS LETTERS   98 ( 8 )   082107   2011年2月

     詳細を見る

    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 INST PHYSICS  

    We have performed high-resolution core level photoemission spectroscopy on a heavily phosphorus (P)-doped diamond film in order to elucidate the chemical sites of doped-phosphorus atoms in diamond. P 2p core level study shows two bulk components, providing spectroscopic evidence for multiple chemical sites of doped-phosphorus atoms. This indicates that only a part of doped-phosphorus atoms contribute to the formation of carriers. From a comparison with band calculations, possible origins for the chemical sites are discussed. (C) 2011 American Institute of Physics. [doi: 10.1063/1.3554699]

    DOI: 10.1063/1.3554699

    Web of Science

    researchmap

  • Spectroscopic evidence of the formation of (V,Ti)O-2 solid solution in VO2 thinner films grown on TiO2(001) substrates 査読

    Y. Muraoka, K. Saeki, R. Eguchi, T. Wakita, M. Hirai, T. Yokoya, S. Shin

    JOURNAL OF APPLIED PHYSICS   109 ( 4 )   043702   2011年2月

     詳細を見る

    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 INST PHYSICS  

    We have prepared VO2 thin films epitaxially grown on TiO2(001) substrates with thickness systematically varied from 2.5 to 13 nm using a pulsed laser deposition method, and studied the transport property and electronic states of the films by means of resistivity and in situ synchrotron photoemission spectroscopy (SRPES). In resistivity measurements, the 13-nm-thick film exhibits a metal-insulator transition at around 290 K on cooling with change of three orders of magnitudes in resistivity. As the film thickness decreases, the metal-insulator transition broadens and the transition temperature increases. Below 4 nm, the films do not show the transition and become insulators. In situ SRPES measurements of near the Fermi level valence band find that the electronic state of the 2.5-nm-thick film is different than that of the temperature-induced insulator phase of VO2 itself although these two states are insulating. Ti 2p core-level photoemission measurements reveal that Ti ions exist near the interface between the films and TiO2 substrates, with a chemical state similar to that in (V,Ti)O-2 solid solution. These results indicate that insulating (V,Ti)O-2 solid solution is formed in the thinner films. We propose a simple growth model of a VO2 thin film on a TiO2(001) substrate. Near the interface, insulating (V,Ti) O-2 solid solution is formed due to the diffusion of Ti ions from the TiO2 substrate into the VO2 film. The concentration of Ti in (V,Ti) O-2 is relatively high near the interface and decreases toward the surface of the film. Beyond a certain film thickness (about 7 nm in the case of the present 13-nm-thick film), the VO2 thin film without any Ti ions starts to grow. Our work suggests that developing a technique for preparing the sharp interface between the VO2 thin films and TiO2 substrates is a key issue to study the physical property of an ultrathin film of "pure" VO2, especially to examine the presence of the novel electronic state called a semi-Dirac point phase predicted by calculations. (c) 2011 American Institute of Physics. [doi:10.1063/1.3549835]

    DOI: 10.1063/1.3549835

    Web of Science

    researchmap

  • Synthesis and physical properties of the hollandite-type titanium oxide KxTi8O16 査読

    Yuji Muraoka, Kengo Noami, Takanori Wakita, Masaaki Hirai, Takayoshi Yokoya, Yukako Kayo, Takayuki Muro, Yusuke Tamenori

    PHYSICA STATUS SOLIDI C: CURRENT TOPICS IN SOLID STATE PHYSICS, VOL 8, NO 2   8 ( 2 )   555 - 557   2011年

     詳細を見る

    記述言語:英語   掲載種別:研究論文(国際会議プロシーディングス)   出版者・発行元:WILEY-V C H VERLAG GMBH  

    Polycrystalline sample of hollandite-type titanium oxide KxTi8O16 has been prepared and studied by magnetization and X-ray photoelectron spectroscopy (XPS). Room temperature ferromagnetic behaviour is observed in the magnetic hysteresis measurements. XPS measurements of the Ti 2p(3/2) core-level finds that the titanium ions take a mixed valence of Ti4+ and Ti3+. In addition, the valence band spectrum reveals that the 3d electrons tend to localize on Ti3+ ions in the hollandite-type TiO2 lattice. Also, analysis of the valence band spectrum shows that the prepared sample is a wide-gap oxide with a band gap of 3.6 eV. These results indicate that the present hollandite-type KxTi8O16 sample can be classified as a TiO2-based wide-gap semiconductor with Curie temperature above room temperature. (C) 2010 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim

    DOI: 10.1002/pssc.201000383

    Web of Science

    researchmap

  • Electronic structure of U(Ru1-xRhx)(2)Si-2 studied by laser angle-resolved photoemission spectroscopy 査読

    R. Yoshida, Y. Nakamura, M. Fukui, Y. Haga, E. Yamamoto, Y. Onuki, M. Okawa, S. Shin, M. Hirai, Y. Muraoka, T. Yokoya

    INTERNATIONAL CONFERENCE ON STRONGLY CORRELATED ELECTRON SYSTEMS (SCES 2010)   273   012021   2011年

     詳細を見る

    記述言語:英語   掲載種別:研究論文(国際会議プロシーディングス)   出版者・発行元:IOP PUBLISHING LTD  

    We have studied electronic structures of U(Ru1-xRhx)(2)Si-2 employing ultrahigh-resolution laser angle-resolved photoemission spectroscopy to understand the effect of Rh substitution. A hole-like dispersive feature, which presumably has Rh d-band character, was observed in U(Ru1-xRhx)(2)Si-2 for both x = 0 and x = 0.03. However, although a heavy quasiparticle band appears in the hidden-order state of URu2Si2 (x = 0), it was not observed for x = 0.03 over the temperature range studied. In addition, it was found that energy-distribution curves at the Fermi vector of the hole-like band for x = 0.03 behave similarly to the Fermi-Dirac function. We also present the mapping of Fermi surfaces formed by the hole-like band, which stay nearly unaffected by Rh substitution.

    DOI: 10.1088/1742-6596/273/1/012021

    Web of Science

    researchmap

  • Electronic Structure of the Novel Filled Skutterudite PrPt4Ge12 Superconductor 査読

    Yoshiaki Nakamura, Hiroyuki Okazaki, Rikiya Yoshida, Takanori Wakita, Masaaki Hirai, Yuji Muraka, Hiroyuki Takeya, Kazuto Hirata, Hiroshi Kumigashira, Masaharu Oshima, Takayoshi Yokoya

    JOURNAL OF THE PHYSICAL SOCIETY OF JAPAN   79 ( 12 )   124701   2010年12月

     詳細を見る

    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 performed soft x-ray photoemission spectroscopy (SXPES) and resonant photoemission spectroscopy (RPES) of the filled skutterudite superconductor PrPt4Ge12 in order to study the electronic structure of valence band and the character of Pr 4f. SXPES of PrPt4Ge12 measured with 1200 eV photon energy, where spectral contribution of Pr 4f is negligible, was found nearly identical with that of LaPt4Ge12, indicating similarity of Pt-Ge derived electronic states of the two compounds. Good correspondence with band calculations allows us to ascribe the dominant Ge 4p character of the density of states at the Fermi level (E-F). Pr 3d -> 4f RPES shows that, although Pr 4f electrons in PrPt4Ge12 are not as strongly hybridized with conduction electrons near E-F as in PrFe4P12, there are finite Pr 4f contribution to the states near E-F in PrPt4Ge12. These PES results give the information of fundamental electronic structure for understanding the physical properties of the novel filled skutterudite superconductor PrPt4Ge12

    DOI: 10.1143/JPSJ.79.124701

    Web of Science

    researchmap

  • Photoemission study of Ca-intercalated graphite superconductor CaC6 査読

    Hiroyuki Okazaki, Rikiya Yoshida, Keisuke Iwai, Kengo Noami, Takayuki Muro, Tetsuya Nakamura, Takanori Wakita, Yuji Muraoka, Masaaki Hirai, Fumiaki Tomioka, Yoshihiko Takano, Asami Takenaka, Masahiro Toyoda, Tamio Oguch, Takayoshi Yokoya

    PHYSICA C-SUPERCONDUCTIVITY AND ITS APPLICATIONS   470   S637 - S638   2010年12月

     詳細を見る

    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  

    In this work, we have performed resonant photoemission studies of Ca-intercalated graphite superconductor CaC6. Using photon energy of the Ca 2p-3d threshold, the photoemission intensity of the peak at Fermi energy (E-F) is resonantly enhanced. This result provides spectroscopic evidence for the existence of Ca 3d states at E-F, and strongly supports that Ca 3d state plays a crucial role for the superconductivity of this material with relatively high T-c. (C) 2009 Elsevier B.V. All rights reserved.

    DOI: 10.1016/j.physc.2009.10.039

    Web of Science

    researchmap

  • Angle-resolved photoemission study of Si electronic structure: Boron concentration dependence 査読

    Takanori Wakita, Hiroyuki Okazaki, Yoshihiko Takano, Masaaki Hirai, Yuji Muraoka, Takayoshi Yokoya

    PHYSICA C-SUPERCONDUCTIVITY AND ITS APPLICATIONS   470   S641 - S643   2010年12月

     詳細を見る

    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 boron concentration dependence of the Si electronic structure of Si(1 00)2 x 1 surfaces were investigated by angle-resolved photoemission spectroscopy (ARPES). The ARPES spectra exhibit rigid shifts toward lower binding energy as the boron concentration increases. The band dispersion was obtained from fitting procedure, and it is found that the top of the valence band does not exceed the Fermi level even with a boron concentration 35 times larger than the critical concentration of the metal-insulator transition. (C) 2009 Elsevier B.V. All rights reserved.

    DOI: 10.1016/j.physc.2009.11.028

    Web of Science

    researchmap

  • Analysis on photoemission spectrum of superconducting FeSe 査読

    Rikiya Yoshida, Takanori Wakita, Hiroyuki Okazaki, Yoshikazu Mizuguchi, Shunsuke Tsuda, Yoshihiko Takano, Hiroyuki Takeya, Kazuto Hirata, Yukako Kato, Takayuki Muro, Mario Okawa, Kyoko Ishizaka, Shik Shin, Hisatomo Harima, Masaaki Hirai, Yuji Muraoka, Takayoshi Yokoya

    PHYSICA C-SUPERCONDUCTIVITY AND ITS APPLICATIONS   470   S389 - S390   2010年12月

     詳細を見る

    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  

    In this paper, we present the result of soft X-ray photoemission spectroscopy and its comparison with the density functional calculation. Although local density approximation seems to be a good starting point for describing the electronic structure of FeSe, the simulated spectrum poorly reproduced the structure around E-B = 2 eV. This result suggests the necessity of theoretical treatment beyond local density approximation. (C) 2009 Elsevier B.V. All rights reserved.

    DOI: 10.1016/j.physc.2009.11.172

    Web of Science

    researchmap

  • Signature of hidden order and evidence for periodicity modification in URu2Si2 査読

    Rikiya Yoshida, Yoshiaki Nakamura, Masaki Fukui, Yoshinori Haga, Etsuji Yamamoto, Yoshichika Onuki, Mario Okawa, Shik Shin, Masaaki Hirai, Yuji Muraoka, Takayoshi Yokoya

    PHYSICAL REVIEW B   82 ( 20 )   205108   2010年11月

     詳細を見る

    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 detail of electronic structures near the Fermi level in URu2Si2 has been investigated employing state-of-art laser angle-resolved photoemission spectroscopy. The observation of a narrow dispersive band near the Fermi level in the ordered state as well as its absence in a Rh-substituted sample strongly suggest that the emergence of the narrow band is a clear signature of the hidden-order transition. The temperature dependence of the narrow band, which appears at the onset of the hidden-order transition, invokes the occurrence of periodicity modification in the ordered state, which is shown for the first time by any spectroscopic probe. We compare our data to other previous studies and discuss possible implications.

    DOI: 10.1103/PhysRevB.82.205108

    Web of Science

    researchmap

  • Electronic structure of pristine and K-doped solid picene: Nonrigid band change and its implication for electron-intramolecular-vibration interaction 査読

    H. Okazaki, T. Wakita, T. Muro, Y. Kaji, X. Lee, H. Mitamura, N. Kawasaki, Y. Kubozono, Y. Yamanari, T. Kambe, T. Kato, M. Hirai, Y. Muraoka, T. Yokoya

    PHYSICAL REVIEW B   82 ( 19 )   195114   2010年11月

     詳細を見る

    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  

    We use photoemission spectroscopy to study electronic structures of pristine and K-doped solid picene. The valence band spectrum of pristine picene consists of three main features with no state at the Fermi level (E(F)) while that of K-doped picene has three structures similar to those of pristine picene with new states near E(F), consistent with the semiconductor-metal transition. The K-induced change cannot be explained with a simple rigid-band model of pristine picene but can be interpreted by molecular-orbital calculations considering electron-intramolecular-vibration interaction. Excellent agreement of the K-doped spectrum with the calculations points to importance of electron-intramolecular-vibration interaction in K-doped picene.

    DOI: 10.1103/PhysRevB.82.195114

    Web of Science

    researchmap

  • Bulk and surface physical properties of a CrO(2) thin film prepared from a Cr(8)O(21) precursor 査読

    K. Iwai, Y. Muraoka, T. Wakita, M. Hirai, T. Yokoya, Y. Kato, T. Muro, Y. Tamenori

    JOURNAL OF APPLIED PHYSICS   108 ( 4 )   043916   2010年8月

     詳細を見る

    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 INST PHYSICS  

    We have prepared a CrO(2) thin film by chemical vapor deposition from a Cr(8)O(21) precursor and studied the bulk and surface physical properties. The CrO(2) thin film is grown on a TiO(2) (100) substrate by heating of a Cr(8)O(21) precursor and TiO(2) (100) substrate together in a sealed quartz tube. The prepared film is found from x-ray diffraction analysis to be an (100)-oriented single phase. The magnetization and resistivity measurements indicate that the film is a ferromagnetic metal with a Curie temperature of about 400 K. Cr 3s core-level and valence band photoelectron spectroscopy spectra reveal the presence of a metallic CrO(2) in the surface region of the film. Our work indicates that preparation from a Cr(8)O(21) precursor is promising for obtaining a CrO(2) thin film with the metallic surface. (C) 2010 American Institute of Physics. [doi: 10.1063/1.3471811]

    DOI: 10.1063/1.3471811

    Web of Science

    researchmap

  • Angle-resolved photoemission spectroscopy for VO2 thin films grown on TiO2 (001) substrates 査読

    Y. Muraoka, K. Saeki, Y. Yao, T. Wakita, M. Hirai, T. Yokoya, R. Eguchi, S. Shin

    JOURNAL OF ELECTRON SPECTROSCOPY AND RELATED PHENOMENA   181 ( 2-3 )   249 - 251   2010年8月

     詳細を見る

    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 present the results of angle-resolved photoemission spectroscopy (ARPES) measurements of metallic VO2 thin films. The VO2 thin films have been grown on TiO2 (0 0 1) single crystal substrates using pulsed laser deposition. The films exhibit a first-order metal-insulator transition (MIT) at 305K. In the ARPES spectra of the metallic phase for the films, the O 2p band shows highly dispersive feature in the binding energy range of 3-8 eV along the Gamma-Z direction. The periodicity of the dispersive band is found to be 2.2 A(-1) which is almost identical with the periodicity expected from the c-axis length of the VO2 thin films. The overall feature of the experimental band structure is similar to the band structure calculations. supporting that we have succeeded in observing the dispersive band of the O 2p state in the metallic VO2 thin film. The present work indicates that the ARPES measurements using epitaxial thin films are promising for determining the band structure of VO2. (C) 2010 Elsevier B.V. All rights reserved.

    DOI: 10.1016/j.elspec.2010.02.003

    Web of Science

    researchmap

  • Room temperature ferromagnetic behavior in the hollandite-type titanium oxide 査読

    K. Noami, Y. Muraoka, T. Wakita, M. Hirai, Y. Kato, T. Muro, Y. Tamenori, T. Yokoya

    JOURNAL OF APPLIED PHYSICS   107 ( 7 )   073910   2010年4月

     詳細を見る

    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 INST PHYSICS  

    A hollandite-type K(x)Ti(8)O(16) polycrystalline sample has been prepared and studied by magnetization, resistivity and x-ray photoelectron spectroscopy (XPS). Room temperature ferromagnetic behavior is observed in the magnetic hysteresis measurement. The sample shows a semiconductive temperature dependence in the resistivity measurement. Analysis of the Ti 2p(3/2) core-level XPS spectrum indicates that the titanium ions have a mixed valence of Ti(4+) and Ti(3+). In addition, the valence band spectrum reveals that the 3d electrons tend to localize on Ti(3+) ions in the hollandite-type TiO(2) lattice. Also, analysis of the valence band spectrum shows that the prepared sample is a wide-gap oxide with a band gap of 3.6 eV. These results indicate that the present hollandite-type K(x)Ti(8)O(16) sample can be classified as a TiO(2)-based wide-gap semiconductor with Curie temperature above room temperature. Room temperature ferromagnetism (RTFM) decreases in the sample prepared under a strong reducing gas atmosphere, accompanied with the decrease in the resistivity. The results imply that the localized 3d electrons are responsible for the RTFM of the K(x)Ti(8)O(16) sample. (C) 2010 American Institute of Physics. [doi: 10.1063/1.3369500]

    DOI: 10.1063/1.3369500

    Web of Science

    researchmap

  • Study of electronic states for V thin films deposited on 6H-SiC substrates by soft X-ray emission spectroscopy 査読

    M. Hirai, H. Okazaki, R. Yoshida, M. Tajima, K. Saeki, Y. Muraoka, T. Yokoya

    APPLIED SURFACE SCIENCE   256 ( 4 )   948 - 949   2009年11月

     詳細を見る

    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  

    Silicon carbide (SiC) is a candidate material for electronic devices to operate upon crucial environment. Electronic states of silicides and/or carbide/graphite formed in metal/SiC contact system is fundamentally important from the view point of device performance.
    We study interface electronic structure of vanadium (V) thin-film deposited on 6H-SiC(0 0 0 1) Si-face by using a soft X-ray emission spectroscopy (SXES). For specimens of V(38 nm)/6H-SiC (substrate) contact systems annealed at 850 degrees C, the Si L(2,3) emission spectra indicate different shapes and peak energies from the substrate. The product of materials such as silicides and/or ternary materials is suggested. Similarly, the C K alpha emission spectra show the shape and peak energy characteristic of vanadium carbide including substrate 6H-SiC signal. (C) 2009 Elsevier B.V. All rights reserved.

    DOI: 10.1016/j.apsusc.2009.05.120

    Web of Science

    researchmap

  • Band dispersion near the Fermi level for VO2 thin films grown on TiO2 (001) substrates 査読

    K. Saeki, T. Wakita, Y. Muraoka, M. Hirai, T. Yokoya, R. Eguchi, S. Shin

    PHYSICAL REVIEW B   80 ( 12 )   125406   2009年9月

     詳細を見る

    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  

    We have performed angle-resolved photoemission spectroscopy (ARPES) measurements of VO2 using epitaxial thin films and observed the band dispersion near the Fermi level (E-F) for this compound. The VO2 thin films have been grown on TiO2 (001) single-crystal substrates using pulsed laser deposition. The films exhibit a first-order metal-insulator transition (MIT) at 305 K. In the ARPES spectra of the metallic phase for the films, the O 2p band shows highly dispersive features in the binding-energy range of 3-8 eV along the Gamma-Z direction. Also, the V 3d state shows two dispersive bands around the Gamma point near E-F, indicative of two electron pockets centered at the Gamma point. Both electron pockets have an occupied bandwidth of about 0.4 eV. Assuming the parabolic energy bands around the Gamma point, the effective-mass ratios of the two electron pockets are estimated to be about 0.2 and 1. The present work indicates that the ARPES measurements using epitaxial thin films are promising for determining the band structure of VO2 and thus would play a crucial role to elucidate the mechanism of the MIT in VO2.

    DOI: 10.1103/PhysRevB.80.125406

    Web of Science

    researchmap

  • The electronic structure of Ca-intercalated superconducting graphite CaC6 査読

    H. Okazaki, R. Yoshida, K. Iwai, K. Noami, T. Muro, T. Nakamura, T. Wakita, Y. Muraoka, M. Hirai, F. Tomioka, Y. Takano, A. Takenaka, M. Toyoda, T. Oguchi, T. Yokoya

    PHYSICA C-SUPERCONDUCTIVITY AND ITS APPLICATIONS   469 ( 15-20 )   1041 - 1044   2009年8月

     詳細を見る

    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 measured Ca-intercalated graphite superconductor CaC6 (T-c = 11.2 K) by soft X-ray photoemission spectroscopy in order to understand the electronic structure. For the valence band, we observed several structures that correspond to those of calculated density of states with the partial density of states of Ca 3d at the Fermi level (E-F). We also observed core level spectra that are a very large asymmetric Ca 2p and asymmetric C 1s for CaC6, suggesting the existence of conduction electrons derived from Ca 3d and a charge transfer from Ca to graphene layer. These results provide spectroscopic evidence for PDOS of Ca 3d at E-F. From a comparison of electronic structure of CaC6 and other graphite intercalation compounds (GICs), we found the difference between CaC6 and other superconducting GICs, which provides deeper understanding of the superconductivity of CaC6. (C) 2009 Elsevier B.V. All rights reserved.

    DOI: 10.1016/j.physc.2009.05.172

    Web of Science

    researchmap

  • Bulk-sensitive spectroscopic studies on noncentrosymmetric superconducting system of Mg–Ir–B 査読

    Physica C-Superconductivity and Its Applications   469 ( 15-20 )   1034 - 1036   2009年8月

     詳細を見る

    記述言語:英語   掲載種別:研究論文(学術雑誌)  

    DOI: 10.1016/j.physc.2009.05.175

    Web of Science

    researchmap

  • Spectroscopic evidence of the existence of substantial Ca 3d derived states at the Fermi level in the Ca-intercalated graphite superconductor CaC6 査読

    H. Okazaki, R. Yoshida, K. Iwai, K. Noami, T. Muro, T. Nakamura, T. Wakita, Y. Muraoka, M. Hirai, F. Tomioka, Y. Takano, A. Takenaka, M. Toyoda, T. Oguchi, T. Yokoya

    PHYSICAL REVIEW B   80 ( 3 )   035420   2009年7月

     詳細を見る

    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  

    We have performed soft x-ray photoemission studies of Ca-intercalated graphite superconductor CaC6 (T-c=11.2 K). The valence-band spectrum shows six main structures, with a peak at the Fermi level (E-F), which correspond to those of calculated DOS. The intensity of the E-F peak is resonantly enhanced at the Ca 2p-3d threshold, providing spectroscopic evidence for the existence of Ca 3d electrons at E-F, which is confirmed experimentally for the first time. The Ca 2p core-level spectrum has a very large asymmetric line shape, which is further possible suggestion of the existence of Ca 3d derived conduction electrons at Ca sites. These results strongly support the picture where Ca 3d derived interlayer band plays a crucial role for the superconductivity of this material with relatively high T-c.

    DOI: 10.1103/PhysRevB.80.035420

    Web of Science

    researchmap

  • Photoinduced conductivity in tin dioxide thin films 査読

    Y. Muraoka, N. Takubo, Z. Hiroi

    JOURNAL OF APPLIED PHYSICS   105 ( 10 )   103702   2009年5月

     詳細を見る

    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 INST PHYSICS  

    The effects of ultraviolet light irradiation on the conducting properties of SnO(2-x) thin films grown epitaxially on TiO(2) or Al(2)O(3) single-crystal substrates are studied at room temperature. A large increase in conductivity by two to four orders of magnitude is observed with light irradiation in an inert atmosphere and remains after the light is removed. The high-conducting state reverts to the original low-conducting state by exposing it to oxygen gas. These reversible phenomena are ascribed to the desorption and adsorption of negatively charged oxygen species at the grain boundaries, which critically change the mobility of electron carriers already present inside grains by changing the potential barrier height at the grain boundary. The UV light irradiation provides us with an easy and useful route to achieve a high-conducting state even at low carrier density in transparent conducting oxides and also to draw an invisible conducting wire or a specific pattern on an insulating film.

    DOI: 10.1063/1.3126713

    Web of Science

    researchmap

  • Conductivity Switching by Ultraviolet Light in Tin Dioxide Thin Films 査読

    Naoko Takubo, Yuji Muraoka, Zenji Hiroi

    APPLIED PHYSICS EXPRESS   2 ( 4 )   045501   2009年4月

     詳細を見る

    記述言語:英語   掲載種別:研究論文(学術雑誌)   出版者・発行元:JAPAN SOCIETY APPLIED PHYSICS  

    The effects of ultraviolet (UV) light irradiation on the conducting properties of SnO(2-x) films are studied at room temperature (RT). Large enhancements in conductivity up to 4 orders of magnitude are observed in vacuum for almost insulating films containing small amounts of oxygen vacancies. It is ascribed to the desorption of negatively-charged oxygen species from the grain boundary, which dramatically enhances the mobility of electron carriers already present in the grains through the reduction of potential barriers at the boundary. The low-resistive state induced by light irradiation recovers to the original insulating state by exposing oxygen gas at FIT. (C) 2009 The Japan Society of Applied Physics

    DOI: 10.1143/APEX.2.045501

    Web of Science

    researchmap

  • Soft X-ray Core-Level Photoemission Study of Boron Sites in Heavily Boron-Doped Diamond Films 査読

    Hiroyuki Okazaki, Rikiya Yoshida, Takayuki Muro, Takanori Wakita, Masaaki Hirai, Yuji Muraoka, Yoshihiko Takano, Shingo Iriyama, Hiroshi Kawarada, Tamio Oguchi, Takayoshi Yokoya

    JOURNAL OF THE PHYSICAL SOCIETY OF JAPAN   78 ( 3 )   034703   2009年3月

     詳細を見る

    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 performed high-resolution soft x-ray B 1s core-level photoemission spectroscopy of heavily boron-doped diamond films in order to study the chemical sites of doped-boron atoms and their relation to the superconducting transition temperature (T-c). We find that B 1s core-level spectra exhibit several fine structures and three bulk components can he resolved from photon energy dependent studies and spectral fittings. These results indicate existence of several chemical environments of doped-boron atoms. One of the bulk components having the lowest binding energy can be assigned to a signal from substitutionally doped-boron atoms. Comparisons of bulk components with T-c suggest spectroscopic evidence for the importance of substitutionally doped-boron atoms for effective carrier and superconductivity.

    DOI: 10.1143/JPSJ.78.034703

    Web of Science

    researchmap

  • Electronic Structure of Superconducting FeSe Studied by High-Resolution Photoemission Spectroscopy 査読

    Rikiya Yoshida, Takanori Wakita, Hiroyuki Okazaki, Yoshikazu Mizuguchi, Shunsuke Tsuda, Yoshihiko Takano, Hiroyuki Takeya, Kazuto Hirata, Takayuki Muro, Mario Okawa, Kyoko Ishizaka, Shik Shin, Hisatomo Harima, Masaaki Hirai, Yuji Muraoka, Takayoshi Yokoya

    JOURNAL OF THE PHYSICAL SOCIETY OF JAPAN   78 ( 3 )   034708   2009年3月

     詳細を見る

    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 pet-formed soft x-ray and Ultralligh-resolution laser-excited photoemission measurements on tetragonal FeSe, which was recently identified as a superconductor. Energy dependent study of valence band is compared to band Structure Calculations and yields a reasonable assignment of partial densities of states. However, the sharp peak near the Fermi level slightly deviates from the calculated energy position, giving rise to the necessity of self energy correction. We have also performed ultrahigh-resolution laser photoemission experiment on FeSe and observed the suppression of intensity around the Fermi level upon cooling.

    DOI: 10.1143/JPSJ.78.034708

    Web of Science

    researchmap

  • Superconducting Gap and Valence Band of Mg10Ir19B16 Studied by Laser and Synchrotron Photoemission Spectroscopy 査読

    Rikiya Yoshida, Hiroyuki Okazaki, Keisuke Iwai, Kengo Noami, Takayuki Muro, Mario Okawa, Kyoko Ishizaka, Shik Shin, Zheng Li, Jianlin Luo, Guo-qing Zheng, Tamio Oguchi, Masaaki Hirai, Yuji Muraoka, Takayoshi Yokoya

    JOURNAL OF THE PHYSICAL SOCIETY OF JAPAN   78 ( 3 )   034705   2009年3月

     詳細を見る

    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 report the results of first photoemission spectroscopy on a newly discovered noncentrosymmetric superconductor Mg10Ir19B16. We measured the valence band structure of Mg10Ir19B16 using soft X-ray photoemission technique and found that the first principal calculation explains our observation well. In the bulk-sensitive laser-excited photoemission study, we observed that the intensity at the Fermi level decreases as we lower the sample temperature, indicative of the opening of superconducting energy gap. Using Dynes' function, we performed fitting analysis on the spectra of superconducting state.

    DOI: 10.1143/JPSJ.78.034705

    Web of Science

    researchmap

  • Effect of UV light irradiation in SnO2 thin film 査読

    Naoko Takubo, Yuji Muraoka, Zenji Hiroi

    LXIII YAMADA CONFERENCE ON PHOTO-INDUCED PHASE TRANSITION AND COOPERATIVE PHENOMENA (PIPT3)   148   012025   2009年

     詳細を見る

    記述言語:英語   掲載種別:研究論文(国際会議プロシーディングス)   出版者・発行元:IOP PUBLISHING LTD  

    We observed a drastic increase in conductivity up to three orders of magnitude as a result of a photo-induced effect at the surface in a tin dioxide (SnO2) thin film. The oxygen-atmosphere effect and the light-intensity dependence of conductivity change were also experimentally studied. The experimental results indicate that the conductivity increase was caused by photo-induced oxygen desorption at the surface of the thin film.

    DOI: 10.1088/1742-6596/148/1/012025

    Web of Science

    researchmap

  • Fully gapped superconductivity and strong electron correlations in the -pyrochlore KOs2O6 査読

    J. Phys. Chem.Solids   69 ( 12 )   3228 - 3231   2008年12月

     詳細を見る

    記述言語:英語   掲載種別:研究論文(学術雑誌)  

    DOI: 10.1016/j.jpcs.2008.06.058

    Web of Science

    researchmap

  • Electronic Structure of Noncentrosymmetric Superconductor Li-2(PdxPt1-x)(3)B Studied by Photoemission Spectroscopy 査読

    Rikiya Yoshida, Hiroyuki Okazaki, Mitsutoshi Tajima, Takayuki Muro, Izumi Hase, Kozo Okada, Hiroyuki Takeya, Kazuto Hirata, Masaaki Hirai, Yuji Muraoka, Takayoshi Yokoya

    JOURNAL OF THE PHYSICAL SOCIETY OF JAPAN   77 ( 10 )   104701   2008年10月

     詳細を見る

    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 performed x-ray photoemission spectroscopy on the system of noncentrosymmetric Superconductor, Li-2(PdxPt1-x)(3)B. For Li2Pt3B, we found two major peaks with two other weak components, and the band calculations were in agreement with the observation. The assignment of valence band features using the calculated partial density of states determined that Pt 5d and B 2p contribute to the density of states at the Fermi level. The effect of antisymmetric spin-orbit coupling on the band Structure might have been probed. and the analysis on the effect of Pt incorporation into the system indicates the smooth evolution of electronic structures. We presented the measurements of core levels (Pd 3d, Pt 4f, and B 1s) and discussed the chemical bonding states and electronic structures from them.

    DOI: 10.1143/JPSJ.77.104701

    Web of Science

    researchmap

  • Photoemission evidence for a Mott-Hubbard metal-insulator transition in VO(2) 査読

    R. Eguchi, M. Taguchi, M. Matsunami, K. Horiba, K. Yamamoto, Y. Ishida, A. Chainani, Y. Takata, M. Yabashi, D. Miwa, Y. Nishino, K. Tamasaku, T. Ishikawa, Y. Senba, H. Ohashi, Y. Muraoka, Z. Hiroi, S. Shin

    PHYSICAL REVIEW B   78 ( 7 )   075115   2008年8月

     詳細を見る

    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 temperature (T)-dependent metal-insulator transition (MIT) in VO(2) is investigated using bulk sensitive hard-x-ray (similar to 8 keV) valence-band, core-level, and V 2p-3d resonant photoemission spectroscopies (PESs). The valence-band and core-level spectra are compared with full-multiplet cluster model calculations including a coherent screening channel. Across the MIT, V 3d spectral weight transfer from the coherent (3d(1)(C) under bar final) states at Fermi level to the incoherent (3d(0)+3d(1)(L) under bar final) states, corresponding to the lower Hubbard band, leads to gap formation. The spectral shape changes in V 1s and V 2p core levels as well as the valence band are nicely reproduced from cluster model calculations, providing electronic structure parameters. Resonant PES finds that the 3d(1)(L) under bar states resonate across the V 2p-3d threshold in addition to the 3d(0) and 3d(1)(C) under bar states. The results support a Mott-Hubbard transition picture for the first-order MIT in VO(2).

    DOI: 10.1103/PhysRevB.78.075115

    Web of Science

    researchmap

  • Preparation and characterization of epitaxial Fe(2-x)Ti(x)O(3) films with various Ti concentrations (0.5 < x < 1.0) 査読

    Takada M. Nakanishi, T. Fujii, J. Takada, Y. Muraoka

    JOURNAL OF APPLIED PHYSICS   104 ( 3 )   033713   2008年8月

     詳細を見る

    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 INST PHYSICS  

    An ilmenite-hematite solid solution (Fe(2-x)Ti(x)O(3)) is one of the candidates for practical magnetic semiconductors with a high Curie temperature. We have prepared well-crystallized epitaxial Fe(2-x)Ti(x)O(3) films with a wide range of Ti concentrations-x=0.50, 0.60, 0.65, 0.76, 0.87, and 0.94-on alpha-Al(2)O(3)(001) substrates. The films are prepared by a reactive helicon plasma sputtering technique to evaporate Fe and TiO targets simultaneously under optimized oxygen pressure conditions. The structural characterizations of the films reveal that all films have a single phase of the ordered structure with R3 symmetry, where Ti-rich and Fe-rich layers are stacked alternately along the c axis. All films have large ferrimagnetic moments at low temperature, and room temperature magnetization is clearly observed at x < 0.7. The inverse temperature dependence of the resistivities of the films indicates their semiconducting behavior. The film resistivities decrease with decreasing Ti concentration. (c) 2008 American Institute of Physics.

    DOI: 10.1063/1.2966298

    Web of Science

    researchmap

  • Full-gap superconductivity with strong electron correlations in the -pyrochlore KOs2O6 査読

    Physica B   403 ( 5-9 )   1068 - 1070   2008年4月

     詳細を見る

    記述言語:英語   掲載種別:研究論文(学術雑誌)  

    DOI: 10.1016/j.physb.2007.10.090

    Web of Science

    researchmap

  • Study of electronic structures for Fe thin films deposited on Si- and C-faces of 4H-SiC substrates by soft X-ray emission spectroscopy 査読

    M. Hirai, T. Wakita, H. Okazaki, D. Koishihara, Y. Muraoka, T. Yokoya

    APPLIED SURFACE SCIENCE   254 ( 1 )   26 - 28   2007年10月

     詳細を見る

    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  

    Silicon carbide (SiC) is a candidate material for electronic devices to operate upon crucial environment. Electronic states of silicides and/or carbide/graphite formed in metal/SiC contact system are fundamentally important from the viewpoint of device performance.
    We study interface electronic structure of iron thin film deposited on silicon (Si)- and carbon (C)-face of 4H-SiC(0 0 0 1) by using a soft X-ray emission spectroscopy (SXES). For specimens of Fe (50 nm)/4H-SiC (substrate) contact systems annealed at 700 and 900 degrees C, the Si L-2,L-3 emission spectra indicate different shapes and peak energies from the substrate depending on thermal-treated temperature. The product of materials such as silicides is suggested. Further, from comparison of Si L-2,L-3 emission spectra between Si- and C-face for the same annealing temperature at 700 degrees C, it is concluded that the similar silicides and/or ternary materials are formed on the two surfaces. However for those of 900 degrees C, the film on substrate is composed of the different silicide and/or ternary materials. (C) 2007 Elsevier B.V. All rights reserved.

    DOI: 10.1016/j.apsusc.2007.07.025

    Web of Science

    researchmap

  • Photoemission study of TiO2/VO2 interfaces 査読

    K. Maekawa, M. Takizawa, H. Wadati, T. Yoshida, A. Fujimori, H. Kumigashira, M. Oshima, Y. Muraoka, Y. Nagao, Z. Hiroi

    PHYSICAL REVIEW B   76 ( 11 )   115121   2007年9月

     詳細を見る

    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  

    We have measured photoemission spectra of two kinds of TiO2-capped VO2 thin films, namely, that with a rutile-type TiO2 capping layer (r-TiO2/VO2) and that with an amorphous TiO2 capping layer (a-TiO2/VO2). Below the metal-insulator transition temperature of the VO2 thin films, similar to 300 K, TiO2 and VO2 form an interface between a band insulator with the d(0) electronic configuration and a Mott (or Mott-Peierls) insulator with the d(1) electronic configuration. Metallic states were, however, not observed at the interfaces, in contrast to the interfaces between the d(0) band insulator SrTiO3 and the d(1) Mott insulator LaTiO3. We discuss possible origins of the difference between TiO2/VO2 and SrTiO3/LaTiO3, and suggest the importance of the polarity discontinuity in the latter interface. The stronger incoherent part was observed in r-TiO2/VO2 than in a-TiO2/VO2, suggesting Ti-V atomic diffusion due to the higher deposition temperature for r-TiO2/VO2.

    DOI: 10.1103/PhysRevB.76.115121

    Web of Science

    researchmap

  • Interplay of superconductivity and rattling phenomena in -pyrochlore KOs2O6 studied by photoemission spectroscopy 査読

    Phys. Rev. Lett.   99 ( 11 )   117003   2007年9月

     詳細を見る

    記述言語:英語   掲載種別:研究論文(学術雑誌)  

    DOI: 10.1103/PhysRevLett.99.117003

    Web of Science

    researchmap

  • Anomalous magnetic phase in an undistorted pyrochlore oxide Cd2Os2O7 induced by geometrical frustration 査読

    Akihiro Koda, Ryosuke Kadono, Kazuki Ohishi, Shanta R. Saha, Wataru Higemoto, Shigeki Yonezawa, Yuji Muraoka, Zenji Hiroi

    JOURNAL OF THE PHYSICAL SOCIETY OF JAPAN   76 ( 6 )   063703   2007年6月

     詳細を見る

    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 report on the muon spin rotation/relaxation study of a pyrochlore oxide, Cd2Os2O7, which exhibits a metal-insulator (MI) transition at T-MI similar or equal to 225 K without structural phase transition. It reveals strong spin fluctuation (>= 10(8) s(-1)) below the MI transition, suggesting a predominant role of geometrical spin frustration amongst Os5+ ions. Meanwhile, upon further cooling, an incommensurate spin density wave discontinuously develops below T-SDW similar or equal to 150 K. These observations strongly suggest the occurrence of an anomalous magnetic transition and associated change in the local spin dynamics in undistorted pyrochlore antiferromagnet.

    DOI: 10.1143/JPSJ.76.063703

    Web of Science

    researchmap

  • Precise control of band filling in NaxCoO2 査読

    Daisuke Yoshizumi, Yuji Muraoka, Yoshihiko Okamoto, Yoko Kiuchi, Jun-Ichi Yamaura, Masahito Mochizuki, Masao Ogata, Zenji Hiroi

    JOURNAL OF THE PHYSICAL SOCIETY OF JAPAN   76 ( 6 )   063705   2007年6月

     詳細を見る

    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  

    Electronic properties of the sodium cobaltate NaxCoO2 are systematically studied through a precise control of band filling. Resistivity, magnetic susceptibility and specific heat measurements are carried out on a series of high-quality polycrystalline samples prepared at 200 degrees C with Na content in a wide range of 0.35 <= x <= 0.70. It is found that dramatic changes in electronic properties take place at a critical Na concentration x* that lies between 0.58 and 0.59, which separates a Pauli paramagnetic and a Curie-Weiss metals. It is suggested that at x* the Fermi level touches the bottom of the a(1g) band at the Gamma point, leading to a crucial change in the density of states across x* and the emergence of a small electron pocket around the Gamma point for x > x*.

    DOI: 10.1143/JPSJ.76.063705

    Web of Science

    researchmap

  • Electronic structure of 3d(1) configuration vanadium oxides studied by soft X-ray and hard X-ray photoemission spectroscopy 査読

    R. Eguchi, M. Taguchi, M. Matsunami, K. Horiba, K. Yamamoto, A. Chainani, Y. Takata, M. Yabashi, D. Miwa, Y. Nishino, K. Tamasaku, T. Ishikawa, Y. Senba, H. Ohashi, I. H. Inoue, Y. Muraoka, Z. Hiroi, S. Shin

    JOURNAL OF ELECTRON SPECTROSCOPY AND RELATED PHENOMENA   156   421 - 425   2007年5月

     詳細を見る

    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 investigate the electronic structure of 3d(1) configuration vanadium oxides (VO2, SrVO3 and CaVO3) using soft X-ray (SX) and hard X-ray (HX) photoemission spectroscopy (PES). The valence band spectra of VO2 in SX- and HX-PES clearly show the opening of a gap at E-F across the metal-insulator transition. Spectral changes in the V 2p and O 1s core levels were also observed. In addition, 3d(1) configuration correlated metals SrVO3 and CaVO3 are typical materials whose valence band spectra are compared with dynamical mean-field theory. The V 2p and V 1s core level HX-PES of SrVO3 and CaVO3 show clear additional well-screened features. These features originate from bulk screening by a coherent band at EF. These spectra are nicely reproduced by a cluster model calculation, indicating a difference of the parameter V* for the interaction strength between the central V 3d orbitals and the coherent band. (c) 2007 Elsevier B.V. All rights reserved.

    DOI: 10.1016/j.elspec.2006.12.055

    Web of Science

    researchmap

  • NMR observation of rattling phonons in the pyrochlore superconductor KOs2O6 査読

    M. Yoshida, K. Arai, R. Kaido, M. Takigawa, S. Yonezawa, Y. Muraoka, Z. Hiroi

    PHYSICAL REVIEW LETTERS   98 ( 19 )   197002   2007年5月

     詳細を見る

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

    We report nuclear magnetic resonance studies on the beta-pyrochlore oxide superconductor KOs2O6. The nuclear relaxation at the K sites is entirely caused by fluctuations of the electric field gradient, which we ascribe to highly anharmonic low frequency oscillation (rattling) of K ions. A phenomenological analysis shows a crossover from overdamped to underdamped behavior of the rattling phonons with decreasing temperature and its sudden sharpening below the superconducting transition temperature T-c. Suppression of the Hebel-Slichter peak in the relaxation rate at the O sites below T-c also indicates strong electron-phonon coupling.

    DOI: 10.1103/PhysRevLett.98.197002

    Web of Science

    researchmap

  • Impurity effects on the Ni3+ triangular lattice of Ag2NiO2 査読

    H. Yoshida, Y. Muraoka, Z. Hiroi

    JOURNAL OF PHYSICS-CONDENSED MATTER   19 ( 14 )   145234   2007年4月

     詳細を見る

    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  

    Silver oxonickelate Ag2NiO2 is a metallic compound presenting a spin- 1/2 triangular lattice. It exhibits a structural transition at T-s = 260 K, which may be related to e(g) orbital ordering, and an antiferromagnetic transition at T-N = 55 K. Impurity effects on its magnetic and electronic properties are examined by substituting Fe for Ni in Ag2Ni1-xFexO2 ( 0 <= x <= 0.3). A Curielike enhancement in magnetic susceptibility is observed at low temperature, which implies that most Fe3+ spins behave as free spins. Moreover, a large enhancement of residual resistivity and its suppression under magnetic fields are observed. Magnetic interactions in the Ni3+ triangular lattice are discussed.

    DOI: 10.1088/0953-8984/19/14/145235

    Web of Science

    researchmap

  • NMR study of -pyrochlore oxide superconductor KOs2O6 査読

    J. Magn. Magn. Mater.   310 ( 2 )   698 - 699   2007年3月

     詳細を見る

    記述言語:英語   掲載種別:研究論文(学術雑誌)  

    DOI: 10.1016/jmmm.2006.10.186

    Web of Science

    researchmap

  • Electronic structure of VO2/TiO2 : Nb upon photocarrier injection 査読

    R. Eguchi, S. Tsuda, T. Kiss, A. Chainani, Y. Muraoka, Z. Hiroi, S. Shin

    PHYSICAL REVIEW B   75 ( 7 )   073102   2007年2月

     詳細を見る

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

    We study the photocarrier injected electronic structure of VO2/TiO2:Nb (equivalent to p-n junction) thin-film heterostructure using photoemission spectroscopy, across the temperature-dependent metal-insulator transition in VO2. The valence band of VO2 shifts systematically to higher binding energy upon photocarrier injection (PCI). In the insulating phase, the energy shift as a function of irradiated power matches the surface photovoltage (SPV) behavior, while in the metallic phase, the energy shift follows the SPV trend but is reduced due to recombination. The temperature dependence of the energy shift between 200 and 330 K varies nearly linearly with the SPV. The study provides evidence for hole doping from TiO2:Nb to VO2 by the PCI effect.

    DOI: 10.1103/PhysRevB.75.073102

    Web of Science

    researchmap

  • Thermal conductivity of the pyrochlore superconductor KOs2O6: Strong electron correlations and fully gapped superconductivity 査読

    Y. Kasahara, Y. Shimono, T. Shibauchi, Y. Matsuda, S. Yonezawa, Y. Muraoka, Z. Hiroi

    PHYSICAL REVIEW LETTERS   96 ( 24 )   247004   2006年6月

     詳細を見る

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

    To elucidate the nature of the superconducting ground state of the geometrically frustrated pyrochlore KOs2O6 (T-c=9.6 K), the thermal conductivity was measured down to low temperatures (similar to T-c/100). We found that the quasiparticle mean free path is strikingly enhanced below a transition at T-p=7.8 K, indicating enormous electron inelastic scattering in the normal state. In magnetic fields, the conduction at T -> 0 K is nearly constant up to similar to 0.4H(c2), in contrast with the rapid growth expected for superconductors with an anisotropic gap. This unambiguously indicates a fully gapped superconductivity, in contrast with previous studies. These results highlight that KOs2O6 is unique among superconductors with strong electron correlations.

    DOI: 10.1103/PhysRevLett.96.247004

    Web of Science

    researchmap

  • High-pressure effects on the superconductivity on -pyrochlore oxides AOs2O6 査読

    Physica B   378-80   882 - 883   2006年5月

     詳細を見る

    記述言語:英語   掲載種別:研究論文(学術雑誌)  

    DOI: 10.1016/j.physb.2006.01.323

    Web of Science

    researchmap

  • NMR studies of -pyrochlore superconductors with osmium, under hydrostatic pressure 査読

    Physica B   378-80   878 - 879   2006年5月

     詳細を見る

    記述言語:英語   掲載種別:研究論文(学術雑誌)  

    DOI: 10.1016/j.physb.2006.01.322

    Web of Science

    researchmap

  • Upper critical field of -pyrochlore KOs2O6 single crystal 査読

    J. Phys. Soc. Jpn.   75 ( 4 )   045002   2006年4月

     詳細を見る

    記述言語:英語   掲載種別:研究論文(学術雑誌)  

    DOI: 10.1143/JPSJ.75.045002

    Web of Science

    researchmap

  • Role of electron-electron and electron-phonon interaction effects in the optical conductivity of VO2 査読

    K Okazaki, S Sugai, Y Muraoka, Z Hiroi

    PHYSICAL REVIEW B   73 ( 16 )   165116   2006年4月

     詳細を見る

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

    We have investigated the charge dynamics of VO2 by optical reflectivity measurements. Optical conductivity clearly shows a metal-insulator transition. In the metallic phase, a broad Drude-like structure is observed. On the other hand, in the insulating phase, a broad peak structure around 1.3 eV is observed. It is found that this broad structure observed in the insulating phase shows a temperature dependence. We attribute this to the electron-phonon interaction as in the photoemission spectra.

    DOI: 10.1103/PhysRevB.73.165116

    Web of Science

    researchmap

  • Crystal structure of the pyrochlore oxide superconductor KOs2O6 査読

    JI Yamaura, S Yonezawa, Y Muraoka, Z Hiroi

    JOURNAL OF SOLID STATE CHEMISTRY   179 ( 1 )   336 - 340   2006年1月

     詳細を見る

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

    We report the single-crystal X-ray analysis of the structure of the pyrochlore oxide superconductor KOs2O6. The structure was identified as the beta-pyrochlore structure with space group Fd (3) over barm and lattice constant a = 10.089(2) angstrom at 300 K: the K atom is located at the 8b site, not at the 16d site as in conventional pyrochlore oxides. We found an anomalously large atomic displacement parameter U-iso = 0.0735(8) angstrom(2) at 300 K for the K cation, which suggests that the K cation weakly bound to an oversized OS12O18 cage exhibits intensive rattling, as recently observed for clathrate compounds. The rattling of A cations is a common feature in the series of flpyrochlore oxide superconductors AOs(2)O(6) (A = Cs, Rb and K), and is greatest for the smallest K cation. (c) 2005 Elsevier Inc. All rights reserved.

    DOI: 10.1016/j.jssc.2005.10.039

    Web of Science

    researchmap

  • Spin-1/2 triangular lattice with orbital degeneracy in a metallic oxide Ag2NiO2 査読

    H Yoshida, Y Muraoka, T Sorgel, M Jansen, Z Hiroi

    PHYSICAL REVIEW B   73 ( 2 )   020408(R)   2006年1月

     詳細を見る

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

    A metallic and magnetic transition metal oxide Ag2NiO2 is studied by means of resistivity, magnetic susceptibility, specific heat, and x-ray diffraction. The crystal structure is characterized by an alternating stacking of a Ni3+O2 layer and a (Ag-2)(+) layer, the former realizing a spin-1/2 triangular lattice with e(g) orbital degeneracy and the latter providing itinerant electrons. It is found that the NiO2 layer exhibits orbital ordering at T-s = 260 K and antiferromagnetic spin ordering at T-N= 56 K. Moreover, a moderately large mass enhancement is found for the itinerant electrons, suggesting a significant contribution from the nearly localized Ni 3d state to the Ag 5s state that forms a broad band.

    DOI: 10.1103/PhysRevB.73.020408

    Web of Science

    researchmap

  • Spin-1/2 triangular laiftice in Ag2NiO2 査読

    Hiroyuki Yoshida, Yuji Muraoka, Zenji Hiroi, Timo Soergel, Martin Jansen

    LOW TEMPERATURE PHYSICS, PTS A AND B   850   1089 - +   2006年

     詳細を見る

    記述言語:英語   掲載種別:研究論文(国際会議プロシーディングス)   出版者・発行元:AMER INST PHYSICS  

    A novel metallic compound with a spin-1/2 triangular lattice is reported. It is a silveroxonickelate Ag2NiO2 containing a NiO2 layer which possesses a spin-1/2 triangular lattice with twofold spin and twofold orbital degeneracy. It is found that a structural transition takes place at T-s = 260 K, which may be related to orbital ordering, and long-range antiferromagnetic order sets in below T-N = 54 K.

    DOI: 10.1063/1.2355083

    Web of Science

    researchmap

  • Metal-insulator transition in VO2 studied by optical spectroscopy

    Kozo Okazaki, Shunji Sugai, Yuji Muraoka, Zenji Hiroi

    LOW TEMPERATURE PHYSICS, PTS A AND B   850   1229 - +   2006年

     詳細を見る

    記述言語:英語   掲載種別:研究論文(国際会議プロシーディングス)   出版者・発行元:AMER INST PHYSICS  

    We have investigated the charge dynamics of VO2 by optical reflectivity measurements. Optical conductivity clearly shows a metal-insulator transition. In the metallic phase, a broad Drude-like structure is observed. On the other hand, in the insulating phase, a broad peak structure around 1.3 eV is observed. It is found that this broad structure observed in the insulating phase shows strong temperature dependence. We attribute this to the electron-phonon interaction as in the photoemission spectra.

    DOI: 10.1063/1.2355148

    Web of Science

    researchmap

  • Photocarrier-injected electronic structure of VO2/TiO2 : Nb 査読

    R Eguchi, S Shin, A Fukushima, T Kiss, T Shimojima, Y Muraoka, Z Hiroi

    APPLIED PHYSICS LETTERS   87 ( 20 )   201912   2005年11月

     詳細を見る

    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 INST PHYSICS  

    We study the effect of photocarrier injection on the electronic structure of VO2/TiO2:Nb thin films using photoemission spectroscopy. The results indicate that the valence band and core electronic states of VO2 shift systematically to lower binding energy upon photocarrier injection, consistent with doping in a rigid-band picture. The shift in binding energy, and its saturation, follows the known photovoltage behavior. In addition, the V 3d states near E-F exhibit a redistribution/transfer of spectral weight, similar to the temperature dependent insulator to metal transition in VO2. The study provides evidence for hole-doping induced electronic structure changes due to the photocarriers in VO2. (C) 2005 American Institute of Physics.

    DOI: 10.1063/1.2132078

    Web of Science

    researchmap

  • Photocarrier injection and current-voltage characteristics of La0.8Sr0.2MnO3/SrTiO3 : Nb heterojunction at low temperature 査読

    T Muramatsu, Y Muraoka, Z Hiroi

    JAPANESE JOURNAL OF APPLIED PHYSICS PART 1-REGULAR PAPERS BRIEF COMMUNICATIONS & REVIEW PAPERS   44 ( 10 )   7367 - 7371   2005年10月

     詳細を見る

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

    An epitaxial heterojunction made of a p-type perovskite manganite La0.8Sr0.2MnO3 film and an n-type strontium titanate SrTiO3:Nb substrate has been fabricated by the pulsed laser deposition technique. The current-voltage (I-V) characteristics and photovoltaic properties are measured under UV light irradiation in a wide temperature range down to 10 K. It is found that the junction acts as an efficient UV photodiode with a large external quantum efficiency of 28%. It is also demonstrated that the manganite film can be doped with a certain amount of holes by photocarrier injection. The maximum surface hole density is estimated to be 3.0 x 10(13) cm(-2).

    DOI: 10.1143/JJAP.44.7367

    Web of Science

    researchmap

  • Anomalous pressure dependence of the superconducting transition temperature of -pyrochlore AOs2O6 oxides 査読

    Phys. Rev. Lett.   95 ( 16 )   167004   2005年10月

     詳細を見る

    記述言語:英語   掲載種別:研究論文(学術雑誌)  

    DOI: 10.1103/PhysRevLett.95.167004

    Web of Science

    researchmap

  • Photocarrier injection to organic compounds 査読

    JI Yamaura, Y Muraoka, T Muramatsu, T Yamauchi, Z Hiroi

    SYNTHETIC METALS   152 ( 1-3 )   385 - 388   2005年9月

     詳細を見る

    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 SA  

    Photocarrier injection (PCI) is efficient method of the carrier control for the inorganic thin films, where the photo-excited holes in the wide-gap semiconductor under the UV light irradiation are injected to the film through the interface. We examine the PCI method to various organic films provided on the inorganic wide-gap semiconductor substrate. We prepared organic films deposited on the surface of a Nb-doped TiO2 (SrTiO3) single crystal substrate, possessing a band gap of 3.0 eV (3.2 eV), by using casting or vacuum evaporation. Fabricated organic films were polythiophene (1), Ni phthalocyanine (2), polyaniline (3), C-60 (4), and DNA (Herring Sperm) (5) on Nb-doped TiO2 substrate. We determined the carrier injection to the organic films from the across-plane open-circuit voltage measurement under the UV light The values of the surface density of the injected holes to organic films are estimated at 1.4 x 10(13) cm(-2) (1), 4.2 x 10(12) cm(-2) (2), 6.9 x 10(12) cm(-2) (3), 1.5 x 10(11) cm(-2) (4), and 8.1 x 10(12) cm(-2) (5) at the irradiance of 10 mW/cm(2). Moreover, we also measure the photovoltages for polythiophene films provided on Nb-doped SrTiO3 substrates with various Nb concentrations.

    DOI: 10.1016/j.synthmet.2005.07.115

    Web of Science

    researchmap

  • Photogenerated carrier injection to an n-type copper oxide superconductor 査読

    Y Muraoka, T Muramatsu, Z Hiroi

    THIN SOLID FILMS   486 ( 1-2 )   82 - 85   2005年8月

     詳細を見る

    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 SA  

    We have fabricated an isotype heterostructure made of an n-type superconductor (Sr0.89Nd0.11)CuO2 film and an n-type SrTiO3:Nb substrate by using the pulsed laser deposition technique and measured the current-voltage and photovoltaic properties under ultraviolet (UV) light irradiation. A large photovoltage of 0.8 V, which is positive to the film, is observed. This means that the photogenerated hole carriers in the SrTiO3:Nb substrate are injected to the film. Under UV light irradiation, the superconducting transition of the film slightly shifts to lower temperature. The effect of the photocarrier injection on the superconducting transition temperature is discussed in terms of a proposed energy level diagram of the (Sr0.89Nd0.11)CuO2/SrTiO3:Nb heterostructure. (c) 2005 Elsevier B.V. All rights reserved.

    DOI: 10.1016/j.tsf.2004.11.212

    Web of Science

    researchmap

  • Second anomaly in the specific heat of -pyrochlore oxide superconductor KOs2O6 査読

    J. Phys. Soc. Jpn.   74 ( 6 )   1682 - 1685   2005年6月

     詳細を見る

    記述言語:英語   掲載種別:研究論文(学術雑誌)  

    DOI: 10.1143/JPSJ.74.1682

    Web of Science

    researchmap

  • Photoemission study of YBa2Cu3Oy thin films under light illumination 査読

    D Asakura, JW Quilty, K Takubo, S Hirata, T Mizokawa, Y Muraoka, Z Hiroi

    JOURNAL OF ELECTRON SPECTROSCOPY AND RELATED PHENOMENA   144   499 - 502   2005年6月

     詳細を見る

    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 photocarrier injection (PCI) effect is observed at the heterojunction of YBa2Cu3Oy (YBCO) thin film and Nb-doped SrTiO3 (STO:Nb) substrate. PCI is expected as a new carrier doping method in strongly correlated systems instead of chemical substitution. We have studied the nature of PCI in YBCO/STO:Nb using X-ray photoemission spectroscopy with pulsed laser excitation. In the core-level spectra, the energy shift to higher binding energy by 0.5 eV is observed under the laser illumination with frequency of 30 Hz. The energy shift corresponds to the photovoltage, which arises in the interface. In addition, we have measured the spectra varying frequency of the laser. The energy shift obviously depends on the frequency, which is related to the lifetime of the injected photoholes. (c) 2005 Elsevier B.V. All rights reserved.

    DOI: 10.1016/j.elspec.2005.01.134

    Web of Science

    researchmap

  • Possible anisotropic order parameter in pyrochlore superconductor KOs2O6 probed by muon spin rotation 査読

    A Koda, W Higemoto, K Ohishi, Saha, SR, R Kadono, S Yonezawa, Y Muraoka, Z Hiroi

    JOURNAL OF THE PHYSICAL SOCIETY OF JAPAN   74 ( 6 )   1678 - 1681   2005年6月

     詳細を見る

    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  

    Magnetic penetration depth (lambda(eff)) in a pyrochlore superconductor KOs2O6 was studied by means of muon spin rotation (mu SR). The temperature dependence of the transverse spin relaxation rate, which is proportional to lambda(-2)(eff), exhibits a considerable deviation from that expected for the empirical two-fluid model (proportional to T-4), obeying a T-2 tendency. Furthermore, lambda(eff) apparently increases with increasing applied field, suggesting the presence of nonlinear and nonlocal effects. The present result strongly suggests that the superconducting order parameter in KOsO6 is anisotropic or multigapped with a small energy gap.

    DOI: 10.1143/JPSJ.74.1678

    Web of Science

    researchmap

  • NMR studies of the new superconductors AOs(2)O(6) (A = K, Rb) 査読

    K Arai, J Kikuchi, K Kodama, M Takigawa, S Yonezawa, Y Muraoka, Z Hiroi

    PHYSICA B-CONDENSED MATTER   359   488 - 490   2005年4月

     詳細を見る

    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 report results of nuclear magnetic resonance (NMR) experiments on K-39 and Rb-87 nuclei in the new superconductors AOs(2)O(6) (A = K or Rb). These compounds crystallize in the beta-pyrochlore structure. In the superconducting phase, we found a small peak in 1/(T1T) for 87 Rb slightly below the superconducting transition temperature (T-c) but no peak for K-39. In the normal state of KOs2O6, we observed a clear pseudogap behavior similar to what has been observed in high T-c cuprates. (c) 2005 Elsevier B.V. All rights reserved.

    DOI: 10.1016/j.physb.2005.01.123

    Web of Science

    researchmap

  • Specific heat of the -pyrochlore oxide superconductors CsOs2O6 and RbOs2O6 査読

    J. Phys. Soc. Jpn.   74 ( 4 )   1255 - 1262   2005年4月

     詳細を見る

    記述言語:英語   掲載種別:研究論文(学術雑誌)  

    DOI: 10.1143/JPSJ.74.1255

    Web of Science

    researchmap

  • Photoemission study of YBa2Cu3Oy thin films under light illumination 査読

    D Asakura, JW Quilty, K Takubo, S Hirata, T Mizokawa, Y Muraoka, Z Hiroi

    PHYSICAL REVIEW LETTERS   93 ( 24 )   2004年12月

     詳細を見る

    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  

    Heterojunctions of Nb-doped SrTiO3 substrate and YBa2Cu3Oy thin films show photoconductivity and photovoltaic effects due to photocarrier injection. Photocarrier injection is expected to be a new carrier doping method in strongly correlated systems instead of chemical substitution. We have studied the nature of photocarrier injection in YBa2Cu3Oy/SrTiO3:Nb using x-ray photoemission spectroscopy with pulsed laser excitation. The core-level spectra shift to higher binding energy by 0.78 eV under pulsed laser illumination at 30 Hz. The energy shift corresponds to the photovoltage, which arises at the interface. In addition, we have observed that the energy shift strongly depends on the frequency of the laser. The lifetime of the injected photoholes has been estimated to be 40 ms by analyzing the frequency dependence.

    DOI: 10.1103/PhysRevLett.93.247006

    Web of Science

    researchmap

  • Photocarrier injection and the I–V characteristics of La0.8Sr0.2MnO3/SrTiO3:Nb heterojunctions 査読

    Solid State Commun.   132 ( 5 )   351 - 354   2004年11月

     詳細を見る

    記述言語:英語   掲載種別:研究論文(学術雑誌)  

    DOI: 10.1016/j.ssc.2004.04.051

    Web of Science

    researchmap

  • Photogenerated hole carrier injection to YBa2Cu 3O7-x in an oxide heterostructure 査読

    Y. Muraoka, T. Muramatsu, J. Yamaura, Z. Hiroi

    Applied Physics Letters   85 ( 14 )   2950 - 2952   2004年10月

     詳細を見る

    記述言語:英語   掲載種別:研究論文(学術雑誌)  

    Hole doping in the YBa2Cu3O7-X in an oxide heterostructure was analyzed. The current-voltage and photovoltaic properties of YBa2Cu3O7-X were also observed under ultraviolet light irradiation at room temperature. The maximum surface hole carrier density injected was found to be 3.5*1013 cm-2 at L=44 mW/cm2. The results show that the photocarrier injection technique could be used in transition metal oxides to control the hole carrier density.

    DOI: 10.1063/1.1803616

    Scopus

    researchmap

  • Photogenerated hole carrier injection to YBa2Cu3O7-x in an oxide heterostructure 査読

    Y Muraoka, T Muramatsu, J Yamaura, Z Hiroi

    APPLIED PHYSICS LETTERS   85 ( 14 )   2950 - 2952   2004年10月

     詳細を見る

    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 INST PHYSICS  

    We have fabricated a YBa2Cu3O7-x/SrTiO3:Nb heterostructure and measured the current-voltage and photovoltaic properties under ultraviolet light irradiation at room temperature. A large photovoltage of 0.8 V is observed and is positive to the film. The photovoltage appears under illumination of light with photon energy larger than 3.2 eV. These results indicate that photogenerated hole carriers in the SrTiO3:Nb substrate are injected to the film. The maximum surface hole density is attained to be 3.5x10(13) cm(-2) at a light power of 44 mW/cm(2). The present photocarrier injection technique could apply to many transition metal oxides to control the hole carrier density externally. (C) 2004 American Institute of Physics.

    DOI: 10.1063/1.1803616

    Web of Science

    researchmap

  • High pressure effects on superconductivity in the -pyrochlore oxides AOs2O6 (A = K, Rb, Cs) 査読

    J. Phys. Soc. Jpn.   73 ( 10 )   2912 - 2913   2004年10月

     詳細を見る

    記述言語:英語   掲載種別:研究論文(学術雑誌)  

    DOI: 10.1143/JPSJ.73.2912

    Web of Science

    researchmap

  • New -pyrochlore oxide superconductor CsOs2O6 査読

    J. Phys. Soc. Jpn.   73 ( 7 )   1655 - 1656   2004年7月

     詳細を見る

    記述言語:英語   掲載種別:研究論文(学術雑誌)  

    DOI: 10.1143/JPSJ.73.1655

    Web of Science

    researchmap

  • Unprecedented superconductivity in -pyrochlore osmate KOs2O6 査読

    J. Phys. Soc. Jpn.   73 ( 7 )   1651 - 1654   2004年7月

     詳細を見る

    記述言語:英語   掲載種別:研究論文(学術雑誌)  

    DOI: 10.1143/JPSJ.73.1651

    Web of Science

    researchmap

  • Photocarrier injection to perovskite manganites 査読

    T. Muramatsu, Y. Muraoka, T. Yamauchi, J. Yamaura, Z. Hiroi

    JOURNAL OF MAGNETISM AND MAGNETIC MATERIALS   272   E787 - E788   2004年5月

     詳細を見る

    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 fabricated (La, Sr)MnO3 thin films on n-type SrTiO3 substrates doped with Nb by means of the pulsed laser deposition technique. It is shown that hole carriers photogenerated in the substrates under UV light irradiation are injected efficiently to the. lms. By measuring the out-of-plane voltage of the heterojunction the surface density of hole carriers injected to (La, Sr)MnO3 is estimated: It is at most 1.6 x 10(13) cm(-2), but is improved up to 3.1 x 10(13) cm(-2) by modifying the junction structure, i.e., inserting a pure SrTiO3 layer between the film and the substrate. (C) 2004 Elsevier B.V. All rights reserved.

    DOI: 10.1016/j.jmmm.2003.12.121

    Web of Science

    researchmap

  • Efficient photocarrier injection to transition metal oxides 査読

    Y Muraoka, T Yamauchi, T Muramatsu, J Yamaura, Z Hiroi

    JOURNAL OF MAGNETISM AND MAGNETIC MATERIALS   272   448 - 449   2004年5月

     詳細を見る

    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 fabricated transition metal oxide (TMO) films on n-type titanium oxide substrates, and measured in-plane resistance under ultraviolet light irradiation. A dramatic decrease in the resistance and enhancement of the superconducting critical temperature are observed for VO2/TiO2:Nb and YBa2Cu3O2/SrTiO3:Nb, respectively. Out-of-plane voltage measurements under light irradiation indicate hole-carrier injection from the substrate to the film in both the cases. The present photocarrier injection technique could apply to many TMOs to control the hole carrier density externally. (C) 2004 Elsevier B.V. All rights reserved.

    DOI: 10.1016/j.jmmm.2003.12.1290

    Web of Science

    researchmap

  • New pyrochlore oxide superconductor RbOs2O6 査読

    S Yonezawa, Y Muraoka, Y Matsushita, Z Hiroi

    JOURNAL OF THE PHYSICAL SOCIETY OF JAPAN   73 ( 4 )   819 - 821   2004年4月

     詳細を見る

    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 report the discovery of a new pyrochlore oxide superconductor RbOs2O6. The compound crystallizes in the same beta-pyrochlore structure as the recently discovered superconductor KOs2O6, where Os atoms form a corner-sharing tetrahedral network called the pyrochlore lattice with Rb or K atoms in the cage. Resistivity, magnetic susceptibility and specific heat measurements on polycrystalline samples evidence a bulk superconductivity with T-c = 6.3 K.

    DOI: 10.1143/JPSJ.73.819

    Web of Science

    researchmap

  • Photoemission study of the metal-insulator transition in VO 2/TiO2(001): Evidence for strong electron-electron and electron-phonon interaction 査読

    K. Okazaki, H. Wadati, A. Fujimori, M. Onoda, Y. Muraoka, Z. Hiroi

    Physical Review B - Condensed Matter and Materials Physics   69 ( 16 )   1 - 165104   2004年4月

     詳細を見る

    記述言語:英語   掲載種別:研究論文(学術雑誌)  

    We have made a detailed temperature-dependent photoemission study of VO2/TiO2(001) thin films, which show a metal-insulator transition at ∼300 K. Clean surfaces were obtained by annealing the films in an oxygen atmosphere. Spectral weight transfer between the coherent and incoherent parts accompanying the metal-insulator transition was clearly observed. We also observed a hysteretic behavior of the spectra for heating-cooling cycles. We have derived the "bulk" spectrum of the metallic phase and found that it has a strong incoherent part. The width of the coherent part is comparable to that given by band-structure calculation in spite of its reduced spectral weight, indicating that the momentum dependence of the self-energy is significant. This is attributed to by ferromagnetic fluctuation arising from Hund's rule coupling between different d orbitals as originally proposed by Zylbersztejn and Mott. In the insulating phase, the width of the V 3d band shows strong temperature dependence. We attribute this to electron-phonon interaction and have reproduced it using the independent boson model with a very large coupling constant.

    DOI: 10.1103/PhysRevB.69.165104

    Scopus

    researchmap

  • Epitaxial strain effects on the metal-insulator transition in V2O3 thin films 査読

    S Yonezawa, Y Muraoka, Y Ueda, Z Hiroi

    SOLID STATE COMMUNICATIONS   129 ( 4 )   245 - 248   2004年1月

     詳細を見る

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

    Effects of epitaxial stress on the metal-insulator transition of V2O3 have been studied for in the form of epitaxial thin films grown on alpha-Al2O3 (0001) and LiTaO3 (0001) substrates. A metallic phase is stabilized down to 2 K in the V2O3 thin film on alpha-Al2O3 (0001), where the a-axis is compressed by 4% owing to large epitaxial stress. On the other hand, the transition temperature T-MI is raised by 20 K from the value of 170 K in bulk samples in the film on LiTaO3 (0001), where the a-axis is expanded. These results suggest an intimate relationship between the a-axis length and T-MI, in V2O3. The conductivity of the metallic ultrathin films shows logarithmic temperature dependence below 20 K, probably due to the Anderson localization in two-dimensional systems. (C) 2003 Elsevier Ltd. All rights reserved.

    DOI: 10.1016/j.ssc.2003.10.024

    Web of Science

    researchmap

  • Superconductivity in a pyrochlore-related oxide KOs2O6 査読

    S Yonezawa, Y Muraoka, Y Matsushita, Z Hiroi

    JOURNAL OF PHYSICS-CONDENSED MATTER   16 ( 3 )   L9 - L12   2004年1月

     詳細を見る

    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 report the discovery of a new superconductor KOs2O6. The compound crystallizes in a defect pyrochlore structure, where Os atoms form a corner-sharing tetrahedral network called the pyrochlore lattice. Resistivity and magnetic susceptibility measurements on a polycrystalline sample provide evidence of bulk superconductivity with T-c = 9.6 K.

    DOI: 10.1088/0953-8984/16/3/L01

    Web of Science

    researchmap

  • Photocarrier injection to YBa2CU3O7-x thin films 査読

    Y Muraoka, T Muramatsu, T Yamauchi, J Yamaura, Z Hiroi

    FRONTIERS IN SUPERCONDUCTING MATERIALS-NEW MATERIALS AND APPLICATIONS   3   173 - 175   2004年

     詳細を見る

    記述言語:英語   掲載種別:研究論文(国際会議プロシーディングス)   出版者・発行元:MATERIALS RESEARCH SOCIETY  

    We have prepared YBa2Cu3O7-x thin films on n-type SrTiO3 substrates doped with Nb, and measured the in-plane resistance under ultraviolet light irradiation. An enhancement of the superconducting critical temperature is observed from 25 K up to 30 K with increasing light irradiance. Out-of-plane voltage measurements under light irradiation indicate hole carrier injection from the substrate to the film.

    Web of Science

    researchmap

  • Efficiency of photocarrier injection in a VO2/TiO2 : Nb heterostructure 査読

    Z Hiroi, T Yamauchi, Y Muraoka, T Muramatsu, JI Yamaura

    JOURNAL OF THE PHYSICAL SOCIETY OF JAPAN   72 ( 12 )   3049 - 3052   2003年12月

     詳細を見る

    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  

    The efficiency of photocarrier injection in a VO2/TiO2:Nb heterostructure is studied by measuring I-V characteristics at room temperature under ultraviolet light irradiation. It is revealed that photogenerated hole carriers in the TiO2:Nb substrate are injected and accumulated in the VO2 film by the photovoltaic effect. The surface charge density is controlled successfully in a wide range of 10(9)-10(13) cm(-2) as a function of light irradiance. The maximum hole density of 9 x 10(18) cm(-3) is attained at a light irradiance of 133 mW/cm(2), which is estimated by assuming the uniform distribution of holes in the film. It is suggested that high efficiency can be achieved by utilizing the large dielectric constant of titanium oxide substrates.

    DOI: 10.1143/JPSJ.72.3049

    Web of Science

    researchmap

  • Ultraviolet light selective photodiode based on an organic-inorganic heterostructure 査読

    J Yamaura, Y Muraoka, T Yamauchi, T Muramatsu, Z Hiroi

    APPLIED PHYSICS LETTERS   83 ( 11 )   2097 - 2099   2003年9月

     詳細を見る

    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 INST PHYSICS  

    We show a perfect ultraviolet (UV) light selective and sensitive photovoltaic cell easily fabricated. The device consists of a water-soluble p-type semiconducting polymer PEDOT-PSS: poly(3,4-ethylenedioxythiophene) doped by poly(4-styrenesulfonate) film deposited on a Nb-doped titanium oxide (SrTiO3:Nb) substrate. For the PEDOT-PSS/SrTiO3:Nb heterostructure, the photosensitivity at zero bias for the UV light with L=1 mW/cm(2) is estimated to be 0.05 A/W, corresponding to a quantum yield of 16% electron/photon. This device is only activated in the UV region (lambda<390 nm), and then, it exhibits a large response to the UV-B light (290-320 nm). (C) 2003 American Institute of Physics.

    DOI: 10.1063/1.1610793

    Web of Science

    researchmap

  • Photocarrier injection to transition metal oxides 査読

    Y Muraoka, Z Hiroi

    JOURNAL OF THE PHYSICAL SOCIETY OF JAPAN   72 ( 4 )   781 - 784   2003年4月

     詳細を見る

    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  

    An efficient and clean method of doping transition metal oxides (TMOs) with hole carriers is presented. We have fabricated oxide heterostructures made of various TMO thin films grown on n-type titanium oxide substrates, and measured in-plane resistance under ultraviolet light irradiation. It is shown that the resistance of the insulating TMOs is reduced significantly with increasing light irradiance, as a result of photoinduced hole carrier injection from the titanium oxide substrates. A generic band structure for the heterojunctions is proposed, in which a large potential slope and a small barrier exist near the interface for photoinduced holes and electrons in the titanium oxides, respectively. This photocarrier injection (PCI) technique would provide us with a useful method to achieve the external control of hole carrier density in TMOs.

    DOI: 10.1143/JPSJ.72.781

    Web of Science

    researchmap

  • Correlations and semimetallic behaviors in pyrochlore oxide Cd2Re2O7 査読

    Z Hiroi, M Hanawa, Y Muraoka, H Harima

    JOURNAL OF THE PHYSICAL SOCIETY OF JAPAN   72 ( 1 )   21 - 24   2003年1月

     詳細を見る

    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  

    Electronic properties of the metallic pyrochlore oxide Cd2Re2O7 are studied by means of electrical resistivity and Hall measurements. Semimetallic band structures are revealed as expected from band structure calculations. It is found that large changes in carrier density and mass occur at the structural phase transition at T-s1 = 200K. A large mass enhancement is observed, particularly for the high-temperature phase with the ideal pyrochlore structure, suggesting that an anomalous correlation has an important effect on the itinerant electrons in the pyrochlore lattice.

    DOI: 10.1143/JPSJ.72.21

    Web of Science

    researchmap

  • Efficient photocarrier injection in a transition metal oxide heterostructure 査読

    Y Muraoka, T Yamauchi, Y Ueda, Z Hiroi

    JOURNAL OF PHYSICS-CONDENSED MATTER   14 ( 49 )   L757 - L763   2002年12月

     詳細を見る

    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  

    An efficient method for doping a transition metal oxide (TMO) with hole carriers is presented: photocarrier injection (PCI) in an oxide heterostructure. It is shown that an insulating vanadium dioxide (VO2) film is rendered metallic under light irradiation by PCI from an n-type titanium dioxide (TiO2) substrate doped with Nb. Consequently, a large photoconductivity, which is exceptional for TMOs, is found in the VO2/TiO2:Nb heterostructure. We propose an electronic band structure where photoinduced holes created in TiO2:Nb can be transferred into the filled V 3d band via the low-lying O 2p band of VO2.

    DOI: 10.1088/0953-8984/14/49/104

    Web of Science

    researchmap

  • Second phase transition in pyrochlore oxide Cd2Re2O7 査読

    Z Hiroi, JI Yamaura, Y Muraoka, M Hanawa

    JOURNAL OF THE PHYSICAL SOCIETY OF JAPAN   71 ( 7 )   1634 - 1636   2002年7月

     詳細を見る

    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  

    Evidence of another phase transition at 120 K in the metallic pyrochlore oxide CdRe2O7, following a structural transition at 200K and followed by a superconducting transition at 1.0K, is obtained by resistivity, magnetoresistance, specific heat, and X-ray diffraction measurements. The results indicate unique successive structural and electronic transitions in the pyrochlore compound, revealing an interesting interplay between the crystal and electronic structures on the itinerant electron system in the pyrochlore lattice.

    DOI: 10.1143/JPSJ.71.1634

    Web of Science

    researchmap

  • Large modification of the metal-insulator transition temperature in strained VO2 films grown on TiO2 substrates 査読

    Y Muraoka, Y Ueda, Z Hiroi

    JOURNAL OF PHYSICS AND CHEMISTRY OF SOLIDS   63 ( 6-8 )   965 - 967   2002年6月

     詳細を見る

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

    Epitaxial thin films of vanadium dioxide (VO2) have been grown on TiO2 (001) and (110) substrates and the effect of uniaxial stress along the c-axis on the metal-insulator transition (MIT) Of VO2 has been studied. A large reduction in the transition temperature T-M1 from 341 K for a single crystal to 300 K has been observed in the film on TiO2 (001) where the c-axis length is compressed owing to an epitaxial stress, while the T-M1 has been increased to 369 K in the film on TiO2 (110) where the c-axis length is expanded. The correlation between the c-axis length and T-M1 is suggested: the shorter c-axis length results in the lower T-M1. (C) 2002 Elsevier Science Ltd. All rights reserved.

    Web of Science

    researchmap

  • Structural phase transition in the superconducting pyrochlore oxide Cd2Re2O7 査読

    M Hanawa, J Yamaura, Y Muraoka, F Sakai, Z Hiroi

    JOURNAL OF PHYSICS AND CHEMISTRY OF SOLIDS   63 ( 6-8 )   1027 - 1030   2002年6月

     詳細を見る

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

    We report a structural phase transition found at T-s = 200 K in a pyrochlore oxide Cd2Re2O7 which shows superconductivity at T-c = 1.0 K. X-ray diffraction experiments indicate that the phase transition is of the second-order, from a high-temperature phase with the ideal cubic pyrochlore structure (space group Fd (3) over barm) to a low-temperature phase with another cubic structure (space group F (4) over bar 3m). It is accompanied by a dramatic change in the resistivity and magnetic susceptibility and thus must induce a significant change in the electronic structure of Cd2Re2O7. (C) 2002 Elsevier Science Ltd. All rights reserved.

    DOI: 10.1016/S0022-3697(02)00090-2

    Web of Science

    researchmap

  • Metal-insulator transition of VO2 thin films grown on TiO2 (001) and (110) substrates 査読

    Y Muraoka, Z Hiroi

    APPLIED PHYSICS LETTERS   80 ( 4 )   583 - 585   2002年1月

     詳細を見る

    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 INST PHYSICS  

    The effect of uniaxial stress along the c axis on the metal-insulator transition of VO2 has been studied in the form of epitaxial thin films grown on TiO2 (001) and (110) substrates. A large reduction in the transition temperature T-MI from 341 K for a single crystal to 300 K has been observed in the film on TiO2 (001) where the c-axis length is compressed owing to an epitaxial stress, while the T-MI has been increased to 369 K in the film on TiO2 (110) where the c-axis length is expanded. The correlation between the c-axis length and T-MI is suggested: the shorter c-axis length results in the lower T-MI. (C) 2002 American Institute of Physics.

    DOI: 10.1063/1.1446215

    Web of Science

    researchmap

  • Superconductivity at 1 K in Cd2Re2O7 査読

    M Hanawa, Y Muraoka, T Tayama, T Sakakibara, J Yamaura, Z Hiroi

    PHYSICAL REVIEW LETTERS   87 ( 18 )   187001   2001年10月

     詳細を見る

    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  

    We report the first pyrochlore oxide superconductor Cd2Re2O7. Resistivity, magnetic susceptibility, and specific heat measurements on single crystals evidence a bulk superconductivity at 1 K. Another phase transition found at 200 K suggests, that a peculiar electronic structure lies behind the superconductivity.

    DOI: 10.1103/PhysRevLett.87.187001

    Web of Science

    researchmap

  • Atomic ordering in the LaFe0.5Mn0.5O3 solid solution film 査読

    K Ueda, Y Muraoka, H Tabata, T Kawai

    APPLIED PHYSICS LETTERS   78 ( 4 )   512 - 514   2001年1月

     詳細を見る

    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 INST PHYSICS  

    LaFe0.5Mn0.5O3 solid solution films have been formed on SrTiO3 (111) substrates using a pulsed laser deposition technique and their magnetic properties have been examined. The films showed ferromagnetic (or ferromagnetic) behavior with a Curie temperature of 380 K and the saturation magnetization was estimated to be about 1.5 mu (B) per magnetic ion site (B site). The x-ray photoemission spectra indicated that this behavior was due to the partial ordering of magnetic ions (Fe and Mn ions) which is caused by the charge disproportion between Fe and Mn ions under the film formation conditions. (C) 2001 American Institute of Physics.

    DOI: 10.1063/1.1343844

    Web of Science

    researchmap

  • Effects of light-irradiation on spin-glass state and magnetoresistive properties of Zn0.5Co0.5Fe2O4 spinel ferrite films 査読

    Y Muraoka, H Tabata, T Kawai

    SOLID STATE COMMUNICATIONS   120 ( 5-6 )   255 - 258   2001年

     詳細を見る

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

    Spin-glass spinel ferrite Zn0.5Co0.5Fe2O4 films were prepared on alpha -Al2O3(0001) substrates and the effect of light-irradiation on the spin-glass state was studied. The magnetization of prepared films showed a broad maximum at 260 K in a zero-field-cooled (ZFC) process, which is characteristic of a spin glass or a cluster glass. When shining light on the film under H = 1 kOe, the magnetization in the ZFC process increased, and returned to its original level when the light was turned off. This switching behavior was confirmed to work even at 350 K. magnetoresistance (MR) and photo-induced MR effects of this film are also described. (C) 2001 Elsevier Science Ltd. All rights reserved.

    DOI: 10.1016/S0038-1098(01)00373-8

    Web of Science

    researchmap

  • Room-temperature spin glass and its photocontrol in spinel ferrite films 査読

    Y Muraoka, H Tabata, T Kawai

    APPLIED PHYSICS LETTERS   77 ( 24 )   4016 - 4018   2000年12月

     詳細を見る

    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 INST PHYSICS  

    Room-temperature spin-glass states have been found in (Mg,Fe){Mg,Fe,Ti}(2)O-4 spinel ferrite thin films formed on Al2O3(0001) and SrTiO3(111) substrates. This elevated-temperature spin-glass state has been achieved by the fine tuning of spin states through the control of composition, random oxygen deficiencies, and the stress induced by the film/substrate lattice mismatch in the ferrite films. We have demonstrated the change of magnetic state by means of light irradiation from spin glass to a ferrimagnet over a wide range of temperatures below 290 K. The direct photoexcitation of spins with photon energy of 2.0 eV, which corresponds to the spin excitation energy for Fe ions, is the most effective for realizing photoinduced magnetization. (C) 2000 American Institute of Physics. [S0003-6951(00)01750-2].

    DOI: 10.1063/1.1331086

    Web of Science

    researchmap

  • Photoexcited spin-glass state in (Mg, Fe){Mg,Fe,Ti}O-4 spinel ferrite films 査読

    Y Muraoka, H Tabata, T Kawai

    JOURNAL OF APPLIED PHYSICS   88 ( 12 )   7223 - 7229   2000年12月

     詳細を見る

    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 INST PHYSICS  

    Spin-glass states above room temperature have been found in (Mg, Fe){Mg,Fe,Ti}(2)O-4 spinel ferrite thin films formed on Al2O3 (0001) and SrTiO3 (111) substrates. The films show a long-time relaxation of the magnetization in zero-field-cooled operation and a frequency dependence of the cusp temperature in ac susceptibility measurement, both of which are typical characteristics of a spin glass. This high-temperature spin-glass state has been achieved by the fine tuning of spin states through the control of composition, random oxygen deficiencies, and the stress induced by the film/substrate lattice mismatch, all of which give rise to effects that enhance the exchange interaction of spins in the ferrite films. We have demonstrated the change of magnetic state by means of light irradiation from spin glass to a ferrimagnet over a wide range of temperatures below 290 K. The direct photoexcitation of spins with photon energy in the visible-light region (1.7-3.2 eV), which corresponds to the spin excitation energy of crystal field for Fe ions located in both tetrahedral and octahedral sites, is effective for realizing photoinduced magnetization. (C) 2000 American Institute of Physics. [S0021-8979(00)05601-8].

    DOI: 10.1063/1.1327601

    Web of Science

    CiNii Article

    researchmap

  • Preparation and thickness dependence of magnetic properties of (111)-oriented Mg1.5FeTi0.5O4 spinel films on sapphire by pulsed laser deposition technique 査読

    Y Muraoka, K Ueda, H Tabata, T Kawai

    VACUUM   59 ( 2-3 )   622 - 627   2000年11月

     詳細を見る

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

    Thin films of (1 1 1)-oriented Mg1.5FeTi0.5O4 spinel have been successfully prepared by a pulsed laser deposition (PLD) technique on alpha -Al2O3 (0001) substrates. The value of the lattice parameter of the (1 1 1) out-of-plane and the Neel temperature of the films depend on the film thickness. The spin-glass behavior has been observed with a freezing temperature of 100 K, which is 80 K higher than that of the bulk material. This freezing temperature is reduced by increasing the oxygen pressure during film preparation. These results show that the PLD technique is promising not only for obtaining thin films of oxide materials under a wide range of conditions but also for controlling the magnetic properties of films. (C) 2000 Elsevier Science Ltd. All rights reserved.

    DOI: 10.1016/S0042-207X(00)00325-0

    Web of Science

    researchmap

  • HRTEM and micro-Raman studies on superconducting-superionic conducting nanohybrid, Ag1.17I1.54Bi2Sr2CaCu2Oy 査読

    JH Choy, YI Kim, SJ Hwang, Y Muraoka, N Ohnishi, K Hiraga, PV Huong

    JOURNAL OF PHYSICAL CHEMISTRY B   104 ( 39 )   9086 - 9090   2000年10月

     詳細を見る

    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  

    The crystal structure of the superconducting-superionic conducting nanohybrid, Ag1.17I1.54Bi2Sr2CaCu2Oy, has been investigated by performing high-resolution transmission electron microscopy (HRTEM) and micro-Raman spectroscopy. From the HRTEM image along the [110] direction, it is found that a hexagonal-like array of AgI4 tetrahedra is stabilized between each [Bi-O](2) double layer with a staggered configuration of host block. The two-dimensionally extended Ag-I sublattice provides a favorable migration path for Ag+ ions that is consistent with high ionic conductivity of the Ag-I intercalate. According to the polarized micro-Raman spectroscopy, the doubly split O-Sr phonon line is collapsed into a single one upon Ag-I intercalation, as observed in the phase of IBi2Sr2CaCu2Oy. Such an evolution of the O-Sr phonon peak is surely attributed to a weakening of the O-Bi-Bi-O-Sr coupling due to the remarkable lattice expansion, which is in good agreement with the HRTEM result.

    DOI: 10.1021/jp993096w

    Web of Science

    researchmap

  • Consolidation of Bi-Sr-Ca-Cu-O superconductors by the shock-loading method 査読

    M Kikuchi, H Faqir, S Kawamata, K Okuda, Y Muraoka, K Fukuoka, Y Syono

    SUPERCONDUCTOR SCIENCE & TECHNOLOGY   13 ( 8 )   1151 - 1154   2000年8月

     詳細を見る

    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  

    Shock compaction experiments were carried out for Bi2223 to prepare a dense, oriented bulk specimen. The shocked specimen exhibited a high degree of crystallographic orientation and a high density, above 96%. The optimal condition of the crystallographic orientation was attained at a shock pressure of 5 GPa and at annealing temperatures between 750 and 800 degrees C. The post annealing of a specimen shocked at 5 GPa was effective in increasing Delta M, indicating the introduction of pinning sites. The magnetic torque measurements showed that a high degree of orientation was attained and many pinning centres were induced by the shock loading.

    DOI: 10.1088/0953-2048/13/8/307

    Web of Science

    researchmap

  • Photocontrol of spin-glass state in Mg1.5FeTi0.5O4 spinel ferrite films 査読

    Y Muraoka, H Tabata, T Kawai

    APPLIED PHYSICS LETTERS   76 ( 9 )   1179 - 1181   2000年2月

     詳細を見る

    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 INST PHYSICS  

    A spin-glass state up to 210 K has been found in (Mg, Fe){Mg,Fe,Ti}(2)O-4 spinel ferrite thin films formed on alpha-Al2O3(0001) substrates. The films exhibit long-time relaxation of the magnetization in zero-field-cooled operation below 210 K; also, the ac susceptibility measurements show the presence of frequency-dependent cusp temperature. Both of the above observations are characteristic features of a spin glass. The change of magnetic state in the films from a spin glass to ferrimagnet has been achieved over a wide temperature range below 160 K by means of light irradiation. (C) 2000 American Institute of Physics. [S0003-6951(00)04209-1].

    DOI: 10.1063/1.125975

    Web of Science

    researchmap

  • Preparation of -MnO2 with an open tunnel 査読

    J. Solid State Chem.   144 ( 1 )   136 - 142   1999年4月

     詳細を見る

    記述言語:英語   掲載種別:研究論文(学術雑誌)  

    DOI: 10.1006/jssc.1999.8133

    Web of Science

    researchmap

  • Preparation of hexagonal MoO3 by "Chimie Douce" reaction with NO2 査読

    Y Muraoka, JC Grenier, S Petit, M Pouchard

    SOLID STATE SCIENCES   1 ( 2-3 )   133 - 148   1999年3月

     詳細を見る

    記述言語:英語   掲載種別:研究論文(学術雑誌)   出版者・発行元:EDITIONS SCIENTIFIQUES MEDICALES ELSEVIER  

    The metastable hexagonal form of MoO3 has been successfully prepared starting from the ammonium molybdate, using a "Chimie Douce" reaction with NO2 gas. The lattice parameters of the as-prepared material were determined by XRD analysis to be : a = 10.633(2) Angstrom, and c = 3.719(1) Angstrom. The composition of this material obtained by physical and chemical analysis is MoO3, 0.09 H2O, showing that a small amount of water molecules remained while there were no more ammonium ions in this structure. The structural transformation from hexagonal to stable orthorhombic alpha-MoO3 phase was observed at 350 degrees C. It was also shown that NO2 reaction is a very useful method to remove topotactically ammonium ions from a parent structure at low temperature. This "Chimie Douce" process appears to be very promising for obtaining new metastable oxides with large tunnels or interlayer distances.

    DOI: 10.1016/S1293-2558(00)80070-9

    Web of Science

    researchmap

  • New synthetic routes for preparing perovskites - Electrochemical oxidation and oxidation by NO2 査読

    JC Grenier, JP Doumerc, Y Muraoka, S Petit, M Pouchard, A Wattiaux

    SOLID STATE IONICS   108 ( 1-4 )   9 - 15   1998年5月

     詳細を見る

    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  

    Two new synthetic low temperature routes for preparing perovskite-related materials, especially metastable phases are depicted. The first one, the electrochemical oxidation, uses the electric field as the driving force for intercalating oxygen atoms within parent oxide networks. The reaction is achieved under anodic potential, in alkaline solution (1 M KOH or NaOH), at room temperature, in air. This process has been used for preparing various perovskite compounds such as AMO(3) (A = Sr, La; M = Fe1-x Co-x) or A(2)MO(4+delta) (A = La, Nd, Sr). The most relevant results are reported. Potentiostatic and galvanostatic experiments have shown that the amount of intercalated oxygen can be controlled and that the process is reversible. Structural as well as electronic aspects of the oxygen intercalation are discussed and a reaction mechanism is proposed. The second route is based on the exothermic reaction of nitrogen dioxide NO2 with NH4+ ions at moderate temperatures (typically T < 300 degrees C), which allowed the destruction of NH4+ cations in situ. Topotactic reactions are described for preparing new hexagonal forms of WO3 or MoO3. The reaction process is discussed. (C) 1998 Elsevier Science B.V. All rights reserved.

    DOI: 10.1016/S0167-2738(98)00012-5

    Web of Science

    researchmap

  • New "chimie douce" oxidizing processes: Electrochemical oxidation and in situ oxidation by NO2 査読

    Jean-Claude Grenier, Jean-Pierre Doumerc, Yuji Muraoka, Stephane Petit, Michel Pouchard, Alain Wattiaux, Fang Zhou

    Molecular Crystals and Liquid Crystals Science and Technology Section A: Molecular Crystals and Liquid Crystals   311   359 - 366   1998年

     詳細を見る

    記述言語:英語   掲載種別:研究論文(学術雑誌)   出版者・発行元:Taylor and Francis Inc.  

    Two new oxidation processes are described : the electrochemical oxidation in alkaline solution uses the electrical potential as the driving force for intercalating oxygen, at room temperature, into oxide networks such as perovskites or Ln2MO4 (M = Ni, Cu) compounds. The second one is based on the in situ destruction of ammonium ions in oxide lattices by interaction with NO2 gas, at moderate temperatures. Pictures of the reaction mechanisms are also proposed. © 1993 OPA (Overseas Publishers Association) Amsterdam B.V. Published under license under the Gordon and Breach Science Publishers imprint.

    DOI: 10.1080/10587259808042411

    Scopus

    researchmap

  • Growth of high-quality Bi2Sr2CaCu2Oz crystal and characterization 査読

    H Faqir, G Vacquier, H Chiba, M Kikuchi, Y Muraoka, Y Syono

    JOURNAL OF MATERIALS RESEARCH   12 ( 10 )   2522 - 2525   1997年10月

     詳細を見る

    記述言語:英語   掲載種別:研究論文(学術雑誌)   出版者・発行元:MATERIALS RESEARCH SOCIETY  

    We report growth of high-quality Bi2Sr2CaCu2Oz single crystals with dimensions 2 x 1 x 0.03 mm(3) with a melt and growth technique. The composition of this crystal is homogeneous and very close to the stoichiometric composition. Structure characterization of a single crystal was realized by measuring the (001) x-ray diffraction. The lattice parameters of a typical crystal are a = 5.414(2) Angstrom, b = 5.413(2) Angstrom, and c = 30.823(10) Angstrom. The superconducting temperature T-c = 95 K with a sharp transition width (10-90% level) between 6 and 10 K was determined from resistivity and de susceptibility. We have measured the magnetization of Bi2Sr2CaCu2Oz single crystal under magnetic field applied along the c-axis. The anomalous second peak effect appeared between 20 and 30 K. We discuss the qualities of these crystals.

    DOI: 10.1557/JMR.1997.0334

    Web of Science

    researchmap

  • Ferromagnetism and large negative magnetoresistance in Bi1-xCaxMnO3 (x>=0.8) perovskite 査読

    H Chiba, M Kikuchi, K Kusaba, Y Muraoka, Y Syono

    SOLID STATE COMMUNICATIONS   99 ( 7 )   499 - 502   1996年8月

     詳細を見る

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

    Polycrystalline perovskite manganites Bi1-xCaxMnO3 (x greater than or equal to 0.8) have been prepared by standard ceramic technique, and their magnetic and electronic property are examined down to 5 K. Ferromagnetic moment and reduced resistivity are observed for Bi1-xCaxMnO3 (x greater than or equal to 0.875), and also large negative magnetoresistances appear below T-c. Copyright (C) 1996 Elsevier Science Ltd

    DOI: 10.1016/0038-1098(96)00305-5

    Web of Science

    researchmap

  • AgI-intercalation into Bi2Sr2CaCu2Oz compound 査読

    Y Muraoka, N Ohnishi, M Nagoshi, Y Morioka, M Kikuchi, K Hiraga, N Kobayashi, Y Syono

    PHYSICA C   263 ( 1-4 )   193 - 196   1996年5月

     詳細を見る

    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  

    Polycrystalline AgI-intercalated Bi2Sr2CaCu2Oz is prepared and the structure and physical properties studied. The lattice parameters a and c are determined to be 5.40 and 22.8 Angstrom, respectively. The expansion of the lattice parameter c is 7.4 Angstrom, compared with that of a Bi2Sr2CaCu2Oz (Bi2212) specimen (c/2: 15.4 Angstrom). This expansion is more than twice as large as that of iodine-intercalation (3.6 Angstrom). The EPMA measurement shows that the I/Ag ratio in the AgI-intercalated specimen is greater than 1.0. The T-c is 69 K, which is lower than that of Bi2212 (75 K) and almost the same as that of IBi2Sr2CaCu2Oz (IBi2212, 67 K). The effect of AgI-intercalation on the superconductivity is discussed.

    DOI: 10.1016/0921-4534(96)00035-4

    Web of Science

    researchmap

  • Synthesis conditions and superconductivity of Pb0.7Cu0.3Sr2Y0.5Ca0.5Cu2Oy 査読

    M Kikuchi, M Shida, E Ohshima, Y Muraoka, Y Syono

    PHYSICA C   263 ( 1-4 )   204 - 207   1996年5月

     詳細を見る

    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  

    Pb0.7Cu0.3Sr2Y0.5Ca0.5Cu2Oy was synthesized as a mother specimen in air and then annealed under two different experimental conditions, in an oxidizing and in a reducing condition. The mother specimen was a nonsuperconductor, but both annealed specimens, one quenched from high temperature and the other treated in high-pressure O-2, were superconductors with T-c's of about 50 K and about 60 K, respectively. The low Cu-valence of the quenched specimen which showed superconductivity suggests a decrease in the Pb-valence, while the high T, of the specimen treated in high-pressure O-2 would be explained by high Cu-valence and Pb4+.

    DOI: 10.1016/0921-4534(95)00824-1

    Web of Science

    researchmap

  • STRUCTURE AND SUPERCONDUCTIVITY OF IODINE-INTERCALATED BI2SR4CU2CO3OZ 査読

    Y MURAOKA, H NAMEKI, M KIKUCHI, S AWAJI, N KOBAYASHI, Y SYONO

    PHYSICA C   233 ( 1-2 )   209 - 213   1994年11月

     詳細を見る

    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  

    Iodine intercalation of a bismuth oxycarbonate, Bi2Sr4Cu2CO3Ox was successfully made. Expansion along the c-axis due to intercalation was estimated to be 3.6 Angstrom per half of the c-dimension in the host material, showing that a stage-1 compound was yielded. Interestingly, the semiconductor host material became superconducting with T-c = 23 K due to intercalation. This result tan be explained as hole doping from the intercalated iodine to the CuO2 sheet of the pristine compound.

    DOI: 10.1016/0921-4534(94)00591-5

    Web of Science

    researchmap

  • Synthesis and superconductivity of ‘Hg2Cl2’-intercalated Bi2Sr2Can-1CunOz (n=1-3) compounds 査読

    Physica C   233 ( 3-4 )   247 - 252   1994年11月

     詳細を見る

    記述言語:英語   掲載種別:研究論文(学術雑誌)  

    DOI: 10.1016/0921-4534(94)90750-1

    Web of Science

    researchmap

  • SYNTHESIS AND SUPERCONDUCTIVITY OF OXYCARBONATES OF THE TL-1201 PHASE 査読

    M KIKUCHI, E OHSHIMA, N OHNISHI, Y MURAOKA, S NAKAJIMA, E AOYAGI, M OGAWA, J AKIMITSU, T OKU, K HIRAGA, Y SYONO

    PHYSICA C   219 ( 1-2 )   200 - 204   1994年1月

     詳細を見る

    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  

    TlBaxSr4-xCu2(CO3)Oy oxycarbonates with the Tl-1201 structure were synthesized over a wide range of x (1.0 less-than-or-equal-to x less-than-or-equal-to 3.2) and examined by X-ray powder diffraction, electron diffraction, high-resolution electron microscopy and magnetometry methods. New phases with the Tl-1201 structure having 6 and 7 times periodicities along the b-axis were isolated. The former was stable for a wide Ba-rich range (1.8 less-than-or-equal-to x less-than-or-equal-to 3.2), and the latter was observed for a smaller Ba content range (1.2 less-than-or-equal-to x less-than-or-equal-to 1.6). The phase stability was found to depend on the synthesis condition. The maximum T(c) of the as-synthesized specimen in this series occurred at about 70 K around x = 2.0. The Meissner volume fraction of the as-synthesized specimen (x = 2.4) was 30% at 5 K.

    DOI: 10.1016/0921-4534(94)90035-3

    Web of Science

    researchmap

  • EFFECTS OF IODINE INTERCALATION ON THE SUPERCONDUCTING PROPERTIES OF THE BI2SR2-XLAXCUOZ COMPOUND 査読

    Y MURAOKA, M KIKUCHI, H NAMEKI, S AWAJI, R SUZUKI, N KOBAYASHI, Y SYONO

    PHYSICA C   215 ( 3-4 )   402 - 406   1993年10月

     詳細を見る

    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  

    Iodine intercalation of Bi2Sr2-xLaxCuOx (0.4 less-than-or-equal-to x less-than-or-equal-to 1.0) was studied. Transition from orthorhombic pristine phase to tetragonal intercalated phase was observed due to iodine intercalation. The expansion of the c-axis of the stage-1 intercalation compound increases slightly with increasing La content x. The T(c) of iodine-intercalated specimens with 0.4 less-than-or-equal-to x less-than-or-equal-to 0.6 decreases from that of the pristine, but in the range of 0.7 less-than-or-equal-to x less-than-or-equal-to 0.9, the T(c) of the intercalated specimen increases with respect to that of the pristine phase. Especially, the non-superconducting specimen with x = 0.9 became superconducting due to intercalation. This result demonstrates hole doping by iodine intercalation, i.e. the Cu valence of the pristine compound is increased.

    DOI: 10.1016/0921-4534(93)90242-I

    Web of Science

    researchmap

  • STRUCTURAL AND SUPERCONDUCTING PROPERTIES OF IODINE-INTERCALATED BI2SR2CA1-XYXCU2OZ 査読

    Y MURAOKA, M KIKUCHI, N OHNISHI, K HIRAGA, R SUZUKI, N KOBAYASHI, Y SYONO

    PHYSICA C   204 ( 1-2 )   65 - 70   1992年12月

     詳細を見る

    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 structual and superconducting properties of Bi2Sr2Ca1-xYxCu2Oz intercalated with iodine between the Bi-O bilayers were studied. Formation of the stage-1 compound was verified by X-ray analysis, TG analysis and TEM observation. Expansion of the c-axis, which is caused by increase in the distance of the BiO-BiO layers, decreases with decreasing intercalated iodine concentration down to 60%. The expansion of the c-axis of fully intercalated compounds increases with increasing Y content from 7.2 angstrom for x = 0 to 7.5 angstrom for x = 1.O. The temperature dependence of resistivity showed that iodine-doped samples (x = 0 and 0.4) were more semiconductive than non-doped samples. The T(c) of the IBi2Sr2Ca1-xYxCu2Oz series in the over-doped region was reduced by 2-10 K compared with non-intercalated samples.

    DOI: 10.1016/0921-4534(92)90573-U

    Web of Science

    researchmap

▼全件表示

MISC

  • Ti-15V-7Al 合金の低温と高温で形成されるマルテンサイト変態 査読

    竹元嘉利, 恒川弥佑, 真鍋侑司, 板野壮志, 村岡祐治

    日本金属学会誌   82 ( 8 )   307 - 313   2018年

     詳細を見る

    記述言語:日本語   掲載種別:記事・総説・解説・論説等(学術雑誌)  

    researchmap

  • Surface physical property of the CrO 2 thin films prepared using a closed chemical vapor deposition method 査読

    Y. Muraoka, S. Yoshida, T. Wakita, M. Hirai, T. Yokoya

    Materials Research Society Symposium Proceedings   1406   17 - 22   2012年

     詳細を見る

    記述言語:英語   掲載種別:記事・総説・解説・論説等(国際会議プロシーディングズ)  

    We have examined the intrinsic surface physical property of a CrO 2 thin film by means of surface sensitive photoemission spectroscopy. Epitaxial thin film of CrO 2(100) has been grown on TiO 2(100) by a closed chemical vapor deposition method using a Cr 8O 21 precursor. Low-energy electron diffraction (LEED) observations find that epitaxial growth of rutile-phase CrO 2 occurs to the top monolayer of the film. Surface sensitive x-ray photoemission spectroscopy (XPS) measurements show a finite intensity in the region of the Fermi energy. The result evidences that the physical nature of near topmost layer of CrO 2 thin film is metallic. Progress of understanding of the surface physical property of CrO 2 thin film helps not only perform a reliable photoemission study to understand the physics of ferromagnetic metal in CrO 2, but also develop the CrO 2-based devices using a half-metallic nature for spintronics applications. © 2012 Materials Research Society.

    DOI: 10.1557/opl.2012.177

    Scopus

    researchmap

  • Preparation of the CrO2 thin films using a Cr8O 21 precursor 査読

    Y. Muraoka, K. Iwai, S. Yoshida, T. Wakita, M. Hirai, T. Yokoya, Y. Kato, T. Muro, Y. Tamenori

    Materials Research Society Symposium Proceedings   1292   87 - 92   2011年

     詳細を見る

    記述言語:英語   掲載種別:記事・総説・解説・論説等(国際会議プロシーディングズ)  

    We have prepared a CrO2 thin film by chemical vapor deposition from a Cr8O21 precursor and studied the bulk and surface physical properties. The CrO2 thin film is grown on TiO 2(100) substrate by heating precursor and TiO2 (100) substrate together in a sealed quartz tube. The prepared film is found from x-ray diffraction analysis to be an (100)-oriented single phase. The magnetization and resistivity measurements indicate that the film is a ferromagnetic metal with a Curie temperature of about 400 K. Cr 3s core-level and valence band photoelectron spectroscopy spectra reveal the presence of a metallic CrO2 in the surface region of the film. Our work indicates that preparation from a Cr8O21 precursor in a closed system is promising for obtaining a CrO2 thin film with the metallic surface. © 2011 Materials Research Society.

    DOI: 10.1557/opl.2011.154

    Scopus

    researchmap

  • 光ドーピングで制御する強相関物性 査読

    村岡祐治, 広井善二

    パリティ   20   52 - 55   2005年

     詳細を見る

    記述言語:日本語   掲載種別:記事・総説・解説・論説等(学術雑誌)  

    researchmap

  • 遷移金属酸化物へテロ接合における光キャリア注入 査読

    広井善二, 村岡祐治, 村松孝樹, 山内徹, 山浦淳一

    固体物理   39   211 - 224   2004年

     詳細を見る

    記述言語:日本語   掲載種別:記事・総説・解説・論説等(学術雑誌)  

    researchmap

  • Effects of iodine intercalation on the structural and superconducting properties of Bi2Sr2-xLnxCuOz (Ln=Nd and Sm) compound

    Y. Muraoka, M. Kikuchi, M. Hiroi, N. Kobayashi, K. Hiraga, Y. Syono

    Advances in Superconductivity   XI   431 - 434   1999年

     詳細を見る

    記述言語:英語   掲載種別:記事・総説・解説・論説等(国際会議プロシーディングズ)  

    researchmap

  • "Creation of Novel Properties on Ferromagnetic・Ferroelectric Superlattices" 共著

    Transaction of the Materials Research Society of Japan   24 ( 1 )   13 - 18   1999年

     詳細を見る

▼全件表示

講演・口頭発表等

  • スピノーダル分解を用いたTiO2-VO2系ナノ構造膜の形成 招待

    第30回日本MRS年次大会  2020年12月10日 

     詳細を見る

    開催年月日: 2020年12月9日 - 2020年12月11日

    記述言語:日本語   会議種別:口頭発表(招待・特別)  

    researchmap

  • DLC膜のsp3量とレーザーエネルギー密度の調整によるQカーボンの作製

    第30回日本MRS年次大会  2020年12月9日 

     詳細を見る

    開催年月日: 2020年12月9日 - 2020年12月11日

    記述言語:日本語   会議種別:口頭発表(一般)  

    researchmap

  • スピノーダル分解したTiO2-VO2系膜における格子歪とラメラ周期の関係

    村岡祐治, 福田貴優, 脇田高徳, 横谷尚睦, 竹元嘉利

    第81回応用物理学会 秋季学術講演会  2020年9月9日 

     詳細を見る

    開催年月日: 2020年9月8日 - 2020年9月11日

    記述言語:日本語   会議種別:口頭発表(一般)  

    researchmap

  • sp3分率とレーザー密度をパラメータとしたQ-カーボンの作製

    村岡祐治, 芳中大樹, 犬伏聖子, 脇田高徳, 横谷尚睦

    第81回応用物理学会 秋季学術講演会  2020年9月8日 

     詳細を見る

    開催年月日: 2020年9月8日 - 2020年9月11日

    記述言語:日本語   会議種別:口頭発表(一般)  

    researchmap

  • sp3量とレーザー出力の調整によるQカーボンの作製

    村岡祐治, 芳中大樹, 犬伏聖子, 脇田高徳, 横谷尚睦

    2020年度 応用物理・物理系学会中国四国支部合同学術講演会  2020年8月2日 

     詳細を見る

    開催年月日: 2020年8月2日

    記述言語:日本語   会議種別:口頭発表(一般)  

    researchmap

  • TiO2-RuO2系膜における異方的スピノーダル分解発生の試み

    村岡祐治, 前川拓哉, 脇田高徳, 横谷尚睦, 竹元嘉利

    第67回応用物理学会 春季学術講演会  2020年3月13日 

     詳細を見る

    開催年月日: 2020年3月12日 - 2020年3月15日

    記述言語:日本語   会議種別:口頭発表(一般)  

    researchmap

  • Change in work function of VO2 at the metal-insulator transition in a VO2/TiO2:Nb(001) heterojunction

    Yuji Muraoka, Yuki Suga, Hayato Nakahara, Takayoshi Yokoya

    International Conference on Strongly Correlated Electron Systems (SCES) 2019, Okayama Convention Center, Okayama, Japan,  2019年9月26日 

     詳細を見る

    記述言語:英語   会議種別:ポスター発表  

    researchmap

  • VO2/TiO2:Nb接合界面を活用したVO2薄膜の仕事関数の評価

    村岡祐治, 壽賀友貴, 脇田高徳, 横谷尚睦

    第80回応用物理学会 秋季学術講演会、北海道大学 札幌キャンパス  2019年9月18日 

     詳細を見る

    記述言語:日本語   会議種別:口頭発表(一般)  

    researchmap

  • VO2の薄膜作製について 招待

    村岡祐治

    日本表面真空学会 スパッタリングおよびプラズマプロセス技術部会 第162回定例研究会「酸化バナジウム薄膜の作製とその応用」  2019年9月13日 

     詳細を見る

    記述言語:日本語   会議種別:口頭発表(招待・特別)  

    researchmap

  • ルチル型複合酸化物薄膜の作製と機能探索 招待

    村岡祐治

    第69回 CVD研究会(第30回夏季セミナー)高知工科大学 永国寺キャンパス  2019年8月8日 

     詳細を見る

    記述言語:日本語   会議種別:口頭発表(招待・特別)  

    researchmap

  • Ti0.4V0.6O2/TiO2(100)膜界面近傍のスピノーダル分解

    村岡祐治, 壽賀友貴, 寺嶋健成, 脇田高徳, 横谷尚睦

    2019年度 応用物理・物理系学会中国四国支部合同学術講演会 高知工科大学 香美キャンパス  2019年7月21日 

     詳細を見る

    記述言語:日本語   会議種別:口頭発表(一般)  

    researchmap

  • ARPES study on a metallic phase of VO2/TiO2(001) thin films

    Yuji Muraoka, Hiroki Nagao, Yuichiro Yao, Takanori Wakita, Kensei Terashima, Takayoshi Yokoya, Hiroshi Kumigashira, Masaharu Oshima

    The 23th Hiroshima International Symposium on Synchrotron Radiation  2019年3月7日 

     詳細を見る

    記述言語:英語   会議種別:ポスター発表  

    researchmap

  • Formation of multilayer structure via spinodal decomposition in TiO2-VO2 epitaxial films 招待

    Y. Muraoka, Y. Matsuura, Y. Takemoto, K. Terashima, T. Wakita, T. Yokoya

    The 2nd International Conference on Advanced Materials and Processes for Environment, Energy and Health, Holiday inn, Montreal, Canada  2018年10月31日 

     詳細を見る

    記述言語:英語   会議種別:口頭発表(招待・特別)  

    researchmap

  • TiO2-VO2系膜におけるスピノーダル分解と格子歪

    村岡祐治, 吉井文哉, 寺嶋健成, 脇田高徳, 横谷尚睦

    第79回応用物理学会 秋季学術講演会、名古屋国際会議場  2018年9月19日 

     詳細を見る

    記述言語:日本語   会議種別:口頭発表(一般)  

    researchmap

  • VO2薄膜金属相の電子状態

    村岡祐治

    第3回「表面界面の機能創製とデバイス応用」セミナー  2018年8月7日 

     詳細を見る

    記述言語:日本語   会議種別:口頭発表(一般)  

    researchmap

  • スピノーダル分解を用いたTiO2-VO2多層構造膜の作製

    村岡 祐治, 松浦 由佳, 真部 侑司, 鈴木 雄基, 荒木 稜, 門脇 賢司, 竹元 嘉利, 寺嶋健成, 脇田 高徳, 横谷 尚睦

    2018年度 応用物理・物理系学会中国四国支部合同学術講演会 広島大学東広島キャンパス  2018年8月4日 

     詳細を見る

    記述言語:日本語   会議種別:口頭発表(一般)  

    researchmap

  • TiO2-VO2系配向膜におけるスピノーダル分解

    村岡祐治, 松浦由佳, 真鍋侑司, 鈴木雄基, 荒木稜, 門脇賢司, 竹元利嘉, 寺嶋健成, 脇田高徳, 横谷尚睦

    第65回応用物理学会 春季学術講演会、早稲田大学 西早稲田キャンパス  2018年3月20日 

     詳細を見る

    記述言語:日本語   会議種別:口頭発表(一般)  

    researchmap

  • XPS study of boron-doped diamond films covered by V2O5

    The 22th Hiroshima International Symposium on Synchrotron Radiation  2018年3月8日 

     詳細を見る

    記述言語:英語   会議種別:ポスター発表  

    researchmap

  • TiO2-VO2系におけるスピノーダル分解膜の作製 招待

    村岡祐治

    第2回「表面界面の機能創製とデバイス応用」セミナー  2018年2月27日 

     詳細を見る

    記述言語:日本語   会議種別:口頭発表(招待・特別)  

    researchmap

  • サファイア基板上へのTiO2-VO2系スピノーダル分解膜の作製

    村岡祐治, 松浦由佳, 門脇賢司, 井尻正孝, 竹元嘉利, 寺嶋健成, 脇田高徳, 横谷尚睦

    2017年度 第78回応用物理学会秋季学術講演会 福岡国際会議場・福岡国際センター・福岡サンパレス  2017年9月7日 

     詳細を見る

    記述言語:日本語   会議種別:口頭発表(一般)  

    researchmap

  • XPS study of TaO2 thin films

    Y. Muraoka, Y. Fujimoto, M. Kameoka, Y. Matsuura, M. Sunagawa, K. Terashima, T. Wakita, T. Yokoya

    The 21th Hiroshima International Symposium on Synchrotron Radiation  2017年3月2日 

     詳細を見る

    記述言語:英語   会議種別:ポスター発表  

    researchmap

  • NbO2テンプレート層を用いた、PLD法によるTaO2薄膜の作製

    村岡祐治, 藤本佑樹, 亀岡美咲, 松浦由佳, 砂川正典, 寺嶋健成, 脇田高徳, 横谷尚睦

    第63回応用物理学会 春季学術講演会、東京工業大学 大岡山キャンパス  2016年3月22日 

     詳細を見る

    記述言語:日本語   会議種別:口頭発表(一般)  

    researchmap

  • TiO2-VO2系における異方的スピノーダル分解とその制御 招待

    村岡祐治

    第76回応用物理学会 秋季学術講演会、名古屋国際会議場  2015年9月15日 

     詳細を見る

    記述言語:日本語   会議種別:口頭発表(招待・特別)  

    researchmap

  • ルチル型 TiO2-VO2 系におけるスピノーダル分解 招待

    村岡祐治

    第3回酸化物研究の新機軸に向けた学際討論会  2015年8月7日 

     詳細を見る

    記述言語:日本語   会議種別:口頭発表(招待・特別)  

    researchmap

  • スピノーダル分解したTiO2-VO2系薄膜の作製

    村岡祐治, 大塚翼, 寺嶋健成, 脇田高徳, 横谷尚睦

    2015年度 応用物理・物理系学会中国四国支部合同学術講演会 徳島大学常三島キャンパス  2015年8月1日 

     詳細を見る

    記述言語:日本語   会議種別:口頭発表(一般)  

    researchmap

  • ホットフィラメントCVD法により作製した高濃度ホウ素ドープダイヤモンド超伝導膜のキャリア濃度とTcの関係

    村岡祐治, 橘高朋子, 犬伏聖子, 寺嶋健成, 脇田高徳, 横谷尚睦

    日本物理学会 第70回年次大会、早稲田大学 早稲田キャンパス  2015年3月22日 

     詳細を見る

    記述言語:日本語   会議種別:口頭発表(一般)  

    researchmap

  • (Ti0.4V0.6)O2薄膜のスピノーダル分解

    村岡祐治, 大塚翼, 寺嶋健成, 脇田高徳, 横谷尚睦

    第62回応用物理学会 春季学術講演会、東海大学 湘南キャンパス  2015年3月12日 

     詳細を見る

    記述言語:日本語   会議種別:口頭発表(一般)  

    researchmap

  • Preparation and characterization of single-phase TaO2 thin films

    Yuji Muraoka, Yuki Fujimoto, Takanori Wakita, Takayoshi Yokoya

    Ushimado International Workshop on Physics and Chemistry of Novel Superconductors and Related Materials  2014年11月9日 

     詳細を見る

    記述言語:英語   会議種別:ポスター発表  

    researchmap

  • Preparation of a single-phase TaO2 thin film

    Yuji Muraoka, Yuki Fujimoto, Takanori Wakita, Takayoshi Yokoya

    第75回応用物理学会秋季学術講演会 北海道大学 札幌キャンパス  2014年9月18日 

     詳細を見る

    記述言語:英語   会議種別:口頭発表(一般)  

    researchmap

  • 単一相ルチル型TaO2薄膜の作製とその伝導特性

    村岡祐治, 藤本佑樹, 脇田高徳, 横谷尚睦

    日本物理学会 2014年秋季大会 中部大学 春日井キャンパス  2014年9月8日 

     詳細を見る

    記述言語:日本語   会議種別:口頭発表(一般)  

    researchmap

  • パルスレーザー堆積法による単一相TaO2薄膜の作製

    村岡祐治, 藤本佑樹, 脇田高徳, 横谷尚睦

    2014年度 応用物理・物理系学会中国四国支部合同学術講演会 島根大学松江キャンパス  2014年7月26日 

     詳細を見る

    記述言語:日本語   会議種別:口頭発表(一般)  

    researchmap

  • VO2薄膜における軟X線誘起絶縁体金属転移

    村岡祐治, 長尾浩樹, 脇田高徳, 横谷尚睦, 組頭広志, 尾嶋正治

    放射光科学による革新的イノベーションワークショップ  2014年3月14日 

     詳細を見る

    記述言語:日本語   会議種別:口頭発表(一般)  

    researchmap

  • Spin-resolved Photoemission Spectroscopy of CrO2 thin films

    The 18th Hiroshima International Symposium on Synchrotron Radiation  2014年3月6日 

     詳細を見る

    記述言語:英語   会議種別:ポスター発表  

    researchmap

  • VO2薄膜の金属相フェルミ面ネスティング

    村岡祐治, 長尾浩樹, 脇田高徳, 横谷尚睦, 組頭広志, 尾嶋正治

    日本物理学会 2013年秋季大会  2013年9月27日 

     詳細を見る

    記述言語:日本語   会議種別:口頭発表(一般)  

    researchmap

  • 低キャリア濃度で高Tcを示すホットフィラメントCVD法製ダイヤモンド超伝導膜

    村岡祐治, 平松千明, 脇田高徳, 横谷尚睦, 組頭広志, 尾嶋正治

    第74回応用物理学会秋季学術講演会  2013年9月18日 

     詳細を見る

    記述言語:日本語   会議種別:口頭発表(一般)  

    researchmap

  • Photocarrier injection to VO2 thin films 招待

    Yuji Muraoka, Takanori Wakita, Takayoshi Yokoya

    2013 JSAP-MRS joint symposia  2013年9月17日 

     詳細を見る

    記述言語:英語   会議種別:口頭発表(招待・特別)  

    researchmap

  • ホットフィラメント法で作製した高濃度ホウ素ドープダイヤモンド超伝導膜におけるホウ素の化学状態

    村岡祐治, 平松千明, 脇田高徳, 横谷尚睦

    応用物理学会中国四国支部、日本物理学会中国支部、四国支部、2013年度支部学術講演会  2013年7月27日 

     詳細を見る

    記述言語:日本語   会議種別:口頭発表(一般)  

    researchmap

  • Photo-induced insulator to metal transition for VO2 thin films

    Y. Muraoka, H. Nagao, T. Wakita, T. Yokoya

    The 17th Hiroshima International Symposium on Synchrotron Radiation  2013年2月28日 

     詳細を見る

    記述言語:英語   会議種別:ポスター発表  

    researchmap

  • Surface physical property of the CrO2 thin films

    Y. Muraoka, S. Yoshida, T. Wakita, M. Hirai, T. Yokoya

    International Symposium on Physics and Chemistry of Novel Superconductors and Related Materials  2012年10月2日 

     詳細を見る

    記述言語:英語   会議種別:ポスター発表  

    researchmap

  • VO2薄膜における光誘起 絶縁体-金属転移とその電子状態の観測

    村岡祐治, 長尾浩樹, 脇田高徳, 横谷尚睦, 組頭広志, 尾嶋正治

    日本物理学会 2012年秋季大会  2012年9月20日 

     詳細を見る

    記述言語:日本語   会議種別:口頭発表(一般)  

    researchmap

  • Effectiveness of a closed CVD method for preparation of CrO2 thin films

    Y. Muraoka, S. Yoshida, T. Wakita, T. Yokoya, H. Kumugashira, M. Oshima

    2012年秋季 第73回応用物理学会学術講演会  2012年9月12日 

     詳細を見る

    記述言語:英語   会議種別:口頭発表(招待・特別)  

    researchmap

  • CrO2単結晶薄膜作製における閉鎖系化学気相法の利点

    村岡祐治, 吉田祥, 脇田高徳, 横谷尚睦

    応用物理学会中国四国支部、日本物理学会中国支部、四国支部  2012年7月28日 

     詳細を見る

    記述言語:日本語   会議種別:口頭発表(一般)  

    researchmap

  • VO2薄膜における放射光誘起絶縁体金属転移

    村岡祐治, 長尾浩樹, 脇田高徳, 横谷尚睦

    応用物理学会中国四国支部、日本物理学会中国支部、四国支部  2012年7月28日 

     詳細を見る

    記述言語:日本語   会議種別:口頭発表(一般)  

    researchmap

  • 閉鎖系化学気相法により作製したCrO2薄膜の表面特性

    村岡祐治, 吉田祥, 脇田高徳, 平井正明, 横谷尚睦

    日本物理学会 第67回年次大会  2012年3月27日 

     詳細を見る

    記述言語:日本語   会議種別:口頭発表(一般)  

    researchmap

  • CrO2薄膜の表面特性

    村岡祐治, 吉田祥, 脇田高徳, 平井正明, 横谷尚睦

    2012年春季 第59回応用物理学関係連合講演会  2012年3月17日 

     詳細を見る

    記述言語:日本語   会議種別:口頭発表(一般)  

    researchmap

  • 光照射によるVO2薄膜への電子キャリア注入

    村岡祐治, 長尾浩樹, 大山卓郎, 脇田高徳, 平井正明, 横谷尚睦

    2012年春季 第59回応用物理学関係連合講演会  2012年3月17日 

     詳細を見る

    記述言語:日本語   会議種別:口頭発表(一般)  

    researchmap

  • Metallic surface of the CrO2 thin films prepared using a closed chemical vapor deposition method

    The 16th Hiroshima International Symposium on Synchrotron Radiation  2012年3月1日 

     詳細を見る

    記述言語:英語   会議種別:ポスター発表  

    researchmap

  • Surface physical property of the CrO2 thin films prepared using a closed chemical vapor deposition method

    2011 Fall Meeting of the Materials Research Society  2011年11月28日 

     詳細を見る

    記述言語:英語   会議種別:ポスター発表  

    researchmap

  • 放射光照射によるVO2薄膜への電子キャリア注入

    村岡祐治, 長尾浩樹, 脇田高徳, 平井正明, 横谷尚睦, 室隆桂之, 為則雄祐

    日本物理学会 2011年秋季大会  2011年9月21日 

     詳細を見る

    記述言語:日本語   会議種別:口頭発表(一般)  

    researchmap

  • Preparation of NbO2 thin films using a pulsed laser deposition method

    Y. Muraoka, Y. Fujimoto, C. Hiramatsu, T. Wakita, M. Hirai, T. Yokoya

    2011年秋季 第72回応用物理学会学術講演会  2011年8月31日 

     詳細を見る

    記述言語:英語   会議種別:口頭発表(一般)  

    researchmap

  • 低キャリア濃度で高Tcを示すホウ素ドープ超伝導ダイヤダイヤモンド膜の作製

    村岡祐治, 土居智彰, 平松千明, 脇田高徳, 平井正明, 横谷尚睦, 室隆桂之, 泉雄大, 為則雄祐

    2011年秋季 第72回応用物理学会学術講演会  2011年8月30日 

     詳細を見る

    記述言語:日本語   会議種別:ポスター発表  

    researchmap

  • VO2薄膜における放射光照射効果

    村岡祐治, 片山晋輔, 長尾浩樹, 脇田高徳, 平井正明, 横谷尚睦, 室隆桂之, 泉雄大, 為則雄祐

    応用物理学会中国四国支部、日本物理学会中国支部、四国支部  2011年7月30日 

     詳細を見る

    記述言語:日本語   会議種別:口頭発表(一般)  

    researchmap

  • ホットフィラメントCVD法により作製したホウ素ドープダイヤモンド膜の超伝導特性

    村岡祐治, 土居智彰, 平松千明, 脇田高徳, 平井正明, 横谷尚睦, 室隆桂之, 泉雄大, 為則雄祐

    応用物理学会中国四国支部、日本物理学会中国支部、四国支部  2011年7月30日 

     詳細を見る

    記述言語:日本語   会議種別:口頭発表(一般)  

    researchmap

  • NbO2薄膜の作製とその電子状態

    村岡祐治, 平松千明, 平井正明, 横谷尚睦

    日本物理学会 第66回年次大会  2011年3月28日 

     詳細を見る

    記述言語:日本語   会議種別:口頭発表(一般)  

    researchmap

  • ホットフィラメントCVD法による超伝導ホウ素ドープダイヤダイヤモンド膜の作製

    村岡祐治, 土居智彰, 平井正明, 横谷尚睦

    2011年春季 第58回応用物理学関係連合講演会  2011年3月26日 

     詳細を見る

    記述言語:日本語   会議種別:口頭発表(一般)  

    researchmap

  • Angle resolved photoemission spectroscopy measurements of metallic VO2 thin films

    The 15th Hiroshima International Symposium on Synchrotron Radiation  2011年3月3日 

     詳細を見る

    記述言語:英語   会議種別:ポスター発表  

    researchmap

  • 機能性ルチル型酸化物薄膜の作製とその電子状態

    村岡祐治

    第10回琉球物性研究会  2010年12月10日 

     詳細を見る

    記述言語:日本語   会議種別:口頭発表(一般)  

    researchmap

  • Preparation of the CrO2 thin films using a Cr8O21 precursor

    2010 Fall Meeting of the Materials Research Society  2010年12月3日 

     詳細を見る

    記述言語:英語   会議種別:ポスター発表  

    researchmap

  • 閉鎖系化学気相成長法によりCr8O21原料から作製したCrO2薄膜のバルクおよび表面特性評価

    村岡祐治, 岩井啓介, 吉田祥, 脇田高徳, 平井正明, 横谷尚睦, 加藤有香子, 室隆桂之, 為則雄祐

    日本物理学会 2010年秋季大会  2010年9月24日 

     詳細を見る

    記述言語:日本語   会議種別:口頭発表(一般)  

    researchmap

  • Bulk and surface physical properties of the CrO2 thin films prepared from a Cr8O21 precursor

    17th International Workshop on Oxide Electronics  2010年9月21日 

     詳細を見る

    記述言語:英語   会議種別:ポスター発表  

    researchmap

  • 閉鎖系化学気相成長法により作製したCrO2薄膜のバルクおよび表面特性

    村岡祐治, 岩井啓介, 吉田祥, 平井正明, 横谷尚睦, 加藤有香子, 室隆桂之, 為則雄祐

    応用物理学会中国四国支部、日本物理学会中国支部、四国支部  2010年7月30日 

     詳細を見る

    記述言語:日本語   会議種別:口頭発表(一般)  

    researchmap

  • Synthesis and physical properties of the hollandite-type titanium oxide KxTi8O16

    The 37th International Symposium on Compound Semiconductors iscs2010  2010年5月31日 

     詳細を見る

    記述言語:英語   会議種別:ポスター発表  

    researchmap

  • Cr8O21を原料に用いたCrO2薄膜の作製とその表面特性

    村岡祐治, 岩井啓介, 脇田高徳, 平井正明, 横谷尚睦, 加藤有香子, 室隆桂之, 為則雄祐

    日本物理学会 第65回大会年次大会  2010年3月23日 

     詳細を見る

    記述言語:日本語   会議種別:口頭発表(一般)  

    researchmap

  • Preparation of surface metallic CrO2 thin films

    The 14th Hiroshima International Symposium on Synchrotron Radiation  2010年3月4日 

     詳細を見る

    記述言語:英語   会議種別:ポスター発表  

    researchmap

  • Band dispersion near the Fermi level for VO2 thin films grown on TiO2 (001) substrates

    11th International Conference on Electronic Spectroscopy and Structure (ICESS-11)  2009年10月6日 

     詳細を見る

    記述言語:英語   会議種別:ポスター発表  

    researchmap

  • 表面まで金属特性を示すCrO2薄膜の作製

    村岡祐治, 岩井啓介, 脇田高徳, 平井正明, 横谷尚睦, 加藤有香子, 室隆桂之, 為則雄祐

    日本物理学会2009年秋季大会  2009年9月28日 

     詳細を見る

    記述言語:日本語   会議種別:口頭発表(一般)  

    researchmap

  • バーネサイト型MnO2におけるMnのスピン状態

    村岡祐治, 田嶋光俊, 脇田高徳, 平井正明, 横谷尚睦, 加藤有香子, 室隆桂之, 為則雄祐

    応用物理学会中国四国支部、日本物理学会中国支部、四国支部  2009年8月1日 

     詳細を見る

    記述言語:日本語   会議種別:口頭発表(一般)  

    researchmap

  • ホランダイト型マンガン酸化物(NH4)xMn8O16内に存在する窒素の役割

    村岡祐治, 田嶋光俊, 脇田高徳, 平井正明, 横谷尚睦, 室隆桂之, 為則雄祐

    2009年春季 第56回応用物理学関係連合講演会  2009年3月29日 

     詳細を見る

    記述言語:日本語   会議種別:口頭発表(一般)  

    researchmap

  • MnO2多形の光電子分光

    村岡祐治, 田嶋光俊, 脇田高徳, 平井正明, 横谷尚睦, 加藤有香子, 室隆桂之, 為則雄祐

    日本物理学会(第64回年次大会)  2009年3月29日 

     詳細を見る

    記述言語:日本語   会議種別:口頭発表(一般)  

    researchmap

  • Spin state of Mn ion in birnessite-type manganese dioxide

    The 13thHiroshima International Symposium on Synchrotron Radiation  2009年3月10日 

     詳細を見る

    記述言語:英語   会議種別:ポスター発表  

    researchmap

  • Research activity at Beamline 5

    The 13thHiroshima International Symposium on Synchrotron Radiation  2009年3月10日 

     詳細を見る

    記述言語:英語   会議種別:ポスター発表  

    researchmap

  • ホランダイト型チタン酸化物の合成と物性

    村岡祐治, 野網健悟, 脇田高徳, 平井正明, 横谷尚睦, 室隆桂之, 為則雄祐

    2008年秋季 第69回応用物理学会学術講演会  2008年9月2日 

     詳細を見る

    記述言語:日本語   会議種別:ポスター発表  

    researchmap

  • ホランダイト型 チタン酸化物の合成、物性および電子状態

    村岡祐治, 野網健悟, 脇田高徳, 平井正明, 横谷尚睦, 室隆桂之, 為則雄祐

    応用物理学会中国四国支部、日本物理学会中国支部、四国支部  2008年8月2日 

     詳細を見る

    記述言語:日本語   会議種別:口頭発表(一般)  

    researchmap

  • VO2/TiO2界面の電子状態

    村岡祐治, 佐伯邦成, 江口律子, 辛埴, 横谷尚睦, 仙波泰徳, 大橋治彦

    2008年春季 第55回応用物理学関係連合講演会  2008年3月30日 

     詳細を見る

    記述言語:日本語   会議種別:口頭発表(一般)  

    researchmap

  • ホランダイト型マンガン酸化物(NH4)xMn8O16の合成と物性II

    村岡祐治, 田嶋光俊, 脇田高徳, 平井正明, 横谷尚睦, 室隆桂之, 為則雄祐

    日本物理学会(第63回年次大会)  2008年3月24日 

     詳細を見る

    記述言語:日本語   会議種別:ポスター発表  

    researchmap

  • Recent activity at Beamline 5

    The 12thHiroshima International Symposium on Synchrotron Radiation  2008年3月13日 

     詳細を見る

    記述言語:英語   会議種別:ポスター発表  

    researchmap

  • ホランダイト型マンガン酸化物(NH4)xMn8O16の合成と物性

    村岡祐治, 田嶋光俊, 脇田高徳, 平井正明, 横谷尚睦, 室隆桂之, 為則雄祐

    日本物理学会(第62回年次大会)  2007年9月21日 

     詳細を見る

    記述言語:日本語   会議種別:口頭発表(一般)  

    researchmap

  • ホランダイト型 (NH4)xMn8O16の合成と物性

    村岡祐治, 田嶋光俊, 脇田高徳, 平井正明, 横谷尚睦, 室隆桂之, 為則雄祐

    応用物理学会中国四国支部、日本物理学会中国支部、四国支部  2007年8月4日 

     詳細を見る

    記述言語:日本語   会議種別:口頭発表(一般)  

    researchmap

  • 永続的光伝導を示すSnO2薄膜のガス応答性

    村岡祐治, 廣井善二

    2007年春季 第54回応用物理学関係連合講演会  2007年3月27日 

     詳細を見る

    記述言語:日本語   会議種別:口頭発表(一般)  

    researchmap

  • VO2薄膜における金属状態の膜厚依存性

    村岡祐治, 佐伯邦成, 江口律子, 仙波泰徳, 大橋治彦, 辛埴, 横谷尚睦

    日本物理学会(2007年春季大会)  2007年3月19日 

     詳細を見る

    記述言語:日本語   会議種別:口頭発表(一般)  

    researchmap

  • Current role at Beamline 5: Research of surface science and education

    The 11thHiroshima International Symposium on Synchrotron Radiation  2007年3月8日 

     詳細を見る

    記述言語:英語   会議種別:ポスター発表  

    researchmap

  • Persistent photoconductivity in an SnO2 thin film

    Kyoto Conference on Solid State Chemistry -Transition metal oxides: Past, Present and Future-  2006年11月15日 

     詳細を見る

    記述言語:英語   会議種別:ポスター発表  

    researchmap

  • SnO2薄膜への光キャリア注入

    村岡祐治, 廣井善二

    2006年春季 第53回応用物理学会関係連合講演会  2006年3月23日 

     詳細を見る

    記述言語:日本語   会議種別:ポスター発表  

    researchmap

  • SnO2薄膜における永続的光伝導

    村岡祐治, 廣井善二

    学術創成研究「新しい研究ネットワークによる電子相関系の研究」-物理学と化学の真の融合を目指してー  2006年1月30日 

     詳細を見る

    記述言語:日本語   会議種別:ポスター発表  

    researchmap

  • ルチル型酸化物への光キャリア注入

    村岡祐治, 廣井善二

    特定領域研究「異常量子物質の創製」-新しい物理を生む新物質―  2005年12月19日 

     詳細を見る

    記述言語:日本語   会議種別:口頭発表(一般)  

    researchmap

  • 光で制御する遷移金属酸化物の物性 招待

    村岡祐治, 廣井善二

    第137回日本金属学会  2005年9月29日 

     詳細を見る

    記述言語:日本語   会議種別:口頭発表(招待・特別)  

    researchmap

  • YBa2Cu3Ox極薄膜への光キャリア注入

    村岡祐治, 村松孝樹, 廣井善二

    日本物理学会第60回年次大会  2005年3月24日 

     詳細を見る

    記述言語:日本語   会議種別:口頭発表(一般)  

    researchmap

  • Photocarrier injection to transition metal oxides

    学術創成研究「新しい研究ネットワークによる電子相関系の研究」-物理学と化学の真の融合を目指してー  2005年3月15日 

     詳細を見る

    記述言語:英語   会議種別:口頭発表(一般)  

    researchmap

  • 光電荷注入による遷移金属酸化物薄膜の物性制御 招待

    村岡祐治, 村松孝樹, 廣井善二

    東北大学金研ワークショップ 「強相関酸化物の機能開発とコンビナトリアル手法の接点」  2005年1月13日 

     詳細を見る

    記述言語:日本語   会議種別:口頭発表(招待・特別)  

    researchmap

  • Photogenerated carrier injection to transition metal oxides

    2004 Materials Research Society Fall Meeting  2004年12月3日 

     詳細を見る

    記述言語:英語   会議種別:口頭発表(一般)  

    researchmap

  • Photogenerated carrier injection to an n-type copper oxide superconductor

    The 11th international workshop on oxide electronics  2004年10月3日 

     詳細を見る

    記述言語:英語   会議種別:ポスター発表  

    researchmap

  • (Sr,Nd)CuO2薄膜への光キャリア注入

    村岡祐治, 村松孝樹, 廣井善二

    日本物理学会秋季大会  2004年9月12日 

     詳細を見る

    記述言語:日本語   会議種別:口頭発表(一般)  

    researchmap

  • 遷移金属酸化物への光キャリアドーピング

    村岡祐治, 村松孝樹, 廣井善二

    学術創成研究「新しい研究ネットワークによる電子相関系の研究」-物理学と化学の真の融合を目指してー  2004年7月7日 

     詳細を見る

    記述言語:日本語   会議種別:口頭発表(一般)  

    researchmap

  • REBa2Cu3O7-x/SrTiO3(100)(RE:希土類)における電気抵抗の光照射効果

    村岡祐治, 村松孝樹, 山浦淳一, 山内徹, 広井善二

    日本物理学会第59回年次大会  2004年3月27日 

     詳細を見る

    記述言語:日本語   会議種別:ポスター発表  

    researchmap

  • Photogenerated hole carrier injection to transition metal oxides

    特定領域研究 「遷移金属酸化物における新しい量子現象」  2004年1月19日 

     詳細を見る

    記述言語:英語   会議種別:ポスター発表  

    researchmap

  • 遷移金属酸化物への光キャリア注入

    村岡祐治, 広井善二

    日本応用磁気学会 第11回化合物新磁性材料専門研究会 「遷移金属元素を含む化合物の光応答」  2003年12月12日 

     詳細を見る

    記述言語:日本語   会議種別:口頭発表(一般)  

    researchmap

  • Efficient Photocarrier Injection to Transition Metal Oxides

    2003 Materials Research Society Fall Meeting  2003年12月1日 

     詳細を見る

    記述言語:英語   会議種別:ポスター発表  

    researchmap

  • 光による遷移金属酸化物の物性制御

    村岡祐治, 山内徹, 村松孝樹, 山浦淳一, 広井善二

    学術創成研究「新しい研究ネットワークによる電子相関系の研究」-物理学と化学の真の融合を目指してー  2003年10月9日 

     詳細を見る

    記述言語:日本語   会議種別:口頭発表(一般)  

    researchmap

  • YBa2Cu3O7-x薄膜への光キャリア注入

    村岡祐治, 村松孝樹, 山内徹, 山浦淳一, 広井善二

    日本物理学会秋季大会  2003年9月23日 

     詳細を見る

    記述言語:日本語   会議種別:口頭発表(一般)  

    researchmap

  • Efficient photocarrier injection to transition metal oxides

    International Conference on Magnetism  2003年7月27日 

     詳細を見る

    記述言語:英語   会議種別:ポスター発表  

    researchmap

  • 薄膜への光キャリア注入 招待

    村岡祐治, 村松孝樹, 山内徹, 山浦淳一, 広井善二

    第36回コンビナトリアルプロジェクト研究会  2003年6月24日 

     詳細を見る

    記述言語:日本語   会議種別:口頭発表(招待・特別)  

    researchmap

  • 遷移金属酸化物への光キャリア注入1, 2

    村岡祐治, 山内徹, 村松孝樹, 山浦淳一, 広井善二

    2003年春季 第50回応用物理学会関連連合講演会  2003年3月28日 

     詳細を見る

    記述言語:日本語   会議種別:口頭発表(一般)  

    researchmap

  • Photocarrier injection I: Giant photoconductivity in transition metal oxides

    特定領域研究 「遷移金属酸化物における新しい量子現象」  2003年1月8日 

     詳細を見る

    記述言語:英語   会議種別:ポスター発表  

    researchmap

  • ルチル型機能性酸化物の作製 招待

    村岡祐治

    第31回マテリアル・テーラリング研究会  2002年3月30日 

     詳細を見る

    記述言語:日本語   会議種別:口頭発表(招待・特別)  

    researchmap

  • スピノーダル分解した(Ti,V)O2の構造と物性

    村岡祐治, 上田寛, 廣井善二

    2002年春季 第49回応用物理学関連連合講演会  2002年3月28日 

     詳細を見る

    記述言語:日本語   会議種別:口頭発表(一般)  

    researchmap

  • スピノーダル分解した(Ti,V)O2の構造と物性

    村岡祐治, 速水宏明, 上田寛, 廣井善二

    日本物理学会第57回年次大会  2002年3月25日 

     詳細を見る

    記述言語:日本語   会議種別:口頭発表(一般)  

    researchmap

  • ルチル型機能性酸化物の作製

    村岡祐治, 速水宏明, 上田寛, 廣井善二

    学術創成研究「新しい研究ネットワークによる電子相関系の研究」-物理学と化学の真の融合を目指してー  2002年2月12日 

     詳細を見る

    記述言語:日本語   会議種別:口頭発表(一般)  

    researchmap

  • Large modification of the metal-insulator transition temperature in strained VO2 films grown on TiO2 substrates

    Institute for Solid State Physics international symposium  2001年11月 

     詳細を見る

    記述言語:英語   会議種別:ポスター発表  

    researchmap

  • VO2 - TiO2系におけるスピノ-ダル分解とその物性

    村岡祐治, 速水宏明, 広井善二

    日本物理学会秋季大会  2001年9月19日 

     詳細を見る

    記述言語:日本語   会議種別:口頭発表(一般)  

    researchmap

  • TiO2基板を用いたVO2の金属絶縁体転移温度の制御

    村岡祐治, 廣井善二

    2001年秋季 第62回応用物理学会学術講演会  2001年9月11日 

     詳細を見る

    記述言語:日本語   会議種別:口頭発表(一般)  

    researchmap

  • VO2薄膜およびVO2-TiO2スピノーダル系における金属絶縁体転移

    村岡祐治, 速水宏明, 廣井善二

    東京大学物性研究所短期研究会「遷移金属酸化物の化学」  2001年1月6日 

     詳細を見る

    記述言語:日本語   会議種別:口頭発表(一般)  

    researchmap

  • PrBa2Cu3Ozバルク体および薄膜の合成と物性

    村岡祐治, 廣井善二

    日本物理学会第55回年次大会  2000年9月23日 

     詳細を見る

    記述言語:英語   会議種別:口頭発表(一般)  

    researchmap

  • スピネルMg1.4Fe1.2Ti0.4O4薄膜における室温スピングラス的振る舞いとその光制御

    村岡祐治, 田畑仁, 川合知二

    2000年春季 第47回応用物理学関係連合講演会  2000年3月31日 

     詳細を見る

    記述言語:日本語   会議種別:口頭発表(一般)  

    researchmap

▼全件表示

産業財産権

  • 転移温度が制御された部材

    廣井善二, 村岡祐治

     詳細を見る

    出願番号:特願2001-182190 

    公開番号:特開2003-002791 

    researchmap

  • 高温スピングラスを有し、また光によりスピン制御可能なスピネル型フェライト薄膜およびその製造方法

    川合知二, 田畑仁, 村岡祐治

     詳細を見る

    出願番号:特願2000-035119 

    公開番号:特開2001-230117 

    特許番号/登録番号:特許4139882 

    6,488,908 B1 (米国)

    researchmap

Works(作品等)

  • Method of prepring High temperature spin-glass and to photo-controlable spinel-type ferrito films.

    1999年

     詳細を見る

受賞

  • 応用物理学会 講演奨励賞

    2000年  

     詳細を見る

    受賞国:日本国

    researchmap

共同研究・競争的資金等の研究

  • 曲がる超硬炭素材料の開発

    2020年04月 - 2021年03月

    岡山工学振興会  一般研究助成 

      詳細を見る

    担当区分:研究代表者 

    researchmap

  • 高出力太陽電池を指向した、スピノーダル分解による超多層ルチル型酸化物膜の開発

    2017年04月 - 2020年03月

    日本学術振興会  科研費 基盤研究(C)(一般) 

    村岡 祐治

      詳細を見る

    担当区分:研究代表者  資金種別:競争的資金

    researchmap

  • 強相関電子物性が制御可能な光キャリア注入法の確立

    2014年04月 - 2017年03月

    日本学術振興会  科研費 基盤研究(C)(一般) 

    村岡 祐治

      詳細を見る

    担当区分:研究代表者  資金種別:競争的資金

    researchmap

  • 光キャリア注入による金属酸化物の物性制御

    2011年04月 - 2014年03月

    日本学術振興会  科研費 基盤研究(C)(一般) 

    村岡 祐治

      詳細を見る

    担当区分:研究代表者  資金種別:競争的資金

    researchmap

  • スピノーダル分解を用いた新規ルチル型機能性酸化物の作製

    2002年04月 - 2005年03月

    日本学術振興会  科研費 若手研究(B) 

    村岡祐治

      詳細を見る

    担当区分:研究代表者  資金種別:競争的資金

    researchmap

  • Synthesis of new transition-metal oxides

      詳細を見る

    資金種別:競争的資金

    researchmap

▼全件表示

その他研究活動

  • 国際共同研究

    1998年
    -
    1999年

     詳細を見る

    フランスCNRS ボルドー固体化学研究所と多孔質物質作製に関する共同研究を行った。

    researchmap

 

担当授業科目

  • 情報物理学実験 II (2021年度) 3・4学期  - 月5,月6,月7,月8

  • 情報物理学実験2 (2021年度) 3・4学期  - 月5,月6,月7,月8

  • 放射光物性学 (2021年度) 前期  - 火3,火4

  • 放射光科学実習 (2021年度) 集中  - その他

  • 教養物理学(力学)1 (2021年度) 第3学期  - 月1~2

  • 教養物理学(力学)2 (2021年度) 第4学期  - 月1~2

  • 物理学実験2 (2021年度) 3・4学期  - [第3学期]月5,月6,月7,月8, [第4学期]月4,月5,月7,月8

  • 界面電子物理学演習 (2021年度) 通年  - その他

  • 薄膜物性物理学 (2021年度) 後期  - その他

  • 情報物理学実験 II (2020年度) 3・4学期  - 月3,月4,月5,月6

  • 情報物理学実験2 (2020年度) 3・4学期  - 月3,月4,月5,月6

  • 放射光物性学 (2020年度) 前期  - 火1,火2

  • 放射光科学実習 (2020年度) 集中  - その他

  • 教養物理学(力学)1 (2020年度) 第3学期  - 月1,月2

  • 教養物理学(力学)2 (2020年度) 第4学期  - 月1,月2

  • 物理学実験2 (2020年度) 3・4学期  - 月3,月4,月5,月6

  • 界面電子物理学演習 (2020年度) 通年  - その他

  • 薄膜物性物理学 (2020年度) 後期  - その他

▼全件表示

 

社会貢献活動

  • さくらサイエンス

    役割:講師, 企画, 運営参加・支援, 実演

    岡山大学  先端物質科学実習  2019年2月17日 - 2019年2月24日

     詳細を見る

    種別:その他

    researchmap

メディア報道

  • 人工ダイヤよりも硬い「Qカーボン」 新炭素材 国内初作製 新聞・雑誌

    山陽新聞  2020年8月22日

     詳細を見る

  • 超強磁場で金属化 新聞・雑誌

    日刊工業新聞  2020年8月18日

     詳細を見る

学術貢献活動

  • 表面界面の機能創製とデバイス応用セミナー

    役割:企画立案・運営等

    村岡祐治  2018年8月7日

     詳細を見る

    種別:学会・研究会等 

    researchmap

  • 応用物理学会・物理系学会中国四国支部 合同学術講演会

    役割:企画立案・運営等

    応用物理学会・物理系学会中国四国支部  2016年7月31日

     詳細を見る

    種別:学会・研究会等 

    researchmap

  • 日本磁気学会専門研究会 化合物新磁性材料専門研究会

    役割:企画立案・運営等

    日本磁気学会専門研究会  2003年4月 - 2006年3月

     詳細を見る

    種別:学会・研究会等 

    researchmap

  • 1) 学術創成研究「新しい研究ネットワークによる電子相関系の研究―物理学と化学の真の融合を目指して―若手の会

    役割:企画立案・運営等

    代表 茅 幸ニ  2001年4月 - 2006年3月

     詳細を見る

    種別:学会・研究会等 

    researchmap