研究者詳細 - 村岡　祐治

論文 - 村岡　祐治

分割表示 184 件中 141 - 160 件目／全件表示 >>

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

T Muramatsu, Y Muraoka, Z Hiroi

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

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

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

85 ( 14 ) 2950 - 2952 2004年10月

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

T Muramatsu, S Yonezawa, Y Muraoka, Z Hiroi

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

New -pyrochlore oxide superconductor CsOs2O6 査読

S Yonezawa, Y Muraoka, Z Hiroi

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

Unprecedented superconductivity in -pyrochlore osmate KOs2O6 査読

Z Hiroi, S Yonezawa, Y Muraoka

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

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

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

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Efficient photocarrier injection to transition metal oxides 査読

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

272 448 - 449 2004年5月

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

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

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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

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

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Photoemission study of the metal-insulator transition in VO2/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 69 ( 16 ) 7 2004年4月

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

We have made a detailed temperature-dependent photoemission study of VO2/TiO2(001) thin films, which show a metal-insulator transition at similar to300 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

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その他リンク： http://orcid.org/0000-0002-2334-918X

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

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

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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

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

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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

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

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

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

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

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

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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

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

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

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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

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

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

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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

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