1999 Fiscal Year Annual Research Report

局在・遍歴電子共存系の磁気相関と電気伝導の協調・競争現象の研究

Research Project

Project/Area Number	10304026
Research Institution	Kyoto University
Principal Investigator	山田和芳京都大学, 化学研究所, 教授 (70133923)
Co-Investigator(Kenkyū-buntansha)	佐藤憲昭名古屋大学, 大学院・理学研究科, 助教授 (30170773)
Keywords	高温超伝導 / 中性子散乱 / 超伝導と磁気秩序の共存 / 単結晶育成
Research Abstract	11年度は、3d電子系の銅酸化物超伝導体ではホールドープ型と電子ドープ型超伝導体の両方の単結晶をFZ電気炉で作成した。また5f電子系では、UNi_<>Al_3の大型単結晶を育成した。ホール系では、La_<2-x>Sr_xCuO_4の単結晶を用いて、いわゆるスピングラス相と3次元反強磁性、あるいは超伝導との境界近傍の磁気相関を中性子散乱で詳細に研究した。その結果、従来超伝導相で見いだされたのとは異なる長周期スピン相関が、スピングラス相で見いだされ、x=0.02の低濃度領域でも、ホールがストライプ的に分布していることがわかった。さらにスピングラス相と超伝導相の境界近傍の超伝導領域内では、スピングラス相に見られる磁気相関が、超伝導相の磁気相関と共存していることがわかった。電子ドープ系では、Nd_<2-x>Ce_xCuO_4の単結晶を用いて、還元処理効果を調べた。その結果、同じCe濃度x=0.15でも、熱処理によって、異なる超伝導転移温度を示す別の相が得られることがわかった。中性子散乱の結果からは、転移温度が高い相ほどドープ量の多いことが予想され、電子ドープ系にも、アンダードープ領域が存在する考えられる。 5f系ではUNi_2Al_3の低温領域における比熱の測定を行った結果、バルク超伝導を示すことが明らかとなった。この試料を用いてグルノーブル・ILLの冷中性子源で中性子非弾性散乱実験を行い、反強磁性秩序状態のゾーン・センター付近に低エネルギー励起が存在することを発見した。また、ミューオン・ナイトシフトの測定を行い、その温度変化が局在モーメントの結晶場効果として説明可能であることを明らかにした。

Research Products

(23 results)

All Other

All Publications (23 results)

[Publications] S.-H.Lee: "Search for Orbital Moments in Underdoped Cuprate Metals"Phys. Rev. B. 60. 10405-10417 (1999)
[Publications] S.Wakimoto: "New Inommensurate Magnetic Correlations at the Lower Critical Concentration of the Superconductivity, La_<1.95>Sr_<0.05>CuO_4"Phys. Rev. B. 60. R769-R772 (1999)
[Publications] T.Sato: "Pseudogap of Optimally Doped La_<1.85>Sr_<0.15>CuO_4 Observed by Ultrahigh-Resolution Photoemision Spectroscopy"Phys. Rev. Lett. 83. 2254-2257 (1999)
[Publications] R.J.Birgeneau: "Instantaneous Spin Correlations in La_2CuO_4"Phys. Rev. B. 59. 13788-13794 (1999)
[Publications] Y.J.Kim: "Quantum Monte Carlo Study of Weakly Coupled Spin Ladders"Phys. Rev. B. 60. 3294-3304 (1999)
[Publications] T.Suzuki: "Conventional Superconductor-like Behaviour of Superconducting Transition of La_2CuO_4 around x=0.12 in Magnetic Fields"Phys. Rev. B. 60. 10500-10503 (1999)
[Publications] Y.S.Lee: "Neutron-scattering Study of Spin-density Wave Order in the Superconducting State of Excess-oxygen-doped La_2CuO_<4+y>"Phys. Rev. B. 60. 3643-3654 (1999)
[Publications] H.Kimura: "Structural Instability Associated with the Tilting of CuO_6 Octahedron in La_<2-x>Sr_xCuO_4"J. Phys. Soc. Jpn.. (to be published). (2000)
[Publications] C.H.Lee: "Energy Spectrum of Spin Fluctuations in the Superconducting La_<2-x>Sr_xCuO_4 (x=0.10. ,0.15, 0.18 and 0.25)"J. Phys. Soc. Jpn.. (to be published). (2000)
[Publications] M.Matsuda: "Freezing of Anisotropic Spin Clusters in La_<1.98>Sr_<0.02>CuO_4"Phys. Rev. B. (to be published). (2000)
[Publications] N.Sato: "Effect of Quasi Two-dimensional Fermi Surfaces on Electronicproperties in YbSb_2"Phys. Rev. B. 59. 4714-4719 (1999)
[Publications] Y.Takahashi: "Crystallographic Parameters in the Compounds La_<1-x>Ce_xB_6"J. Phys. Soc. Jpn.. 68. 692-693 (1999)
[Publications] N.Sato: "Possible Negative Mode-mode Coupling in Upd_2Al_3"J. Phys.: Condens. Matter. 11. 3405-3412 (1999)
[Publications] S.Fujimori: "Absence of U 5f Band States in Resonant Photoemission Spectrum of Upd_2Al_3"Phys. Rev. B. 59. 10469-10472 (1999)
[Publications] N.Sato: "Correlation between Low-energy Spin Fluctuations and Superconductivity in Upd_2Al_3 and Upt_3"Physica B. 259-261. 634-635 (1999)
[Publications] N.Bernfoeft: "Magnetic Fluctuations above and below T_c in the Heavy Fermion Superconductor Upd_2Al_3"Physica B. 259-261. 614-620 (1999)
[Publications] N.Aso: "Single Crystal Growth and Physical Properties in Upd_2(Al_<(1-x)>Ga_x)_3"Physica B. 259-261. 636-637 (1999)
[Publications] A.V.Kolomiets: "Magnetism and Transport in Uga_2 Single Crystal"Physica B. 259-261. 238-239 (1999)
[Publications] N.Sato: "Static and Dynamical Properties in the Heavy Fermion Superconductors Upd_2Al_3 and Uni_2Al_3"J .J. A. P. Series. 11. 56-58 (1999)
[Publications] S.Fujimori: "Photoemission and Inverse-photoemission Study of Heavy-fermion Uranium Compounds"J. J. A. P. Series. 11. 215-217 (1999)
[Publications] K.Sugiyama: "Metamagnetic Transition of Heavy Fermion Uranium Compounds: Upd_2Al_3, Uru_2Si_2 and Upt_3"J.J.A.P.Series. 11. 18-20 (1999)
[Publications] N.Mori: "Anomalous Transport Phenomena in SmS ans TmSe with Pressure-induced Valence Transitions"J. J. A. P. Series. 11. 129-131 (1999)
[Publications] A.Schenck: "Study of the Positive Muon Knight Shift in Uni_2Al_3: Evidence for a Tetravalent U^<4+> -state and Crystalline Electric Field (CEF) Splitting"Eur. Phys. J. B.. 13. 245 (2000)

1999 Fiscal Year Annual Research Report

局在・遍歴電子共存系の磁気相関と電気伝導の協調・競争現象の研究

Principal Investigator

山田 和芳 京都大学, 化学研究所, 教授 (70133923)

Research Products

[Publications] S.-H.Lee: "Search for Orbital Moments in Underdoped Cuprate Metals"Phys. Rev. B. 60. 10405-10417 (1999)

[Publications] S.Wakimoto: "New Inommensurate Magnetic Correlations at the Lower Critical Concentration of the Superconductivity, La_<1.95>Sr_<0.05>CuO_4"Phys. Rev. B. 60. R769-R772 (1999)

[Publications] T.Sato: "Pseudogap of Optimally Doped La_<1.85>Sr_<0.15>CuO_4 Observed by Ultrahigh-Resolution Photoemision Spectroscopy"Phys. Rev. Lett. 83. 2254-2257 (1999)

[Publications] R.J.Birgeneau: "Instantaneous Spin Correlations in La_2CuO_4"Phys. Rev. B. 59. 13788-13794 (1999)

[Publications] Y.J.Kim: "Quantum Monte Carlo Study of Weakly Coupled Spin Ladders"Phys. Rev. B. 60. 3294-3304 (1999)

[Publications] T.Suzuki: "Conventional Superconductor-like Behaviour of Superconducting Transition of La_2CuO_4 around x=0.12 in Magnetic Fields"Phys. Rev. B. 60. 10500-10503 (1999)

[Publications] Y.S.Lee: "Neutron-scattering Study of Spin-density Wave Order in the Superconducting State of Excess-oxygen-doped La_2CuO_<4+y>"Phys. Rev. B. 60. 3643-3654 (1999)

[Publications] H.Kimura: "Structural Instability Associated with the Tilting of CuO_6 Octahedron in La_<2-x>Sr_xCuO_4"J. Phys. Soc. Jpn.. (to be published). (2000)

[Publications] C.H.Lee: "Energy Spectrum of Spin Fluctuations in the Superconducting La_<2-x>Sr_xCuO_4 (x=0.10. ,0.15, 0.18 and 0.25)"J. Phys. Soc. Jpn.. (to be published). (2000)

[Publications] M.Matsuda: "Freezing of Anisotropic Spin Clusters in La_<1.98>Sr_<0.02>CuO_4"Phys. Rev. B. (to be published). (2000)

[Publications] N.Sato: "Effect of Quasi Two-dimensional Fermi Surfaces on Electronicproperties in YbSb_2"Phys. Rev. B. 59. 4714-4719 (1999)

[Publications] Y.Takahashi: "Crystallographic Parameters in the Compounds La_<1-x>Ce_xB_6"J. Phys. Soc. Jpn.. 68. 692-693 (1999)

[Publications] N.Sato: "Possible Negative Mode-mode Coupling in Upd_2Al_3"J. Phys.: Condens. Matter. 11. 3405-3412 (1999)

[Publications] S.Fujimori: "Absence of U 5f Band States in Resonant Photoemission Spectrum of Upd_2Al_3"Phys. Rev. B. 59. 10469-10472 (1999)

[Publications] N.Sato: "Correlation between Low-energy Spin Fluctuations and Superconductivity in Upd_2Al_3 and Upt_3"Physica B. 259-261. 634-635 (1999)

[Publications] N.Bernfoeft: "Magnetic Fluctuations above and below T_c in the Heavy Fermion Superconductor Upd_2Al_3"Physica B. 259-261. 614-620 (1999)

[Publications] N.Aso: "Single Crystal Growth and Physical Properties in Upd_2(Al_<(1-x)>Ga_x)_3"Physica B. 259-261. 636-637 (1999)

[Publications] A.V.Kolomiets: "Magnetism and Transport in Uga_2 Single Crystal"Physica B. 259-261. 238-239 (1999)

[Publications] N.Sato: "Static and Dynamical Properties in the Heavy Fermion Superconductors Upd_2Al_3 and Uni_2Al_3"J .J. A. P. Series. 11. 56-58 (1999)

[Publications] S.Fujimori: "Photoemission and Inverse-photoemission Study of Heavy-fermion Uranium Compounds"J. J. A. P. Series. 11. 215-217 (1999)

[Publications] K.Sugiyama: "Metamagnetic Transition of Heavy Fermion Uranium Compounds: Upd_2Al_3, Uru_2Si_2 and Upt_3"J.J.A.P.Series. 11. 18-20 (1999)

[Publications] N.Mori: "Anomalous Transport Phenomena in SmS ans TmSe with Pressure-induced Valence Transitions"J. J. A. P. Series. 11. 129-131 (1999)

[Publications] A.Schenck: "Study of the Positive Muon Knight Shift in Uni_2Al_3: Evidence for a Tetravalent U^<4+> -state and Crystalline Electric Field (CEF) Splitting"Eur. Phys. J. B.. 13. 245 (2000)

山田和芳京都大学, 化学研究所, 教授 (70133923)