| Project/Area Number |
10044083
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| Research Category |
Grant-in-Aid for Scientific Research (B).
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| Allocation Type | Single-year Grants |
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| Section | 一般 |
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| Research Field |
固体物性Ⅱ(磁性・金属・低温)
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| Research Institution | Osaka University |
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Principal Investigator |
KITAOKA Yoshio Graduate School of Engineering Science, Osaka University, Professor, 基礎工学研究科, 教授 (70110707)
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| Co-Investigator(Kenkyū-buntansha) |
ZHENG Guo-qing Graduate School of Engineering Science, Osaka University Research Associate, 基礎工学研究科, 助手 (50231444)
MIYAKE Kazumasa Graduate School of Engineering Science, Osaka University Professor, 基礎工学研究科, 教授 (90109265)
AMAYA Kiichi Graduate School of Engineering Science, Osaka University Professor, 基礎工学研究科, 教授 (80029503)
ISHIDA Kenji Graduate School of Engineering Science, Osaka University Research Associate, 基礎工学研究科, 助手 (90243196)
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| Project Period (FY) |
1998 – 1999
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| Project Status |
Completed (Fiscal Year 1999)
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| Budget Amount *help |
¥6,200,000 (Direct Cost: ¥6,200,000)
Fiscal Year 1999: ¥2,700,000 (Direct Cost: ¥2,700,000)
Fiscal Year 1998: ¥3,500,000 (Direct Cost: ¥3,500,000)
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| Keywords | Heavy-Fermion Superconductors / High-TィイD2cィエD2 Cuprates / Antiferromagnetic to Superconducting Transitions / High-Pressure Induced Superconductivity / Spin Gap / Quantum Criticality / NMR / New Superconducting Mechanism / 反強磁性・異邦的超伝導転移 |
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| Research Abstract |
This research project was planed to investigate the novel electron phases in strongly correlated-electron systems, heavy-fermion, high-temperature cuprate and low dimensional organic materials under multiple extreme conditions. Obtained results are listed below.
1. On the basis of Cu-NQR measurements, we have found that the ground state in a series of CeィイD2xィエD2CuィイD22ィエD2SiィイD22ィエD2 compounds evolves from magnetically ordered phase at x=0.975 to heavy-electron superconducting (SC) phase at x=1.025. The sample of x=0.99 does not exhibit any trace of magnetic phase transition down to 0.012 K, but is dominated by slow magnetic fluctuations with low frequencies comparable to the NQR frequency. For the samples of x=1.00 and 1.025 such a state is expelled by the onset of the SC state.
2. From the NQR results under pressure (P) on near stoichiometric CeィイD20.99ィエD2CuィイD22ィエD2SiィイD22ィエD2 (TィイD2cィエD2=0.65 K), an exotic superconducting (SC) state due to an interplay with slowly-varying-magnetic-
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fluctuation-modes was found to be suppressed and replaced by a strong heavy-fermion SC phase at minute pressures exceeding P〜0.2 GPa. The TィイD21ィエD2 data in the high-P range 0.85-2.58 GPa are shown to be accountable by the "SCR theory". In P<0.2 GPa, an exotic interplay between magnetic and SC phase is implied.
3. The magnetic-field dependencies of the pseudogap behavior in the underdoped YBaィイD22ィエD2CuィイD24ィエD2OィイD28ィエD2 (Y1248) was measured up to 23 T at the NHMF Laboratory (Tallahassee, Florida) and up to 28.5 T on the slightly overdoped TISrィイD22ィエD2CaCuィイD22ィエD2OィイD26.88ィエD2 with TィイD2cィエD2=68 K (TI1212). In the overdoped TI1212, we showed that the scalings found in the T and magnetic field dependencies of 1/TィイD21ィエD2 and Knight shift are consistent with the superconducting (SC) fluctuations. By contrast, even though 23.2 T reduces TィイD2cィエD2 by 26% in Y1248, no effect is seen on the normal-state pseudogap behavior. This was ascribed as due to the stronger coupling nature of the pairing than in TI1212.
We have thus clarified the novel characteristics of anomalous magentism and unconventional superconductivity in the heavy-fermion and high-TィイD2cィエD2 cuprate oxides under multiple extreme conditions. The present research project enabled us to open new frontiers in the field. Less
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