| Project/Area Number |
10640351
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| Research Category |
Grant-in-Aid for Scientific Research (C)
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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 | Ehime University |
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Principal Investigator |
HIRAOKA Koichi Ehime University,Faculty of Engimeering, Associate Professor, 工学部, 助教授 (00199043)
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| Co-Investigator(Kenkyū-buntansha) |
TOMIYOSHI Shoichi Ehime University,Faculty of Engimeering, Professor, 工学部, 教授 (50005922)
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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 |
¥2,900,000 (Direct Cost: ¥2,900,000)
Fiscal Year 1999: ¥300,000 (Direct Cost: ¥300,000)
Fiscal Year 1998: ¥2,600,000 (Direct Cost: ¥2,600,000)
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| Keywords | Valence Phase Transition / NQR / High Pressure / Spin-Lattice Pelaxation Time / Rare-Earth Compounds / 価数相転移化合物 / 強相関電子系 / スピン-格子暖和時間 |
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| Research Abstract |
ィイD163ィエD1CU NQR in YbInCuィイD24ィエD2 have been measured on powdered samples prepared from single crystal, which were grown by a flux method. In YbInCuィイD24ィエD2 the ィイD163ィエD1Cu NQR results are almost in agreement with the previous ones for polycrystalline samples, except for a smaller value of (TィイD21ィエD2T)ィイD1-1ィエD1 low temperature phase. The temperature dependence of ィイD163ィエD1Cu NQR frequency vq and spin-lattice relaxation rates TィイD3-1(/)1ィエD3 were measured as a function of pressure up to 17 kbar. The pressure in the clamp cell were determined by pressure dependence of NMR frequency for ィイD159ィエD1Co nuclei in ferromagnetic fcc-Co with an accuracy of ±0.2 kbar. The results of NQR measurements under high pressure are as follows.
(1)The temperature dependence of vィイD2qィエD2 showed anomalous increase at the phase transition temperature under high pressure.
2)The valence phase transition temperatures were decreasing with increasing pressure at a rate of -2.2 K/kbar.
(3)The spin-lattice relaxation rates TィイD3-1(/)1ィエD3 showed Korringa like temperature dependence in the low temperature phase. On the other hand, no temperature dependence of TィイD3-1(/)1ィエD3 was detected in the high temperature phase.
These results show that the 4f electrons of Yb ions in low temperature phase are itinerant and the density of states at the Fermi level increases with increasing pressure. It is suggested that the mechanism of valence phase transition is strongly depend on the band structure in YbInCuィイD24.ィエD2 The theoretical analysis will be made for the valence phase transition in YbInCuィイD24ィエD2 based on the results of this research.
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