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ィイD163ィエD1Cu NQR Studies in YbInCuィイD24ィエD2 under High Pressure

高压下 YbInCuD24D2 中的 D163D1Cu NQR 研究

基本信息

批准号：
10640351
负责人：
HIRAOKA Koichi
金额：
$ 1.86万
依托单位：
Ehime University
依托单位国家：
日本
项目类别：
Grant-in-Aid for Scientific Research (C)
财政年份：
1998
资助国家：
日本
起止时间：
1998 至 1999
项目状态：
已结题

项目摘要

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.

在熔剂法生长的单晶粉末样品上，测量了ィイD163ィエD1CuD24ィイD2中的ィエNQR。在YbInCuィイD24ィエD2样品中，ィイD163ィエD1CuNQR结果与前人对多晶样品的NQR结果基本一致，只是(TィイD21ィエD2T)ィイD 1-1ィエD 1低温相的值较小。测量了ィイD163、ィエD1Cunqr频率Vq和自旋晶格驰豫速率TィイD3-1(/)1ィエD3随压力的变化关系，最大压力为17kbar。通过铁磁性fcc-Co中ィイD159ィエD1Co核的核磁共振频率与压力的关系来确定钳腔内的压力，精度为±0.2kbar。高压下的核磁共振测量结果如下：(1)在高压下，v-ィイD2q-ィエD2的相变温度反常地增加.2)在-2.2K/kbar的速率下，价相变温度随压力的升高而降低.(3)低温相的自旋-晶格驰豫速率TィイD3-1(/)1ィエD3表现出类似Korringa的温度依赖关系.另一方面，在高温相没有观察到TィイD3-1(/)1ィエD3的温度依赖性，这表明Yb离子在低温相的4f电子是巡游的，费米能级的态密度随着压强的增加而增加。结果表明，YbInCuD24的价态相变机制与ィイ的能带结构密切相关。在此基础上，对ィエィイD24ィエD2的价态相变进行了理论分析。