NMR Study of Magnetic Property in Heavy Fermion Superconductor CeCu_2Si_2

重费米子超导体CeCu_2Si_2磁性能的NMR研究

基本信息

批准号：
03452041
负责人：
KITAOKA Yoshio
金额：
$ 3.78万
依托单位：
Osaka University
依托单位国家：
日本
项目类别：
Grant-in-Aid for General Scientific Research (B)
财政年份：
1991
资助国家：
日本
起止时间：
1991 至 1992
项目状态：
已结题

来源：
https://kaken.nii.ac.jp/en/grant/KAKENHI-PROJECT-03452041/
关键词：
Heavy Fermion Superconductivity Magnetic Transition CeCu_2Si_2 NMR NQR

项目摘要

The magnetic correlation in the heavy fermion superconductor, CeCu<@D22.02@>D2Si<@D22@>D2 and Th-doped Ce<@D21-x@>D2Th<@D2x@>D2Cu<@D22.2@>D2Si<@D22@>D2, has been investigated by Cu nuclear magnetic resonance (NMR) and nuclear quadrupoleresonance (NQR). For CeCu<@D22.02@>D2Si<@D22@>D2 with T<@D2c@>D2 = 0.72KJ, a "magnetic transition" has been found at around 0.8 K in applied fields up to 3.5T. Below the transition temperature, Cu NMR loses the intensity suddenly without any broadening and shift of the spectrum, and the spin-echo decay rate, 1/T<@D22@>D2, at H = 13.3kOe, increases with decreasing temperature, which is different from the behavior expected in a static magnetically ordered state. The "magnetic transition" just above T<@D2c@>D2 is quite unusual in a sense that the ordered state may not be in a completely static regime, but possesses some dynamic aspect. We have constructed a magnetic phase diagram in the field-temperature plane for CeCu<@D22.02@>D2Si<@D22@>D2. To ensure the magnetic instability in CeCu<@D22@>D2 we have investigated a magnetic and superconducting phase diagram of Th-doped Ce<@D21-x@>D2Th<@D2x@>D2Cu<@D22.2@>D2Si<@D22@>D2. Static magnetic ordering with T<@D2n@>D2 = 2.4K and 4.5K for x=0.08 and 0.12, respectively, is evidenced by a pronounced broadening of the <@D163@>D1Cu-NQR and -NMR spectra and a mean-field type of anomaly in the specific heat. In contrast, for the lightly Th-doped compounds with x (] SY.ltoreq.[) 0.064, there has been observed neither any signature of a broadening of the NQR and NMR spectra nor an anomaly of the specific heat, but a dramatic reduction of the NMR and NQR intensities below a temperature ranging from 0.9 K to 1.3 K upon increasing Th-content. It is emphasized that the unusual "magnetic transition" found in undoped and lightly Th-doped CeCu<@D22.2@>D2Si<@D22@>D2 should be distinguished from the static magnetic ordering in the heavily Th-doped systems.

The magnetic correlation in the heavy fermion superconductor, CeCu<@D22.02@>D2Si<@D22@>D2 and Th-doped Ce<@D21-x@>D2Th<@D2x@>D2Cu<@D22.2@>D2Si<@D22@>D2, has been investigated by Cu nuclear magnetic resonance (NMR) and nuclear四翼固定（NQR）。对于Cecu <@d22.02@> d2si <@d22@> d2带有t <@d2c@> d2 = 0.72kj，在3.5t的应用场中，在0.8 k的位置发现了“磁过渡”。在过渡温度以下，Cu NMR突然失去了强度，而没有任何频谱的扩大和移动，而自旋回波衰减速率为1/t <@d22@> d2，在h = 13.3koe时，随着温度的降低，这与静态有序的磁性磁性状态的行为不同。在t <@d2c@> d2上方的“磁过渡”从某种意义上说，有序状态可能不处于完全静态状态，而是具有一定的动态方面。我们已经在CECU <@d22.02@> d2si <@d22@> d2的场温度平面上构造了一个磁相图。为了确保CECU <@d22@> D2中的磁不稳定性，我们研究了TH掺杂CE <@d21-x@> d2th <@d2x@> d2cu <@d22.2@> d22.2@> d2si@> d2si <@d22222222@> d2@> d2@> d2@> d2@> d2@> d2@> d2。用T <@d2n@> d2 = 2.4k和4.5k的静态磁排序分别为x = 0.08和0.12，可以通过明显扩大<@d163@> d1cu-nqr和-nmr spectra和平均型号的态度在特定的热量中的偏移型。相反，对于具有X（] Sy.ltoreq。[）0.064的轻度Th掺杂化合物，既没有观察到NQR和NMR频谱拓宽的任何签名，也没有特定热量的异常，而是在NMR和NQR强度下方降低0.9 k至1.3 k的温度下，而不是特定的热量的异常。强调的是，在未源和轻度的CECU <@d22.2@> d2si <@d22@> D2中发现的异常“磁过渡”应与重度TH掺杂系统中的静态磁顺序区分开。