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.

重费米子超导体 CeCu<@D22.02@>D2Si<@D22@>D2 和 Th 掺杂 Ce<@D21-x@>D2Th<@D2x@>D2Cu<@D22.2@> 中的磁关联D2Si<@D22@>D2，已通过Cu核磁共振(NMR)和核四极共振(NQR)进行了研究。对于 CeCu<@D22.02@>D2Si<@D22@>D2（T<@D2c@>D2 = 0.72KJ），在高达 3.5T 的外加磁场中，在 0.8 K 左右发现了“磁转变”。在转变温度以下，Cu NMR 突然失去强度，而没有任何光谱的展宽和移动，并且自旋回波衰减率 1/T<@D22@>D2，在 H = 13.3kOe 时，随着温度的降低而增加，这与静态磁有序状态下预期的行为不同。 T<@D2c@>D2 上方的“磁转变”在某种意义上是相当不寻常的，因为有序态可能不处于完全静态状态，而是具有一些动态方面。我们构建了 CeCu<@D22.02@>D2Si<@D22@>D2 的场温平面磁相图。为了确保 CeCu<@D22@>D2 的磁不稳定性，我们研究了 Th 掺杂 Ce<@D21-x@>D2Th<@D2x@>D2Cu<@D22.2@>D2Si< 的磁性和超导相图。 @D22@>D2。当 x=0.08 和 0.12 时，T<@D2n@>D2 = 2.4K 和 4.5K 的静态磁排序分别通过 <@D163@>D1Cu-NQR 和 -NMR 谱的显着展宽以及平均 -场类型的比热异常。相比之下，对于 x (] SY.ltoreq.[) 0.064 的轻 Th 掺杂化合物，既没有观察到 NQR 和 NMR 光谱变宽的任何特征，也没有观察到比热的异常，而是观察到急剧的降低。增加 Th 含量后，在 0.9 K 至 1.3 K 温度范围内的 NMR 和 NQR 强度的变化。需要强调的是，在未掺杂和轻掺杂Th的CeCu<@D22@>D2Si<@D22@>D2中发现的不寻常的“磁转变”应该与重Th掺杂系统中的静态磁有序区分开来。