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NMR Study of Pressure-induced Superconductivity and Pressure-induced Weak Magnetism in f-electron Systems

f电子系统中压力诱导超导和压力诱导弱磁性的核磁共振研究

基本信息

批准号：
12640358
负责人：
KOHARA Takao
金额：
$ 2.56万
依托单位：
Himeji Institution of Technology
依托单位国家：
日本
项目类别：
Grant-in-Aid for Scientific Research (C)
财政年份：
2000
资助国家：
日本
起止时间：
2000 至 2001
项目状态：
已结题

来源：
https://kaken.nii.ac.jp/grant/KAKENHI-PROJECT-12640358/
关键词：
Pressure-induced Superconductors Nuclear Magnetic Resonance Nuclear Quadrupole Resonance d-wave Superconductivity Spin Fluctuation f-electron Compounds Heavy Electron Systems Low Temperature Material Sciences under High Pressure Ce化合物高圧

项目摘要

The main purpose of this subject is for exploring the mechanisms of unconventional superconductivity and a tiny magnetic moment induced by applied high pressure in f-electron compounds. This project consists of two-sample groups; (1) pressure induced superconductors of CeTIn_5 (T= Rh, Co, Ir) and CeRh_2Si_2 and (2) Uru_2Si_2 with tiny magnetic moments. Present ^<115>NQR measurements in the super conducting state were performed on CeCoIn_5, Celrln_5 and CeRhln_5 under high pressure above the critical pressure of 1.7GPa. As for CeTIn_5 in the super conducting state, the nuclear magnetic relaxation rate has T^3 -dependence and the spin susceptibility decreases upon cooling. These results indicate that these systems exhibit d-wave superconductivity. On the other hand, CeCoIn_5 in the normal state is located just at antiferromagnetic instability and CeRhln_5 above the critical pressure and Celrln_5 are in the nearly antiferromagnetic region. Next, we have found new ^<29>Si NMR signals coming from the antiferromagnetic region in Uru_2Si_2 together with previously reported Si NMR signals from the paramagnetic region. These signal-intensities compete with each other depending on temperature and applied pressure. This result gives evidence for spatially inhomogeneous development of antiferromagnetic ordering below characteristic temperature. The ordered magnetic moments of U are expected as about 0.4 μ, B, which is of about one order of magnitude larger than 0.03 μ B measured by many neutron diffraction experiments. This picture of inhomogeneous development of antiferromagnetic region will bring us to the new scenario of understanding of hidden order parameters, which is still unsolved since the discovery of this interesting material in '85.

本课题的主要目的是探索f电子化合物中超导电性和高压下产生微小磁矩的机制。本项目包括两个样品组：（1）CeTIn_5（T= Rh，Co，Ir）和CeRh_2Si_2的压感超导体;（2）具有微小磁矩的Ce_2Si_2。本文<115>对CeCoIn_5、CeRIn_5和CeRhIn_5在1.7GPa以上的高压下进行了超导态下的NQR测量。对于超导态的CeTIn_5，其核磁弛豫速率具有T^3依赖性，自旋磁化率随温度的降低而降低。这些结果表明，这些系统表现出d波超导性。另一方面，正常态的CeCoIn_5正好处于反铁磁不稳定状态，而CeRhIn_5在临界压力以上处于反铁磁不稳定状态，而CelrIn_5处于近反铁磁不稳定状态。其次，我们发现了新的~ 13 <29>Si NMR信号来自反铁磁区的Si_2Si_2与以前报道的顺磁区的Si NMR信号。这些信号强度根据温度和施加的压力而相互竞争。这一结果提供了证据的空间非均匀发展的反铁磁有序低于特征温度。U的有序磁矩预计约为0.4 μ，B，比许多中子衍射实验测得的0.03 μ B大一个数量级。这幅反铁磁区不均匀发展的图像将把我们带到理解隐藏序参数的新场景，这是自85年发现这种有趣的材料以来尚未解决的问题。