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Ultralow-Temperature Properties of Conduction Electrons and Nuclear Spins Interacting with the Singlet Ground State

传导电子和核自旋与单线态基态相互作用的超低温特性

基本信息

批准号：
09640444
负责人：
ISHII Hiroumi
金额：
$ 0.96万
依托单位：
Osaka City University
依托单位国家：
日本
项目类别：
Grant-in-Aid for Scientific Research (C)
财政年份：
1997
资助国家：
日本
起止时间：
1997 至 1998
项目状态：
已结题

项目摘要

In this research project we have studied following two themes.1. Ultralow temperature property of systems consisting of conduction electrons and nuclear spins in the crystalline field singlet ground state (CFSGS).(1) We have studied the effect of the Coulomb interaction on the superconductivity mediated by the virtual excitation of the CFSGS. The superconducting transition temperature is lowered somewhat, but the effect is not pronounced.(2) We have derived the Coqblin-Schrieffer type s-f exchange interaction for (4f)ィイD12ィエD1 configuration with strong Hund and LS couplings. On the basis of it the RKKY interaction is derived for nuclear spins in the CFSGS system. It is of tensorial form and brings sinusoidal or helical nuclear spin structures.(3) Nuclear magnetism of PrCu6 is studied theoretically. Experimental study by Hata, one of the investigator of this project, found an evidence for a cannted weak ferromagnet, i. e., antiferromagnetic along the b axis and ferromagnetic along the c-axis together with a hysteresis phenomenon. We payed attention to the monoclinic crystal structure in which the inversion symmetry does not hold, and then derived a Dzyaloshinsky-Moriya type RKKY interaction for nuclear spins. The theory can explain the magnetic properties found in the experiment.2. Nuclear spin relaxation at ultralow temperatures.(4) We have solved the anomaly found experimentally in Rh near T=0, i. e., the nuclear spin relaxation is two-times slower at negative T than at positive T. We have derived a formula for relaxation effective at ultralow temperatures and applied the high-T expansion method to it to explain the experiment.

在这个研究项目中，我们研究了以下两个主题： 1．晶体场单重态基态(CFSGS)中传导电子和核自旋组成的体系的超低温特性。(1)研究了库仑相互作用对CFSGS虚激发介导的超导性的影响。超导转变温度有所降低，但效果并不明显。(2)我们推导了具有强Hund和LS耦合的(4f)ィイD12ィエD1构型的Coqblin-Schrieffer型s-f交换相互作用。在此基础上，推导出 CFSGS 系统中核自旋的 RKKY 相互作用。它是张量形式的，并带来正弦或螺旋核自旋结构。(3)从理论上研究了PrCu6的核磁性。该项目的研究人员之一哈塔（Hata）的实验研究发现了存在弯曲弱铁磁体的证据，即。即，沿 b 轴的反铁磁和沿 c 轴的铁磁以及磁滞现象。我们关注了不存在反演对称性的单斜晶体结构，然后推导了核自旋的 Dzyaloshinsky-Moriya 型 RKKY 相互作用。该理论可以解释实验中发现的磁特性。 2．超低温下的核自旋弛豫。(4)解决了Rh在T=0附近实验发现的异常现象，即。即，核自旋弛豫在负 T 温度下比在正 T 温度下慢两倍。我们推导了超低温下有效的弛豫公式，并应用高 T 展开方法来解释实验。