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

In this研究项目我们已经研究了两个主题1. Ultralow temperature property ofsystems consisting of conduction electrons and nuclear spins in the crystalline field singlet ground1 .我们已经研究了Coulomb interaction on the superconductivitymediated by the virtual excitation of the CFSGS. the superconducting transition temperature islowered somewhat,(2)我们曾引用过Coqblin-Schrieffer type s-f exchangeinteraction for (4f) D12 - D1 configuration with strong Hund and LS couplings. On the basis of itthe RKKY interaction is derived for nuclear spins in the CFSGS system.它是tensorial form andbrings sinusoidal or helical nuclear spin结构。(3)nuclear magnetism of PrCu6 is studiedtheoretically. 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 hysteresisphenomenon. We payed attention to the monoclinic crystal structure in which the inversion symmetrydoes not hold，然后derived a Dzyaloshinsky-Moriya type RKKY interaction for nuclear spins. The theory canexplain the magnetic properties found in the experiment.2.核分裂反应在ultralow(4)我们已经解决了anomaly found experimentally in Rh near T=0, i.e.，nuclear spin relaxation is two-times slower at negative T than at positive T. We have derived aformula for relaxation effective at ultralow temperatures and applied the high-T expansion method toit to explain the experiment。

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.