NMR STUDY OF HEAVY FERMION SUPERCONDUCTOR AT ULTRA LOW TEMPERATURE.

摘要在^3He-^4He稀释制冷机中，通过对换热器的改造和新型核磁共振混合室的建造，开发了一种超低温核磁共振技术。使用该仪器得到了以下结果：在温度低于60mK时，硅和铜的骑士位移K值下降到正常值的-50%。结合已经观测到的T_1^<-1>的T^3依赖性，结果表明在超导态下实现了d波库珀对。在-3t的外场中，超导性被破坏，核磁共振信号随着温度的降低而减小，表明在-0.6k.2以下出现反铁磁样序。Pt的T_1^<-1>在低温下未表现出BCS型增强，仅在T_c以下随t_3成比例下降。这表明超导性质要么是单重态d波强自旋轨道散射，要么是三重态p波。k的完全不变似乎支持后者。没有观察到磁有序的迹象，这是由sr和中子衍射测量报告的。在ceecu_2si_2和UPt_3中观察到的超导性的各向异性表明存在很强的现场群伦排斥。反铁磁自旋涨落被认为是超导现象发生的根源。从A1、Cu和IN的T_2和线宽测量中，我们发现CeAl_3和CeInCu_2分别在1.2 k和1.1K时具有反铁磁类有序。

WE DEVELOPED AN ULTRA LOW TEMPERATURE NMR TECHNIQUE BY RECONSTRUCTING THE HEAT EXCHANGER AND BY CONSTRUCTING A NEW TYPE MIXING CHAMBER FOR NMR IN ^3He-^4He DILUTION REFRIGERATOR. FOLLOWING RESULTS HAVE BEEN OBTAINED BY USING THIS APPARATUS.1. CeCu_2Si_2 THE KNIGHT SHIFT K OF Si AND Cu ARE COMFIRMED TO DECREASE TO -50% OF THE NORMAL VALUE BELOW T_c DOWN TO 60mK. TOGETHER WITH THE T^3 DEPENDENCE OF T_1^<-1> ALREADY OBSERVED, THE RESULT SHOWS A d WAVE COOPER PAIRING IS REALIZED IN THE SUPERCONDUCTING STATE.IN THE EXTERNAL FIELD OF -3T, WHERE THE SUPERCONDUCTIVITY IS DESTROYED, THE NMR SIGNAL IS FOUND TO DECREASE WITH LOWERING TEMPERATURE, INDICATING AN ANTIFERROMAGNETIC LIKE ORDERING TO APPEAR BELOW -0.6K.2. UPt_3 K OF Pt BELOW T_c DOES NOT CHANGE BELOW T_c DOWN TO 50 mK, WHILE T_1^<-1> OF Pt DOES NOT SHOW BCS TYPE ENHANCEMENT JUST BELOW T_c DECREASING IN PROPORTION TO T^3 AT LOW TEMPERATURE. THIS INDICATES THAT THE SUPERCONDUCTING NATURE IS EITHER SINGLET d WAVE STRONG SPIN-ORBIT SCATTERING OR TRIPLET p WAVE. PERFECT NO-CHANGE OF K SEEMS TO SUPPORT THE LATTER. NO INDICATION OF MAGNETIC ORDERING IS OBSERVED WHICH IS REPORTED BY SR AND NEUTRON DIFFRACTION MEASUREMENT.THE ANISOTROPIC NATURE OF THE SUPERCONDUCTIVITY OBSERVED IN CeCu_2Si_2 AND UPt_3 INDICATES THE EXISTENCE OF A STRONG ON-SITE CONLOMB REPULSION. THE ANTIFERROMAGNETIC SPIN FLUCTUATIONS ARE CONSIDERED TO BE THE ORIGIN OF THE OCCURRENCE FOR THE SUPERCONDUCTIVITY.3. CeAl_3 AND CeInCu_2 WE HAVE FOUND AN ANTIFERROMAGNETIC LIKE ORDERING IN CeAl_3 AND CeInCu_2 AT 1.2 AND 1.1K, RESPECTIVELY, FROM THE T_2 AND LINE WIDTH MEASUREMENT OF A1, Cu and In.