Coherence and Spin correlations in Kondo Semiconductors

用中子散射、MuSR和低温磁测量研究了近藤半导体中的相干和自旋关联。1.中子散射研究(1)在12T以下的磁场中研究了CeNiSn中的自旋激子。能量为4 meV的自旋激子的场依赖于比热。(2)在4kbar的临界压强附近，Ce7Ni3的非弹性散射可以用欧米伽/T的普适函数来描述。(3)YbB12在14 meV处的自旋激子强度与Q有很强的依赖关系，在(111)处有最大值。2.Muon自旋弛豫研究(I)CeNil-xCuxSnx在x=0.06附近表现出非磁-磁相变。(2)Ce7Ni3的互自旋共振结果表明，在1.8K处发生一级SDW相变，在0处发生二级相变。Ce离子的磁矩方向从c轴倾斜。3.量子临界行为的低温研究(I)CeNi0.95Cu0.05锡的比热除以温度和磁化率继续增加到0.025K。(2)在0.5K以上的压力下观察到的Ce7Ni3的非费米液体行为与0.2K以下的费米液体行为是交叉的。

The coherence and spin correlations in Kondo semiconductors have been studied by neutron scattering, muSR and low-temperature magnetic measurements on single crystals of CeNiSn, Ce7Ni3 and YbB12 grown at Hiroshima University.1.Neutron scattering study(1) The spin excitaion in CeNiSn was studied in magnetic fields up to 12 T.The field dependence of the peak at an energy of 4 meV traces that of the specific heat. This quasi-one dimensional correlation is found to be essential for gap formation in CeNiSn.(2) The inelastic scattering from Ce7Ni3 near the critical pressure of 4 kbar can be described by a universal function of omega/T.(3) The intensity of spin excitaion of YbB12 at 14 meV shows strong q dependence with a sharp maximum at (111).2.Muon spin relaxation study(I) CeNil-xCuxSn exhibits a nonmagnetic-magnetic transition near x=0.06.(2) The muSR results on Ce7Ni3 indicates the first-order SDW transition at 1.8K and second-order transition at 0.7K.The direction of the magnetic moment of Ce ions tilts from the c axis.3.Low-temperature study of quantum critical behavior(I) Both the specific heat divided by temperature and magnetic susceptibility of CeNi0.95Cu0.05Sn continue to increase down to 0.025K.(2) Non-Fermi liquid behavior in the specific heat of Ce7Ni3 observed above 0.5K under a pressure of 0.4 GPa is found to be a crossover to the Fermi liquid behavior below 0.2K.