Magnetic and transport properties of low carrier-concentration materials and RCrSb(3).

摘要

Experimental results of magnetization and electrical resistivity measurements are presented for the low carrier-concentration systems Ce 5Ge3Six (x = 0, 0.75, and 1), Ce5Ge 3Cu, Y1-xYbxBiPt and Ca1-xCe xB6. In addition, magnetization and electrical resistivity measurements are presented for the series of low dimensional compounds RCrSb 3 (R = La, Ce, Pr, Nd, Sm and Gd).; Ce5Ge3 forms in the hexagonal Mn5Si 3 structure. This structure has two inequivalent Mn sites and accommodates interstitial atoms inside trigonal antiprism along the (001) direction. The use of interstitial atoms allows some control over the conduction electron concentration. This type of environment might be right for a rare earth like Ce to exhibit mixed valent behavior.; The RBiPt series form a set of cubic compounds known as half-Heuslers. One member of this set, YbBiPt, is a heavy fermion compound with gamma = 8 J/K2 per mol Yb. Electron spin resonance (ESR) and magnetic susceptibility measurements on single crystals of Y1-xYb xBiPt for a nominal concentration of x = 0.10 have been used to derive a crystal-field level scheme that is consistent with earlier neutron results.; CeB6 is one of the rare cases where we find a Gamma 8 crystal-field ground state. Previous studies of the alloy La 1-xCexB6 show that the Gamma8 quartet remains the ground state for Ce concentrations in the range 0.03⩽x⩽0.75 . Susceptibility measurements also show that single ion effects dominate the magnetism throughout this doping range as one can collapse all of the susceptibility data onto a singe curve by normalizing per mole of Ce.; CaB6 is an unusual material with a low carrier-concentration, possibly an excitonic insulator. Doping CaB6 with Ce adds one f moment and one conduction electron per Ce substitution. Magnetization and electrical resistivity data for Ca1-xCexB 6 show that doping into the low carrier-concentration material CaB 6 is not the same as doping into the metal LaB6.; The compounds RCrSb3 (R = La-Nd, Sm, and Gd-Dy) crystallize in an orthorhombic structure. They consist of two distinct layers parallel to the (100) plane separated by rare earth ions and are therefore of lower dimension. These compounds exhibit both ferromagnetic and antiferromagnetic phase transitions. SmCrSb3 shows a first order phase transition at T = 29K.