competition of kondo spin fluctuations and RKKY interactions in CeRh₂si_2-xGe_x and CeM₂X₂ compounds: a kondo necklace problem

Abstract

We present the results of our measurements of the lattice constants and magnetic susceptibility of the pseudo-ternary system CeRh₂Si_2-xGe_x which crystallizes in the tetragonal ThCr₂Si₂ structure. Both of the cell constants a and c increase linearly with x. The magnetic ordering temperature T_N exhibits initially an enhancement with the increase in x (T_N=36.9 K for x=0 and 38.3 K for x=0.125) and then decreases as x continues to increase further. These results, along with those on the pressure dependence of T_N in CeRh₂Si₂, can be understood on the basis of the Doniach's model of a Kondo necklace. We discuss also the applicability of this model to describe the strong correlation between the structural aspects and the ground-state properties of the whole series of Ce-based ternaries CeM₂X₂(M=3d, 4d and 5d elements; X = Si, Ge) of the ThCr₂Si₂ structure.