Role of Ce sublattices in the thermal and magnetic properties of Ce7 X 3 (X=Ni, Ru, Rh, Ir, Pd, and Pt) compounds

Abstract

The role of the Ce sublattices in the thermal and magnetic properties of the Ce7X3 (X=Ni, Ru, Rh, Ir, Pd, and Pt) family of compounds is studied by means of ac and dc magnetic susceptibility, magnetization and mainly specific-heat experiments in applied magnetic field. The experimental data show that in these compounds there is coexistence of magnetic order, heavyfermion and intermediate-valence behavior, which is interpreted in terms of the contribution of the three different sublattices present in the crystalline structure of Th7Fe3-type (denoted by 1CeI, 3CeII, and 3CeIII). From the available volume of the CeIII atoms in their crystallographic environment it is found that sublattice CeIII has an intermediate-valence behavior, whereas from entropic considerations sublattices CeI and CeII are identified as responsible for the magnetic order or heavy-fermion behavior, depending on the Ce-ligand electronic structure. This systematics evidences a clear correlation between the thermal and magnetic properties of these compounds and the position of the respective Ce-ligands in the periodic table, through the particular sensitivity of Ce to the environmental conditions.