ROLE OF CE SUBLATTICES IN THE THERMAL AND MAGNETIC-PROPERTIES OF CE7X3 (X=NI, RU, RH, IR, PD, AND PT) COMPOUNDS

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 s tudied by means of ac and dc magnetic susceptibility, mngnetization an d mainly specific-heat experiments in applied magnetic field. The expe rimental data show that in these compounds there is coexistence of mag netic order, heavy-fermion and intermediate-valence behavior, which is interpreted in terms of the contribution of the three different subla ttices present in the crystalline structure of Th7Fe3-type (denoted by 1Ce(I), 3Ce(II) and 3Ce(III)). From the available volume of the Ce-II I atoms in their crystallographic environment it is found that sublatt ice Ce-III has an intermediate-valence behavior, whereas from entropic considerations sublattices Ce-I and Ce-II are identified as responsib le for the magnetic order or heavy-fermion behavior, depending on the Ce-ligand electronic structure. This systematics evidences a clear cor relation between the thermal and magnetic properties of these compound s and the position of the respective Ce-ligands in the periodic table, through the particular sensitivity of Ce to the environmental conditi ons.