The influence of Gd/Ce substitution on the magnetic properties, electronic structure and the valence of cerium in the solid solution CexGd1−xNi3

Abstract

The polycrystalline compounds CexGd1−xNi3 with a rhombohedral PuNi3 (x ≤ 0.2) and hexagonal CeNi3 (x ≥ 0.8) – type of crystal structures have been obtained. The change of the lattice parameters may suggest an unstable valence of cerium in the studied system. The effect of partial substitution of Gd by Ce is reflected in a change of the cell volume V(x), the Curie temperature TC(x) and in the temperature dependence of the magnetic susceptibility and electrical resistivity. Thus, TC(x) decreases from 115 K (x = 0) to ∼6.8 K (x = 0.8). The XPS spectra have been measured at room temperature. The valence band spectra (VB) as well as the core level lines have been analysed as influence of the Gd/Ce substitution on the electronic structure. The VB near the Fermi level (EF) is dominated by Ni3d states. In the VB region some slight effects of hybridization and changes of intensity of states on EF have been noticed. The analysis of Ce core level lines reveals the occurrence of possible intermediate valence. The values of the Ce4f - state occupation parameter (nf) and the hybridization energy (Δ) have been estimated. The gradual filling of the Ni3d band is revealed by a reduction of the 6 eV satellite intensities in the Ni2p core level spectrum. All these effects can modify the magnetic properties of the investigated compounds.