Valence state and magnetism of CeNi4Si and YbNi4Si

The studies of the magnetic susceptibility χ, X-ray photoemission spectra (XPS) and electrical resistivity of RNi4Si (R=Ce, Yb) compounds are reported. CeNi4Si is paramagnetic and follows the Curie–Weiss law with μeff=0.52 μB/f.u. and θ=−2 K. This effective paramagnetic moment is lower than the free Ce3+ ion value. The f-occupancy nf and the coupling Δ between the f level and the conduction states are derived to be about 0.91 and 36 meV, respectively. Both the susceptibility data and the XPS spectra have shown that Ce ions are in the intermediate valence state in CeNi4Si. In the case of YbNi4Si the valence state of the ytterbium ion is close to 3+. These results are comparable to those obtained in the case of RNi4M (M=B, Al, Ga, Cu) series and show that the substitution of M for Si preserves the general properties of these compounds.