Magnetic properties of CeyFe4−xNixSb12

The structural and magnetic properties of the metallic skutterudite CeFe4Sb12 have been investigated, with those of CeyFe4−xNixSbz with compositions approaching the relations y=(4−2x)/3, z=12 for which the materials are semiconductors. The large and temperature-dependent contribution of Fe to the magnetic susceptibility of CeFe4Sb12 has been isolated from the Ce contribution, which makes possible a quantitative analysis of the Kondo lattice behavior. In CeFe4Sb12 the Wilson-Sommerfeld ratio is modified by a factor two with respect to former analyses where the magnetic contribution of Fe had been neglected. The main effect of the reduction of the free carrier (hole) concentration in CeyFe4Sb12 is to suppress the Kondo effect and the Fe contribution to the magnetic susceptibility. The samples with theoretical hole concentration per unit cell p∗=z−8−3y−2x smaller than 0.5 behave like semiconductors in which the exchange between localized Ce3+ spins is negligible, and are most promising for a potential use as thermoelements.