Electronic structure of the intermetallic compounds Ce2Fe17 and Ce2Fe15.3M1.7 (M = Al, Si): Experiment and theory

The electronic structure of the intermetallic compounds Ce2Fe17 and Ce2Fe15.3M1.7 (M = Al, Si) is theoretically calculated in the local-spin-density approximation. It is shown that a considerable increase in the Curie temperature upon introduction of Al and Si impurities is accompanied by a proportional increase in the exchange interaction parameters Jij within the Heisenberg model for iron ions in the 6c crystallographic positions. The experimental optical conductivities of the compounds under investigation are interpreted in terms of the calculated electronic structure. The experimental valences obtained for the cerium ions from an analysis of the Ce L3 x-ray absorption spectra indicate that cerium in these intermetallic compounds is in intermediate valence states.