Cerium L-III-edge x-ray absorption study of the CexFe4-yCoySb12 skutterudites

The cerium L-III-edge x-ray absorption near-edge spectra of the CexFe4-yCoy Sb12 compounds have been obtained at 295 K and unambiguously indicate that cerium is in the 4f(1) electronic ground state for all values of 0.22 less than or equal tox less than or equal to0.98 and 0.0 less than or equal toy less than or equal to3.5. This stable trivalent state of cerium is in agree ment with the proposed (CeFe4Sb12)(1-alpha)(square Co4Sb12)(alpha), solid s olution structure, in which the cerium atoms are always surrounded by twelv e antimony first neighbors and six iron second neighbors, the observed magn etic properties of CeFe4Sb12 and Ce0.9Fe3CoSb12, and the electronic structu re of CeFe4Sb12 obtained from hand-structure calculations.