Electrical and Magnetic Properties of La1-xCexRu4P12and CeOs4P12with the Skutterudite Structure

The crystal structures of LaRu4P12and CeRu4P12are refined by the Rietveld analysis of the powderX-ray diffraction data. The bond distances and bond angles in both phosphides are obtained. La1-xCexRu4P12(x=0, 0.1, 0.2, 0.3, 0.4, 0.5, 0.6, 0.7, 0.75, 0.8, 0.9, and 1) and CeOs4P12are prepared at high temperatures and high pressures. Powder X-ray diffractions of the alloys are studied at room temperature. The lattice parameters of the alloys do not change linearly with increasingxand markedly deviate from linear betweenx<0.4 andx=0.6. The formal oxidation number of Ce atoms in the alloys is +3 belowx= 0.6. The electrical and magnetic properties of the alloys CeRu4P12and CeOs4P12are studied at low temperatures. The metalto-insulator transition and magnetic ordering appear at aroundx=0.6. Abovex=0.7 the alloys behave as a semiconductor. CeOs4P12exhibits a semiconducting behavior, with an activation energy of 0.034 eV. CeRu4P12and CeOs4P12show a very small, nearly temperature-independent susceptibility. Electrical and magnetic properties of the alloys, CeRu4P12and CeOs4P12are discussed.