Half-metallic electronic structures of giant magnetoresistive spinels:: Fe1-xCuxCr2S4 (x = 0.0,0.5,1.0)

Electronic structures of Cr-based chalcogenide spinels Fe1-xCuxCr2S4 (x = 0.0,0.5,1.0) are investigated by using the Linearized muffin-tin orbital (LMTO) band method in both the local-spin-density approximation (LSDA) and the LSDA + U. The LSDA yields the half-metallic electronic structures for x = 0.0,1.0 and the insulating electronic structure for x = 0.5. The LSDA + U yields the insulating electronic:structures for x = 0.0 in agreement with experiments. The orbital ordering driven by the on-site Coulomb interaction for x = 0.0 is demonstrated based on the LSDA + U electronic structures. Orbital magnetic moment Morb is obtained by taking into account the spin-orbit interaction. M-orb'S of Fe and Cu in these compounds are found to be very large, reflecting the localized features of 3d band electrons. Conduction models for x = 0.0,0.5,1.0 are discussed with the schematic energy diagrams incorporating the Jahn-Teller effect and the half-metallic electronic structures, [S0163-1829(99)15515-2].