Soft-x-ray magnetic-circular-dichroism study of the colossal-magnetoresistance spinel Fe0.5Cu0.5Cr2S4 -: art. no. 014427

We have investigated the electronic and magnetic structure of the colossal magnetoresistive Cr-based spinel Fe0.5Cu0.5Cr2S4 employing magnetic circular dichroism (MCD) of core level absorption (x-ray absorption spectroscopy) spectra in the soft x-ray region. The results here clearly establish that Fe is in the formal trivalent state (Fe3+) in this compound, resolving previous controversies. The Cr 2p and Fe 2p x-ray absorption and MCD spectra shows that the magnetic moment of the tetrahedrally coordinated Fe3+ are aligned antiparallel to those of the octahedrally coordinated Cr3+. The observed Cu 2p MCD spectra show existence of very small magnetic moments (<0.20mu(B)) on the copper sites. The magnetic moments at the Fe and the Cr sites have been obtained based on the magneto-optical sum rules. The results are consistent with the band structure calculation based on the full potential augmented plane wave method.