Soft x-ray magnetic circular dichroism study of the ferromagnetic spinel-type Cr chalcogenides

We have observed magnetic circular dichroism (MCD) in the soft x-ray absorption spectra of the semiconducting ferromagnet CdCr2Se4 and the metallic ferromagnets CuCr2S4 and CuCr2Se4. The Cr 2p x-ray absorption and MCD spectra show that the d-electron occupancies of the Cr atom in the Cu based Cr sulfide and selenide are not much different from that in the CdCr2Se4 in spite of the different formal valencies Cr3.5+ and Cr3+ respectively. The observed Cu 2p MCD spectra show the existence of small magnetic moments on the Cu sites which are aligned antiparallel to the Cr 3d moment in CuCr2S4 and CuCr2Se4, consistent with band-structure calculation.