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 Cr^3.5+ 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.