Element-specific magnetic moments and spin-resolved density of states in CoFeMnZ (Z = Al, Ga; Si, Ge)

Using circular dichroism in x-ray-absorption spectroscopy (XAS/XMCD), we determined element-specific magnetic moments and spin-resolved unoccupied densities of states (DOS) for Co, Fe, and Mn in the quaternary Heusler compounds CoFeMnZ (Z = Al, Ga; Si, Ge). These compounds belong to a class of highly spin-polarized materials with cubic LiMgPdSn-type structure. Different structure models for the sublattice occupation leading to similar average magnetization values can be distinguished by comparison of element-specific moments with theory. We find that the compounds form similar structures, where Co, Fe, Mn, and Z occupy the X, X', Y, and Z sublattice of the related X(2)YZ L2(1)-Heusler structure, for which half-metallic behavior was predicted. The unoccupied partial DOS as derived from the XAS/XMCD spectra for Co, Fe, and Mn are compared to theoretical results. A good agreement is found for Co and Fe, while Mn spectra reveal additional final-state effects (multiplets).