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 CoFeMn$Z$ ($Z=\text{Al}$, 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 $X$, $X^{\prime }$, $Y$, and $Z$ sublattice of the related $X_{2}YZ$ $L{2}_1$-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).

• Received 8 July 2011

DOI:https://doi.org/10.1103/PhysRevB.84.144413