Magnetic K-edge absorption in 3d elements and its relation to local magnetic structure

In this paper we present a selection of circular magnetic x-ray dichroism (CMXD) measurements at the K edges of Fe, Ni, Co, and Mn in various alloys and compounds. We investigate the correlation between the measured spin-dependent absorption signal and the p-like spin polarization of the unoccupied bands at the Fermi level. In the case of Fe we find a direct correlation of the spin-dependent absorption profile to the p-like spin polarizations. This is discussed for various alloys. The measured CMXD signals are compared with theoretical calculations for the absorption spectra. For Fe and Ni we have performed spin-polarized relativistic Korringa-Kohn-Rostoker Green’s function calculations, which give a parameter-free description of the spin-dependent absorption process. The content of information in the experimental CMXD spectra on the local magnetic p and d moments is discussed in comparison with the calculated changes of the p and d moments. In the case of the Co and Ni K edges we find a direct correlation of the average strength of the spin-dependent absorption signal to the p moment. For Co also a direct correlation to the d moment is indicated. At Fe K edges no proportionality of any features of the spin-dependent absorption profile to p or d moments have been found.