Influence of interdiffusion on the magnetic moments in Co∕Au multilayers

The electronic and magnetic structures of a Co₁₁Au₄ multilayer, as well as the corresponding Au L_2,3-edge x-ray magnetic dichroism (XMCD) spectra, are calculated for various degrees of interdiffusion at the Co∕Au interface. The experimental Au L_2,3-edge XMCD signal [ F. Wilhelm et al. Phys. Rev. B 69 220404 (2004)] cannot be reproduced unless a considerable interdiffusion at the Co∕Au interface is assumed. Interdiffusion enhances the induced magnetism of Au, and the magnitudes of spin and orbital magnetic moments of Au increase linearly with the number of Co neighbors. For Co, there is a competition between lattice dilatation, which enhances magnetism, and having Au as a neighbor, which suppresses magnetism of Co atoms. Low symmetry and inhomogeneity of the interface region cause the magnetic-dipole term T_z and the number of holes in the d band to have a significant influence on quantities related to the XMCD sum rules.