Spin-polarized relativistic band structure calculations and their application to the magnetic x-ray dichrosim

The recent development of fully relativistic spin-polarized schemes of band structure calculations allows us nowadays to investigate physical phenomena that are caused by the interplay of spin-orbital coupling and spin polarization, without using a perturbational approach. Among these effects, the magnetic X-ray dichroism is receiving much interest because it allows us to probe the magnetic aspects of electronic structure in a rather direct and detailed way. This is demonstrated by a comparison of experimental data for 5d impurities in Fe with corresponding theoretical data, obtained by using a spin-polarized relativistic multiple-scattering formalism. The spectra calculated for the L$_2$ and L$_3$ edges are found to be in excellent agreement with experiment. It is shown that a very reliable estimate for the local spin magnetic moments of the 5d atoms can be deduced from the experimental spectra. This is not possible in the case of pure Gd, although our calculations give a very satisfying description for the various L-edge spectra of this f-electron metal