MXD - MODEL-CALCULATIONS AND A FULLY RELATIVISTIC THEORY FOR MAGNETICEXAFS

New theoretical developments based on a fully relativistic description of magnetic dichroism (MXD) in X-ray absorption spectroscopy are pres ented. It is demonstrated that it is possible to achieve within this s ophisticated framework an unambiguous identification of the role of ex change splitting and spin-orbit coupling for the MXD by means of model calculations. A description of this approach that consists in the sep arate manipulation of both sources of the MXD is presented together wi th several applications to K-and L-2,L-3-edge-spectra of transition me tals. All fully relativistic calculations on the MXD have been done so far in the XANES region using the standard relativistic (kappa,mu)-re presentation. In dealing with magnetic EXAFS (MEXAFS) it seems to be m ore advantageous to treat the multiple scattering for the final states in real-space adopting the (I,m(l),m(s))-representation. A correspond ing generalization for the matrix inversion as well as the expansion t echniques will be presented.