MXD - Model Calculations and a Fully Relativistic Theory for Magnetic EXAFS

Abstract
New theoretical developments based on a fully relativistic description of magnetic dichroism (MXD) in X-ray absorption spectroscopy are presented. It is demonstrated that it is possible to achieve within this sophisticated framework an unambiguous identification of the role of exchange splitting and spin-orbit coupling for the MXD by means of model calculations. A description of this approach that consists in the separate manipulation of both sources of the MXD is presented together with several applications to K-and L_2,3-edge-spectra of transition metals. All fully relativistic calculations on the MXD have been done so far in the XANES region using the standard relativistic (κ, µ)-representation. In dealing with magnetic EXAFS (MEXAFS) it seems to be more advantageous to treat the multiple scattering for the final states in real-space adopting the (l, m_l, m_s)-representation. A corresponding generalization for the matrix inversion as well as the expansion techniques will be presented.