X-RAY MAGNETIC CIRCULAR-DICHROISM IN THE NEAR AND EXTENDED ABSORPTION-EDGE STRUCTURE (INVITED)

Magnetic circular dichroism (MCD) studies at K and L edges using hard and soft x rays are presented. The relation of this universal phenomen on in the x-ray absorption near-edge structure (XANES) and extended x- ray absorption fine structure (EXAFS) regions to local magnetic struct ures in the case of 3d and 4f elements is illustrated. The validity of atomic and band-structure pictures to describe the MCD in the XANES r ange are outlined and the applicability of sum rules and two-step vect or coupling models to deduce spin and orbital moments of the absorbing atom as well as spin-density profiles from the experimental data are critically discussed. The correlation of the dichroic contribution in the EXAFS to the magnetic moments and spin densities of the neighborin g atoms are addressed by systematic studies which provide new insights into the exchange phenomena of the interaction of spin-polarized elec trons with ferromagnetic media. The potential but also the limitations of this new spectroscopy is demonstrated.