X-ray magnetic circular dichroism in the near and extended absorption edge structure (invited)

Abstract

Magnetic circular dichroism (MCD) studies at K and L edges using hard and soft x rays are presented. The relation of this universal phenomenon in the x-ray absorption near-edge structure (XANES) and extended x-ray absorption fine structure (EXAFS) regions to local magnetic structures 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 range are outlined and the applicability of sum rules and two-step vector 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 neighboring atoms are addressed by systematic studies which provide new insights into the exchange phenomena of the interaction of spin-polarized electrons with ferromagnetic media. The potential but also the limitations of this new spectroscopy is demonstrated.