THEORY OF MAGNETIC CIRCULAR X-RAY DICHROISM AT THE FE K-EDGE IN RARE-EARTH IRON GARNETS

A mechanism is proposed for the magnetic circular X-ray dichroism (MCX D) at the pre-peak of the Fe K-edge in rare-earth iron garnets. It is found based on a cluster model that, at the pre-peak, the hybridizatio n between the 3d state and the 4p state of an Fe ion on the tetrahedra l site through the ligand 2p states is responsible for the weak electr ic-dipole absorption while the combined effect of the spin-orbit inter action and the spin polarization in the 3d states give rise to its MCX D. In addition, the configuration interaction is shown to be important in explaining the asymmetric dispersion-type MCXD spectra observed. T he effects of the core hole as well as of the band character of the 4p states are discussed briefly in connection is with MCXD observed in t he main X-edge region.