Magnetic circular X-ray dichroism spectra at L_2,3 edges of rare-earth compounds

We report a systematic interpretation of the trend observed in the magnetic circular X-ray dichroism (MCXD) at the L_2,3 edges for the entire series of rare-earth elements. It is shown that the MCXD spectra consisting mainly of the electric dipole transition are dominated by the enhancement of the dipole matrix element as well as by the polarization effect of the 5d ground state, both of which are due to the 4f-5d exchange interaction. A complemental contribution from the electric quadrupole transition is found to be appreciable, by reproducing the experimental spectra as a superposition of both contributions.