Theoretical study of the magnetic X-ray dichroism of hcp-Gd

The X-ray absorption coefficient of Gd at the $L_{1-};, L_{2-};$ and $L_{3-}$edges for circularly polarized radiation has been calculated on the basis of spin-polarized relativistic KKR-band structure calculations, which treated the f-electrons as band electrons. The resulting spectra for unpolarized X-rays as well as their dependency on the helicity of the radiation is found in very satisfying agreement with former experimental work. Although for the investigated spectra the f-electrons are involved only via weak dipole-forbidden contributions and hybridization effects, it is argued that the band picture is an adequate description for the f-electrons in the case of Gd. In contrast to the results for the transition metal systems studied recently, it is found that the relative difference in absorption of left and right circularly polarized radiation at the L2- and L3-edges cannot be used as a measure for the spin-polarization of the final d-like bands