Effects of Spin-Dependent Spectral Weight on Magnetic Circular X-Ray Dichroism: Application to R(NixCo1-x)5 Intermetallic Compounds

Systematic study of the RE(NixCo1-x)5 compounds (RE=La, Gd and Tb) has allowed to investigate the combined effects of the 3d-5d hybridization and 4f-5d exchange on the RE L2,3-edge MCXD signal. In La(NixCo1-x)5 compounds, where the Sd polarization results only from the hybridization between the 5d and 3d bands, the MCXD signal scales with the Sd moment and can be explained by a one-particle model for the absorption process [1-3]. When only the 4f-5d exchange intervenes, like in the GdNi5 and TbNi5 compounds, its effects on the MCXD sign and amplitude are very important, they are understood in term of spin-dependence of the radial matrix elements. When both the 3d-5d hybridization and the 4f-5d exchange are present like in the Tb(NixCo1-x)5 compounds, the amplitude variations of the L2,3-edge MCXD spectra may be qualitatively descripted by a balanced contribution of both effects