Study of 5d magnetism in rare-earth-transition-metal (Fe, Co) intermetallic compounds by magnetic circular X-ray dichroism

Magnetic circular X-ray dichroism (MCXD) experiments have been performed at the L_2,3 of rare-earth (RE) elements in several Re-transition-metal (Fe, Co) compounds. Experiments at the L_2,3 edges give, in principle, direct information on the 5d magnetic properties of the RE atom which results from the hybridization between the 3d and the 5d electrons. We show in this paper that the use of MCXD experiments at the L_2,3 absorption edges seems to be really complicated when localized 4f electrons are present in the ground state. This unexpected situation is clearly demonstrated by comparing the results obtained on a cerium mixed-valent compound (CeFe₂), in which the 4f electrons are highly hybridized with the conduction electrons, and those obtained on a normal trivalent cerium (4f¹) compound (CeRu₂Ge₂). Our results suggest that the 4f electrons play an essential role in the description of MCXD at the edges of rare earths.