ORBITAL MAGNETISM IN ENERGY-BANDS

Recent work on orbital magnetism in itinerant magnets is reviewed. It is shown that such an orbital contribution to the magnetic moment is especially important for magnets involving actinide systems and that it is of a size comparable to the spin contribution. In particular, the results for the AnFe2 (An = U, Np and Pu) compounds are discussed and their anomalous properties, as compared to corresponding standard rare-earth systems, are explained in terms of 3d-5f hybridization and orbital polarization within the 5f band manifold. As an introduction to the AnFe2 systems we discuss CeFe2 for which we predict 4f band magnetism in addition to the normal iron magnetism. It is most significant that, in agreement with experiment, the size of the iron moment is found to be reduced in comparison to its value in rare-earth magnets like YFe2. The alpha-gamma transition in Ce metal is also treated and the calculated volume collapse agrees with experiment. Related calculations for Pr and Nd are also briefly discussed. Finally, the orbital contribution to the magnetism in Fe, Co and Ni is considered, and its maximum for Co is explained as the result of the HCP crystal structure.