Magnetic properties of actinide intermetallic compounds are strongly dependent on the amount of 5f-electron hybridization with other electrons in the valence and conduction bands. Because of the hybridization, the magnetic moment of the actinide ion in many intermetallic compounds deviates strongly from theoretically calculated values based on free-ion or crystal-field models. The effective valence and bonding scheme of the monosulfides AnS, and monophosphides AnP, with An = U, Np, Pu are studied in the self-consistent local density theory using an embedded cluster model. The potential of the host rock-salt lattice is determined self-consistently from least-squares representations of the cluster charge and spin density obtained from variational solutions of the relativistic Dirac-Slater equations. Involvement of actinide 5f orbitals in bonding to ligands as well as in "crystal field" states is noted. A moment-polarized method is used to explore magnetization densities in these compounds in a fully relativistic framework. Net magnetic moments calculated from partially occupied Kramer's pairs are found to depend strongly upon bond length, with obvious implications for pressure and composition dependence of magnetic properties.
ASJC Scopus subject areas