Ab initio study of anisotropic magnetism in uranium compounds

Abstract

We have applied two methods to investigate the origin in the electronic structure of the unusual magnetic behavior of the uranium monochalcogenides and monopnictides. First, we have carried out spin-polarized electronic structure calculations based on the full-potential linearized muffin-tin orbital (FPLMTO) method with only spin-polarization (orbital polarization only via spin-orbit coupling) and also with orbital polarization correction. Second, we have carried out first-principles calculations synthesizing (1) a phenomenological theory of orbitally driven magnetism using a model Hamiltonian which incorporates explicitly the hybridization-induced and Coulomb exchange interactions on an equal footing, and (2) FPLMTO electronic structure calculations allowing a first-principles evaluation of the parameters entering the model Hamiltonian. Within the purely band calculation greater success is obtained for the zero-temperature ordered moments for the more itinerant compounds (US and UP), while the synthesis of phenomenology and electronic structure method gives better agreement with experiment for the more localized pnictides (UBi, USb). Results for the ordered moments and ordering temperatures are presented, and the validity and limitations of the two methods are discussed.