The magnetism of UX3 compounds (X = In, Pb, Ga) from symmetry considerations and perturbed-angular-correlation spectroscopy

We show how symmetry considerations and ab initio calculations within the f ramework of the density-functional theory can be used in the analysis of th e appearance and orientation of magnetic hyperfine fields. This approach, i n which the incorporation of spin-orbit coupling is essential, provides inf ormation about hyperfine fields also for the sites where the Heisenberg exc hange field is zero. This is of crucial importance in the interpretation of magnetic hyperfine-field measurements. We apply this theoretical scheme an d perturbed-angular-correlation experiments to study the magnetic structure of UX3 compounds with X = Ga, In, Pb. For UPb3 we find a triaxial structur e with U moments along the [111] axes. In UIn3 the U moments are arranged i n a type-II antiferromagnetic structure with moments along [110].