An ab-initio investigation of magnetism in two-dimensional uranium systems

The orbital and spin magnetic moments, and the X-ray-magnetic circular-dichroism (XMCD) spectra at the $M_{4,5}$ edges of the U atoms in a UAs/Co multilayer and in an $\alpha$-U film are calculated within the framework of the density-functional theory in combination with the local-spin-density approximation (LSDA), the generalized-gradient approximation (GGA) and the LDA+$U$ method. The antiparallel arrangement between the U and Co spin magnetic moments at the interface results in the vanishing of ferromagnetism for the case of very thin Co layers. The U moments decay rapidly with the distance from the film surface. The magnitude of the magnetic-dipole term $<T_z>$, which appears in the spin XMCD sum rule, is small. The different exchange-correlation treatments do not yield qualitatively different results.