Surface effective-medium approach to the magnetic properties of 3d adatoms on metals

By using a jellium model surface and a realistic one, the magnetic properties of a single Fe adatom on Al are studied. For the jellium surface the effect of a true semi-infinite solid is taken into account by a nonlocal potential via the embedding method, while the realistic Al(100) surface is modeled by a slab of five metal layers. In this latter case a dilute enough coverage of Fe is considered for comparison with the results of the isolated adatom on jellium. The full potential linearized augmented plane-wave method within an ab initio density-functional theory framework is used to describe the atoms in both approaches. Our calculations show that the electronic properties such as charge densities, densities of states, and the adatom magnetic moments of both models are in very good agreement. These results, corroborated by further calculations for a Co adatom, suggest that a relationship between the adatom magnetic moment and the local unperturbed charge density of the substrate exists, at least for simple metals. So a surface effective-medium approach for the adatom magnetic moments is proposed. The validity of such a method for 3d adatoms on noble metals is shown by comparison of surface jellium calculations with existing ones.