Ab-initio study of rare-earth adatoms on a MgO film

Individual magnetic adatoms at surfaces have been shown by using scanning tunneling microscopy and spectroscopy (STM/S) to function as single atom magnets with significant coercive field and remnant field, and long spin relaxation time at several tens of kelvin. A recent addition of a capability of electron spin resonance to STM/S allows unprecedented energy resolution in measurements and enables coherent controls of spin states of the adatoms. Among such single atom magnets, a family of rare-earth adatoms has emerged a promising candidate for magnetic storage due to strong spin-orbit coupling and isolated nature of 4f valence orbitals from environment. So far, most of theoretical studies of rare-earth adatoms at surfaces are performed using density-functional theory (DFT), although 4f valence states are not reliably characterized by DFT. Here we study electronic structure and magnetic properties of several rare-earth adatoms at surfaces of magnesium oxide films by applying the ab-initio multiconfigurational method including spin-orbit coupling along with the embedding potential method. We compare our results to experiments and propose new applications of magnetic adatoms for quantum information science.