Orbital magnetic moment enhancement at surfaces and interfaces within the framework of the local density approximation + U method

Stimulated by MCXD measurements, the determination of orbital magnetic moments, ML, at surfaces and interfaces has become a subject of strong interest. We combine the rotationally invariant local density approximation (LDA)+U total energy functional with a relativistic self-consistent spin-polarized version of the total energy full-potential linearized augmented plane wave method in order to determine ML at surfaces and interfaces. As illustration, the method is applied to Co overlayers on Cu(001). We find an enhancement of the Co orbital magnetic moment in LDA+ U calculations in comparison with local spin density functional approximation (LSDA) results. ML as a function of magnetic Co-film thickness is analyzed. The M_L/M_S ratio is calculated to be different for different Co layers (i.e., interface, surface, or remaining Co layers) in Co/Cu(001), and is shown to be dependent on the Co overlayer thickness. Finally, the use of LDA+U is shown to give M_L/M _S in better agreement with MCXD data than does LSDA.