Influence of spin-orbit coupling on the magnetic dipole term T α

The influence of the spin-orbit coupling (SOC) on the magnetic dipole term Tα is studied across a range of systems in order to check whether the Tα term can be eliminated from analysis of x-ray magnetic circular dichroism spectra performed via the spin moment sum rule. Fully relativistic Korringa-Kohn-Rostoker Green's function calculations for Co monolayers and adatoms on Cu, Pd, Ag, Pt, and Au (111) surfaces were performed to verify whether the sum over magnetic dipole terms Tx+Ty+Tz is zero and whether the angular dependence of the Tα term goes as 3cos2θ−1. It follows that there are circumstances when the influence of the SOC on Tα cannot be neglected even for 3d atoms where the SOC is nominally small. The crucial factor appears to be the dimensionality of the system: For 3d adatoms, the influence of SOC on Tα can be significant whereas for monolayers it is always practically negligible. Apart from the dimensionality, hybridization between adatom and substrate states is also important: Small hybridization enhances the importance of the SOC and vice versa.