Predicted spin and orbital contributions to the magnetic structure of Co/2X superlattices (abstract)

The neighboring elements Rh, Ir, Pd, and Pt are used as bilayers in Co/2X superlattices in an effort to systematically examine properties advantageous to short wavelength MO recording. The calculations presented here use the local spin-density approximation to the potential within the layer Korringa-Kohn-Rostoker method. The set of coupled differential equations produced by the inclusion of the spin-orbit interaction is solved by the method of Boardman.¹ Interfaces occur along the (111) plane of the fcc lattice. In all cases, the Co moment is found to be strongly enhanced relative to bulk and the bilayer element atoms are substantially polarized. However, in the case of the Rh and Ir bilayers, we predict antiferromagnetic coupling of the spin polarizations of neighboring layers within the bilayer. This probably explains the mysteriously low magnetization experimentally found in CoIr alloys. In contrast, Pd and Pt bilayers exhibit ferromagnetic coupling. The Pd spin polarization is approximately 30% larger than the Pt value; however, the orbital contributions exhibit the opposite trend with the value for Pt about 40% larger. This is in qualitative agreement with Kerr data which reflects the orbital polarization. Directing the Co/2Pd superlattice spin along the interface plane is found to decrease the orbital polarization. This may explain why our preliminary calculated results for anisotropy constant, like experiment, find an easy axis perpendicular to the interface plane.