Microscopic theory of spin waves in ultrathin ferromagnetic films: Fe on W(110)

We present theoretical studies of the spin wave excitations in ultrathin Fe films adsorbed on the W(110) surface, within the framework of itinerant electron theory, and with use of a realistic electronic structure. The electronic structure of the films and the substrate, taken as semi-infinite, is described by the empirical tight-binding scheme with ferromagnetism in the film driven by intra-atomic Coulomb interactions within the d shell. We calculate the exchange stiffness directly, then explore spin wave dispersion relations and Landau damping throughout the surface Brillouin zone through use of the random phase approximation. We also compare dispersion relations so generated with results based on the adiabatic description of spin motions; the latter approach overlooks Landau damping, of course, which we find appreciable at the shorter wavelengths. We comment also on apparent hybridization gaps and 'optical' spin waves which have appeared in earlier theoretical studies of spin waves in the bulk transition metal ferromagnets.