The role of oblique-to-surface disposition of neighbours in the emergence of surface spin waves in magnetic films

This work is aimed at a numerical investigation of the spin-wave energies and respective band structures throughout the two-dimensional Brillouin zone in magnetic (cubic) thin films for the surface orientations sc(001), bcc(001) and fcc(001). We apply the Heisenberg localized spin model assuming exchange nearest (NN) and next-nearest (NNN) neighbour interactions and elucidate the role of the geometrical disposition of the NN and NNN neighbourhoods for the emergence of the surface spin-waves. The necessary condition for the emergence of the surface spin-waves is turned out to require the bands to be cut at the surface 'obliquely' thereto irrespective of whether these 'oblique' interactions are of the NN or NNN type. (author)