Some remarks on the surface inhomogeneity model in thin ferromagnetic films

Collinear ferromagnetic spin ordering in a thin film with pinned surface spins is shown to be stable only for certain orientations of the magnetisation vector. Also, the magnon potential is shown to extend outward from the film surface; according to whether the surface spins are pinned more strongly or less strongly than the internal spins, the potential becomes infinite at a distance outward from the surface smaller or larger than one lattice constant.