SWR in amorphous thin films: Decoupling and linewidths

Recently spin wave resonance experiments have been performed in amorphous thin films with evidence for a spin wave decoupling between different parts of the films and for narrow linewidths which depend on the spin wave wavelength. This is analyzed here in terms of a Hamiltonian with short range exchange and anisotropy forces; emphasis is placed on the SWR plane wave selection rule. Anisotropy is shown to lead to the decoupling and linewidth processes for long spin wave wavelength, while exchange leads to the short wavelength contribution.