Energy shift and damping of dipole-exchange spin waves in ultrathin ferromagnetic films

A finite-temperature perturbation formalism is developed to study the proce sses of spin-wave interactions in ultrathin ferromagnetic films including t he effects of both the long-range magnetic dipole-dipole interactions and t he short-range exchange interactions By contrast with previous macroscopic methods for evaluating spin-wave interactions, the dipolar terms are treate d here within a Hamiltonian method together with exchange and anisotropy te rms to obtain a theory applicable to ultrathin films at temperatures below the Curie temperature. The contributions to the energy shift and the dampin g (or reciprocal lifetime) of the dipole-exchange spin waves due to three-m agnon and four magnon processes are calculated. Numerical examples are pres ented (C) 1999 Acta Metallurgica Inc.