Phenomenological Theory of Magnon Sideband Shapes in a Ferromagnet with Impurities

Abstract

A simple model Hamiltonian is used to calculate exactly the line shapes of magnon sidebands in excitonic spectra in a ferromagnet, using Green functions. The effect of a spin defect in the crystal is included in the calculation. In contrast to previous work, no approximations involving Green function decoupling are necessary for this Hamiltonian which, however, contains the essential physical features of the problem. Some one-dimensional crystal line shapes are calculated to illustrate the features of the theory, and application to realistic crystals is discussed.