Ferromagnetic resonance line width in insulating materials

Abstract It has recently been recognized that the energy spectrum of spin waves in a ferromagnetic body of finite size is very different from the spectrum in an infinitely extended body. In a finite sample a degeneracy exists between the spin wave of wave vector k = 0 and a manifold of short wavelength spin waves. In the presence of irregularities in the magnetic lattice, such as are necessarily present in magnetic insulators having an inverted spinel structure, the degeneracy leads to a resonance line width comparable to those experimentally observed. This line width depends upon the magnetization of the material, the shape of the sample, the Curie temperature and the degree of ordering of the magnetic lattice.