Spin wave calculations in the t matrix approximation with many bands

Abstract

The transverse susceptibility is derived by means of Green function techniques in the itinerant model for a ferromagnet. Correlations within the many band system were taken into account through the t matrix approximation. The expression for the susceptibility was found to decompose naturally into two parts from which the collective excitations and, in particular, the spin wave modes can be determined. Explicit expressions were obtained for both the acoustic and the optical modes for some simple cases.