Spinwellen in Ferromagneten mit indirektem Austausch

Abstract

We consider a lattice of localized, ferromagnetically ordered spins, exchange-inter-acting with a simple conduction band and give a unified theory of the elementary spin excitations. Spinwaves of the Heisenberg-model type and collective spinwaves, characteristic of a Fermigas with repulsive interactions, are coupled and give rise to an acoustical branch of predominantly localized and an optical branch of predominantly collective character which should appear in the infrared.

In its most idealized version the model needs only three parameter: effective massm ⋆, interband exchange energy$\tilde J$ and effective electron-electron repulsion$\tilde v$ to describe this entire spectrum.