Spin waves in narrow band ferromagnet

Abstract

Spin Green functions in narrow band ferromagnets are calculated within the Hubbard model and s-d exchange model. The exact expressions are obtained in linear approximation with respect to the current carrier concentration at zero temperature. The generalisation of these expressions for the case of finite concentrations and temperatures is carried out by means of the 1/z expansion, z being the nearest-neighbour number. The spin wave damping, temperature dependence of the spin wave stiffness and the stability of the saturated ferromagnetic state in the Hubbard model are investigated. The rate of the longitudinal nuclear magnetic relaxation in the saturated conducting ferromagnet is calculated.