Spin-wave excitations in the modified zener model

Abstract

Dynamical susceptibility of the modified Zener model has been calculated in the limit of infinitely large intra-atomic correlations between the Zener electrons. The poles of the susceptibility give the spectrum of the spin waves which, due to the two nonequivalent spin systems, consists of acoustic and optic branches. It is found that if W/2>J>|ε_F| (where J is the coupling parameter between localized spin and the Zener electron spin, W is the bandwidth of the Zener electrons and ε_F is the Fermi energy, the energy being measured from the middle of the band) the optic branch is highly damped as its energy lies within the single-particle continuum and at the same time the acoustic branch is well defined. It is possible to explain the fact that so far the optic branch has not been observed in transition metal ferromagnets where J is expected to be smaller than W/2.