A contribution to the ferromagnetic resonance linewidth of <i>M</i>-phase barium ferrite

Abstract

Mössbauer and neutron diffraction studies of barium ferrite show that the iron ion in the 2b (trigonal bipyramid) site oscillates or hops between two equilibrium positions on either side of the mirror plane of the bipyramid, for temperatures above 80 K. Since this motion is uncorrelated from one (2b) site to another, it can lead to two-magnon scattering of spin waves due to the time-dependent fluctuation in the anisotropy energy. The contribution of this mechanism to the ferromagnetic resonance linewidth of barium ferrite is calculated, using time-dependent perturbation theory. For reasonable values of the parameters, this linewidth is of the order of 10 Oe at 300 K.