Light scattering in Heisenberg paramagnets

Abstract

Two-spin light scattering in the disordered phase of Heisenberg antiferromagnets is investigated by means of a modified Markoffian approximation for the continued-fraction representation of the shape function. The necessary frequency moments are evaluated: they are found to be dominated by the contribution of zone-boundary wave vectors. The predicted spectral shapes are in good agreement with the experimental spectra in RbMn${\mathrm{F}}_3$ and KNi${\mathrm{F}}_3$ both at high temperatures and in the neighborhood of the Néel point.