Spin-wave widths in antiferromagnets at intermediate temperatures

A comparison is made between experimental and theoretical results for the damping of long-wavelength spin waves in weakly anisotropic antiferromagnets at temperatures between the low-temperature and the critical regimes. A high-density theory with no adjustable parameters is shown to account well for the wave-vector and temperature dependence of the widths measured by neutron scattering from spin waves in Mn${\mathrm{F}}_2$. The magnitudes of the theoretical widths agree with those observed to within 30% or better.