Intersublattice relaxation of excitons inMnF2

Abstract

The intersublattice relaxation rate is measured as a function of the temperature for the excitons arising from the ${}_{}{}^6{}_{}{}^{}$ ${\mathit{A}}_1$ ${\to }^4$ ${\mathit{T}}_1$(I) transition in ${\mathrm{MnF}}_2$. It is found that this rate is dominated by scattering with thermal magnons at temperatures above 10 K. The matrix element governing the magnon-induced intersublattice coupling is determined to be 0.086±0.006 ${\mathrm{cm}}^{\mathrm{-}1}$. The relaxation rate at lower temperatures amounts to (0.75±0.15)×${10}^6$ ${\mathrm{s}}^{\mathrm{-}1}$, and is consistent with exchange coupling perturbed by the spin-orbit interaction. The low-temperature rate is found to increase by the addition of ${\mathrm{Zn}}^{2+}$ impurities up to concentrations of order 1 at. %.