INTERSUBLATTICE RELAXATION OF EXCITONS IN MNF2

The intersublattice relaxation rate is measured as a function of the t emperature for the excitons arising from the 6A1 --> 4T1(I) transition in MnF2. It is found that this rate is dominated by scattering with t hermal magnons at temperatures above 10 K. The matrix element governin g the magnon-induced intersublattice coupling is determined to be 0.08 6 +/- 0.006 cm-1. The relaxation rate at lower temperatures amounts to (0.75 +/- 0.15) x 10(6) s-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 Zn2+ impurities up to concentrati ons of order 1 at. %.