Intersublattice relaxation of excitons in MnF2
M. L. J. Hollman, A. F. M. Arts, and H. W. de Wijn
Faculty of Physics and Astronomy, and Debye Institute, Utrecht
University, P.O. Box 80.000, 3508 TA Utrecht, The Netherlands
The intersublattice relaxation rate is measured as a function of the
temperature for the excitons arising from the
6A1 \rightarrow
4T1(I) transition in MnF2.
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 cm-1. The relaxation rate at lower temperatures amounts
to (0.75 ± 0.15) × 106 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 concentrations of order 1 at.%.