Shift and broadening of optical transitions in MnF2: Zn

Abstract

The perburation on the optical properties of Mn${\mathrm{F}}_2$, caused by the presence of small amounts of ${\mathrm{Zn}}^{2+}$ ions substituted for ${\mathrm{Mn}}^{2+}$ ions, is studied for Zn concentrations up to 1 at.%. In nominally pure Mn${\mathrm{F}}_2$ pure electronic sharp-line and magnon sideband transitions involving the ${}_{}{}^6{}_{}{}^{}A_{1g}^{}{}_{}{}^{}$ ground state and the ${}_{}{}^4{}_{}{}^{}T_{1g}^{}{}_{}{}^{}$ excited state of Mn are observed in absorption and luminescence. These transitions shift to lower energies and broaden as the Zn concentration is increased. The broadening and shift are explained on the basis of the inhomogeneous strains introduced into the lattice by the Zn impurities and a simple strain theory of line broadening applied to Mn${\mathrm{F}}_2$ yields values for the broadening which are close to the observed values.