Optical Evidence for the Dynamic Jahn-Teller Effect in N${\mathrm{d}}_{0.7}$S${\mathrm{r}}_{0.3}$Mn${\mathrm{O}}_3$

The optical properties of N${\mathrm{d}}_{0.7}$S${\mathrm{r}}_{0.3}$Mn${\mathrm{O}}_3$ thin films have been studied over a broad spectral range, at temperatures down to 15 K and magnetic fields up to 8.9 T. A large transfer of spectral weight from high energy to low energy occurs as this material is cooled into the ferromagnetic phase, or as the magnetic field is increased near the phase boundary. The optical data are found to be consistent with models that include both the double-exchange interaction and the dynamic Jahn-Teller effect on the ${\mathrm{Mn}}^{3+}$ $e_g$ levels.