SPIN-WAVE-ASSISTED PHOTOLUMINESCENCE IN MNO CRYSTALS

The authors report the observation of photoluminescence in antiferromagnetic and paramagnetic MnO. Two strong emission bands centred at 1.66 and 1.25 eV are observed below the Neel temperature, 118 K, in MnO crystals. Above the Neel temperature, the emission band centred at 1.66 eV vanishes, while the band centred at 1.25 eV persists and remains in the paramagnetic phase at least to room temperature. The photoluminescence is interpreted in terms of a model in which the emissions originate from the impurity-perturbed Mn2+ excitons. In the model, the observed emissions arise from the transitions assisted by magnons and the short-wavelength magnetic excitations. The excitation spectra, the time-resolved emission spectra, and the heat-treatment effect on the emission spectra are also reported and discussed.