Magnetoelectric Spectroscopy of Electronic Transitions in Antiferromagnetic Cr2O3

Optical effects due to electric dipole–magnetic dipole interference were predicted for crystals which are noninvariant under space-inversion and time-reversal symmetry. We report measurements of the nonreciprocal rotation and ellipticity of light reflected from antiferromagnetic-magnetoelectric C${\mathrm{r}}_2$ ${\mathrm{O}}_3$ in a spectral range from 1.6 to 2.5 eV, which comprises ${}_{}{}^4{}_{}{}^{}A_2^{}{}_{}{}^{}\to {}_{}{}^2{}_{}{}^{}E$, ${}_{}{}^2{}_{}{}^{}T_1^{}{}_{}{}^{}$, and ${}_{}{}^4{}_{}{}^{}T_2^{}{}_{}{}^{}$ transitions. An analysis provides new information about symmetries of excited states and shows that previous assignments of excitonic lines cannot be entirely reconciled with our data.