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 Cr2O3 in a spectral range from 1.6 to 2.5 eV, which comprises (4)A(2) --> (2)E, T-2(1), and T-4(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.