NONRECIPROCAL OPTICAL-RESPONSES OF ANTIFERROMAGNETIC CR2O3

We will present a microscopic model to understand the nonreciprocal op tical responses, i.e., the second-harmonic generation through electric and magnetic dipole moments and the magneto-electric effects. Here th e twist crystalline field, which reflects the real crystal structure, is found to play an important role in both channels of the second-harm onic generation. Then we can explain the spectra of the second-harmoni c generation through electric and magnetic dipoles. Absolute as well a s relative magnitudes of the second-order susceptibilities through bot h channels are also estimated to be reasonable. In terms of the same m odel, we can also understand the magneto-electric spectra, i.e., the e lectric- and magnetic-dipole interference in the linear response. (C) 1998 Elseiver Science B.V. All rights reserved.