Showing papers by "Roman V. Pisarev published in 1987"

Electromagnetooptical effects in ferri- and antiferromagnets

Abstract: Optical methods open new horizons in studying magnetoelectric interaction in magnetically ordered crystals. In the present paper we shall report on some new optical effects observed in two model crystals: in antiferromagnetic Cr2O3 and in ferrimagnetic Y3Fe5O12. In Cr2O3 we observed a nonreciprocal rotation or plane-polarized light induced by ac electric field applied along optical axis. The temperature variation of this rotation was found to differ substantially from that of magnetoelectric effect in a low-frequency range. New antiferromagnetic mechanism of nonreciprocal rotation was suggested to exist in an optical spectral range. In Cr2O3 a second order optical magnetoelectric effect was observed for the first time which was related to an antiferromagnetic domain switching. In Y3Fe5O12 electromagnetooptical effects were observed mainly in the regions of domain wall movement and rotation of magnetization. Much better resolution was obtained in comparison to a low-frequency study of magnetoelectric interaction. A forbidden, linear in electric field, effect was observed in Y3Fe5O12 and we relate it to crystal imperfections, which destroy the symmetry center.

Two-photon absorption spectroscopy of electronic

Abstract: Two-photon absorption spectra have been studied for the first time in Y3Fe5O12.The study has been made in the spectral range from 2.50 eV to 3.51 eV in the temperature interval 90-300 K. It was found that at high temperatures (140-300 K) real intermediate electronic 3d-states play an important role in forming nonlinear optical spectra of magnetic insulators. In the case of YIG this intermediate state is a 4T1g state of Fe3+ - ion in the octahedral sublattice. A precise value of Eg = 2.66 eV (at 300 K) has been deduced from the two-photon absorption spectra and it has been attributed to the gap between 2p-valence band of oxygen and 3d-conduction band of iron.