GYROTROPIC PROPERTIES OF ANTIFERROMAGNETS NEAR AFMR - SUBMILLIMETER QUASI-OPTICAL SPECTROSCOPY OF YFEO3 AND CR2O3

Magnetic gyrotropy effects near antiferromagnetic resonance (AFMR) det ermined by weak ferromagnetism (YFeO3) and magnetoelectric effect (Cr2 O3) have been studied using quasi-optical submillimeter backward-wave- oscillator technique in the frequency range 3.2-13 cm(-1). A noticeabl e rotation of an optical indicatrix and increase of an ellipticity hav e been revealed near AFMR in both antiferromagnets, which present a ma nifestation of a Faraday rotation in YFeO3 and gyrotropic birefringenc e in Cr2O3. Theoretical calculations and computer simulations made it possible to describe the observed spectral taking into account the res onance behaviour of magnetic, magnetoelectric and electric susceptibil ities, and to determine corresponding parameters, in particular, an AF MR mode contribution to the static magnetic and magnetoelectric suscep tibilities. (C) 1998 Elsevier Science B.V. All rights reserved.