Magneto-optics of antiferromagnets

Abstract

Antiferromagnetic crystals in which crystallographic sites occupied by magnetic ions from various sublattices are not transnationally equivalent and are not associated with each other by a symmetry center can have magneto-optic properties distinct from the properties of other antiferromagnets. In particular, birefringence and dichroism of linear polarized light can be observed which are directly proportional to the magnetic field strength, as well as magnetic rotation and circular dichroism quadratic in the field strength. Both effect—the linear magneto-optic effect and quadratic magnetic gyration — are sensitive to the crystal magnetic symmetry and to reorientation of the antiferromagnetic vector. Both effects reverse their signs when the directions of the magnetic moments of a sublattice are changed. These properties of new magneto-optic effects can be used to study the time-reversed domain structure of antiferromagnets, to define the symmetry of magnetic ordering and to study the magnetic crystal energy spectra by spectroscopic methods. The results of experimental studies of the linear magneto-optic effect and quadratic magnetic rotation in tetragonal antiferromagnetic fluorides of transition metals, manganese-germanium garnet and other antiferromagnets are reported. Experimental results on the domain structure of high symmetric antiferromagnets, the point magnetic symmetry of non-collinear multisublattice antiferromagnetic garnet MnGeG are discussed.