QUADRATIC MAGNETIC ROTATION OF POLARIZATI ON-PLANE OF LIGHT IN ANTIFERROMAGNETIC CAMNGE GARNET

The magnetic rotation of light polarization plane proportional to the square magnetic field strength has been revealed in tetragonal antifer romagnetic crystal Ca3Mn2Ge3O12. The dependence of the quadratic magne tic rotation on the orientation of the field in the (001) plane has be en studied. It was established that this dependence is described by PH I0 cos 2phi. Maximum specific rotation 0.43 min/kOe2.mm at lambda = 63 28 angstrom and T = 6 K was observed al the magnetic field oriented al ong the [100] axis of the cubic phase of this crystal. It is concluded that the magnetic point group of antiferromagnetic CaMnGe garnet does not include the pure rotation operation 4, and includes and rotation operation 4(z)'.