Anisotropic magnetic and magneto-optic behavior of thin garnet films with high Q-values

The anisotropic behavior of the magnetic and magneto-optic properties of a thin garnet film has been studied. A Bi, Tm substituted garnet film with Hu=2370 G and 4πMs= 100 G was grown along the [111] orientation by liquid phase epitaxy. The transmitted laser light intensity was measured as the magnetic field was swept ±6 kG for the parallel and slightly off parallel orientation of the film plane which was placed between crossed polarizers. Two peaks in the light intensity are observed on each side of zero field for limited regions of the magnetic field angle and the sample crystal axis orientation from [110] and [112]. A theory is presented that predicts the region of twin peak formation. It is shown that the cubic anisotropy energy must be included to account for the twin peak effect and that the magnitude of the first order cubic anisotropy constant can be measured magnetooptically. Excellent agreement between the theory and experiment is obtained.