Optical Faraday rotation in ferrimagnetic garnets

Abstract

The ferrimagnetic garnets exhibit à large optical Faraday rotation. The transitions involved are both spin and parity forbidden. A non-zero transition probability arises from the combined action of spin-orbit coupling, and lattice vibrations which augment the ground and excited states with odd-parity angular momentum states. These states are split in the presence of the exchange field by spin-orbit coupling and lead to Faraday rotation. The ratio of rotation to absorption is calculated and found to give satisfactory agreement with experiment