Anisotropy of the magnetization and Faraday rotation in paramagnetic erbium gallium garnet under high magnetic field

The anisotropy of the magnetization and Faraday rotation in paramagnetic erbium gallium garnet (ErGaG) is reported. Generally speaking, the exchange interactions between rare-earth ions can be neglected in ferrimagnetic rare-earth garnet. It is pointed out that the exchange interaction is a non-negligible factor in the magnetic and MO properties in paramagnetic ErGaG. Meanwhile, the exchange interaction presents anisotropic property and demagnetizing effect. In addition, we conclude that the Faraday rotation in paramagnetic media under high magnetic field is determined by the magnetization as well as the applied magnetic field. Furthermore, the Faraday rotations are qualitatively simulated at 633 and 550 nm in ErGaG where a complicated temperature dependence of the exchange interaction is introduced. The theoretical results are compared with the experimental data measured by Guillot et al.