Temperature dependence of Faraday rotation in Bi-substituted terbium iron garnet films

Abstract

The role of Tb3+ in the Faraday rotation θF of (Bi,Lu)-substituted terbium iron garnet Tb3−x−yLuyBixIG (x=0–1.1, y=0–0.9) films is studied. The temperature dependence of θF at λ=633 nm is measured in the temperature range of 10–600 K and the saturation magnetization 4πMs is measured in the temperature range of 4.2–450 K to clarify the contribution of the dodecahedral Tb3+. The temperature dependence of θF is analyzed by using two different models based on the three sublattice magnetizations. It is found that in the model where the Fe3+ contributions to θF in Bi-substituted iron garnet are assumed to be the same in all rare-earth iron garnets, the contribution of the Tb3+ site to θF is increased by Bi substitution. The variations of the Tb3+ coefficients with Bi content and temperature are also presented and discussed.