Polycrystalline magnetic garnet films comprising weakly coupled crystallites for piezoelectrically-driven magneto-optic spatial light modulators

We have investigated the magnetization process of the polycrystalline magnetic garnet films in order to determine the most suitable composition of garnet films for piezoelectrically-driven magneto-optic spatial light modulators (MOSLMs). For experiment, the bismuth–dysprosium–aluminum-substituted yttrium iron (Bi1.3Dy0.7Y1.0Fe3.1Al1.9O12) garnet films were deposited by an RF magnetron sputter and annealed at 700 °C in air. The annealing time was varied in a range of several minutes to control the grain size. The saturation magnetization, the remanent magnetization and the composition of the fabricated garnet films slightly changed versus the annealing time. Experiments showed that the coercivity and the grain size increased at longer annealing; the coercivity was larger for films with bigger grains. This work shows that garnet films with smaller coercivity are most suitable for controlling the magnetization of garnet and, correspondingly, the magneto-optical rotation of MOSLM pixels driven by piezoelectrics.