Annealing Effects on Properties of Bi-Substituted Garnet Films with Perpendicular Anisotropy Prepared by a Sol-Gel Method

Bi-substituted garnet films with perpendicular anisotropy have been prepared by a sol-gel method. Annealing effects on magneto-optical properties and structures of the films are studied. The results indicate that the Kerr hysteresis loops of garnet films have good squareness at annealing temperatures above 650°C, the coercive force H_c of these films increases from 1070 to 1570 Oe with the increasing temperature from 650°C to 700°C. The Kerr rotation of the films was changed with the increasing annealing temperature, and there is a maximum value (0.82°C) at 675°C. It was found that the structure of the films is a single phase of garnet without preferring orientation when the annealing temperature is about 650°C, but a new phase (Bi₂Al₄O₉) can be formed when the annealing temperature reaches 675°C, another new phase (Bi₂Fe₄O₉) appears when the annealing temperature is about 700°C.