rf sputtering of highly Bi-substituted garnet films on glass substrates for magneto-optic memory

Abstract

Using glass substrates, we have prepared highly Bi‐substituted garnet [(Bi,Y,Fe,Al)₈O₁₂ and (Bi,Gd,Fe,Al)₈O₁₂] films by rf diode sputtering which was followed by annealing for crystallization. The films were polycrystalline garnet with no preferred orientation and no impurity crystalline phase detectable by x‐ray analysis, which contained 1.1–1.4 Bi ions per formula unit. The films crystallized directly during the sputter deposition when the substrate temperature T_s>440 °C. Film quality was best when T_s was just below 440 °C. The film had magnetic anisotropy perpendicular to the film plane, which is stress induced. In the (Bi,Gd,Fe,Al)₈O₁₂ film, the magnetization normal to the film plane exhibited strong coercivity, H_c=600 Oe, and a large remanence‐to‐saturation ratio, M_r/M_s=1, while in the (Bi,Y,Fe,Al)₈O₁₂ film, weak H_c (200 Oe) and small M_r/M_s (0.47). These films had large Faraday rotation, typically 1.5×10⁴ deg/cm at λ=633 nm, owing to the high Bi substitution.