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

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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 Ts>440 °C. Film quality was best when Ts 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, Hc=600 Oe, and a large remanence‐to‐saturation ratio, Mr/Ms=1, while in the (Bi,Y,Fe,Al)8O12 film, weak Hc (200 Oe) and small Mr/Ms (0.47). These films had large Faraday rotation, typically 1.5×104 deg/cm at λ=633 nm, owing to the high Bi substitution.