スパッタ法によるγ-Fe2O3薄膜の磁気特性

概要

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Thin films of γ-Fe2O3 have been studied for application in high density magnetic recording media because of their superior magnetic properties, wear resistance and chemical stability. The authors have developed a γ-Fe3O3 film preparation process consisting of three steps; a reactive sputtering step for depositing an α-Fe2O3 film in oxidizing atmospheres using an Fe alloy target a heat treatment reduction step to convert the film into a Fe2O4 phase and a subsequent oxidizing heat treatment step to obtain a γ-Fe2O3 film. The authors examined the influences of the sputtering atmosphere composition on the magnetic properties of the γ-Fe2O3 films which are related to the α-Fe2O3 film microstructures. The α-Fe2O3 films deposited in an O2 atmosphere contain a large amount of amorphous like phase that results in inferior magnetic properties. On the other hand a rather small amount of amorphous like phase is detected in the α-Fe2O3 films deposited in 20-94% Ar+O2 atmosphere. Consequently, γ-Fe2O3 films prepared by sputtering in an Ar+O2 atmosphere have higher saturation magnetization of 3000-3350 Gauss and higher coercive squareness (S*) of 0.71-0.82 than those of films prepared by sputtering in an O2 atmosphere.
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