Influence of Oxygen on Magnetic Properties in Amorphous GdCo Sputtered Films

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Influences of oxygen on magnetic properties in amorphous GdCo sputtered films were studied by annealing them in air at various temperatures. Oxidation causes the increase in the perpendicular magnetic anisotropy energy Ku for zero bias sputtered films whose film structure is columnar, while it causes the decrease in Ku for bias-sputtered films whose film structure is ultra-fine or fiber-like. It is found from AES depth profiles that there are two modes in the oxidation process, and that they depend on the film structure. Mode I and II are observed in the columnar and the fiber structures, respectively. The surface oxidized layer in the low-bias films with the columnar structure, where the magnetization lies in the film plane, is fairly stable against annealing, and a small amount of oxygen penetrates uniformly into the internal part of the film up to the substrate (mode I) along the columnar boundaries. In the mode I oxidation, Ku of the order of 104 erg/cm3 is induced by the preferential oxidation of the boundaries. On the other hand, the surface oxidized layer with the fiber structure propagates toward the substrate (mode II). This is more prominent for higher bias films. The mode II oxidation causes the decrease in Ku.
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