Effect of Annealing on Magnetic Properties of Sputtered CoPt Alloy Films

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Abstract
CoPt alloy films with perpendicular magnetic anisotropy were sputtered on Pt buffer layers. In spite of rather large perpendicular anisotropy, the coercivity H c and squareness ratio S of the perpendicular magnetization curve were very low. It was found that annealing at 300°C in air resulted in a drastic increase in H c and S, while magnetic moment was reduced. The effect of annealing on magnetic properties was more marked in a thinner film. Auger electron spectroscopy and X-ray photoelectron spectroscopy revealed that cobalt atoms were preferentially oxidized to form CoO during annealing.