Origin of Large Perpendicular Anisotropy in Co3Pt Alloy Thin Film.

The origin of a magnetic anisotropy of the order of 107 erg/cm3 observed in Co3Pt alloy thin films deposited onto Al2O3(00·1) substrates is investigated. The magnetic anisotropy constant Ku increases with the substrate deposition temperature Ts, which exhibits a maximum at Ts ≈ 400°C. The Co3Pt ordered phase is found to exist in these films. The order parameter S estimated by X-ray diffraction reaches a maximum at Ts ≈ 400°C. The behaviors of Ku and S with respect to Ts are similar when Ts is greater than about 380°C. The samples show a larger Ku with higher S. However, Ku still remains 107 erg/cm3 at S=0. Both Ku and S can be enhanced by reducing the deposition rate at Ts ≈ 330°C. On the basis of these experimental results, a model is proposed to account for the dependence of Ku on S. In this model, the observed Ku is assumed to include two components of the disordered and ordered phases. The contributions of the disordered and ordered phases to the total magnetic anisotropy can be reasonably well quantified on the basis of the model.