Thickness dependence of crystallographic and magnetic properties for L10-CoPt thin films

Thickness dependence of crystallographic and magnetic properties is investigated from the analyses of the order parameter S, chemically ordered fraction f0, and internal stress of the L10 Co49Pt51 film. Coercivity Hc was increased from 5.1 kOe to a maximum value of 13.3 kOe as the thickness of the film (δ) was raised from 10 nm to 50 nm.This is due to the increase of S from 0.30 to 0.64 and the increase of f0 from 0.52 to 0.75. For thicker samples (δ≧50 nm), a dramatic drop-off in Hc was observed at δ=80nm. The quantity of ordered phase, measured by X-ray diffractometry, is closely related to the Hc value of the Co49Pt51 thin film for δ<50nm. However, the existence of “domain wall-like magnetization structure” in thicker Co49Pt51 samples is harmful for Hc. The decrease in Hc can also be partially attributed to the thermal-stress-induced (0 0 1) texture.