Microstructure and Magnetic Performance of Perpendicularly Magnetic Anisotropic Fe$_{3}$Pt/Fe$_{2}$Pt/$L1_{0}$-FePt(001)/MgO(002) Graded Films

Abstract

L10-FePt(001) films with compositional gradient was proposed to realize the graded film with magnetic perpendicular anisotropy in this study. A hard magnetic layer of 5 nm-thick stoichiometry L10 FePt was initially deposited onto a glass substrate with a thin MgO underlayer. The hard layer exhibits strong (001) texture, island-type surface morphology, high perpendicular magnetic anisotropy (PMA), and large out-of-plane coercivity (Hc⊥) of about 20 kOe at room temperature (RT). A 5-nm-thick compositionally graded Fe-Pt layer was then deposited on the L10 FePt hard layer at deposition temperatures (Td) from 300 to 450°C. Good (001)-texture is retained in the graded layer and the island-type morphology is preserved when Td ≤ 400°C. A significant reduction in Hc⊥ from 20 to around 7 kOe was achieved. Besides, the graded films exhibit magnetically single-phase reversal behavior with a high anisotropy field (H0) of ~90 kOe. When Td > 400°C, PMA of the films was reduced due to the extensive diffusion between the Fe-rich graded and hard layers. Our proposed scheme demonstrate the feasibility of magnetic gradation induced by binary composition variation in FePt films, providing useful information for designing future ultrahigh magnetic recording media.