Microstructures and magnetic properties of L10 FePt films deposited on NaCl-type films

A single-layered FePt film of 30 nm thickness with perpendicular magnetic anisotropy is achieved by depositing the film onto a heated Si(100) substrate at 620 °C. Its perpendicular coercivity (Hc⊥), saturation magnetization (Ms) and perpendicular squareness (S⊥) are as high as 1113 kA/m, 0.594 Wb/m2 and 0.96, respectively. The perpendicular magnetic anisotropy degrades when a 5-nm NiO film is introduced under this single-layered film. Upon further increasing the thickness of the NiO film to 10 nm, the Hc⊥ of the single-layered film decreases greatly to around 330 kA/m. Compared to a NiO underlayer, the Hc⊥ of the FePt film remains above 1000 kA/m when a 10-nm MgO underlayer is introduced. Furthermore, when the thickness of the MgO underlayer is decreased to 5 nm, the perpendicular magnetic anisotropy of the single-layered FePt film is further enhanced. Its Hc⊥ stays high at 1081 kA/m; however, S⊥ increases significantly to 1.

► A thin MgO underlayer enhances the perpendicular magnetic anisotropy of FePt film.
► A NiO underlayer degrades the perpendicular magnetic anisotropy of the film.
► Ni atoms diffuse from NiO underlayer into FePt layer forming NiFe compounds.