Fabrication of ultrathin epitaxial γ-Fe2O3 films by reactive sputtering

Ultrathin epitaxial γ-Fe2O3 (0 0 1) and (0 1 1) films are synthesized by reactive sputtering on corresponding MgO substrates. The average roughness of the epitaxial films increases with decreasing film thickness, and that of ∼5 nm thick films is ∼4.2 Å. The easy axis of the epitaxial γ-Fe2O3 films is verified to be ⟨1 1 1⟩ by angular dependence of hysteresis loops measured by a vibrating sample magnetometer with a sample rotator. The saturation magnetization of the ultrathin epitaxial γ-Fe2O3 films is close to the bulk value of ∼390 emu cm−3 and independent of film thickness when the thickness is above 5 nm, which is crucial for their practical applications in spin filter devices.