Fabrication of ultrathin epitaxial γ-Fe2O3 films by reactive sputtering

Ultrathin epitaxial gamma-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 similar to 5 nm thick films is similar to 4.2 angstrom. The easy axis of the epitaxial gamma-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 gamma-Fe2O3 films is close to the bulk value of similar to 90 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.