Thickness-dependent coercivity and magnetization process of Co/GaAs (1 0 0)

Abstract The magnetization and coercivity of Co films in the thickness range of 10–200 nm deposited onto GaAs (1 0 0) substrate are studied. The in-plane coercivity of the Co films is enhanced anomalously and is observed to have strong thickness dependency. The coercivity of the Co/GaAs having Co thicknesses larger than a threshold value (50 nm) is enhanced at 4.2 K. The Co film having thickness 50 nm exhibits a coercive field of 10 Oe, but the same for thickness 125 nm increases to 120 Oe. The squareness of the hysteresis loop becomes as high as 94%. The atomic magnetic moment of the Co film is found to be 1.5  μ B . The AFM images show that surface roughness increases with the increases of film thickness. The enhancement of coercivity is due to the surface roughness of the Co film.