Engineered magneto-optical response of cobalt ferrite thin films deposited on self-assembled colloidal crystal

Oriented growth of patterned cobalt ferrite magnetic thin films on polymeric colloidal crystal films has been carried out employing a room-temperature pulse laser deposition method. The series of colloidal crystal films containing uniform polystyrene particles (180-420 nm) were prepared by self-assembly. Scanning electron microscopy and optical reflectometry were used to confirm the assembly of well-arranged colloidal crystal films. Magnetic films of different thicknesses were deposited. X-ray diffraction measurements confirmed the nano-crystalline structure of cobalt ferrite grown on the spherical-shaped surface. Magneto-optical effects of the patterned thin films were examined and the results illustrated that the increase in film thickness leads to the decrease in coercivity, while the saturation magnetization increases. Furthermore, the magnetic origin of the coercivity variation dependence on the colloidal diameter and film thickness are discussed. Our results suggest that the preparation conditions of the deposited films should be tailored to obtain perpendicular anisotropy in cobalt ferrite films. The adjustable magnetic anisotropy was obtained due to substrate-induced magnetic shape anisotropy.