Magnetic and magneto-optical properties of the Co-γFe2O3 perpendicular magnetic films

Co-γFe2O3 films have been prepared by annealing Fe3O4/CoO multilayers. The crystalline orientation of multilayers change with bilayer thickness Λ; the [100] axis of Fe3O4 and CoO orients perpendicular to the film plane for Λ<80 Å and the [111] axis orients for Λ≳100 Å. The Co-γFe2O3 films obtained from multilayers of Λ<80 Å have positive perpendicular anisotropy. The magnetic coercivity and the squareness of perpendicular hysteresis curves are about 5.0 kOe and 0.8, respectively. The films show high magneto-optical effects and the figure of merit is 5.5 deg, which is about three times larger than that of CoFe2O4.