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 A and the [111] axis orients for Λ≳100 A. The Co‐γFe2O3 films obtained from multilayers of Λ<80 A 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.