Preparation of amorphous cobalt ferrite films with perpendicular anisotropy and their magnetooptical properties

Amorphous CoFe2O4films were made from CoFe2alloy and P2O5as the starting materials by the double source evaporation method. As the films were made in various levels of pressure of evaporated P2O5(Pp2o5) in the bell jar, different crystal phases and perpendicular anisotropy constants (Ku) of the films were obtained. More precisely, when Pp2o5was higher than 5×10^-3torr, the amorphous films were produced and under Pp2o5of higher than 10^-2torr the maximum Ku of the films with the perpendicular anisotropy was 1.8×10⁵erg/cm³. The perpendicular anisotropy seemed to be induced by both shape anisotropy with the columnar structure and uniaxial magnetic anisotropy of Co²⁺and Fe²⁺. For amorphous CoFe2O4films, the dependence of the polar Kerr rotation angle on the wave length became complicated with the increase in Pp2o5. A curve showing the relation between polar Kerr rotation angle and the wave length had a broad, positive peak in the region from 300 nm to 500 nm which was characteristic of amorphous CoFe2O4films.