AbstractAmorphous cobalt ferrite (CoFe2O4) films were formed by a two‐source vacuum evaporation technique, using CoFe2 alloy and P2O5 as the source materials. It was found that the crystalline phase and perpendicular anisotropy constant (Ku) were dependent on the pressure of P2O5 during film deposition. When the pressure of P2O5 was higher than 5 × 10−3 torr, the film was amorphous. When the pressure of P2O5 was higher than 8 × 10−3 torr, the film had perpendicular anisotropy. The maximum perpendicular anisotropy constant was obtained (1.8 × 105 erg/cm3) when the film was formed under a P2O5 pressure of 10−2 torr. This value is one order of magnitude higher than that of amorphous nickel ferrite films. The cause of the perpendicular anisotropy is thought to be due to the columnar structure formation of Co2+ and Fe2+ perpendicular to the film surface. When the amorphous CoFe2O5 film with perpendicular magnetization is heat‐treated under the P2O5 pressure (Pp2O5) of 10−2 torr, Ku also increases with the increase of the treatment temperature; Ku of the amorphous CoFe2O5 film with perpendicular magnetization is comparable with those of barium ferrite and single crystalline CoFe2O4 films. Therefore, this film can be used for the magnetic recording media.