Iron-oxygen–based perpendicular magnetic thin films

Nonstoichiometric FexO1−x and FexMyO1−x−y films, where M is either a nonmagnetic element, e.g., Si, or a magnetic element, e.g., Co, were prepared by sputter deposition. They showed increasing ferromagnetic magnetization with decreasing oxygen concentration below 1−x−y<0.5, and strong perpendicular magnetic anisotropy which overwhelmed the shape anisotropy of the thin ferromagnetic films in certain composition ranges. The magnetization of perpendicular magnetic films attained more than 500 emu/cm3 with an anisotropy energy of 2×106 erg/cm3. Ferromagnetic amorphous metallic phases precipitated between columnar structure of nonmagnetic oxide phase were considered to be responsible for the ferromagnetism of these films. The perpendicular anisotropy was also interpreted by the internal shape effect arising from fine elongated ferromagnetic phases distributed in a nonmagnetic phase with their long axis perpendicular to the film plane. They had an appropriate coercivity for the perpendicular magnetic recording media with a high resistance against wear and corrosion and a low friction constant.