Perpendicular magnetization in Co-CoO film prepared by reactive RF sputtering

The perpendicular magnetization state is realized in Co-CoO film prepared by reactive RF sputtering in argon-oxygen mixture. With increasing the oxygen partial pressure, saturation magnetization of the deposited film decreases monotonically due to the formation of CoO. The film is composed of fine particles of hcp Co and fcc CoO. The perpendicular magnetic anisotropy energy and the coercivity reach to 3 × 10⁶erg/cm³and 2 kOe, respectively. Above a critical partial pressure of oxygen, the deposited film has no spontaneous magnetization with a Co3O4single phase. The observed columnar structure in the Co-CoO film becomes fine with increasing the oxygen partial pressure. The exchange anisotropy is found in the Co-CoO film. The perpendicular magnetic anisotropy in the film is likely to be originated from an anisotropic assembly of ferromagnetic Co particles and antiferromagnetic CoO particles.