Origins of the perpendicular magnetic anisotropy of reactive evaporated Co-CoO thin film

Abstract

The composition, microstructure and variation of the perpendicular magnetic properties with temperature of perpendicular magnetized Co-CoO film were measured. Origins of the perpendicular magnetic anisotropy and their contribution to the perpendicular coercivity H ⊥ c were studied. We have found that due to the existence of an exchange coupling interaction between the spins of the ferromagnetic hcp Co atoms and the spins of the Co ions in the antiferromagnetic fcc CoO, when the film is cooled to a low temperature below the Néel temperature of CoO in zero field, it possesses very strong uniaxial exchange anisotropy, and this has a great influence on the perpendicular coercivity. When the film is cooled from room temperature down to a similar low temperature in the presence of a strong orientation field vertical to the film plane, not only the unidirectional exchange anisotropy exist within the film and causes the hysteresis loop to be displaced along the H axis as others have described, but also simultaneously a uniaxial exchange anisotropy exists, that we believe, have not been previously reported.