Magnetic properties and structure on bias modulated Co-CoO multi-layer sputtered films.

Co-CoO multilayer films were prepared using a conventional sputtering method, modulating the substrate bias voltage. The periodicity of these films, with periods ranging from 60 to 300 angstrom, was confirmed by X-ray small-angle scattering. For films with periods less than 60 angstrom X-ray diffraction peaks at low angles did not appear. Bias-modulated Co-CoO films with periods of 60 angstrom or less show a perpendicular magnetization, although films with the same period prepared by modulating the oxygen partial pressure in the sputtering chamber had an in-plane magnetization. The interfaces between the Co layers and the CoO layers of these films were different from those of the bias modulated films, which is the reason for their different magnetic properties.