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 Å, was confirmed by X-ray small-angle scattering. For films with periods less than 60 Å, however, X-ray diffraction peaks at low angles did not appear. Bias modulated Co-CoO films with periods of 60 Å or less show a perpendicular magnetization, though films with the same period prepared by modulating the oxygen partial pressure (P_o2) in the sputtering chamber had an in-plane magnetization. The interfaces between the Co layers and the CoO layers of bias-modulated films were different from those of P_o2-modulated films. This is the reason for their different magnetic properties.