Effects of Bias Modulation on Magnetic Properties of Co/Pt Multilayered Films

Co/Pt multilayer films were prepared by rf sputtering. A substrate bias voltage VB of 0 V to ¿70 V was applied while sputtering either Co or Pt onto glass substrate. In Co biased films (prepared with VB applied while depositing Co only), the perpendicular anisotropy Ku increases with VB and peaks at ¿50 V, because the flatness and sharpness of the interfaces and the fcc (111) orientation are optimum at this bias voltage. The increase in Ku arises from the improvement in both the surface and volume anisotropy. On the other hand, in Pt biased films mixing of Co and Pt occurs at layer boundaries, resulting in a decrease in Ku for VB¿¿50 V.