Effect of underlayers on magnetic properties of Co/Pd multilayer perpendicular magnetic recording media

Abstract

Amorphous C and Si films were sputter-deposited as underlayers of Co/Pd multilayer perpendicular magnetic recording media. The magnetic properties of the media were significantly affected by the underlayer thickness; namely, the values of coercivity H c and nucleation field − H n increased and the value of α decreased with merely increasing the thickness of C or Si underlayer, where α is the derivative of M– H loop at the value of coercivity. The coercivity was not always affected by magnetic anisotropy constant K u for the Co/Pd media. In read–write experiments, the higher S/N ratio was obtained for the media with the thicker C or Si underlayer, which exhibited low α and high H c. In the time decay experiments of magnetization, the Co/Pd multilayer media with C or Si underlayer possessed good thermal stability. This study demonstrated that the introduction of C or Si underlayer greatly improves magnetic properties, read–write characteristics, and thermal stability of Co/Pd multilayer perpendicular magnetic recording media.