Effect of Ni addition into Co ferrite thin films for perpendicular recording media

Abstract

The present article describes effects of doping Ni 2+ ions into Co ferrite plated films on film structure, magnetic properties, and read/write characteristics. While thinner films are required for low noise level even in perpendicular recording media, average surface roughness R a of the Co ferrite films increased from 4 to 6 nm with decreasing the film thickness from 100 to 50 nm. Adding Ni 2+ ions had an effect on controlling the grain growth, resulting in a reduction in R a to 3-4 nm for the 50-nm-thick films by adding a small amount of Ni 2+ ions {r m[=C Ni/(C Co+C Ni)]=0.1}. Perpendicular coercivity H c⊥ of the Co-Ni ferrite film at r m=0.1 was 2500 Oe, which is almost the same as that of the Co ferrite films, and H c⊥ decreased with increasing r m. Atomic force microscope images showed that the Co-Ni ferrite films were composed of uniform and isolated grains without coagulation. As a result, a Co-Ni ferrite medium fabricated at r m=0.1 exhibited lower noise level than a Co ferrite medium without Ni addition. © 2000 American Institute of Physics.