The present paper describes the effects of adding Ni²⁺ ions into Co ferrite films fabricated by the spin-spray ferrite-plating method for perpendicular magnetic recording media. Surface roughness of the Co ferrite-plated films increased with decreasing their thickness due to grains as large as 100nm formed at the initial growth, though a thin recording layer below 50nm is required for high-density recording media with lower noise level. Adding Ni²⁺ ions into the films suppressed the formation of such large grains, and the surface of Co-Ni ferrite-plated films was composed of uniform grains of 40-50nm in size. As a result, the surface roughness was reduced from 5-6nm to 3-4nm for 45nm-thick films, and such improvement in the microstructure led to the reduction of media noise.