The effects of corrosion on MR disk

With use of MR heads, drives will be increasingly sensitive to corrosion and contamination. Particularly, heating of MR sensor due to contact with corrosion products and other contaminants on the disk causes a thermal asperity. This paper focuses on investigation of the effect of corrosion on occurrence of thermal asperities. Several factors which influence corrosion in high temperature and humidity were investigated using ion chromatography and TOF-SIMS. It is found that corrosion causes significant migration of cobalt and nickel compounds from the disk. Higher cobalt migration causes more thermal asperities, but nickel migration does not. Hydrogenated carbon overcoat showed the least cobalt migration among different overcoat layers. However, the most effective way to reduce cobalt migration is the application of Cr layer between carbon overcoat and magnetic layer. Nickel in NiP layer can migrate onto the disk surface when carbon overcoat is thin and water contact angle is low.