Ruthenium interlayer as diffusion barrier under carbon overcoat in magnetic recording media

A Magnetic film of ternary CoCrTa alloy was deposited onto textured NiP/Al substrate. Then, an atomic (8 A) layer of ruthenium (Ru) film was sputtered before a layer of hydrogenated amorphous carbon (a-C:H) was deposited by hot filament Plasma Enhanced Chemical Vapor Deposition method. Dynamic remanent magnetization and thickness product (MrT) measurement showed that samples without Ru interlayer were susceptible to plasma damage during carbon deposition compared to samples with Ru interlayer. The impact was more obvious as the substrate bias was increased during carbon deposition. Having an intermediate layer of ruthenium film in between magnetic layer and carbon overcoat made magnetic performance of the film more stable. After annealed for 30 minutes under 1 atm of N2 environment, MrT values dropped drastically in samples without Ru interlayer but varied only a little in samples with the interlayer. Water contact angle measurement showed little difference in surface energy with or without the interlayer. XPS studies indicated that Tantalum carbide formed in samples without Ru interlayer. Formation of metal carbide was not found in samples with Ru interlayer.