Composition and underlayer effects on media noise and off-track error rate performance of CoCrPtTa sputtered films on alternative substrates

Signal-to-media-noise-ratio (SNR) and off-track-capability (OTC) were studied as a function of alloy composition and underlayer structure for alternative substrate recording media having coercivity of 2200 Oe and remanence of 1.0 memu/cm(2). Higher Cr content up to 15 at% and Ta content up to 6% gave better SNR and OTC performance in CoCrPtTa alloys. Replacement of Cr with CrV as buffer/underlayer significantly improved SNR and OTC. The mechanism is the effective reduction of grain size and narrowing of grain size distribution while keeping the grain crystallographic structure and orientation unchanged from that using Cr underlayer. High performance discs on glass-ceramic substrates with enhanced SNR and OTC were made by optimizing buffer/underlayer and CoCrPtTa alloy composition.