Low noise properties and thermal stability of Co-based thin film media for high density longitudinal recording

Media with excellent signal to noise properties and adequate high temperature thermal stability have been developed for over 20 Gbit/in² recording. The media are fabricated by dc magnetron sputtering onto textured NiP films on Al-Mg substrates. The magnetic layer is a CoCr-based quaternary alloy with (11.0) preferred orientation on a Cr alloy [002] underlayer. The average grain diameter has been reduced to an average of <10 nm. TEM-EDX studies revealed that Cr segregation has been enhanced compared to a previous CoCrPtTa media used for 15 Gbit/in² recording resulting in improved Co to Cr core composition and increased grain boundary Cr content. Spinstand measurements of the thermal decay after annealing at 65°C indicate sufficient thermal stability at 400 kfci for media with Mrδ>0.3 memu/cm² consistent with magnetometry measurements.