Thermal stability of granular-type FePt-MgO perpendicular recording media with soft underlayers

Double-layered disc with stack structure [MgO x nm/FePt y nm]_n/MgO /SiO₂/Fe-Ta-C are fabricated by sputtering onto a glass disc substrate. The read/write recording performance of the discs is tested using a spin-stand. The written bits are observed by magnetic force microscopy (MFM) at various temperatures increasing from room temperature up to 200°C with an increasing interval of 25°C. Temperature dependent magnetic properties are correlated with MFM signal decay. No measurable decay in signal amplitude is observed for both discs below 100°C. Signal decay is however observed to be more prominent for lower frequency bits compared to higher frequency bits.