Micromagnetic analysis of bit decay in perpendicular recording media

The life time of stored data depends on the storage density as well as the physical properties and microstructure of the media. Perpendicular media for ultra-high density recording needs to have high anisotropy to withstand thermal instabilities over long time. In this study, we used a micromagnetic model based on a scaling method to numerically calculate the percentage of magnetic decay caused by thermal fluctuations after ten years. Realistic grain configurations for 1 Tbit/in² and 125 Gbit/in² recording were used to seek the critical grain magnetization and anisotropy field of magnetic media that are thermally stable for ten years. For less than 10% decay, an H_K of 20 kOe and M_S^grain of 600 emu/cm³ is required. Alternatively, H_K can be reduced to 16 kOe if M_S^grain is 800 emu/cm³.