Media noise, nonlinear distortions, and thermal stability in high density recording

Low media noise and high thermal stability are required to achieve high den sity magnetic recording. Reduction of magnetic grain size is required in or der to minimize transition jitter, However, very small grains become unstab le and spontaneously reverse their magnetization due to thermal fluctuation s. Future high density (>20 Gbit/in(2)) recording systems are likely to ope rate in a media noise dominated environment and could exhibit a certain amo unt of signal decay, Recording performance degradation caused by media nois e and thermal decay is evaluated. Density-dependent amplitude decay is caus ed by the presence of demagnetization fields and results in increasing leve l of nonlinear distortions and overwrite degradation. Magnetization decay i s accompanied by changes in media noise in an unstable media as determined by the relative contributions of the transition and particulate noises. Exp erimental measurements suggest, that channel bit error rate degradation in an unstable medium is determined by signal and noise evolution, as well as by pattern-dependent distortions.