Grain height fluctuation and medium noise in longitudinal thin film recording media

The effect of grain height variation on medium noise at small head-medium spacing has been studied by micromagnetic modeling. The reverse DC erasure process using a thin film head at low-fly height is simulated for two types of films: a film with grain height fluctuation and a film with identical grain height. Results show that grain height variation at microscopic scale does not significantly affect the noise behavior of the thin film media and the domain widths are mainly determined by magnetic interactions. Calculations show that the magnetization cross-track correlation lengths for both films are essentially the same. The noise power as a function of erasure field exhibits a linear relation with the field derivative of the remanent hysteresis curve, consistent with recent experimental results