Noise spectrum analysis in perpendicular magnetic recording of double-layered media

Noise spectrum properties of double-layered perpendicular magnetic recording media were studied for two dominant medium noises, a transition jitter noise and a reversed domain noise. It was found that the transition jitter noise spectrum was delivered from the derivative of the transition shape, while the reversed domain noise spectrum was derived from a simple model of the impulsive reversed domain. The noise enhancement in a low-frequency region with increasing the recording density was found to be attributed to the relative increase in the jitter noise. The noise spectra for both sources were theoretically whitened when the transition width and the reversed domain size became negligibly small against reproducing resolution.