The influence of thermal relaxation on the readback waveforms from perpendicular magnetic recording media was experimentally investigated in time-domain measurements. The signal decay rate at the magnetization transition was smaller than that in between the transitions, reflecting the demagnetization field distribution. The time dependence of the noise in the waveform was characterized as pulsewidth, transition jitter, and pulsewidth fluctuations. While the transition width decreased with elapsed time, the jitter and pulsewidth fluctuations were stable. These time-dependant results could be interpreted by considering the demagnetizing field distribution near the transitions and in between the transitions, which govern the random magnetization domain reversals.
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