We have applied our precision disk tester and noise measurement procedures to perpendicular media. We look at the randomness of dc media noise from write to write, quantify the deterministic component of this noise, and investigate the head noise and dc track edge noise of perpendicular heads and media. These results are compared with those obtained for longitudinal media. We observe lower correlation coefficients than those for longitudinal media, suggesting that there is more randomness associated with the reversal mechanisms involved in our experiment. We also see that the dc track edge noise is imperceptibly small using our testing operation, implying that double-layered perpendicular dc track edges are of a different form than those of thin film longitudinal single-layered media.
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Indeck et al. (1991) studied this question.