In perpendicular magnetic recording, medium noise characterization is necessary to improve head and disk performance, and to establish the signal processing strategy. We examined the medium noise of CoPtCrSiO
2 perpendicular recording media with various SiO
2 concentrations deposited by separating noise into transition jitter, pulse width breathing, and reversed domain noise. Since the reversed domain noise magnitude was small near transitions, the noise power decreased in proportion to linear density, and disappeared at densities higher than 200 kFCI. Thus, the signal–to–noise ratios at high linear densities were determined by jitter noise and pulse width breathing. Although the reversed domain noise increased for disks with higher SiO
2 concentrations, error rate performance was improved. Therefore, the significant parameter was the transition jitter, and the influence of reversed domain noise was small.
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