A general approach for overwrite spectra

Abstract

A generalized analysis has been presented for describing the influence of overwrite (or reverse overwrite) interferences on the spectra of readback signal, which extends the previous theory in describing the spectra characteristics caused by the hard–easy transition shift. Interestingly, it also suggests that the residual signal from the overwritten data pattern could be periodic as well. Essentially, an imprint effect arising from old data pattern could also create an amplitude-modulated signal that generates sidebands around the fundamental and odd harmonics of the overwriting signal.

Media saturation and overwrite in perpendicular recording

“…This modulation is caused by the magnetization "imprint" effect, which is explained by incomplete media saturation, resulting in the exercising of an only minor -loop [3], [4]. The "hard" magnetic transition of the new data pattern is recorded opposite to the old data magnetization, its magnetization level is smaller compared to the magnetization of the "easy" transition .…”

“…Fig. 15 illustrates the time-domain media noise measurement of the isolated transition [3]. The transition recorded with current overshoot has smaller transition noise power and a reduced dc noise under the pole, indicating better media saturation during the recording process.…”

“…The on-track overwrite signal in longitudinal recording is generated by the hard transition shift (HTS) effect, causing timing delay of the hard transition (written against old media magnetization) relative to the easy transition. The resulting timing modulation causes significant bit-error-rate degradation [2], [3].…”

“…Down-track and cross-track distributions of the medium magnetization, the noise, and the overwrite are determined by the recording pole field profile and the switching dynamics [1], [3].…”

Analysis of overwrite spectrum in perpendicular magnetic recording

“…Moreover, the higher The mode of the overwrite process should change with the recording current of the head, and the overwrite spectra are expected to reflect the change of the mode. Few reports have discussed the overwrite spectrum in accordance with the recording current [1]. In this paper, overwrite spectra in perpendicular magnetic recording were analyzed varying the recording current.…”