Theoretical study of the overwrite spectra due to hard-transition effects (magnetic recording)

Analysis of overwrite spectrum in perpendicular magnetic recording

“…Eq. (1) represents that the frequency components generated from easy/hard transitions appear only around the even harmonics of the postrecording signal as the sideband having the odd harmonics of the pre-recorded signal, which is the same property as that of longitudinal recording [2]. Therefore, the first odd sideband component around the zero order harmonic of the postrecording signal is located at the frequency of the pre-recorded signal.…”

“…In longitudinal recording, the recording head field is reduced by the demagnetizing field in the medium when the post-recording magnetization is in the reverse direction to that of the pre-recorded magnetization, then the phase of a magnetization reversal lags behind (hard transition), while no demagnetizing field and no phase shift (so-called easy transition) are expected for the same direction to the pre-recorded magnetization [2].…”

“…The overwrite modulation on the post-recording signal is caused by easy/hard transition shifts from the pre-recorded signal in both perpendicular and longitudinal recording [2,3]. Easy/hard transition denotes that there are easy and hard directions for the recording head field corresponding to the recording magnetization of the medium.…”

“…2 schematically explains the difference between the two. As a result, the spectrum of a reproduced signal in perpendicular recording under the overwrite modulation by the transition shift is denoted as follows [2]:…”

Overwrite Induced Divergent Transition by Trapezoid Pole Head

“…Overwriting (OW) characteristics are among the most important factors in evaluating the writing performance of a recording head [2]. When a high-frequency signal is overwritten by a lowfrequency signal, the influence of the transition shift is periodic and it does not affect the OW performance [3].…”