Effect of Track-Edge Medium Noise on High Track-Density Recording

Abstract

From the viewpoint of high track-density media design, cross-track performance of medium noise was investigated through micro-magnetic simulation considering a combination of capped media and wrap around shielded writer. For two capped media with different inter-grain exchange coupling <i xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">A</i> <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">grain</sub> , noise in the track-edge region was found to boost the on-track noise level while played-back under realistic read-conditions. Medium having larger <i xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">A</i> <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">grain</sub> exhibited higher track-edge noise due to the formation of larger magnetic cluster at the track-edge region. Furthermore, for the medium with larger <i xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">A</i> <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">grain</sub> , higher track-edge noise was found to increase the noise level along the cross-track direction and shrink the off-track capability of signal-to-noise ratio (SNR). Although both the media exhibited similar track-width, medium showing higher track-edge noise was found to lose SNR while squeezed by a neighboring track. On the other hand, medium having smaller <i xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">A</i> <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">grain</sub> exhibited lower track-edge noise, which was found to be helpful to keep the on-track SNR loss smaller while squeezed at a fixed track-pitch condition. Control of cluster formation through the optimization of <i xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">A</i> <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">grain</sub> should be effective to suppress the track-edge noise.