Wide band erasure caused by SUL domain wall in perpendicular recording media

The paper points out that soft magnetic underlayer (SUL) domain wall causes wide-band erasure in perpendicular recording media, and that laminated or multi-layered SUL can avoid this problem. Additionally, the spike noise produced by SUL causes bit error rate (BER) degradation. The types of SUL required to solve neighboring track erasure are similar to the approaches proposed to solve the spike noise problem. Thus, controlling the SUL domain is very important, not only for BER performance, but also for the reliability of the recorded information.