Characterization of Skip or Far Track Erasure in a Side Shield Design

Side track erasure (STE), either skip or far track, has been studied for a PMR writer with side shielded (SS) design. Both bit error rate (BER) and noise amplitude based STE measurements indicate the side writing fields are strong at SS bottom corners and/or inner edges. With DC background low-frequency noise amplitude measurement, the root cause of the STE is characterized as flux from main pole tip going into media soft under-layer (SUL) and returning to SS bottom corners and/or inner edges. Moreover, the return flux path is identified with a unique one-sided signature depending on the pole polarity and shield initialization direction and can switch side when pole polarity or shield initialization direction is changed. By employing magnetic force microscope (MFM) analysis of a SS head under two shield initialization directions, we can explain this unique one-sided flux path by the observed SS domain structure. Furthermore, a micro-magnetic modeling of the SS design is constructed to understand the observation qualitatively.