Overwrite Induced Divergent Transition by Trapezoid Pole Head

Perpendicular magnetic recording has to use a trapezoid writing pole in order not to enlarge the width of the erasing band at large skew angles. During the overwriting process, the footprint of a trapezoidal field bubble occupies a portion of the rectangular or parallelogram shaped bit(s) to be overwritten. When the magnetization of an unoccupied portion is in the opposite direction of the head field, the demagnetizing field from the unoccupied region shifts the trailing edge transition. When the skew angle is large, this effect can make the center transition line not parallel to the reader sensor. In this condition, one can observe a clear variation when the head reads at the two sides of the track. We call it a divergent transition, meaning the transition line diverges away from the plane of reader sensor. In this study, experimental observations prove the existence of this phenomenon. A simulation study illustrates the observation and clearly gives a complete understanding of this phenomenon.