Zig-zag transition region of bit written by various heads

The zig-zag transition region of magnetization reversals written by ferrite, MIG (metal-in-gap), and thin-film heads (TFHs) on a thin-film disk is surveyed from the viewpoint of the writing head field. Zig-zag transition lengths are evaluated through colloid-SEM (scanning electron microscopy) observations. Writing head fields are analyzed using the finite-element method, with magnetic saturation taken into account. It is found that zig-zag transition lengths are in inverse proportion to the head field gradient until they reach a minimum length depending on medium characteristics. The effect of the field gradient on the transition length agrees with previous theoretical analysis. It is clarified that lack of saturation of the trailing core in the MIG head and a high incident angle of flux from the interior of the core to the surface in the TFH are responsible for the high field gradient. This furnishes a head design guideline for high-density recording on thin-film disk by means of writing a shorter zig-zag transition length