Overwrite characteristics of thin film head and media systems

The authors measured the saturation properties of overwrite on three thin-film heads with pole lengths of P=2.6 μm, 3.6 μm, and 4.4 μm in combination with three thin-film media with coercivities of H_c=1200 Oe, 1300 Oe, and 1550 Oe. The 4.4-μm head shows an interesting saturation profile in which overwrite first reaches the minimum MMF (magnetomotive force) value of around 0.45 AT and then increases for larger MMF. Regarding this resonance-like phenomenon, the overwrite properties were shown to be strongly dependent upon leading pole length and overwritten (LF) bit length, as well as on the overwriting frequency (HF). It is concluded that when designing heads, the optimum pole length should be selected to satisfy both the overwrite and readback characteristics at any track of the drive