Gap dependence of the shielded pole heads

The shielded pole writer improves the write field gradient of a perpendicular write pole by placing a shield close to it on the down stream side. It also improves writability by enhancing the longitudinal component of the field and thus providing more tipping field, which reduces the Stoner-Wolfarth switching threshold. However the flux leakage from the write pole to the shield causes saturation to occur sooner and thus reduces the maximum field strength available. Therefore there is a trade-off to be made between the gain in gradient and the loss in field as the gap is reduced. These results are supported by a large statistics experiment in which the write gaps of 50, 75, and 200 nm were investigated.