Williams-Comstock type model for sawtooth transitions in thin film media

We describe a model of the write process of saw-tooth transitions on longitudinal thin film media. The width of the transitions is determined by the combined action of the head and dipolar fields against the coercivity of the film. We use the model to predict the dependence of transition width and location of the transition center on flying height, gap width, and write current for a Karlqvist head field. The transition width approaches the minimum permitted by the transition´s dipolar field for low flying height. Unlike models of the write process on particulate media, it predicts that the transition does not relax after the film leaves the write head.