Augmenting the Williams-Comstock model to predict effects of varying write current

The Williams-Comstock write model is modified and extended to include variable write current amplitude. Additionally, this model takes into account the saturation magnetization, M_s, (not in the Williams-Comstock model) as well as the remanent magnetization, M_r , and coercive squareness, S*, of the medium. An alternate method to the one used by Williams-Comstock for cases of high medium magnetization and low spacing is outlined. This model predicts a minimum value for the transition parameter, a, less than Williams-Comstock and at a larger value of optimum write current. Predictions from this model are compared with a fully self-consistent, computer-based model. Agreement is reasonably good, particularly for low medium magnetization. A sensitivity analysis shows that the transition parameter, a, is relatively insensitive to changes in write current compared to the transition location, x_t