Study of the effect of defect sizes and their distribution on the coercivity of magnetic media

The nature of domain-wall motion coercivity in magnetic media is studied using a two-dimensional numerical micromagnetic model. It is necessarily assumed that the source of the coercivity is cylindrical anomalies in the material that have anisotropy or exchange parameters which are either larger or smaller than that of the surrounding media. Varying these parameters from those required to obtain the observed coercivity shows that a larger decrease in either parameter is required to obtain the same change in coercivity as a given increase. Thus, the dependence of coercivity on these parameters is nonlinear. It was also found that the computed coercivity decreases with an increase in the separation of the defects, and increases with an increase in defect size. It is shown that a correction for the calculated coercivity is required to account for the statistical distribution in defect sizes and locations. Finally, a suitable variation in the defect parameters can accurately characterize the temperature behavior of the coercivity.