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 studi ed using a two-dimensional numerical micromagnetic model. It is necess arily assumed that the source of the coercivity is cylindrical anomali es in the material that have anisotropy or exchange parameters which a re either larger or smaller than that of the surrounding media. Varyin g these parameters from those required to obtain the observed coercivi ty shows that a larger decrease in either parameter is required to obt ain the same change in coercivity as a given increase. Thus, the depen dence of coercivity on these parameters is nonlinear. It was also foun d that the computed coercivity decreases with an increase in the separ ation of the defects, and increases with an increase in defect size. I t is shown that a correction for the calculated coercivity is required to account for the statistical distribution in defect sizes and locat ions. Finally, a suitable variation in the defect parameters can accur ately characterize the temperature behavior of the coercivity.