The micromagnetics of defects in film stacks with interlayer exchange coupling

The impact of defects in trilayers comprising two ferromagnetic layers, being mutually exchange coupled via a nonferromagnetic layer, are theoretically studied on the basis of a numerical model. The defect region is characterized by deviations in the uniaxial and cubic anisotropy, in the interlayer coupling, bulk exchange constants and/or saturation magnetization. The model is two-dimensional and employs the Ritz method to evaluate the four walls that are bounding the defect. Three irreversible processes are distinguished at which the splitting up of the above edge walls is most striking. Hysteresis curves of stacks with both cubic and uniaxial anisotropy are shown. The implications of the defects for giant magnetoresistive signals are given, at which the change in the overall hysteresis loop and in the magnetization distribution near the defect is distinguished