Numerical simulation of domain walls in Fe whiskers and their interaction with deposited thin films

The domain wall structures in a single-crystalline (Fe-whisker/nonmagnetic-layer/Fe-film)--sandwich system were studied by numerical micromagnetic simulations applying a modified boundary element method. Residual stray fields, emerging from the 180^∘{} vortex wall in the whisker, are responsible for the formation of a 180^∘{} N\'eel wall and a head-on domain configuration in the film. Both walls are modified by mutual interaction. The calculations confirm previous experimental observations of complex magnetization processes in a 20-monolayer-thick iron film that were explained to be caused by stray-field interaction between whisker and film walls across an MgO tunneling barrier layer.