Micromagnetic simulation of domain structures in patterned magnetic tunnel junctions

The magnetization reversal process of patterned magnetic tunnel junctions was investigated using finite element micromagnetics, taking into account the magnetostatic interactions between the pinned and the free layer. Two different reversal modes were observed in the simulations depending on the domain structure for zero applied field. In order to reduce the magnetostatic energy, end domains form in the free layer either in the S state or the C state. If the system is in the S state, the end domains grow under the influence of a reversed field. The end domains touch each other, leading to the reversal of the center. Finally, the residual domains along the edges parallel to the field direction reverse. If the system is in the C state, the growth of the end domains leads to a four domain flux closure structure. The domain with the magnetization in favor of the field direction expands until the free layer becomes reversed at a field. The S state and the C state were found to differ in energy by less than 0.2%.