Micromagnetic simulation of domain structures in patterned magnetic tunneljunctions

The magnetization reversal process of patterned magnetic tunnel junctions w as investigated using finite element micromagnetics, taking into account th e magnetostatic interactions between the pinned and the free layer. Two dif ferent reversal modes were observed in the simulations depending on the dom ain 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 s tate. If the system is in the S state, the end domains grow under the influ ence of a reversed field. The end domains touch each other, leading to the reversal of the center. Finally, the residual domains along the edges paral lel to the field direction reverse. If the system is in the C state, the gr owth 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 we re found to differ in energy by less than 0.2%. (C) 2001 American Institute of Physics.