Magnetic domain wall formation in ferromagnetic wires with a nanoconstriction

The magnetization distribution and the formation of magnetic domain wall (DW) in ferromagnetic metal wires with a nanoscale constriction have been investigated in details using the micromagnetic simulation. It is found that the angle of the nanoconstriction plays an important role in controlling the formation of the magnetic DW. For different ferromagnetic metals, NiFe, Ni, Fe and Co, the domain structures and formation of the DW are also found to be distinctly different. In the NiFe wires, the optimum constriction angle for a well defined head-to-head/tail-to-tail DW is around 10 degrees while in Ni, it is around 14 degrees. For large constriction angles in Fe and Co wires, the magnetizations across the nanocontact tend to align along the same direction without a DW. However, Fe and Co wires tend to form complex vortex magnetic domains or single domains in the wires and across the nanocontacts in sharp contrast with the NiFe and Ni wires of the same shape and size.