The creation of 360° domain walls in ferromagnetic nanorings by circular applied magnetic fields

Switching behavior in ferromagnetic nanostructures is often determined by the formation and annihilation of domain walls (DWs). In contrast to the more familiar 180 degrees DWs found in most nanostructures, 360 degrees DWs are the proposed transition state of nanorings. This paper examines the formation of 360 degrees DWs created by the application of a circular magnetic field using micromagnetic simulations. 360 degrees DWs form from pairs of canting moments that are oppositely aligned, which each grow to form rotated domains bounded by two 180 degrees DWs and the 180 degrees DWs combine to form 360 degrees DWs. The resulting 360 degrees DWs occur in pairs of opposite topological winding number due to these domains of opposite canting direction. The final number of DWs formed is greatly impacted by symmetry, both of the ring and of the placement of the circular magnetic field. (C) 2014 AIP Publishing LLC.