Formation of 360° Domain Wall in a Ferromagnetic Nanowire by Splitting and Recombination of 180° Domain Wall

The domain wall (DW) motion in ferromagnetic nanostructures is of paramount importance for realizing high density magnetic data storage applications. In this work, we have investigated the vortex domain wall (VDW) motion in a ferromagnetic nanowire with a rectangular anti-dot using micromagnetic simulations. We found that the anti-dot acts as a pinning site resulting in either splitting or transformation of VDW to a transverse DW depending on the anti-dot width. The DW splitting and recombination result in the formation of a 360° DW from a single 180° VDW. The whole process follows the conservation of the topological charge associated with the DWs in the system. We found that energy distribution across the transverse domain wall (TDW) plays an important role in both the DW splitting and formation of 360° DW. The DW splitting field has shown a crossover as a function of anti-dot width which is attributed to the dependance of pinning field on the DW size as seen by the pinning site. This work reveals a novel method to stabilize 360° DW in a simple, compact and experimentally realizable ferromagnetic nanostructure under the application of a linear magnetic field.