Domain walls (DWs) in magnetic nanostructures have long been a subject of much interest[1]. The majority of work so far has focused on 90° and 100° DWs. However, recently the field has seen promising developments in 360° DWs, stable topological defects consisting of two strongly-coupled 180° DWs of opposite chirality[2] 360° DWs have several interesting properties relating to behaviour in applied field[3], interactions with spin-waves[4] and high density DW systems such as racetrack memory[4]. Here we demonstrate their utility as a tool for controlling global magnetization states of nanostructures comprised of interconnected nanowires.

By using a novel 360° DW injection technique we are able to introduce DWs of desired chirality to any point in a structure. Choosing these points carefully allows the injected DWs to mediate controlled switching events throughout the nanostructure, resulting in new magnetization states without the application of a global field or current. This behaviour is confirmed via MFM data supported by micromagnetic simulations.

Figure 1: Micromagnetic simulation & corresponding MFM data showing 360° DW mediated switching. An initially left-magnetised structure i) has a 360° DW injected at its centre ii) resulting in a new magnetization state oriented down-left after the composite 180° DWs have spread through the structure iii).

[1] Klaui, M. JOP: Cond. Matt. 20(31), 2008
[2] McMichael, R.D. and Donahue, M.J - IEEE Trans. Mag. 33(5), 1997
[3] Mascaro, M. D. and Ross, C. A. PRB 82(21), 2010
[4] Roy, P.E., Trypiniotis, T. and Barnes, C. H. W. PRB 82(13), 2010