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^o and 180^o DWs. However, recently the field has seen promising developments in 360^o DWs, stable topological defects consisting of two strongly-coupled 180^o DWs of opposite chirality[1]. 360^o DWs have several interesting properties relating to behaviour in applied field[3], interactions with spin-waves[2] and high density DW systems such as racetrack memory. [4].

Here we demonstrate a novel 360^o DW injection technique using an MFM tip. This enables the introduction of DWs of desired chirality to any point in a structure. When the injection point is separated from other micromagnetic features by more than a 360^o DWs width, the 360^o DW is stable. When injected close to a magnetic junction, the 360^o DW is unstable and collapses in a chirality-dependent manner. Choosing injection points carefully allows the injected DWs to mediate controlled switching events throughout the nanostructure, resulting in new magnetisation states.

Using MFM data supported by micromagnetic simulations we demonstrate the utility of this as a tool for controlling global magnetisation states of nanostructures comprised of interconnected nanowires without applied current or global field.