  The formation of 360{\deg} magnetic domain walls (360DWs) in Co and Ni80Fe20
thin film wires was demonstrated experimentally for different wire widths, by
successively injecting two 180{\deg} domain walls (180DWs) into the wire. For
narrow wires (less than 50 nm wide for Co), edge roughness prevented the
combination of the 180DWs into a 360DW, and for wide wires (200 nm for Co) the
360DW collapsed, but over an intermediate range of wire widths, reproducible
360DW formation occurred. The annihilation and dissociation of 360DWs was
demonstrated by applying a magnetic field parallel to the wire, showing that
annihilation fields were several times higher than dissociation fields in
agreement with micromagnetic modeling. The annihilation of a 360DW by current
pulsing was demonstrated.
