  Realising the promise of next-generation magnetic nanotechnologies is
contingent on the development of novel methods for controlling magnetic states
at the nanoscale. There is currently demand for simple and flexible techniques
to access exotic magnetisation states without convoluted fabrication and
application processes. 360 degree domain walls (metastable twists in
magnetisation separating two domains with parallel magnetisation) are one such
state, which is currently of great interest in data storage and magnonics.
Here, we demonstrate a straightforward and powerful process whereby a moving
magnetic charge, provided experimentally by a magnetic force microscope tip,
can write and manipulate magnetic charge states in ferromagnetic nanowires. The
method is applicable to a wide range of nanowire architectures with
considerable benefits over existing techniques. We confirm the method's
efficacy via the injection and spatial manipulation of 360 degree domain walls
in Py and Co nanowires. Experimental results are supported by micromagnetic
simulations of the tip-nanowire interaction.
