Interest in the dynamics of domain walls in magnetic nanowires has increased rapidly in recent years, largely due to their potential in novel spintronic applications. Domain wall dynamics are key to device operation speeds, which are ultimately limited by the domain wall velocity.

Typically, domain wall velocity increases linearly with applied field up to the Walker field. This field marks the onset of Walker breakdown, after which a dramatic reduction in the time-averaged velocity occurs due to the nucleation of a vortex core originating from a structural instability in the wall. Further increase in the applied field leads to a gradual increase in velocity interrupted by further breakdown events. Walker breakdown can be suppressed with the application of transverse fields, which shifts breakdown to higher fields [1]. Edge roughness can also suppress Walker breakdown by dissipation of wall energy preventing vortex core formation, but by its nature this is hard to control [2]. Subsequent theoretical work has shown modulation of the edges modifies the energy landscape and thus affects wall propagation [3].

Here, a detailed systematic micromagnetic analysis of small amplitude periodically modulated nanowires has been performed. The periodicity dependence shows how energy dissipation via spin wave emission from domain walls can reduce the structural instability of the wall. Edge modulated nanowires can be tuned to match the period of vortex nucleation giving rise to a regime where fast, constant domain wall motion can be achieved at fields above that usually resulting in Walker breakdown.

[1] M.T. Bryan et.al., J. Appl. Phys. 103, 073906 (2008).
[2] Y. Nakatani et.al., Nature Materials 2, 521 (2003).
[3] J. Ieda et.al., J. Magn. Magn. Mater. 322, 1363 (2010).