Chiral symmetry breaking and pair-creation mediated Walker breakdown in magnetic nanotubes

Field-driven domain wall (DW) propagation in ferromagnetic nanotubes displays unusual effects, as revealed by a micromagnetic study. The left-right symmetry of the DW dynamics is broken, yielding markedly different DW mobilities for opposite propagation directions. This asymmetry arises from the tubular geometry and its impact on the DW structure. Also, the Walker breakdown field and velocity are found to be asymmetric for opposite directions. In certain cases, the breakdown can even be suppressed in one or both directions. Topological constraint requires a vortex-antivortex pair mediated breakdown, contrary to the single (anti) vortex in flat strips. This results in a higher breakdown velocity. (C) 2012 American Institute of Physics. [http://dx.doi.org/10.1063/1.4727909]