The domain wall motion along a helix-shaped nanowire is studied for the case of spin-current driving via the Zhang-Li mechanism. The analysis is based on the collective variable approach. Two effects are ascertained: (i) the curvature results in the appearance of the Walker limit for a uniaxial wire, and (ii) the torsion results in effective shift of the nonadiabatic spin torque parameter β. The latter effect changes considerably the domain wall velocity and can result in negative domain wall mobility. This effect can be also used for an experimental determination of the nonadiabatic parameter β and damping coefficient α.
Phys. Rev. B. 92, 094418 (2016), PDF