Curvature and torsion effects in the spin-current driven domain wall motion

TL;DR

This paper investigates how curvature and torsion in helix-shaped nanowires influence spin-current driven domain wall motion, revealing new effects on Walker limit and nonadiabatic torque, with implications for experimental parameter estimation.

Contribution

It introduces the effects of curvature and torsion on domain wall dynamics in helix-shaped wires, including the Walker limit emergence and effective shift of the nonadiabatic parameter.

Findings

Curvature induces a Walker limit in uniaxial wires.

Torsion causes an effective shift in the nonadiabatic spin torque parameter.

Torsion can lead to negative domain wall mobility.

Abstract

The domain wall motion along a helix-shaped nanowire is studied for the case of spin-current driving via Bazaliy-Zhang-Li mechanism. The analysis is based on collective variable approach. Two new effects are ascertained: (i) the curvature results in appearance of the Walker limit for a uniaxial wire, (ii) the torsion results in effective shift of the nonadiabatic spin torque parameter $\beta$. 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 $\beta$ and damping coefficient $\alpha$.