Micromagnetic modelling of magnetic domain walls in curved cylindrical nanotubes and nanowires

TL;DR

This study uses micromagnetic simulations to explore how curvature affects the energy, stability, and types of domain walls in curved cylindrical nanotubes and nanowires, revealing curvature-induced effects on domain wall configurations.

Contribution

It provides the first detailed phase diagram of domain wall states in curved nanotubes and nanowires, highlighting the impact of curvature on domain wall stability and transformations.

Findings

Curvature shifts the ground state from vortex to transverse walls at higher diameters.

Curvature increases the metastability range of domain walls.

In tubes, curvature suppresses TW to VW transformation; in wires, it promotes VW to TW transformation.

Abstract

We investigate the effect of curvature on the energy and stability of domain wall configurations in curved cylindrical nanotubes and nanowires. We use micromagnetic simulations to calculate the phase diagram for the transverse wall (TW) and vortex wall (VW) states in tubes, finding the ground state configuration and the metastability region where both types of walls can exist. The introduction of curvature shifts the range for which the TW is the ground state domain wall to higher diameters, and increases the range of metastability. We interpret this behavior to be primarily due to the curvature-induced effective Dzyaloshinskii-Moriya term in the exchange energy. Furthermore, we demonstrate qualitatively the same behavior in solid cylindrical nanowires. Comparing both tubes and wires, we observe how while in tubes curvature tends to suppress the transformation from the TW to VW, in wires it promotes the transformation of the VW containing the Bloch point into the TW. These findings have important implications in the fundamental understanding of domain walls in 3D geometries, and the design of future domain wall devices.