# Tailoring dual reversal modes by helicity control in ferromagnetic nanotubes

## TL;DR

This study explores how controlling helicity in ferromagnetic nanotubes influences their magnetization reversal modes, revealing four classes of hysteresis behavior linked to metastable states and demonstrating mode tailoring via initial vortex configurations.

## Contribution

It introduces a method to tailor dual reversal modes in ferromagnetic nanotubes by helicity control, based on atomistic and micromagnetic simulations, expanding understanding of reversal mechanisms.

## Key findings

- Four classes of hysteresis loops linked to reversal modes.
- Reversal modes can be tailored by initial vortex chirality.
- Dual switching modes are observable in microscopic nanotubes.

## Abstract

We investigate the effects of the competition between exchange ($J$) and dipolar ($D$) interactions on the magnetization reversal mechanisms of ferromagnetic nanotubes. Using first atomistic Monte Carlo (MC) simulations for a model with Heisenberg spins on a cylindrical surface, we compute hysteresis loops for a wide range of the $\gamma=D/J$ parameter, characterizing the reversal behavior in terms of the cylindrical magnetization components and the vorticity parameter along the tube length. For $\gamma$'s close to the value for which helical (H) states are stable at zero applied field, we show that the hysteresis loops can occur in four different classes that are combinations of two reversal modes with well-differentiated coercivities with probabilities that depend on the tube length and radius. This variety in the reversal modes is found to be linked to the metastability of the $H$ states during the reversal that induce different paths followed along the energy landscape as the field is changed. We further demonstrate that reversal by either of the two modes can be induced by tailoring the nanotube initial state so that vortices with equal or contrary chirality are formed at the ends, thus achieving low or high coercive fields at will without changing $\gamma$. Finally, the results of additional micromagnetic simulations performed on tubes with similar aspect ratio show that dual switching modes and its tailoring can also be observed in tubes with more microscopic dimensions.