# Imaging magnetic vortex configurations in ferromagnetic nanotubes

## TL;DR

This paper uses advanced microscopy and simulations to image and control vortex magnetization states in ferromagnetic nanotubes, revealing flux-closure configurations and the ability to program vortex states by adjusting nanotube aspect ratios.

## Contribution

It provides direct imaging evidence of vortex states in nanotubes and demonstrates how to program these states through aspect ratio manipulation.

## Key findings

- Vortex states confirmed in CoFeB and permalloy nanotubes.
- Flux-closure configurations observed via microscopy.
- Vortex states can be programmed by changing nanotube aspect ratio.

## Abstract

We image the remnant magnetization configurations of CoFeB and permalloy nanotubes (NTs) using x-ray magnetic circular dichroism photo-emission electron microscopy. The images provide direct evidence for flux-closure configurations, including a global vortex state, in which magnetization points circumferentially around the NT axis. Furthermore, micromagnetic simulations predict and measurements confirm that vortex states can be programmed as the equilibrium remnant magnetization configurations by reducing the NT aspect ratio.