# Flux-closure domains in high aspect ratio electroless-deposited CoNiB nanotubes

## TL;DR

This study visualizes magnetic domain structures in high aspect ratio CoNiB nanotubes, revealing unexpected azimuthal domains likely caused by strain and grain effects, with implications for data storage and magnetic wave phenomena.

## Contribution

It provides the first imaging evidence of azimuthal magnetic domains in electroless-deposited CoNiB nanotubes and explores their possible origins.

## Key findings

- Azimuthal domains observed in long nanotubes.
- Magneto-elastic and interfacial anisotropy likely influence domain structure.
- Potential applications in data storage and spin-wave devices.

## Abstract

We report the imaging of magnetic domains in ferromagnetic CoNiB nanotubes with very long aspect ratio, fabricated by electroless plating. While axial magnetization is expected for long tubes made of soft magnetic materials, we evidence series of azimuthal domains. We tentatively explain these by the interplay of anisotropic strain and/or grain size, with magneto-elasticity and/or anisotropic interfacial magnetic anisotropy. This material could be interesting for dense data storage, as well as curvature-induced magnetic phenomena such as the non-reciprocity of spin-wave propagation.