# Probing the stability and magnetic properties of magnetosome chains in freeze-dried magnetotactic bacteria

## TL;DR

This study investigates the magnetic stability and properties of magnetosome chains in freeze-dried magnetotactic bacteria using magnetometry and neutron scattering, revealing preserved chain structure and magnetic behavior post-lyophilization.

## Contribution

It provides new insights into the magnetic stability and structural preservation of magnetosome chains in bacteria after freeze-drying, using combined experimental techniques.

## Key findings

- Magnetosome chains retain their structure after freeze-drying.
- Individual magnetite nanoparticles are single-domain and align via Nél-like rotation.
- No significant dipolar interactions observed between chains.

## Abstract

\textit{Magnetospirillum gryphiswaldense} biosynthesize high quality magnetite nanoparticles, called magnetosomes, and arrange them into a chain that behaves like a magnetic compass. Here we perform magnetometry and polarized small-angle neutron scattering (SANS) experiments on a powder of freeze-dried and immobilized \textit{M. gryphiswaldense}. We confirm that the individual nanoparticles are single-domain particles and that an alignment of the particle moments in field direction occurs exclusively by a N\'eel-like rotation. Our magnetometry results of the bacteria powder indicate an absence of dipolar interactions between the particle chains and a dominant uniaxial magnetic anisotropy. Finally, we can verify by SANS that the chain structure within the immobilized, freeze-dried bacteria is preserved also after application of large magnetic fields of up to 1\,T.