# Supraferromagnetic correlations in clusters of magnetic nanoflowers

## TL;DR

This study reveals hierarchical magnetic coupling in nanoflower clusters, showing that nanoflowers tend to align their magnetic moments parallel, which enhances their performance in magnetic hyperthermia applications.

## Contribution

It uncovers the hierarchical magnetic structure of nanoflower clusters and demonstrates supraferromagnetic coupling using spin-resolved neutron scattering.

## Key findings

- Nanoflowers exhibit parallel magnetic moment alignment.
- Hierarchical structure includes nanocrystallites, nanoflowers, and clusters.
- Enhanced hyperthermia performance linked to supraferromagnetic coupling.

## Abstract

Magnetic nanoflowers are densely packed aggregates of superferromagnetically coupled iron oxide nanocrystallites, which excel during magnetic hyperthermia experiments. Here, we investigate the nature of the moment coupling within a powder of such nanoflowers using spin-resolved small-angle neutron scattering. Within the powder the nanoparticles are agglomerated to clusters, and we can show that the moments of neighboring nanoflowers tend to align parallel to each other. Thus, the whole system resembles a hierarchical magnetic nanostructure consisting of three distinct levels, i.e. (i) the ferrimagnetic nanocrystallites as building blocks, (ii) the superferromagnetic nanoflowers, and (iii) the \textit{supra}ferromagnetic clusters of nanoflowers. We surmise that such a supraferromagnetic coupling explains the enhanced magnetic hyperthermia performance in case of interacting nanoflowers.