# Swarming of micron-sized hematite cubes in a rotating magnetic field -- Experiments

## TL;DR

This study investigates how micron-sized hematite cubes form rotating swarms under a magnetic field, revealing their behavior, limits, and dependence on field parameters, with a theoretical model explaining their angular velocity.

## Contribution

It provides the first detailed experimental analysis of swarm formation of hematite cubes and compares results with a theoretical model, highlighting shape effects.

## Key findings

- Swarming behavior depends on magnetic field strength and frequency.
- Quantitative agreement between experimental data and the theoretical model.
- Non-spherical hematite particles do not form swarms.

## Abstract

Energy input by under-field rotation of particles drives the systems to emergent non-equilibrium states. Here we investigate the suspension of rotating magnetic cubes. Micron-sized hematite cubes are synthesized and observed microscopically. When exposed to a rotating magnetic field, they form rotating swarms that interact with each other like liquid droplets. We describe the swarming behaviour and its limits and characterize swarm size and angular velocity dependence on magnetic field strength and frequency. A quantitative agreement with a theoretical model is found for the angular velocity of swarms as a function of field frequency. It is interesting to note that hematite particles with peanut or ellipsoidal shapes do not form swarms.