# Sedimentation of a suspension of paramagnetic particles in an external magnetic field

## TL;DR

This study examines how an external magnetic field affects the sedimentation behavior of paramagnetic particles in water, revealing increased cohesion in packed particles despite weak magnetic susceptibility.

## Contribution

It demonstrates that even with small magnetic susceptibility, an external magnetic field can significantly influence particle cohesion and sedimentation dynamics in a Hele-Shaw cell.

## Key findings

- Magnetic field reduces decompaction rate of particles.
- Induced magnetic interactions enhance particle cohesion.
- Magnetic influence on dispersed particles remains minimal.

## Abstract

We investigate the sedimentation of initially packed paramagnetic particles in presence of a homogeneous external magnetic field, in a Hele-Shaw cell filled with water. Although the magnetic susceptibility of the particles is small and the particle-particle induced magnetic interactions are significantly smaller compared to the gravitational acceleration, we do observe a measurable reduction of the decompaction rate as the amplitude of the applied magnetic field is increased. While induced magnetic dipole-dipole interactions between particles can be either attracting or repulsive depending on the particles relative alignment, our observations reveal an effective overall enhancement of the cohesion of the initial pack of particles due to the induced interactions, very likely promoting internal chain forces in the initial pack of particles. The influence of the magnetic field on the particles once they disperse after being decompacted is on the other hand found to remain marginal.