Surface Instabilities and Magnetic Soft Matter

TL;DR

This study investigates surface instabilities in thermoreversible ferrogel under magnetic fields, revealing how temperature-dependent viscoelastic properties influence the formation of magnetic surface patterns, with experimental results aligning with theoretical models.

Contribution

It demonstrates the tunability of ferrogel surface instabilities through temperature-controlled viscoelastic properties and provides experimental validation of theoretical magnetic threshold predictions.

Findings

Stress relaxation follows a stretched exponential with beta=1/3.

Magnetic threshold for Rosensweig-cusp formation varies with temperature.

Experimental results agree with existing theoretical models.

Abstract

We report on the formation of surface instabilities in a layer of thermoreversible ferrogel when exposed to a vertical magnetic field. Both static and time dependent magnetic fields are employed. Under variations of temperature, the viscoelastic properties of our soft magnetic matter can be tuned. Stress relaxation experiments unveil a stretched exponential scaling of the shear modulus, with an exponent of beta=1/3. The resulting magnetic threshold for the formation of Rosensweig-cusps is measured for different temperatures, and compared with theoretical predictions by Bohlius et. al. in J. Phys.: Condens. Matter., 2006, 18, 2671-2684.