Frequency-dependent magnetic susceptibility of magnetic nanoparticles in a polymer solution: a simulation study

TL;DR

This simulation study investigates how magnetic nanoparticles in a polymer solution respond to alternating magnetic fields, highlighting the role of hydrodynamic interactions and polymer concentration on magnetic susceptibility.

Contribution

It provides new insights into the microscopic coupling mechanisms affecting magnetic susceptibility in polymer-nanoparticle composites through simulation and comparison with experimental data.

Findings

Hydrodynamic interactions significantly influence AC susceptibility.

Polymer concentration and length affect magnetic response.

Simulation results align with experimental measurements.

Abstract

Magnetic composite materials i.e. elastomers, polymer gels, or polymer solutions with embedded magnetic nanoparticles are useful for many technical and bio-medical applications. However, the microscopic details of the coupling mechanisms between the magnetic properties of the particles and the mechanical properties of the (visco)elastic polymer matrix remain unresolved. Here we study the response of a single-domain spherical magnetic nanoparticle that is suspended in a polymer solution to alternating magnetic fields. As interactions we consider only excluded volume interactions with the polymers and hydrodynamic interactions mediated through the solvent. The AC susceptibility spectra are calculated using a linear response Green-Kubo approach, and the influences of changing polymer concentration and polymer length are investigated. Our data is compared to recent measurements of the AC susceptibility for a typical magnetic composite system [Roeben et al., Colloid and Polymer Science, 2014, 2013--2023], and demonstrates the importance of hydrodynamic coupling in such systems.