Magnetization of polydisperse colloidal ferrofluids: Effect of magnetostriction

TL;DR

This paper investigates how magnetostriction influences the nonlinear magnetic response of polydisperse ferrofluids, revealing that higher-order harmonics in magnetization can indicate particle size distribution.

Contribution

It introduces a thermodynamical approach to derive nonlinear magnetic susceptibility considering magnetostriction in polydisperse ferrofluids, validated against statistical methods.

Findings

Higher-order harmonics depend on particle distribution and anisotropy.

Magnetization is greater in polydisperse than monodisperse ferrofluids.

Harmonics measurement can reveal particle size distribution.

Abstract

We exploit magnetostriction in polydisperse ferrofluids in order to generate nonlinear responses, and apply a thermodynamical method to derive the desired nonlinear magnetic susceptibility. For an ideal gas, this method has been demonstrated to be in excellent agreement with a statistical method. In the presence of a sinusoidal ac magnetic field, the magnetization of the polydisperse ferrofluid contains higher-order harmonics, which can be extracted analytically by using a perturbation approach. We find that the harmonics are sensitive to the particle distribution and the degree of field-induced anisotropy of the system. In addition, we find that the magnetization is higher in the polydisperse system than in the monodisperse one, as also found by a recent Monte Carlo simulation. Thus, it seems possible to detect the size distribution in a polydisperse ferrofluid by measuring the harmonics of the magnetization under the influence of magnetostriction.