Nonlinear response of the magnetophoresis in inverse ferrofluids

TL;DR

This paper models the nonlinear magnetophoretic response of inverse ferrofluids considering structural transitions, long-range interactions, and anisotropy, revealing harmonic generation and conditions for force vanishing.

Contribution

It develops a combined theoretical framework using Ewald-Kornfeld and Maxwell-Garnett theories to analyze anisotropic inverse ferrofluids under complex magnetic fields.

Findings

Coupling of ac and dc fields induces harmonic responses.

Aspect ratio changes affect harmonic and nonharmonic responses.

Magnetophoretic force can vanish under certain anisotropic conditions.

Abstract

Taking into account the structural transition and long-range interaction (lattice effect), we resort to the Ewald-Kornfeld formulation and developed Maxwell-Garnett theory for uniaxially anisotropic suspensions to calculate the effective permeability of inverse ferrofluids. And we also consider the effect of volume fraction to the magnetophoretic force on the nonmagnetic spherical particles submerged in ferrofluids in the presence of nonuniform magnetic field. We find that the coupling of ac and dc field case can lead to fundamental and third harmonic response in the effective magnetophoresis and changing the aspect ratio in both prolate and oblate particles can alter the harmonic and nonharmonic response and cause the magnetophoretic force vanish.