Nonlinear dynamic susceptibilities of interacting and noninteracting nanoparticle systems

TL;DR

This study investigates how dipole-dipole interactions affect the nonlinear dynamic susceptibilities of maghemite nanoparticle dispersions across different concentrations, revealing behaviors similar to spin glasses at higher concentrations.

Contribution

It provides experimental measurements of nonlinear susceptibilities in nanoparticle systems and compares dilute and concentrated samples to existing theories and spin glass behavior.

Findings

Dilute samples agree with noninteracting particle theory.

Concentrated samples show spin glass-like features.

Nonlinear response varies significantly with particle concentration.

Abstract

The linear and cubic dynamic susceptibilities of solid dispersions of nano-sized maghemite particles have been measured for three samples with a volume concentration of magnetic particles ranging from 0.3 % to 17 %, in order to study the effect of dipole-dipole interactions. Significant differences between the dynamic response of the three samples are observed. The dynamic susceptibilities of the most dilute sample compare reasonably well with an existing theory for the linear and cubic dynamic susceptibilities of an assembly of noninteracting, uniaxial magnetic particles. The nonlinear dynamic response of the most concentrated sample exhibits at low temperatures some of the features observed in a Ag(11 at.% Mn) spin glass.