Effects of dipolar interactions on the zero-field-cooled magnetization of a nanoparticle assembly

TL;DR

This paper studies how weak dipolar interactions influence the temperature at the peak of zero-field-cooled magnetization in nanoparticle assemblies, extending existing models to include these effects.

Contribution

The authors extend the Gittleman-Abeles-Bozowski model to incorporate dipolar interactions, explaining their impact on magnetization behavior.

Findings

Dipolar interactions cause the temperature at the magnetization peak to shift from bell-shaped to decreasing with field.

Increasing sample concentration enhances dipolar effects, altering magnetization curves.

Model predictions align qualitatively with experimental observations.

Abstract

We investigate the effect of (weak) dipolar interactions on the field behavior of the temperature at the maximum of the zero-field-cooled magnetization of a polydisperse assembly of nanoparticles. For this purpose, we extend the Gittleman-Abeles-Bozowski model for the zero-field-cooled magnetization by computing the contribution of dipolar interactions to the longitudinal relaxation time. We show, in good qualitative agreement with many experimental observations, that the temperature at the maximum of the zero-field-cooled magnetization as a function of the applied field changes from a bell-like to a monotonically decreasing curve when the intensity of the dipolar interactions, or equivalently the sample concentration, increases.