Underlying magnetization responses of magnetic nanoparticles in assemblies

TL;DR

This paper introduces a universal magnetic characterization method to analyze the reversible and irreversible magnetization responses of magnetic nanoparticle assemblies, revealing how intrinsic properties and porosity influence these responses.

Contribution

The study demonstrates a novel magnetic characterization technique and elucidates the relationship between magnetization responses, intrinsic properties, and porosity in nanoparticle assemblies.

Findings

Reversible magnetization depends on the interaction field to coercivity ratio.

Interaction field varies linearly with porosity at high porosity levels.

Nonlinear relationship between interaction field and porosity at low porosity levels.

Abstract

Magnetic nanoparticles (MNPs) have been proposed as an ultimate solution for diverse applications including nanomedicine and logic devices over decades. However, none has emerged revolutionary because realizing their magnetization response in an assembly is, surprisingly, still elusive. We employ our fast and universal magnetic characterization method, called the projection method, to underlie the reversible (irreversible) magnetization response of several assemblies. We then illustrate how the reversible (irreversible) magnetization response is correlated to the intrinsic properties (the coercivity and interaction fields) of the MNPs in an assembly. Our experimental observations indicate that the reversible magnetization does not solely depend on the interaction field, but it is indeed a function of the interaction field to coercivity ratio. Furthermore, for large porosities, the interaction field linearly changes with the porosity highlighting the predominant effects of dipole-dipole interactions on the interaction fields. However, at low porosities, the interaction field shows a nonlinear relationship with the porosity indicating the dipole fluctuations effects dominantly determine the interaction fields.