Spherical magnetic nanoparticles: magnetic structure and interparticle interaction

TL;DR

This paper investigates the magnetic interactions between spherical vortex-structured magnetic nanoparticles using micromagnetic simulations, emphasizing the influence of dipolar interactions and particle anisotropy.

Contribution

It provides an analytical model for nanoparticle interactions considering vortex core magnetization and susceptibility, based on micromagnetic simulations.

Findings

Vortex core orientation depends on particle size and anisotropy.

Dipolar interactions influence nanoparticle polarization.

Analytic expression for interaction energy involving vortex properties.

Abstract

The interaction between spherical magnetic nanoparticles is investigated from micromagnetic simulations and ananlysed in terms of the leading dipolar interaction energy between magnetic dipoles. We focus mainly on the case where the particles present a vortex structure. In a first step the local magnetic structure in the isolated particle is revisited. For particles bearing a uniaxial magnetocrystaline anisotropy, it is shown that the vortex core orientation relative to the easy axis depends on both the particle size and the anisotropy constant. When the particles magnetization present a vortex structure, it is shown that the polarization of the particles by the dipolar field of the other one must be taken into account in the interaction. An analytic form is deduced for the interaction which involves the vortex core magnetization and the magnetic susceptibility which are obtained from the magnetic properties of the isolated particle.