Configuration dependent demagnetizing field in assemblies of interacting magnetic particles

TL;DR

This paper introduces a mean field model for the configuration-dependent demagnetizing and anisotropy fields in assemblies of magnetic particles, validated through experiments on nanowire arrays and chains, highlighting shape and interaction effects.

Contribution

It presents a novel mean field approach to quantify demagnetizing and anisotropy fields considering particle shape and assembly configuration, validated with experimental data.

Findings

Demagnetizing field is lower in 2D assemblies than in continuous thin films.

Model accurately describes magnetic behavior in nanowire arrays and chains.

Shape and arrangement significantly influence dipolar interactions and magnetic anisotropy.

Abstract

A mean field model is presented for the configuration dependent effective demagnetizing and anisotropy fields in assemblies of exchange decoupled magnetic particles of arbitrary shape which are expressed in terms of the demagnetizing factors of the particles and the volumetric shape containing the assembly. Perpendicularly magnetized 2D assemblies have been considered, for which it is shown that the demagnetizing field is lower than the continuous thin film. As an example of these 2D systems, arrays of bistable cylindrical nanowires have been characterized by remanence curves as well as ferromagnetic resonance, which have served to show the correspondence of these measurements with the model and also to validate the mean field approach. Linear chains of cylinders and spheres have been analyzed leading to simple expressions to describe the easy axis rotation induced by the interaction field in chains of low aspect ratio cylindrical particles, and the dipolar magnetic anisotropy observed in the linear chain of spheres. These examples serve to underline the dependence on the dipolar interaction field and effective demagnetizing factor on the contributions that arise from the shape of the outer volume.