Elementary transitions and magnetic correlations in two-dimensional disordered nanoparticle ensembles

TL;DR

This paper investigates how structural disorder affects magnetic relaxation and correlations in two-dimensional nanoparticle ensembles through numerical simulations, revealing increased localization of elementary processes with disorder.

Contribution

It provides a detailed analysis of energy landscapes, saddle points, and magnetic correlations in disordered nanoparticle systems, highlighting the impact of disorder on relaxation mechanisms.

Findings

Magnetic correlation range decreases with increasing disorder.

Elementary relaxation processes become more localized as disorder increases.

Distribution of energy barriers correlates with magnetic configuration changes.

Abstract

The magnetic relaxation processes in disordered two-dimensional ensembles of dipole-coupled magnetic nanoparticles are theoretically investigated by performing numerical simulations. The energy landscape of the system is explored by determining saddle points, adjacent local minima, energy barriers, and the associated minimum energy paths (MEPs) as functions of the structural disorder and particle density. The changes in the magnetic order of the nanostructure along the MEPs connecting adjacent minima are analyzed from a local perspective. In particular, we determine the extension of the correlated region where the directions of the particle magnetic moments vary significantly. It is shown that with increasing degree of disorder the magnetic correlation range decreases, i.e., the elementary relaxation processes become more localized. The distribution of the energy barriers, and their relation to the changes in the magnetic configurations are quantified. Finally, some implications for the long-time magnetic relaxation dynamics of nanostructures are discussed.