Role of geometrical symmetry in thermally activated processes in clusters of interacting dipolar moments

TL;DR

This study investigates how geometrical symmetry influences thermally activated magnetization decay in clusters of interacting dipolar moments, revealing symmetry-dependent deviations from traditional energy barrier models.

Contribution

It introduces a semi-analytical approach and a simple two-state model to explain symmetry-dependent anomalies in relaxation rates, supported by kinetic Monte-Carlo simulations.

Findings

Deviations from the energy barrier picture depend on structural symmetry.

Reduced symmetry leads to stronger interaction effects on relaxation.

The developed models accurately reproduce observed anomalies.

Abstract

Thermally activated magnetization decay is studied in ensembles of clusters of interacting dipolar moments by applying the master-equation formalism, as a model of thermal relaxation in systems of interacting single-domain ferromagnetic particles. Solving the associated master-equation reveals a breakdown of the energy barrier picture depending on the geometrical symmetry of structures. Deviations are most pronounced for reduced symmetry and result in a strong interaction dependence of relaxation rates on the memory of system initialization. A simple two-state system description of an ensemble of clusters is developed which accounts for the observed anomalies. These results follow from a semi-analytical treatment, and are fully supported by kinetic Monte-Carlo simulations.