Induced magnetization and power loss for a periodically driven system of ferromagnetic nanoparticles with randomly oriented easy axes

TL;DR

This paper develops a perturbation theory to analyze how elliptically polarized magnetic fields affect the magnetization and power loss in a system of ferromagnetic nanoparticles with randomly oriented easy axes, considering both small and arbitrary field amplitudes.

Contribution

It introduces a general perturbation approach for the Landau-Lifshitz-Gilbert equation to analytically and numerically study magnetization and power loss in nanoparticle systems under periodic magnetic fields.

Findings

Second-order expressions for magnetization and power loss derived

Frequency dependence of magnetization and power loss analyzed

Transitions between regular and chaotic magnetization dynamics examined

Abstract

We study the effect of an elliptically polarized magnetic field on a system of non-interacting, single-domain ferromagnetic nanoparticles characterized by a uniform distribution of easy axis directions. Our main goal is to determine the average magnetization of this system and the power loss in it. In order to calculate these quantities analytically, we develop a general perturbation theory for the Landau-Lifshitz-Gilbert (LLG) equation and find its steady-state solution for small magnetic field amplitudes. On this basis, we derive the second-order expressions for the average magnetization and power loss, investigate their dependence on the magnetic field frequency, and analyze the role of subharmonic resonances resulting from the nonlinear nature of the LLG equation. For arbitrary amplitudes, the frequency dependence of these quantities is obtained from the numerical solution of this equation. The impact of transitions between different regimes of regular and chaotic dynamics of magnetization, which can be induced in nanoparticles by changing the magnetic field frequency, is examined in detail.