Narrow autoresonant magnetization structures in finite length ferromagnetic nanoparticles

TL;DR

This paper proposes and analyzes a method for exciting and controlling large amplitude magnetization structures in ferromagnetic nanoparticles using autoresonance, with insights into threshold behavior, dissipation effects, and localized solutions.

Contribution

It introduces a novel autoresonant excitation approach for finite ferromagnetic nanoparticles and analyzes the resulting localized magnetization structures within the Landau-Lifshitz-Gilbert framework.

Findings

Autoresonant excitation can effectively control magnetization structures.

Threshold amplitude depends on dissipation effects.

Localized solutions approach soliton profiles with increasing size.

Abstract

The autoresonant approach to excitation and control of large amplitude uniformly precessing magnetization structures in finite length easy axis ferromagnetic nanoparticles is suggested and analyzed within the Landau-Lifshitz-Gilbert model. These structures are excited by using a spatially uniform, oscillating, chirped frequency magnetic field, while the localization is imposed via boundary conditions. The excitation requires the amplitude of the driving oscillations to exceed a threshold. The dissipation effect on the threshold is also discussed. The autoresonant driving effectively compensates the effect of dissipation, but lowers the maximum amplitude of the excited structures. Fully nonlinear localized autoresonant solutions are illustrated in simulations and described via an analog of a quasi-particle in an effective potential. The precession frequency of these solutions is continuously locked to that of the drive, while the spatial magnetization profile approaches the soliton limit when the length of the nanoparticle and the amplitude of the excited solution increase.