Dynamical and thermal effects in nanoparticle systems driven by a rotating magnetic field

TL;DR

This paper investigates how a rotating magnetic field affects the dynamical behavior and thermal stability of nanoparticle magnetic moments, providing analytical and stochastic methods to understand magnetization and switching phenomena.

Contribution

It introduces a comprehensive analytical framework combining deterministic and stochastic equations to analyze nanoparticle magnetic dynamics under rotating fields, including stability and relaxation.

Findings

Stable steady-state precession characterized

Magnetic switching influenced by rotating field

Mean residence times in magnetic states calculated

Abstract

We study dynamical and thermal effects that are induced in nanoparticle systems by a rotating magnetic field. Using the deterministic Landau-Lifshitz equation and appropriate rotating coordinate systems, we derive the equations that characterize the steady-state precession of the nanoparticle magnetic moments and study a stability criterion for this type of motion. On this basis, we describe (i) the influence of the rotating field on the stability of the small-angle precession, (ii) the dynamical magnetization of nanoparticle systems, and (iii) the switching of the magnetic moments under the action of the rotating field. Using the backward Fokker-Planck equation, which corresponds to the stochastic Landau-Lifshitz equation, we develop a method for calculating the mean residence times that the driven magnetic moments dwell in the up and down states. Within this framework, the features of the induced magnetization and magnetic relaxation are elucidated.