Signatures of Chaos in Thermal Switching of Nanomagnets

TL;DR

This paper investigates how strong microwave fields induce chaotic magnetization dynamics in nanomagnets, leading to increased escape rates from stable states, with implications for understanding thermal switching behavior.

Contribution

It reveals the role of heteroclinic chaos in thermal switching of nanomagnets and connects chaotic dynamics to escape times via a generalized Arrhenius law.

Findings

Chaotic magnetization dynamics occur near saddle points under strong microwave fields.

Erosion of the safe basin around stable states is caused by heteroclinic chaos.

Escape times follow a generalized Arrhenius law influenced by chaos and external parameters.

Abstract

Thermally-activated magnetization dynamics of small nanoparticles subject to microwave (AC) external fields is studied. It is shown that, under sufficiently strong microwave excitations, chaotic magnetization dynamics may occur close to saddle-type heteroclinic connections, and this heteroclinic chaos is responsible for the erosion of the safe basin around stable magnetization states. The erosion phenomenon is then connected to the escape problem from the energy well surrounding a stable equilibrium. It is shown that escape times follow a generalized Arrhenius' law governed by temperature, microwave field amplitude, frequency and heteroclinic chaos threshold.