Input-driven chaotic dynamics in vortex spin-torque oscillator

TL;DR

This paper investigates how vortex spin-torque oscillators exhibit input-driven synchronization and chaos under random magnetic fields, revealing complex dynamics relevant for brain-inspired computing.

Contribution

It introduces the study of chaotic and synchronized behaviors in vortex STOs driven by random magnetic fields, linking these dynamics to reservoir computing capabilities.

Findings

Input-driven synchronization occurs in weak perturbation limits.

Chaotic vortex core dynamics are observed over a wide parameter range.

Dynamical phases are characterized by Lyapunov exponents.

Abstract

A new research topic in spintronics relating to the operation principles of brain-inspired computing is input-driven magnetization dynamics in nanomagnet. In this paper, the magnetization dynamics in a vortex spin-torque oscillator (STO) driven by a series of random magnetic field are studied through a numerical simulation of the Thiele equation. It is found that input-driven synchronization occurs in the weak perturbation limit, as found recently. As well, chaotic behavior is newly found to occur in the vortex core dynamics for a wide range of parameters, where synchronized behavior is disrupted by an intermittency. Ordered and chaotic dynamical phases are examined by evaluating the Lyapunov exponent. The relation between the dynamical phase and the computational capability of physical reservoir computing is also studied.