Thermally-Assisted Spin-Transfer Torque Dynamics in Energy Space

TL;DR

This paper analyzes the magnetization dynamics of a macrospin magnet under spin-torque and thermal fluctuations, deriving conditions for limit cycles and discussing the applicability of energy-averaged equations.

Contribution

It introduces an analytical approach to study thermally-assisted spin-torque dynamics using energy orbit averaging in the Landau-Lifshitz-Gilbert framework.

Findings

Derived current ranges for limit cycle existence.

Identified regimes where energy orbit averaging is valid.

Provided analytical insights into thermally activated magnetization behavior.

Abstract

We consider the general Landau-Lifshitz-Gilbert theory underlying the magnetization dynamics of a macrospin magnet subject to spin-torque effects and thermal fluctuations. Thermally activated dynamical properties are analyzed by averaging the full magnetization equations over constant- energy orbits. After averaging, all the relevant dynamical scenarios are a function of the ratio between hard and easy axis anisotropies. We derive analytically the range of currents for which limit cycles exist and discuss the regimes in which the constant energy orbit averaging technique is applicable.