A reduced model for precessional switching of thin-film nanomagnets under the influence of spin-torque

TL;DR

This paper develops a simplified model for the precessional switching of thin-film nanomagnets influenced by spin-torque, providing analytical insights and validating against full micromagnetic equations.

Contribution

A reduced PDE model for in-plane magnetization dynamics under spin-torque, with analytical treatment and comparison to full Landau-Lifshitz-Gilbert equations.

Findings

Reduced model accurately predicts switching behavior.

Analytical orbit-averaging reveals transition mechanisms.

Model agrees with full micromagnetic simulations.

Abstract

We study the magnetization dynamics of thin-film magnetic elements with in-plane magnetization subject to a spin-current flowing perpendicular to the film plane. We derive a reduced partial differential equation for the in-plane magnetization angle in a weakly damped regime. We then apply this model to study the experimentally relevant problem of switching of an elliptical element when the spin-polarization has a component perpendicular to the film plane, restricting the reduced model to a macrospin approximation. The macrospin ordinary differential equation is treated analytically as a weakly damped Hamiltonian system, and an orbit-averaging method is used to understand transitions in solution behaviors in terms of a discrete dynamical system. The predictions of our reduced model are compared to those of the full Landau--Lifshitz--Gilbert--Slonczewski equation for a macrospin.