Transition state dynamics of a driven magnetic free layer

TL;DR

This paper studies how magnetization switches in a ferromagnetic free layer under oscillating magnetic fields, using transition state theory to compute switching rates considering inertial damping effects.

Contribution

It applies recent transition state theory extensions to a driven magnetic system, providing a novel approach to calculate switching rates in oscillating fields.

Findings

Computed time-dependent switching rates.

Analyzed effects of inertial damping.

Identified saddle crossing dynamics.

Abstract

Magnetization switching in ferromagnetic structures is an important process for technical applications such as data storage in spintronics, and therefore the determination of the corresponding switching rates becomes essential. We investigate a free-layer system in an oscillating external magnetic field resulting in an additional torque on the spin. The magnetization dynamics including inertial damping can be described by the phenomenological Gilbert equation. The magnetization switching between the two stable orientations on the sphere then requires the crossing of a potential region characterized by a moving rank-1 saddle. We adopt and apply recent extensions of transition state theory for driven systems to compute both the time-dependent and average switching rates of the activated spin system in the saddle region.