Spin-torque shot noise in magnetic tunnel junctions

TL;DR

This paper derives a stochastic model for magnetization dynamics in magnetic tunnel junctions, revealing how non-equilibrium shot noise influences the precession spectrum and linewidth in spin-torque phenomena.

Contribution

It introduces a stochastic Landau-Lifshitz-Gilbert equation and solves the Fokker-Planck equation to analyze shot noise effects in magnetic tunnel junctions.

Findings

Non-monotonous dependence of precession linewidth on current

Shot noise affects magnetization precession spectrum

Derived stochastic equations for magnetization dynamics

Abstract

Spin polarized current may transfer angular momentum to a ferromagnet, resulting in a spin-torque phenomenon. At the same time the shot noise, associated with the current, leads to a non-equilibrium stochastic force acting on the ferromagnet. We derive stochastic version of Landau-Lifshitz-Gilbert equation for a magnetization of a ''free'' ferromagnetic layer in contact with a ''fixed'' ferromagnet. We solve the corresponding Fokker-Planck equation and show that the non-equilibrium noise yields to a non-monotonous dependence of the precession spectrum linewidth on the current.