Spin Torque Dynamics with Noise in Magnetic Nano-System

TL;DR

This paper explores how equilibrium and nonequilibrium noise influence magnetization dynamics in ferromagnetic nano-systems, deriving a microscopic model and analyzing noise effects on spin torque and switching behavior.

Contribution

It provides a detailed derivation of spin shot noise correlator and examines the impact of nonequilibrium noise on spin torque and switching, introducing a generalized Fokker-Planck approach.

Findings

Nonequilibrium noise affects spin torque dynamics.

Spin shot noise leads to effective temperature renormalization.

Creation of hot and cold noise spots observed.

Abstract

We investigate the role of equilibrium and nonequilibrium noise in the magnetization dynamics on mono-domain ferromagnets. Starting from a microscopic model we present a detailed derivation of the spin shot noise correlator. We investigate the ramifications of the nonequilibrium noise on the spin torque dynamics, both in the steady state precessional regime and the spin switching regime. In the latter case we apply a generalized Fokker-Planck approach to spin switching, which models the switching by an Arrhenius law with an effective elevated temperature. We calculate the renormalization of the effective temperature due to spin shot noise and show that the nonequilibrium noise leads to the creation of cold and hot spot with respect to the noise intensity.