Magnetization noise in magnetoelectronic nanostructures

TL;DR

This paper demonstrates how spin current noise, including Johnson-Nyquist and shot noise, enhances magnetization noise in nanoscale ferromagnetic structures through spin-transfer torque, linking it to damping and fluctuation-dissipation.

Contribution

It introduces a scattering theory approach to quantify how spin current noise affects magnetization fluctuations in magnetoelectronic nanostructures.

Findings

Spin current noise increases magnetization noise via fluctuating spin-transfer torque.

Johnson-Nyquist noise relates to increased Gilbert damping through spin pumping.

At low temperatures, spin current shot noise dominates magnetization noise.

Abstract

By scattering theory we show that spin current noise in normal electric conductors in contact with nanoscale ferromagnets increases the magnetization noise by means of a fluctuating spin-transfer torque. Johnson-Nyquist noise in the spin current is related to the increased Gilbert damping due to spin pumping, in accordance with the fluctuation-dissipation theorem. Spin current shot noise in the presence of an applied bias is the dominant contribution to the magnetization noise at low temperatures.