Shot noise of spin current in ferromagnet-normal-metal systems

TL;DR

This paper introduces a three-terminal spin-valve setup to measure spin-dependent shot noise, revealing its dependence on spin-flip scattering rates and offering a sensitive method to probe spin relaxation in ferromagnet-normal-metal systems.

Contribution

It presents a novel experimental setup and theoretical analysis to determine spin-flip scattering rates via spin Fano factor measurements in a spin-valve system.

Findings

Spin Fano factor depends strongly on spin-flip scattering rate.

In parallel configuration, the spin Fano factor decreases with increased spin injection.

In antiparallel configuration, the spin Fano factor varies nonmonotonically.

Abstract

We propose a three-terminal spin-valve setup, to determine experimentally the spin-dependent shot noise, which carries information on the spin-relaxation processes. Based on a spin-dependent Boltzmann-Langevin approach, we show that the spin Fano factor, defined as the spin shot noise to the mean charge current, strongly depends on the spin-flip scattering rate in the normal wire. While in the parallel configuration the spin Fano factor always decreases below its unpolarized value with increasing spin injection, for the antiparallel case it varies nonmonotonically. We also show that in contrast to the charge current Fano factor, which varies appreciable only in the antiparallel case, the spin Fano factor allows for a more sensitive determination of the spin-flip scattering rate.