Shot noise in diffusive ferromagnetic metals

TL;DR

This paper investigates how shot noise in diffusive ferromagnetic wires with tunnel contacts can reveal intrinsic and extrinsic spin-polarization effects, especially under different electrode polarization configurations and spin-flip scattering conditions.

Contribution

It demonstrates that shot noise measurements can distinguish between density of states and impurity scattering contributions to spin-polarization in ferromagnetic conductors.

Findings

Shot noise is more sensitive to density of states polarization when electrodes are oppositely polarized.

Spin-flip scattering increases shot noise, reaching Poissonian levels with full polarization.

Shot noise depends on the relative sign of intrinsic and extrinsic polarizations in parallel configurations.

Abstract

We show that shot noise in a diffusive ferromagnetic wire connected by tunnel contacts to two ferromagnetic electrodes can probe the intrinsic density of states and the extrinsic impurity scattering spin-polarization contributions in the polarization of the wire conductivity. The effect is more pronounced when the electrodes are perfectly polarized in opposite directions. While in this case the shot noise has a weak dependence on the impurity scattering polarization, it is strongly affected by the polarization of the density of states. For a finite spin-flip scattering rate the shot noise increases well above the normal state value and can reach the full Poissonian value when the density of states tends to be perfectly polarized. For the parallel configuration we find that the shot noise depends on the relative sign of the intrinsic and the extrinsic polarizations.