# Backflow Effect on Spin Diffusion Near Ferromagnet-Superconductor Interface

## TL;DR

This paper investigates how the backflow effect influences spin diffusion measurements near ferromagnet-superconductor interfaces, revealing that accounting for backflow significantly increases the estimated spin diffusion length in gold.

## Contribution

It introduces an experimental approach using Andreev contacts to probe backflow effects on spin diffusion near ferromagnet-superconductor interfaces, providing more accurate measurements.

## Key findings

- Spin diffusion length in Au is 285 nm when considering backflow.
- Backflow effect causes underestimation of spin diffusion length if neglected.
- Results align with a gradual decay of spin polarization with film thickness.

## Abstract

The behavior of spin propagation in metals in various measurement schemes is shown to be qualitatively different than a simple exponential decay - due to the backflow effect on spin diffusion in the presence of interfaces. To probe this effect we utilize the spin sensitivity of an Andreev contact between gold films of variable thickness deposited on top of a spin injector, Co$_{2}$Mn$_{0.5}$Fe$_{0.5}$Si, with the spin polarization of approximately 45\%, and Nb superconducting tip. While the results are consistent with gradually decaying spin polarization as the film thickness increases, the spin diffusion length in Au found to be 285 nm, is more than two times larger that one would have obtained without taking the backflow effect into account.