Theory of spin loss at metallic interfaces

TL;DR

This paper develops a theoretical framework linking interfacial spin-flip scattering parameters to microscopic transmission and reflection probabilities, validated by first-principles calculations for Cu/Pd interfaces.

Contribution

It introduces a generalized circuit theory connecting the spin-loss parameter to microscopic scattering probabilities at metallic interfaces.

Findings

The parameter δ is proportional to the square root of spin-flip scattering probability.

First-principles calculations of Cu/Pd interfaces agree with experimental δ values.

Derived relations improve understanding of spin loss in magnetoelectronic devices.

Abstract

Interfacial spin-flip scattering plays an important role in magnetoelectronic devices. Spin loss at metallic interfaces is usually quantified by matching the magnetoresistance data for multilayers to the Valet-Fert model, while treating each interface as a fictitious bulk layer whose thickness is $\delta$ times the spin-diffusion length. By employing the properly generalized circuit theory and the scattering matrix approaches, we derive the relation of the parameter $\delta$ to the spin-flip transmission and reflection probabilities at an individual interface. It is found that $\delta$ is proportional to the square root of the probability of spin-flip scattering. We calculate the spin-flip transmission probability for flat and rough Cu/Pd interfaces using the Landauer-B\"uttiker method based on the first-principles electronic structure and find $\delta$ in reasonable agreement with experiment.