Interface-generated spin currents

TL;DR

This paper demonstrates that interfaces in certain metal heterostructures generate significant out-of-plane spin currents driven by in-plane electric fields, offering a new mechanism for spin torque control in magnetic devices.

Contribution

The study reveals that interface-generated spin currents can be comparable to bulk spin Hall effects and introduces a novel spin polarization mechanism controlled by magnetization.

Findings

Large interface-generated spin currents at Co/Pt, Co/Cu, and Pt/Cu interfaces.

Spin currents flow out-of-plane with polarization along dcd d7 deE.

Additional spin polarization controlled by magnetization in magnetic trilayers.

Abstract

Transport calculations based on ab-initio band structures reveal large interface-generated spin currents at Co/Pt, Co/Cu, and Pt/Cu interfaces. These spin currents are driven by in-plane electric fields but flow out-of-plane, and can have similar strengths to spin currents generated by the spin Hall effect in bulk Pt. Each interface generates spin currents with polarization along $\bf{\hat{z}} \times \bf{E}$, where $\bf{\hat{z}}$ is the interface normal and $\bf{E}$ denotes the electric field. The Co/Cu and Co/Pt interfaces additionally generate spin currents with polarization along $\bf{\hat{m}} \times (\bf{\hat{z}} \times \bf{E})$, where $\bf{\hat{m}}$ gives the magnetization direction of Co. The latter spin polarization is controlled by---but not aligned with---the magnetization, providing a novel mechanism for generating spin torques in magnetic trilayers.