Interface-Generated Spin Currents

TLDR

Spin polarization at interfaces is controlled by, but not aligned with, the magnetization, enabling a novel mechanism for generating spin torques in magnetic trilayers. Transport calculations show that Co/Pt, Co/Cu, and Pt/Cu interfaces generate large spin currents driven by in‑plane electric fields, with polarizations along \( \hat{z}\times\mathbf{E}\) and, for Co interfaces, also along \( \hat{m}\times(\hat{z}\times\mathbf{E})\), comparable in magnitude to bulk Pt spin‑Hall currents.

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 z[over ^]×E, where z[over ^] is the interface normal and E denotes the electric field. The Co/Cu and Co/Pt interfaces additionally generate spin currents with polarization along m[over ^]×(z[over ^]×E), where m[over ^] 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.