Spin-orbit torques driven by the interface-generated spin currents

TL;DR

This paper investigates spin-orbit torques in Ru/Fe heterostructures, demonstrating effective spin current generation despite a smaller spin Hall angle, and highlights the influence of interface conductivity on spin current efficiency.

Contribution

It introduces a new method for generating spin currents in ferromagnet/nonmagnetic metal bilayers, expanding understanding of spin dynamics and transport mechanisms.

Findings

Reversible SOT observed in Ru/Fe heterostructures.

Effective spin Hall angle in Ru/Fe compared with Pt.

Spin current driven by interface depends on electrical conductivity.

Abstract

The spin currents generated by spin-orbit coupling (SOC) in the nonmagnetic metal layer or at the interface with broken inversion symmetry are of particular interest and importance. Here, we have explored the spin current generation mechanisms through the spin-orbit torques (SOTs) measurements in the Ru/Fe heterostructures with weak perpendicular magnetic anisotropy (PMA). Although the spin Hall angle (SHA) of Ru is smaller than that in Pt, Ta or W, reversible SOT in Ru/Fe heterostructures can still be realized. Through non-adiabatic harmonic Hall voltage measurements and macrospin simulation, the effective SHA in Ru/Fe heterostructures is compared with Pt. Moreover, we also explore that the spin current driven by interface strongly depends on the electrical conductivities. Our results suggest a new method for efficiently generating finite spin currents in ferromagnet/nonmagnetic metal bilayers, which establishes new opportunities for fundamental study of spin dynamics and transport in ferromagnetic systems.