Dependence of the Efficiency of Spin Hall Torque on the Transparency of Pt-Ferromagnetic Layer Interfaces

TL;DR

This study investigates how the efficiency of spin Hall torque in Pt-ferromagnet interfaces varies with interface properties, layer thickness, and processing, highlighting the importance of interface engineering for spintronic device performance.

Contribution

It demonstrates the strong dependence of spin current transport on interface conditions and provides quantitative estimates of spin Hall angles considering interfacial effects.

Findings

Spin Hall torque efficiency varies from <0.05 to >0.10 with interface conditions.

Temperature dependence of spin torque efficiencies is interface-dependent.

Estimated internal spin Hall angle of Pt is ~0.20 after accounting for interfacial transmission.

Abstract

We report that spin current transport across Pt-ferromagnet (FM) interfaces is strongly dependent on the type and the thickness of the FM layer and on post-deposition processing protocols. By employing both harmonic voltage measurements and spin-torque ferromagnetic resonance measurements, we find that the efficiency of the Pt spin Hall effect in exerting a damping-like spin torque on the FM ranges from < 0.05 to > 0.10 under different interfacial conditions. We also show that the temperature dependence of the spin torque efficiencies for both the damping-like torque and field-like torque is dependent upon the details of the Pt-FM interface. The "internal" spin Hall angle of the Pt thin films used in this study, after taking the interfacial spin transmission factor into account, is estimated to be ~ 0.20. This suggests that a careful engineering of Pt-FM interfaces can improve the spin-Hall-torque efficiency of Pt-based spintronic devices.