Enhancing Spin-Orbit Torque by Strong Interfacial Scattering From Ultrathin Insertion Layers

Increasing dampinglike spin-orbit torque (SOT) is of fundamental importance for enabling new research into spintronics phenomena and also technologically urgent for advancing low-power spin-torque memory, logic, and oscillator devices. Here, we demonstrate that enhancing interfacial scattering by inserting ultrathin layers within spin Hall metals with intrinsic or side jump mechanisms can significantly enhance the spin Hall ratio. The dampinglike SOT is enhanced by a factor of 2 via submonolayer Hf insertion, as evidenced by both harmonic response measurements and current-induced switching of in-plane magnetized magnetic memory devices with the record low critical switching current of approximately 73 mu A (switching current density of approximately 3.6 x 10(6) A/cm(2)). This work demonstrates a very effective strategy for maximizing dampinglike SOT for low-power spin-torque devices.