Increasing dampinglike spin-orbit torque (SOT) is both 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 ultra-thin layers within a spin Hall metals with intrinsic or side-jump mechanisms can significantly enhance the spin Hall ratio. The dampinglike SOT was enhanced by a factor of 2 via sub-monolayer 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 ~73 uA (switching current density of 3.6x10^6 A/cm^2). This work demonstrates a very effective strategy for maximizing dampinglike SOT for low-power spin-torque devices.
@article{arxiv.1904.07800,
title = {Enhancing spin-orbit torque by strong interfacial scattering from ultra-thin insertion layers},
author = {Lijun Zhu and Lujun Zhu and Shengjie Shi and Manling Sui and D. C. Ralph and R. A. Buhrman},
journal= {arXiv preprint arXiv:1904.07800},
year = {2019}
}