Tunable Spin-Orbit Torques in Cu-Ta Binary Alloy Heterostructures

Abstract

The spin Hall effect (SHE) is found to be strong in heavy transition metals (HM), such as Ta and W, in their amorphous and/or high resistivity form. In this work, we show that by employing a Cu-Ta binary alloy as buffer layer in an amorphous Cu${}_{100-x}$Ta${}_x$-based magnetic heterostructure with perpendicular magnetic anisotropy (PMA), the SHE-induced damping-like spin-orbit torque (DL-SOT) efficiency $|{\xi }_{DL}|$ can be linearly tuned by adjusting the buffer layer resistivity. Current-induced SOT switching can also be achieved in these Cu${}_{100-x}$Ta${}_x$-based magnetic heterostructures, and we find the switching behavior better explained by a SOT-assisted domain wall propagation picture. Through systematic studies on Cu${}_{100-x}$Ta${}_x$-based samples with various compositions, we determine the lower bound of spin Hall conductivity $|{\sigma }_{SH}|\approx 2.02\times 10^4[\hslash /2e]{\Omega }^{-1}\cdot m^{-1}$ in the Ta-rich regime. Based on the idea of resistivity tuning, we further demonstrate that $|{\xi }_{DL}|$ can be enhanced from 0.087 for pure Ta to 0.152 by employing a resistive TaN buffer layer.

References in corpus (2)

• Study of Intrinsic Spin Hall Effect and Orbital Hall Effect in 4d- and 5d- Transition Metals
• Enhancement of the Anti-Damping Spin Torque Efficacy of Platinum by Interface Modification

Cited by in corpus (1)

• A Comparative Study on Spin-Orbit Torque Efficiencies from W/ferromagnetic and W/ferrimagnetic Heterostructures