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

• Received 26 July 2017
• Revised 11 September 2017

DOI:https://doi.org/10.1103/PhysRevB.96.104434