Tunable spin-orbit torque in Cu-Ta binary alloy heterostructures
Journal
Physical Review B
Journal Volume
96
Journal Issue
10
Date Issued
2017
Author(s)
Abstract
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 Cu100-xTax-based magnetic heterostructure with perpendicular magnetic anisotropy, the SHE-induced dampinglike spin-orbit torque (DL-SOT) efficiency |ξDL| can be tuned linearly by adjusting the buffer layer resistivity. Current-induced SOT switching can also be achieved in these Cu100-xTax-based magnetic heterostructures, and we find the switching behavior better explained by a SOT-assisted domain-wall propagation picture. Through systematic studies on Cu100-xTax-based samples with various compositions, we determine the lower bound of spin-Hall conductivity |σSH|≈2.02×104[/2e]Ω-1m-1 in the Ta-rich regime. Based on the idea of resistivity tuning, we further demonstrate that |ξDL| can be enhanced from 0.087 for pure Ta to 0.152 by employing a resistive TaN buffer layer.
Type
journal article