Tunable Spin Hall Effect from a Ta Alloy System
Chen Tian-Yue1*, Pai Chi-Feng1
1Material Science and Engineering, National Taiwan University, Taipei, Taiwan
* Presenter:Chen Tian-Yue
The spin Hall effect from heavy transition metals is an efficient mechanism to generate spin current and therefore spin-orbit torque (SOT) to control magnetization in heavy metal/ferromagnetic metal (HM/FM) bilayer structures. Previous study has shown that the spin Hall ratio in Pt is proportional to the resistivity therein, which can be controlled by the sputtered Pt film thickness. In this work, we study the correlation between Ta resistivity and its spin Hall ratio with the spin Hall material thickness fixed.
In order to tune the resistivity, we introduce conductive metallic elements as dopants to decrease the effective resistivity of the Ta-dopant alloying layer. We perform the SOT-assisted hysteresis loop shift measurements to characterize SOT efficiencies of Ta alloy magnetic heterostructures with various dopant concentrations. Our preliminary discovery shows that the damping-like SOT efficiencies from Ta (alloy) systems are linearly proportional to the effective resistivity. Current-induced SOT switching can also be achieved in the lower resistivity regime. Our work indicates that a precise tuning of spin Hall ratio and SOT efficiency in SOT-MRAM devices can be achieved by a simple alloying/doping process.

Keywords: Spintronics, spin Hall effect, spin-orbit torque