Large Damping-like Spin-Orbit Torque and Improved Device Performance Utilizing Mixed-Phase Ta

The beta phase of Ta is known to exhibit higher spin Hall efficiency compared to other heavy metals such as Pt. However, the larger resistivity of beta-phase Ta leads to higher power consumption for spin-orbit torque (SOT)-based devices. In this work, we measure the efficiency of damping-like torque and field-like torque in Ni80Fe20/Ta using spin-torque ferromagnetic resonance technique. We report a larger damping-like torque efficiency of -(0.52 +/- 0.01) for Ni80Fe20/Ta with low-resistive mixed (alpha + beta)-phase Ta, which is about 40% larger compared to beta-phase Ta. The field-like torque efficiency is found to be lower (by approximate to 400%) and of opposite sign compared to beta-phase Ta. The estimated power consumption is found to be lower in the mixed-phase Ta system compared to the beta-phase Ta as well as some Pt-based systems. Using micromagnetic simulations, we show that the measured values of damping-like torque and field-like torque for mixed-phase Ta lead to improved device performance, namely, (i) a lower switching time in a nanopillar-based SOT device and (ii) improved phase noise in a nanoconstriction-based spin Hall nano-oscillator.

Automated summary

The study compares the spin Hall efficiency, damping-like torque efficiency, and field-like torque efficiency in Ni80Fe20/Ta with mixed-phase Ta and beta-phase Ta. The results show that the mixed-phase Ta has higher damping-like torque efficiency, lower field-like torque efficiency, and lower power consumption compared to beta-phase Ta.