Enhancement of spin Hall conductivity in W-Ta alloy

TL;DR

This study demonstrates that alloying tungsten with tantalum enhances the spin Hall conductivity and reduces resistivity, leading to more efficient and power-saving spin current generation in spintronic devices.

Contribution

It reports the enhancement of spin Hall conductivity in W-Ta alloys, showing a significant increase in spin Hall angle and reduction in resistivity at specific compositions.

Findings

Spin Hall angle increased to -0.3 at 11% Ta

Resistivity decreased to 100 μΩ·cm at optimal alloy composition

W-Ta alloys enable low-power spin current generation

Abstract

Generating pure spin currents via the spin Hall effect in heavy metals has been an active topic of research in the last decade. In order to reduce the energy required to efficiently switch neighbouring ferromagnetic layers for applications, one should not only increase the charge- to-spin conversion efficiency but also decrease the longitudinal resistivity of the heavy metal. In this work, we investigate the spin Hall conductivity in W_{1-x}Ta_{x} / CoFeB / MgO (x = 0 - 0.2) using spin torque ferromagnetic resonance measurements. Alloying W with Ta leads to a factor of two change in both the damping-like effective spin Hall angle (from - 0.15 to - 0.3) and longitudinal resistivity (60 - 120 {\mu}W cm). At 11% Ta concentration, a remarkably high spin Hall angle value of - 0.3 is achieved with a low longitudinal resistivity 100 {\mu}W cm, which could lead to a very low power consumption for this W-based alloy. This work demonstrates sputter-deposited W-Ta alloys could be a promising material for power-efficient spin current generation.