Spin Hall effect in the high-resistivity high-entropy alloy AlCrMoW

Abstract

We study thin films of the high-entropy alloy system Al${}_x$(CrMoW)${}_{1-x}$, grown on Ta seed layers by magnetron co-sputtering. Between $x=0.2$ and $x=0.6$, a resistivity larger than 100$\mu \Omega$cm is achieved, with a peak of 180$\mu \Omega$cm at $x=0.5$. Around the stoichiometric composition AlCrMoW, the alloy forms a bcc solid solution. The harmonic Hall method was used to characterize the spin Hall angle of the alloy series, where a maximum spin Hall angle of $\theta =-0.12\pm 0.01$ is observed for $x=0.25$. The implied spin Hall conductivity is ${\sigma }_{\mathrm{SH}}\approx -72000\hslash /(2e)$\,S/m. The experimental results show excellent agreement with density functional theory calculations, which show similar trends and values. The results demonstrate that high-entropy alloys with a main-group element component can form a simple crystal structure and show high resistivity. This suggests that a whole new class of materials for spin Hall device engineering is available with simple methods.

6 pages, 3 figures