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Spin orbit torque (SOT) is an essential ingredient in spintronics owing to its low switching current and short switching time of a few nanoseconds. [1-2] The efficiency of SOT is commonly quantified by a spin Hall angle (\theta_{SH}), which is a ratio of spin Hall conductivity to charge conductivity. To enhance \theta_{SH}, large spin Hall conductivity is needed. In this context, β-tungsten in A15 structure has attracted attention due to large spin Hall conductivity (σxy) and spin Hall angle (\theta_{SH}). β-tungsten reaches up to -0.4, [1-2] higher than 0.10 of Pt. [3] So far, enhancements of σxy are found in many β-tungsten alloys: W-Si, W-N, W-Ti. [5-10] Here, we investigate spin Hall conductivities of W1-xMox alloys using first-principles calculations. Overall, W1-xMox alloys show enhanced σxy over β-tungsten with a particularly large value of -1857 S/cm at x = 12.5%. To clarify the origin of σxy, we analyze the Berry curvature (\mathrm{\Omega}{xy}) with band resolved contributions in Brillouin zone. We found that the increase in {|\mathrm{\Omega}}{xy}| leads to the enhancement of σxy in the W1-xMox alloys. Moreover, the enhancement σxy is due to the dominant contribution of \mathrm{\Omega}{xy}<0, particularly along XM, ΓM, and RX. At higher doping concentration (x = 25, 50 %), lower symmetry leads to pronounced degeneracy lifting, causing signs of Berry curvature oscillate, where \mathrm{\Omega}{xy}>0 compensate \mathrm{\Omega}_{xy}<0.
[1] G. W. Kim et al., NPG Asia Mater. 13(1), 1 (2021).
[2] C. Safeer et al., Nat. Nanotechnol. 11, 143 (2016).
[3] Q. Hao and G. Xiao, Phys. Rev. Appl. 3, 034009 (2015).
[4] C.-F. Pai et al., Appl. Phys. Lett. 101, 122404 (2012).
[5] O. Mosendz et al., Phys. Rev. Lett. 104, 046601 (2010).
[6] Taehyun Kim et al., Appl. Surf. Sci. 609, 155352 (2023).
[7] Quynh Anh T. Nguyen et al., J.Magn. 29(2), 155-159 (2024).
[9] Quynh Anh T. Nguyen et al., Phys. Rev. B 112, 134401 (2025).
[10] Jiyoung Lee et al., Appl. Surf. Sci. 682, 161671 (2025).
