Spin hydrodynamic generation (SHDG) is a method used to generate an electric voltage via a spin current, which is caused by coupling between the mechanical angular momentum of fluid rotation, vorticity, and electron spin. Since a 2016 report by Takahashi et al. about SHDG with mercury ($\mathrm{Hg}$), SHDG has attracted attention in many fields including spintronics and fluid dynamics. SHDG is characterized by a product of three parameters, i.e., the spin-diffusion length, the spin Hall angle, and an additional viscosity caused by the interaction between the spin current and the vorticity. To move SHDG research out of its infancy, it is necessary to reveal the physical properties of its parameter product. Here, we apply SHDG to gallium ($\mathrm{Ga}$), whose spin-orbit interaction is known to be weaker than that of $\mathrm{Hg}$. The results demonstrate that the parameter product of $\mathrm{Ga}$ is larger than that of $\mathrm{Hg}$, indicating that the additional viscosity caused by SHDG shows little dependence on the spin-orbit interaction. Our measurements also show no notable dependence on temperature, suggesting that the additional viscosity is less influenced by Newtonian fluid viscosity, which changes markedly in the temperature range that we use. These results can provide a general guideline in the search for materials that are suitable for SHDG. In addition, the insensitivity to environmental temperature variations could be useful in a variety of applications.

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• Inverse spin Hall effect
• Magnetohydrodynamics
• Spin current
• Spin diffusion
• Spin-orbit coupling
• Spintronics
• Elemental metals
• Liquid metals