Determination of spin Hall angle in the Weyl ferromagnet Co2MnGa by taking into account the thermoelectric contributions

The spin Hall effects of various materials, including Weyl semimetals, have been studied by the spin absorption method with the nonlocal spin valve structures. Here, we study ${\mathrm{Co}}₂\mathrm{MnGa}$ (CMG) by using the standard spin absorption method. A considerable amount of thermoelectric signal superimposes on the inverse spin Hall signal in the measurement configuration: the applied electric current between the spin injector (permalloy) and bridge (copper) wires produces heating or cooling at the interface via the Peltier effect, which causes an out-of-plane temperature gradient in CMG. As a result, a voltage signal induced by the anomalous Nernst effect (ANE) of CMG comes into the inverse spin Hall signal. We quantitatively separate these signals by combining the experiment and a numerical simulation. About 75% of the detected signal is found attributable to the thermoelectric effects. The superposing thermoelectric contribution is a general and unavoidable problem in this method when the spin Hall materials exhibit ANE. After eliminating the thermoelectric signal, the spin Hall angle of CMG turns out to be $\ensuremath{\theta}=\ensuremath{-}0.09$ at room temperature.