Large anomalous Nernst effect in polycrystalline thin films of the Weyl ferromagnet Co₂MnGa

Recent discoveries of topological magnets have opened up diverse spintronic applications of their large responses beyond magnetization scaling observed in conventional ferromagnets. A prominent example is the anomalous Nernst effect (ANE), a transverse magneto-thermoelectric phenomenon that produces an electromotive force orthogonal to the heat flux and magnetization. Unlike the Seebeck effect (SE) generating an electromotive force parallel to the heat flux, transverse thermoelectric properties of ANE well fit in the lateral configurations of devices fabricated through conventional thin-film fabrication processes. This feature enables distinct device applications through a simplified fabrication process, reduced production cost, extensive area coverage, and enhanced flexibility. In this study, we report the highest ANE ever recorded among all reported polycrystalline films to date by using a topological ferromagnet. In particular, we have successfully fabricated high-quality polycrystalline thin films of the Weyl ferromagnet Co₂MnGa that exhibit a large ANE of more than 5 μV/K. By retaining a high film density, we demonstrate the sizable ANE in the films obtained using a simple fabrication process well-suited for device developments. Establishing a thin-film fabrication technique capable of producing a giant ANE facilitates spintronic applications of the Weyl ferromagnet, including diverse ANE-based device applications.