Giant and Robust Anomalous Nernst Effect in a Polycrystalline Topological Ferromagnet at Room Temperature

Abstract Recent discoveries of the topological magnets have opened a new path for developing a much simpler thermoelectric conversion module using the anomalous Nernst effect (ANE). To accelerate such innovation, it is essential to design materials suitable for industrial processes, and thus a high‐ANE polycrystalline material has been highly desired. Recently, the giant room‐temperature ANE has been reported in single crystals of the topological ferromagnet Fe₃Ga. Owning to its cubic structure, the anomalous Hall effect and ANE are isotropic. These properties potentially allow to employ a polycrystalline form of the material to design an ANE‐based thermopile. Here, a giant and robust room‐temperature ANE in the polycrystalline Fe_xGa_4−x (2.96 < x < 3.15) is reported, which can be enhanced up to 5.4 µV K⁻¹; this value hits the highest room‐temperature record for polycrystalline magnets. Comparison of the experimental results with the theoretical study of the Fe‐doping effect on the transport properties of Fe_xGa_4−x reveals that the Fermi energy tuning near the topological nodal‐web structure is the key to enhancing the ANE. Moreover, the large value of more than 5.1 µV K⁻¹ is observed for an extended region of composition, confirming the robust characteristics of the topological electronic structure.