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

摘要

Recent discoveries of the topological magnets have opened a new path fordeveloping a much simpler thermoelectric conversion module using theanomalous Nernst effect (ANE). To accelerate such innovation, it is essentialto design materials suitable for industrial processes, and thus a high-ANEpolycrystalline material has been highly desired. Recently, the giant roomtemperatureANE has been reported in single crystals of the topologicalferromagnet Fe_3Ga. Owning to its cubic structure, the anomalous Hall effectand ANE are isotropic. These properties potentially allow to employ a polycrystallineform 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); thisvalue hits the highest room-temperature record for polycrystalline magnets.Comparison of the experimental results with the theoretical study ofthe Fe-doping effect on the transport properties of Fe_xGa_(4?x) reveals that theFermi energy tuning near the topological nodal-web structure is the key toenhancing the ANE. Moreover, the large value of more than 5.1 μV K~(?1) isobserved for an extended region of composition, confirming the robust characteristicsof the topological electronic structure.