Giant Anomalous Nernst Effect in Nodal Web Ferromagnets Fe₃<i>X</i> (<i>X</i> = Ga, Al)

Recently, large anomalous Hall effect (AHE) and anomalous Nernst effect (ANE) have been reported in topological magnets, where the large Berry curvature is induced by characteristic band crossings so-called Weyl points and nodal lines [1-4]. For example, Weyl ferromagnet Co₂MnGa shows a large ANE ~6 μV/K at room temperature (T) [5]. This enables us to study thermoelectric applications by ANE, which has great potential such as efficient and flexible coverage of a heat source. For this purpose, substantial improvements are still necessary not only for the performance but also for the associated material costs, safety, and stability.

In this talk, we will present the newly discovered topological magnet Fe₃X (X = Ga, Al) [6]. ANE for Fe₃Ga and Fe₃Al reaches ~5.5 μV/K and ~4 μV/K at room T, respectively. The transverse thermoelectric coefficient α_xy reaches the record high value ~5.2 A/(Km) in Fe₃Ga at ~200 K, originating from the nodal web structure near L point.

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[2] N. Kiyohara et al., Phys. Rev. Applied 5, 064009 (2016).
[3] K. Kuroda, T. Tomita et al., Nat. Mater. 16, 1090 (2017).
[4] M. Ikhlas et al., Nat. Phys. 13, 1085 (2017).
[5] A. Sakai et al., Nat. Phys. 14, 1119 (2018).
[6] A. Sakai et al., Nature 581, 53 (2020).