Large enhancement in anomalous Nernst effect of the iron-based binary ferromagnet Fe3Ga through trace doping of the rare-earth element Ho

Magnetic topological materials exhibit large intrinsic anomalous Nernst effect (ANE) driven by Berry curvature near the Fermi surface, having great potential in manufacturing transverse thermoelectric devices for converting waste heat into electricity. However, candidate topological magnets with large anomalous Nernst thermopower, S_yx, remain rare. Moreover, it is extremely challenging to maximize the ANE for a given topological magnet because of their large and complex Fermi surfaces. Herein, we report a significant enhancement of ANE in an iron-based binary topological ferromagnet by trace doping of a rare-earth element. Through 0.3 at.% Ho doping, the room temperature S_yx of Fe₃Ga is raised remarkably from 3.6 μVK^-1 to 5.2 μVK^-1, an enhancement of approximately 44%, in addition to a large increase of approximately 60 K in the Curie temperature. Microstructure investigations reveal that the doping decreases the lattice parameter as well as the grain sizes, which also induces nanoprecipitates of Ga-enriched modified D0_-3 structure into the D0_-3 matrix. Density functional theory (DFT) calculations reveal that combined effects of Fermi-level shifting induced by Ga vacancies in the primary D0_-3 phase and the increased number of Berry curvature sources due to the reduced symmetry underlying the large enhancement in ANE. Our findings demonstrate a universal and effective approach for giant improvement of the ANE in Fe_-3X (X = Ga, Al, Pt, Sn, Si) topological materials, opening avenues for designing high-performance transverse thermoelectric devices for practical applications.