A temperature gradient in a ferromagnetic conductor can generate a transverse voltage drop perpendicular to both the magnetization and heat current. This anomalous Nernst effect has been considered to be proportional to the magnetization, and thus observed only in ferromagnets. Theoretically, however, the anomalous Nernst effect provides a measure of the Berry curvature at the Fermi energy, and so may be seen in magnets with no net magnetization. Here, we report the observation of a large anomalous Nernst effect in the chiral antiferromagnet Mn 3 Sn (ref.). Despite a very small magnetization 1/40.002 μ B per Mn, the transverse Seebeck coefficient at zero magnetic field is 1/40.35 μV K '1 at room temperature and reaches 1/40.6 μV K '1 at 200 K, which is comparable to the maximum value known for a ferromagnetic metal. Our first-principles calculations reveal that this arises from a significantly enhanced Berry curvature associated with Weyl points near the Fermi energy. As this effect is geometrically convenient for thermoelectric power generation - it enables a lateral configuration of modules to cover a heat source - these observations suggest that a new class of thermoelectric materials could be developed that exploit topological magnets to fabricate efficient, densely integrated thermopiles.
ASJC Scopus subject areas
- Physics and Astronomy(all)