Large anomalous Nernst effect at room temperature in a chiral antiferromagnet

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(1- 7), and thus observed only in ferromagnets. Theoretically, however, the anomalous Nernst effect provides a measure of the Berry curvature at the Fermi energy(8,9), 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 Mn3Sn (ref. 10). Despite a very small magnetization similar to 0.002 mu(B) per Mn, the transverse Seebeck coeffcient at zero magnetic field is similar to 0.35 mu VK-1 at room temperature and reaches similar to 0.6 mu VK-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(11). As this effect is geometrically convenient for thermoelectric power geceration-it enables a lateral configuration of modules to cover a heat source6-these observations suggest that a new class of thermoelectric materials could be developed that exploit topological magnets to fabricate effcient, densely integrated thermopiles.