Giant anomalous Nernst signal in the antiferromagnet YbMnBi2

TL;DR

YbMnBi2, a canted antiferromagnet with low magnetization, exhibits an exceptionally large anomalous Nernst effect, surpassing ferromagnets, due to its unique spin structure, strong spin-orbit coupling, and dispersive orbitals, making it promising for thermoelectric applications.

Contribution

This work demonstrates that YbMnBi2 achieves a large anomalous Nernst effect with minimal magnetization, offering a new pathway for efficient thermoelectric materials.

Findings

YbMnBi2 has an ANE conductivity of ~10 Am-1K-1.

The material's weak magnetization reduces magnetic disturbances.

High ANE performance is linked to spin-orbit coupling and orbital dispersion.

Abstract

Searching for a high anomalous Nernst effect (ANE) is crucial for thermoelectric energy conversion applications because the associated unique transverse geometry facilitates module fabrication. Topological ferromagnets with large Berry curvatures show high ANEs; however, they face drawbacks such as strong magnetic disturbances and low mobility due to high magnetization. Herein, we demonstrate that YbMnBi2, a canted antiferromagnet, has a large ANE conductivity of ~10 Am-1K-1 that surpasses the common high values (i.e. 3-5 Am-1K-1) observed so far in ferromagnets. The canted spin structure of Mn guarantees a nonzero Berry curvature but generates only a weak magnetization three orders of magnitude lower than that of general ferromagnets. The heavy Bi with a large spin-orbit coupling enables a high ANE and low thermal conductivity, whereas its highly dispersive px/y orbitals ensure low resistivity. The high anomalous transverse thermoelectric performance and extremely small magnetization makes YbMnBi2 an excellent candidate for transverse thermoelectrics.