Large anomalous Nernst effect and nodal plane in an iron-based kagome ferromagnet

Anomalous Nernst effect (ANE), converting a heat flow to transverse electric voltage, originates from the Berry phase of electronic wave function near the Fermi energy EF. Thus, the ANE provides a sensitive probe to detect a topological state that produces large Berry curvature. In addition, a magnet that exhibits a large ANE using low-cost and safe elements will be useful to develop a novel energy harvesting technology. Here, we report our observation of a high ANE exceeding 3 microvolts per kelvin above room temperature in the kagome ferromagnet Fe3Sn with the Curie temperature of 760 kelvin. Our theoretical analysis clarifies that a nodal plane produces a flat hexagonal frame with strongly enhanced Berry curvature, resulting in the large ANE. Our discovery of the large ANE in Fe3Sn opens the path for the previously unexplored functionality of flat degenerate electronic states and for developing flexible film thermopile and heat current sensors.

Automated summary

The anomalous Nernst effect (ANE), which converts heat flow into transverse electric voltage, is caused by the Berry phase of the electronic wave function near the Fermi energy EF. Therefore, it can be used as a sensitive probe to detect a topological state with large Berry curvature. In this study, we observe a high ANE exceeding 3 microvolts per kelvin above room temperature in the kagome ferromagnet Fe3Sn with a Curie temperature of 760 kelvin. The large ANE is a result of a nodal plane that produces a flat hexagonal frame with strongly enhanced Berry curvature. Our discovery of the large ANE in Fe3Sn opens up possibilities for exploring the functionality of flat degenerate electronic states and developing flexible film thermopiles and heat current sensors.