Anomalous Nernst effect in honeycomb and kagome magnet LaCo5 at room temperature

Magnetic order-induced time reversal symmetry breaking in the kagome lattice is predicted to generate Weyl semimetal and Chern insulating phases. The two-dimensional (2D) honeycomb lattices with spin orbit coupling (SOC) and ferromagnetism are also known to host the Chern insulating phase. Here, we study the transport properties of the ferromagnetic topological material LaCo5 crystals with TC = 840 K, which is the highest among the reported magnetic topological materials up to now. It is composed of 2D Co2 kagome layers that are separated by La-Co1 layers, in which the Co1 atoms exhibit a honeycomb structure. Both the 2D kagome and honeycomb layers exhibit out-of-plane magnetization. The large intrinsic anomalous Hall effect and anomalous Nernst effect of about 4.6 mu VK-1 are observed in the ab plane with the B//c configuration at room temperature, which can be attributed to non-zero Berry curvature according to the first-principles calculations. Our results enrich the magnetic topological materials with honeycomb and kagome lattices, providing a good platform for the further study of the QAHE. The excellent thermoelectric performance, high TC, nontoxicity, and low cost also make LaCo5 a promising candidate for the applications of thermoelectric generators and heat flow sensors at high temperatures.

Automated summary

Predicted magnetic order-induced time reversal symmetry breaking in the kagome lattice can generate Weyl semimetal and Chern insulating phases. Honeycomb lattices with spin orbit coupling (SOC) and ferromagnetism are also known to host the Chern insulating phase. In this study, the transport properties of the ferromagnetic topological material LaCo5 crystals with TC = 840 K were investigated, and it was found to have the highest TC among reported magnetic topological materials. LaCo5 is composed of 2D Co2 kagome layers separated by La-Co1 layers with a honeycomb structure. Both the kagome and honeycomb layers exhibit out-of-plane magnetization. The large intrinsic anomalous Hall effect and anomalous Nernst effect observed in the ab plane at room temperature can be attributed to non-zero Berry curvature according to first-principles calculations. The results of this study enrich the understanding of magnetic topological materials with honeycomb and kagome lattices and provide a good platform for further study of the quantum anomalous Hall effect (QAHE). The excellent thermoelectric performance, high TC, nontoxicity, and low cost also make LaCo5 a promising candidate for applications in thermoelectric generators and heat flow sensors at high temperatures.