Magneto-thermoelectric effect in lanthanum orthoferrite with Pt overlayer*

Spin caloritronic phenomena, utilizing heat flow to transport spin signals with minimal or no charge current, are of fundamental interest with important applications. We have observed nontrivial magneto-thermoelectric effects in lanthanum orthoferrite (LaFeO₃) perovskite single crystals with Pt overlayer at room temperature. The LaFeO₃ is a canted antiferromagnetic insulator with weak magnetization of about 0.04 μ_B per Fe atom along the c-axis, which is only 1% of that of the common ferromagnet iron. The amplitude of magneto-thermovoltage in the Pt/LaFeO₃ with an in-plane temperature gradient is comparable to those of the longitudinal spin Seebeck effect and inverse spin Hall effect in Pt/yttrium iron garnet. It provides a sensitive probe of very weak magnetization in the insulator, which can be manipulated by a magnetic field of the order of 10 mT. However, from the thermoelectric measurement configurations and the angular dependence on the applied magnetic field, our results are distinctly different from those of the anomalous Nernst effect and longitudinal spin Seebeck effect. We attribute our results to a thermal magnon transport at the Pt/LaFeO₃ interface.