Anomalous Nernst thermopile made of a single element iron

Abstract

Anomalous Nernst thermopiles that utilize spin–orbit coupling in magnetic materials are beneficial for energy harvesting. Under an out-of-plane temperature gradient, the thermopiles can generate sizable and scalable thermoelectric voltages due to the anomalous Nernst effect (ANE). In this work, we show that a thermopile made of only one element, Iron (Fe), can generate a significant spin-dependent thermoelectric signal. We find that by varying the thickness of Fe, the anomalous Nernst signal changes sign and becomes exceptionally large in the thinner-thickness region. As a result, the anomalous Nernst thermopile consisting of only Fe exhibits a sizable thermoelectric signal. Moreover, the plateau behavior in the thermopile owing to the sequential flipping of magnetic moments demonstrates that the ANE could serve as a sensitive tool to detect magnetic switching. The multi-level ANE signals further indicate the anomalous Nernst thermopiles can be utilized as the ANE valve for logic gates. These results provide an essential guide for energy harvesting and spin-dependent electrothermal sensor using magnetic materials.