Direct-Contact Seebeck-Driven Transverse Magneto-Thermoelectric Generation in Magnetic/Thermoelectric Bilayers

Abstract

Transverse thermoelectric generation converts temperature gradient in one direction into an electric field perpendicular to that direction and is expected to be a promising alternative in creating simple-structured thermoelectric modules that can avoid the challenging problems facing traditional Seebeck-effect-based modules. Recently, large transverse thermopower has been observed in closed circuits consisting of magnetic and thermoelectric materials, called the Seebeck-driven transverse magneto-thermoelectric generation (STTG). However, the closed-circuit structure complicates its broad applications. Here, STTG is realized in the simplest way to combine magnetic and thermoelectric materials, namely, by stacking a magnetic layer and a thermoelectric layer together to form a bilayer. The transverse thermopower is predicted to vary with changing layer thicknesses and peaks at a much larger value under an optimal thickness ratio. This behavior is verified in the experiment, through a series of samples prepared by depositing Fe–Ga alloy thin films of various thicknesses onto n-type Si substrates. The measured transverse thermopower reaches 15.2 ± 0.4 µV K−1, which is a fivefold increase from that of Fe–Ga alloy and much larger than the current room temperature record observed in Weyl semimetal Co2MnGa. The findings highlight the potential of combining magnetic and thermoelectric materials for transverse thermoelectric applications.