Energy Harvest in Ferromagnet‐Embedded Surface Acoustic Wave Devices

Surface acoustic wave (SAW) filters are at the center of the radio frequency module in mobile terminals. With the increase of SAW frequency and the miniaturization of devices, the heat generation becomes prominent in SAW devices, providing a potential platform for thermal energy harvesting. Here ferromagnetic materials are embedded into SAW delay lines to demonstrate that thermal energy can be harvested to generate robust transverse electrical signals via anomalous Nernst effect, which are comparable with the anomalous Hall signals when an electric current is intensively applied. The transverse voltage exhibits nonreciprocal features, both amplitude and polarity are dependent on the propagation direction of SAW in contrast to its longitudinal counterpart, which only changes the amplitude but remains polarity with opposite SAW direction. The finding provides a different platform for thermoelectric energy conversion and opens a window for thermal energy harvesting and acoustic or heat flow sensing in SAW devices.