This article has been reviewed according to Science X's editorial process and policies. Editors have highlighted the following attributes while ensuring the content's credibility: A joint research team from NIMS and the University of Tokyo has developed a new composite in which three-dimensional nano-interfaces are distributed throughout the material by coating the surfaces of magnetic-insulator powders with a metal and sintering them. Using this structure, the team succeeded in observing thermoelectric conversion driven by spins in an insulator, a phenomenon previously observed only at nanoscale thin-film interfaces, in a macroscale material.
This research was published in Nature Communications. Thermoelectric conversion, which uses the vast amounts of waste heat and unused heat around us as electrical energy, is one of the key technologies for improving energy-use efficiency and achieving carbon neutrality. The spin Seebeck effect is a physical phenomenon discovered in Japan in 2008 in which applying a temperature gradient to a magnetic material enables thermoelectric conversion via spin currents.
However, conventional spin Seebeck devices use a layered structure consisting of a magnetic material and a thin metal film, limiting increases in output power through greater device thickness or additional layers. In this study, the research team coated the surfaces of yttrium iron garnet (YIG) powder, a magnetic insulator, with platinum (Pt) and sintered it at low temperature under high pressure to develop a bulk composite in which YIG/Pt nanoscale interfaces are distributed throughout the material in three dimensions. Unlike conventional thin-film layered devices, this composite can achieve thermoelectric conversion through the spin Seebeck effect using interfaces distributed throughout the bulk.
The team showed that the spin Seebeck effect is generated in the fabricated YIG-Pt bulk composite and that using metal channels distributed within the material facilitates scaling in the thickness direction. This research demonstrates the concept of the trans-scale spin Seebeck effect, which extends a nanoscale interfacial phenomenon to macroscale energy conversion. In addition, by forming nanoscale interfaces throughout a material in three dimensions, a spin-based thermoelectric phenomenon previously limited to thin-film interfaces can be extended to a bulk material.
In the future, thermoelectric conversion performance is expected to improve further through optimization of the design and control of the three-dimensional interface structure and materials. By demonstrating the conversion of thermal energy in an insulator into electrical energy in a macroscopic material, which is difficult to achieve using conventional thermoelectric technologies, the team's work opens a path toward new thermal management devices. Park et al, Trans-scale spin Seebeck effect in nanostructured bulk composites based on magnetic insulator, Nature Communications (2026).
DOI: 10.1038/s41467-026-75232-0 Journal information: Nature Communications Provided by National Institute for Materials Science BSc Life Sciences & Ecology. Microbiology lab background with pharmaceutical news experience in oil, gas, and renewable industries. Full profile → Bachelor's in mathematical biology, Master's in creative writing.
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