  Functional materials such as magnetic, thermoelectric, and battery materials
have been revolutionized through nanostructure engineering. However, spin
caloritronics, an advancing field based on spintronics and thermoelectrics with
fundamental physics studies, has focused only on uniform materials without
complex microstructures. Here, we show how nanostructure engineering enables
transforming simple magnetic alloys into spin-caloritronic materials displaying
significantly large transverse thermoelectric conversion properties. The
anomalous Nernst effect (ANE), a promising transverse thermoelectric phenomenon
for energy harvesting and heat sensing, has been challenging to utilize due to
the scarcity of materials with large anomalous Nernst coefficients. We
demonstrate a remarkable improvement in the anomalous Nernst coefficients in
flexible Fe-based amorphous materials through nanostructural engineering,
without altering their composition. This surpasses all reported amorphous
alloys and is comparable to single crystals showing large ANE. The enhancement
is attributed to Cu nano-clustering, facilitating efficient transverse
thermoelectric conversion. This discovery advances the materials science of
spin caloritronics, opening new avenues for designing high-performance
transverse thermoelectric devices for practical applications.
