Scalable spin Seebeck thermoelectric generation using Fe-oxide nanoparticle assembled film on flexible substrate

We fabricated Fe₃O₄ nanoparticle (NP)-assembled films on flexible polyimide sheets with Pt or Ta cap layer using a spin coating method and DC sputtering. The films were elaborated for spin Seebeck thermoelectric generator applications, and their spin Seebeck voltages were observed. We showed that the thermoelectric power of [Pt film/Fe₃O₄ NP]_n multilayered films increases with increasing number of stacking n. Additionally, we prepared spin Seebeck thermopile devices in which the Fe₃O₄ NP-assembled films capped by Pt and Ta are connected alternately in series. We demonstrated that spin Seebeck voltages of the thermopile devices are larger than those of single [Pt or Ta film/Fe₃O₄ NP]_n piece. Our results indicate that the spin Seebeck thermoelectric power of Fe₃O₄ NPs can be enhanced using a simple fabrication process without lithography technique.