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

Abstract

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.

Inkjet‐Printed Flexible Spin Seebeck Thermopile Device for Low‐Cost Spintronics Device Fabrication

“…The SSE thermopile device of an epitaxial Fe 3 O 4 film/Pt film patterned by optical lithography has been investigated by Ramos et al [ 16 ] The value of their device is 50 μV K −1 , which is higher than that obtained in the current study, although their device has a lower area and N (5 × 1.7 mm, N = 6) than ours. As mentioned in our previous study, [ 29 ] this is caused by boundary scattering of the phonons and magnons in the Fe 3 O 4 ‐NP‐assembled film. The V SSE value is reduced when the grain size is significantly smaller than the mean free paths of magnons and phonons.…”

“…In recent years, spin‐momentum‐mediated heat–charge conversion technologies aimed at the development of thin thermoelectric generators and heat flow sensors have been extensively studied. [ 1–29 ] The thermoelectric generation (TEG) based on the spin Seebeck (SSE) effect is a promising technology. [ 1–5,7–13,15–20,22,23,25–29 ] The SSE converts the temperature difference into spin current in a magnetic material.…”

“…[ 1–29 ] The thermoelectric generation (TEG) based on the spin Seebeck (SSE) effect is a promising technology. [ 1–5,7–13,15–20,22,23,25–29 ] The SSE converts the temperature difference into spin current in a magnetic material. When a heavy metal (HM) with a large spin–orbit coupling is attached to a magnetic material, the spin current generates an electric current according to the inverse spin Hall effect (ISHE).…”

“…In our previous study, to observe flexible SSE‐TEG, the SSE in an Fe 3 O 4 ‐nanoparticle (NP)‐assembled film with a Pt thin film on a flexible polyimide sheet was investigated. [ 29 ] We have demonstrated that an Fe 3 O 4 ‐NP‐assembled film with a Pt thin film on a flexible polyimide sheet possesses sufficient V SSE . Further, it also has the good scalability for practical application because the NP‐assembled films can be fabricated using a simple spin‐coating method.…”

“…In previous study, we successfully increased the V SSE using an SSE thermopile device based on an Fe 3 O 4 ‐NP‐assembled film. [ 29 ] However, SSE thermopiles were fabricated using handcrafted methods. This results in a decrease in the scalability of SSE thermopile devices based on NP‐assembled films.…”