Annealing-temperature-dependent voltage-sign reversal in all-oxide spin Seebeck devices using RuO2

Akihiro Kirihara, Masahiko Ishida, Ryota Yuge, Kazuki Ihara, Yuma Iwasaki, Ryohto Sawada, Hiroko Someya, Ryo Iguchi, Ken Ichi Uchida, Eiji Saitoh, Shinichi Yorozu

Research output: Contribution to journalArticlepeer-review

4 Citations (Scopus)

Abstract

Thermoelectric converters based on the spin Seebeck effect (SSE) have attracted great attention due to their potential to offer novel applications such as energy harvesting and heat-flow sensing. For converting a SSE-induced spin current into an electric current, a transition metal film such as Pt, which exhibits large inverse spin-Hall effect (ISHE), has been typically used. In this work, we show an all-oxide SSE device using ruthenium oxide (RuO2) as a conductive film. We found that both the sign and magnitude of the SSE-induced ISHE voltage V appearing in the RuO2 film changes depending on the post annealing temperature, and that the magnitude can become larger than that of a standard SSE device using Pt. The similar sign change was also observed in Hall-resistance measurements of the RuO2 films. X-ray absorption fine structure (XAFS) spectra of as-deposited and annealed RuO2 revealed that the annealing process substantially improved the long-range crystalline order in RuO2. This suggests that change in the crystalline order may modify the dominant ISHE mechanism or electronic states in RuO2, leading to the sign reversal of V as well as the Hall coefficient. Our result demonstrates that RuO2 is an interesting material not only as a practical ISHE film but also as a testbed to study physics of spin-to-charge converters that depend on their crystalline order.

Original languageEnglish
Article number154002
JournalJournal of Physics D: Applied Physics
Volume51
Issue number15
DOIs
Publication statusPublished - 2018 Mar 21

Keywords

  • conductive oxide
  • inverse spin Hall effect
  • spin Seebeck effect
  • thermoelectric converter

ASJC Scopus subject areas

  • Electronic, Optical and Magnetic Materials
  • Condensed Matter Physics
  • Acoustics and Ultrasonics
  • Surfaces, Coatings and Films

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