Thermographic Measurements of the Spin Peltier Effect in Metal/Yttrium-Iron-Garnet Junction Systems

The spin Peltier effect (SPE) refers to heat-current generation in linear response to spin-current injection [1]. Recently, we established new measurement technique for investigating the SPE based on lock-in thermography (LIT) [2]. The LIT technique enables contact-free measurements of the spatial distribution of the SPE signals with high temperature resolution and realizes quantitative evaluation of the SPE signals. In this study, we report the thermal imaging of the SPE by means of LIT in various metal (Pt, W, Au, or Pt/Cu)/ferrimagnetic insulator [yttrium-iron-garnet (YIG)] junction systems. We successfully observed the clear temperature modulation induced by the spin-current injection not only in the Pt/YIG and W/YIG systems, but also in the Au/YIG and Pt/Cu/YIG systems. These results exclude the possible contamination of the SPE signal by anomalous Ettingshausen effects due to proximity-induced ferromagnetism near the metal/YIG interface. [1] J. Flipse et al., Phys. Rev. Lett. 113, 027601 (2014); [2] S. Daimon et al., Nat. Commun. 7, 13754 (2016), Phys. Rev. B 96, 024424 (2017).