# Thermographic measurements of the spin Peltier effect in metal/yttrium-iron-garnet junction systems

## TL;DR

This study uses lock-in thermography to observe the spin Peltier effect in various metal/YIG junctions, confirming its presence beyond platinum and W, and exploring its relation to the spin Seebeck effect.

## Contribution

It demonstrates the detection of the spin Peltier effect in multiple metal/YIG systems using thermography, expanding understanding of spin-caloritronic phenomena.

## Key findings

- SPE observed in Pt/YIG, W/YIG, Au/YIG, and Pt/Cu/YIG systems.
- SPE signals are localized near the metal/YIG interface.
- YIG-thickness dependence of SPE resembles that of the spin Seebeck effect.

## Abstract

The spin Peltier effect (SPE), heat-current generation due to spin-current injection, in various metal (Pt, W, and Au single layers and Pt/Cu bilayer)/ferrimagnetic insulator (yttrium iron garnet: YIG) junction systems has been investigated by means of a lock-in thermography (LIT) method. The SPE is excited by a spin current across the metal/YIG interface, which is generated by applying a charge current to the metallic layer via the spin Hall effect. The LIT method enables the thermal imaging of the SPE free from the Joule-heating contribution. Importantly, we observed spin-current-induced temperature modulation not only in the Pt/YIG and W/YIG systems but also in the Au/YIG and Pt/Cu/YIG systems, excluding the possible contamination by anomalous Ettingshausen effects due to proximity-induced ferromagnetism near the metal/YIG interface. As demonstrated in our previous study, the SPE signals are confined only in the vicinity of the metal/YIG interface; we buttress this conclusion by reducing a spatial blur due to thermal diffusion in an infrared emission layer on the sample surface used for the LIT measurements. We also found that the YIG-thickness dependence of the SPE is similar to that of the spin Seebeck effect measured in the same Pt/YIG sample, implying the reciprocal relation between them.