Thermographic measurements of spin-current-induced temperature modulation in metallic bilayers

TL;DR

This study uses thermography to measure how spin currents in metallic bilayers induce temperature changes, revealing effects related to the spin Hall effect and contributions from electron and magnon-driven Peltier effects.

Contribution

It provides the first thermographic measurements of spin-current-induced temperature modulation in PM/FM bilayers, highlighting the roles of electron and magnon contributions.

Findings

Spin-current-induced temperature modulation varies with the spin Hall angle.

Pt/CoFeB shows larger temperature effects than Pt/permalloy.

Signals include electron-driven and magnon-driven spin Peltier effects.

Abstract

Spin-to-heat current conversion effects have been investigated in bilayer films consisting of a paramagnetic metal (PM; Pt, W, or Ta) and a ferromagnetic metal (FM; CoFeB or permalloy). When a charge current is applied to the PM/FM bilayer film, a spin current is generated across the PM/FM interface owing to the spin Hall effect in PM. The spin current was found to exhibit cooling and heating features depending on the sign of the spin Hall angle of PM, where the spin-current-induced contribution is estimated by subtracting the contribution of the anomalous Ettingshausen effect in FM monolayer films. We also found that the magnitude of the spin-current-induced temperature modulation in the Pt/CoFeB film is greater than but comparable to that in the Pt/permalloy film, although the spin dependence of the Peltier coefficient for CoFeB is expected to be greater than that for permalloy. We discuss the origin of the observed behaviors with the aid of model calculations; the signals in the PM/FM films may contain the contributions not only from the electron-driven spin-dependent Peltier effect but also from the magnon-driven spin Peltier effect.