Non-equilibrium thermodynamics of the spin Seebeck and spin Peltier effects

TL;DR

This paper develops a thermodynamic theory for magnetization and heat currents in ferromagnetic insulators, specifically applied to the spin Seebeck and Peltier effects in YIG/Pt systems, providing predictions aligned with experimental data.

Contribution

It introduces a detailed thermodynamic framework for spin and heat transport in magnetic insulators, deriving key coefficients and optimal conditions for spin caloritronic effects.

Findings

Estimated magnetization diffusion length: ~0.4 μm

Thermomagnetic power coefficient: ~10^{-2} TK^{-1}

Predictions match experimental observations

Abstract

We study the problem of magnetization and heat currents and their associated thermodynamic forces in a magnetic system by focusing on the magnetization transport in ferromagnetic insulators like YIG. The resulting theory is applied to the longitudinal spin Seebeck and the spin Peltier effects. By focusing on the specific geometry with one YIG layer and one Pt layer, we obtain the optimal conditions for generating large magnetization currents into Pt or large temperature effects in YIG. The theoretical predictions are compared with experiments from the literature permitting to derive the values of the thermomagnetic coefficients of YIG: the magnetization diffusion length $l_M \sim 0.4 \, \mu$m and the absolute thermomagnetic power coefficient $\epsilon_M \sim 10^{-2}$ TK$^{-1}$.