Spin caloritronics in magnetic tunnel junctions: Ab initio studies

TL;DR

This paper uses ab initio calculations to study magneto-thermoelectric effects in MgO-based magnetic tunnel junctions, revealing large spin-Seebeck coefficients and temperature-dependent behaviors.

Contribution

It provides the first ab initio analysis of MTEP and spin-Seebeck effects in MgO tunnel junctions with Fe and Co leads, including quantitative agreement with experiments.

Findings

Normal thermopower matches experimental data for Fe and Co.

Spin-Seebeck coefficients can exceed 100 μV/K.

MTEP ratio can surpass 1000% and diverge at certain temperatures.

Abstract

This Letter presents ab initio calculations of the magneto-thermoelectric power (MTEP) and of the spin-Seebeck coefficient in MgO based tunnel junctions with Fe and Co leads. In addition, the normal thermopower is calculated and gives for pure Fe and Co an quantitative agreement with experiments. Consequently, the calculated values in tunnel junctions are a good estimation of upper limits. In particular, spin-Seebeck coefficients of more than 100 \mu V/K are possible. The MTEP ratio exceed several 1000% and depends strongly on temperature. In the case of Fe leads the MTEP ratio diverges even to infinity at certain temperatures. The spin-Seebeck coefficient as a function of temperature shows a non-trivial dependence. For Fe/MgO/Fe even the sign of the coefficient changes with temperature.