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Spin caloritronics in magnetic tunnel junctions:<i>Ab initio</i>studies

Michael Czerner, Michaël Bachmann, Christian Heiliger

Physical Review B · 2011 · 105 citations · 13 references

Open access

TL;DR

The study performs ab initio calculations of magneto‑thermoelectric power and spin‑Seebeck coefficient in MgO‑based tunnel junctions with Fe and Co leads. The authors compute MTEP, spin‑Seebeck, and normal thermopower using ab initio methods, comparing Fe and Co leads to experimental data. Calculated values provide upper limits, with spin‑Seebeck coefficients exceeding 100 µV/K, MTEP ratios surpassing 1000 % and diverging to infinity for Fe leads at certain temperatures, and temperature‑dependent sign changes in Fe/MgO/Fe.

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.