Comparison of laser induced and intrinsic tunnel magneto-Seebeck effect in CoFeB/MgAl$_2$O$_4$ and CoFeB/MgO magnetic tunnel junctions

TL;DR

This paper compares laser-induced and intrinsic tunnel magneto-Seebeck effects in CoFeB/MgAl$_2$O$_4$ and CoFeB/MgO magnetic tunnel junctions, revealing differences in sign, magnitude, and the influence of barrier asymmetry.

Contribution

It demonstrates that the symmetry analysis for intrinsic effects is insufficient to unambiguously identify the tunnel magneto-Seebeck effect.

Findings

The TMS ratio is 3% for MAO and 23% for MgO junctions.

Intrinsic and laser heating methods yield different results in sign and magnitude.

Symmetric contributions are solely influenced by barrier asymmetry.

Abstract

We present a comparison of the tunnel magneto-Seebeck effect for laser induced and intrinsic heating. Therefore, Co$_{40}$Fe$_{40}$B$_{20}$/MgAl$_2$O$_4$ and Co$_{25}$Fe$_{55}$B$_{20}$/MgO magnetic tunnel junctions have been prepared. The TMS ratio of 3\,\% in case of the MAO MTJ agrees well with ratios found for other barrier materials, while the TMS ratio of 23\,\% of the MgO MTJ emphasizes the influence of the CoFe composition. We find results using the intrinsic method that differ in sign and magnitude in comparison to the results of the laser heating. The intrinsic contributions can alternatively be explained by the Brinkman model and the given junction properties. Especially, we are able to demonstrate that the symmetric contribution is solely influenced by the barrier asymmetry. Thus, we conclude that the symmetry analysis used for the intrinsic method is not suitable to unambiguously identify an intrinsic tunnel magneto-Seebeck effect.