Decomposing measurements of the anomalous Nernst and spin Seebeck effects in Fe-based metallic multilayers

Anomalous Nernst (ANE) and spin Seebeck effects (SSE) are ubiquitous in conducting magnetic materials subject to temperature gradients. Their characterization in metallic systems is especially strenuous because of their indistinguishable symmetry. Here, we report on the accurate characterization of the ANE and SSE in Fe-based multilayers at and above room temperature. We reveal that both effects consist of temperature-dependent and -independent components. At high temperatures, we provide evidence that the ANE decreases mainly due to reduced magnetization and spin polarization of free electrons, whereas the SSE increases owing to the enhanced thermal magnon density. We show that the relative strength of ANE and SSE can be tuned by thickness, stacking order, and doping concentration in various Fe-based multilayers, opening the way for thermoelectric device engineering.