Low Temperature Suppression of the Spin Nernst Angle in Pt

TL;DR

This study investigates the temperature-dependent suppression of the spin Nernst angle in platinum when interfaced with antiferromagnetic hematite, revealing the role of extrinsic effects and the Nernst vector's orientation.

Contribution

It demonstrates the low temperature suppression of the spin Nernst angle in Pt/hematite bilayers and clarifies the influence of interfacial spin accumulation and Nél vector orientation.

Findings

TSNM vanishes below ~100 K

Excellent agreement with theoretical calculations

Extrinsic contributions dominate the spin Nernst effect at low temperatures

Abstract

We demonstrate the low temperature suppression of the platinum (Pt) spin Nernst angle in bilayers consisting of the antiferromagnetic insulator hematite ($\alpha$-Fe$_2$O$_3$) and Pt upon measuring the transverse spin Nernst magnetothermopower (TSNM). We show that the observed signal stems from the interplay between the interfacial spin accumulation in Pt originating from the spin Nernst effect and the orientation of the N\'eel vector of $\alpha$-Fe$_2$O$_3$, rather than its net magnetization. Since the latter is negligible in an antiferromagnet, our device is superior to ferromagnetic structures, allowing to unambiguously distinguish the TSNM from thermally excited magnon transport (TMT), which usually dominates in ferri/ferromagnets due to their non-zero magnetization. Evaluating the temperature dependence of the effect, we observe a vanishing TSNM below ~100 K. We compare these results with theoretical calculations of the temperature dependent spin Nernst conductivity and find excellent agreement. This provides evidence for a vanishing spin Nernst angle of Pt at low temperatures and the dominance of extrinsic contributions to the spin Nernst effect.