Local and nonlocal spin Seebeck effect in lateral Pt-$\mathrm{Cr_2O_3}$-Pt devices at low temperatures

TL;DR

This study investigates the temperature-dependent local and nonlocal spin Seebeck effects in antiferromagnetic Cr2O3/Pt heterostructures at low temperatures, revealing short magnon relaxation lengths and the importance of inelastic scattering.

Contribution

It provides the first detailed analysis of temperature effects on both local and nonlocal SSE signals in Cr2O3-based devices, highlighting magnon relaxation mechanisms.

Findings

Both SSE signals decrease with temperature and vanish above 100 K and 20 K.

The nonlocal SSE decays exponentially with distance, indicating magnon transport.

Magnon relaxation length is approximately 500 nm at 3 K.

Abstract

We have studied thermally driven magnon spin transport (spin Seebeck effect, SSE) in heterostructures of antiferromagnetic $\alpha$-$\mathrm{Cr_2O_3}$ and Pt at low temperatures. Monitoring the amplitude of the local and nonlocal SSE signals as a function of temperature, we found that both decrease with increasing temperature and disappear above 100 K and 20 K, respectively. Additionally, both SSE signals show a tendency to saturate at low temperatures. The nonlocal SSE signal decays exponentially for intermediate injector-detector separation, consistent with magnon spin current transport in the relaxation regime. We estimate the magnon relaxation length of our $\alpha$-$\mathrm{Cr_2O_3}$ films to be around 500 nm at 3 K. This short magnon relaxation length along with the strong temperature dependence of the SSE signal indicates that temperature-dependent inelastic magnon scattering processes play an important role in the intermediate range magnon transport. Our observation is relevant to low-dissipation antiferromagnetic magnon memory and logic devices involving thermal magnon generation and transport.