Thermal generation of spin current in an antiferromagnet

TL;DR

This study demonstrates that temperature gradients in an antiferromagnetic insulator can generate spin currents detectable via inverse spin Hall voltage, with phonon-drag effects enhancing the signal at lower temperatures.

Contribution

It reveals that high-frequency antiferromagnetic spin waves can effectively carry spin currents driven by thermal gradients, highlighting a new mechanism for spin caloritronics.

Findings

Inverse spin Hall voltage proportional to magnetization in Cr2O3

Significant voltage enhancement at lower temperatures due to phonon-drag

Antiferromagnetic spin waves above 100 GHz can carry spin current

Abstract

Longitudinal spin Seebeck effect has been investigated for an uniaxial antiferromagnetic insulator Cr2O3, characterized by a spin-flop transition under magnetic field along the c-axis. We have found that temperature gradient applied normal to Cr2O3/Pt interface induces inverse spin Hall voltage of spin current origin in Pt, whose magnitude turns out to be always proportional to magnetization in Cr2O3. The observed voltage shows significant enhancement for the lower temperature region, which can be ascribed to the phonon-drag effect on the relevant spin excitations. The above results establish that antiferromagnetic spin waves with high frequency above 100 GHz can be an effective carrier of spin current.