Observation of Vector Spin Seebeck Effect in a Noncollinear Antiferromagnet

TL;DR

This paper reports the first observation of a vector spin Seebeck effect in a noncollinear antiferromagnet, enabling spin current generation in multiple directions without external magnetic fields, advancing spin caloritronics and magnonics.

Contribution

It demonstrates the vector SSE in LuFeO3, showing controllable spin current injection in multiple directions at room temperature without large magnetic fields.

Findings

Vector SSE observed in LuFeO3 with temperature gradients in multiple directions.

Spin currents generated via inverse spin Hall effect in a noncollinear AF.

Vector SSE controllable with small magnetic fields at room temperature.

Abstract

Spintronic phenomena to date have been established in magnets with collinear moments, where the spin injection through the spin Seebeck effect (SSE) is always along the out-of-plane direction. Here, we report the observation of a vector SSE in a noncollinear antiferromagnet (AF) LuFeO$_3$, where temperature gradient along the out-of-plane and also the in-plane directions can both inject a pure spin current and generate a voltage in the heavy metal via the inverse spin Hall effect (ISHE). We show that the thermovoltages are due to the magnetization from canted spins in LuFeO$_3$. Furthermore, in contrast to the challenges of generating, manipulating and detecting spin current in collinear AFs, the vector SSE in LuFeO$_3$ is readily viable in zero magnetic field and can be controlled by a small magnetic field of about 150 Oe at room temperature. The noncollinear AFs expand new realms for exploring spin phenomena and provide a new route to low-field antiferromagnetic spin caloritronics and magnonics.