  Antiferromagnets (AFs) are prospective for next-generation high-density and
high-speed spintronic applications due to their negligible stray field and
ultrafast spin dynamics, notwithstanding the challenges in detecting and
manipulating AF order with no magnetization (M = 0). Among the AFs,
non-collinear AFs are of particular interest because of their unique properties
arising from the non-collinear spin structure and the small magnetization M. In
this work, we describe the recently observed vector spin Seebeck effect in
non-collinear LuFeO$_3$, where the magneto-thermovoltage under an in-plane
temperature gradient, not previously observed, is consistent with the predicted
spin swapping effect. Our results shed light on the importance of the
non-collinear spin structure in the emerging spin phenomena in non-collinear
AFs and offer a new class of materials for AF spintronics and spin
caloritronics.
