Observation of spin swapping effect in non-collinear antiferromagnets

A pure spin current without a charge current carries spin angular momentum with minimal carriers in ferromagnetic (FM) metals and no carriers at all in FM insulators. Pure spin current phenomena, including injection/detection of pure current and spin orbit torque switching, have been realized in collinear FM materials with a large magnetization (M), but not in collinear antiferromagnetic (AF) materials with M = 0 unless under a sizable external field. Spin swapping effect, where the spin current direction and spin index interchanged as it traverses through a material, has been an intriguing spintronic effect since its prediction in 2009 [1], but not observed in collinear FM and AF materials. Spin swapping effect has recently been observed in non-collinear AF spin structure of LuFeO₃ [2] and LuFeO₃ [3]. The pure spin current effects in non-collinear AFs increase, as opposed to those in collinear FM materials that decrease, with increasing temperatures indicating new mechanisms [4]. One may exploit spin swapping effect for lateral spintronic devices, and non-collinear AFs for low-field AF spintronics.