Magnetic Spin Hall Effect of a Topological Chiral Antiferromagnet Mn₃Sn

A chiral antiferromagnet Mn₃Sn exhibits a substantial anomalous Hall effect (AHE) at room temperature, the magnitude of which reaches almost the same order of magnitude as in ferromagnetic metals irrespective of a small spontaneous magnetization of about 1 mT [1]. This large AHE originates from a significantly enhanced Berry curvature associated with the formation of Weyl points near Fermi energy [2]. A detailed comparison between angle-resolved photoemission spectroscopy measurements and density functional theory calculations revealed significant bandwidth renormalization and damping effects due to the strong correlation among Mn 3d electrons. Magnetotransport measurements provide strong evidence for the chiral anomaly of Weyl fermions[3]. All the above characteristic electronic properties of Mn₃Sn imply that the spin Hall effect could also take place in the Mn₃Sn.
Our SHE experiments showed that the non-collinear antiferromagnet Mn₃Sn has richer spin Hall properties than non-magnetic materials, that is, the SHE has an unusual sign change when its triangularly ordered moments switch orientation. Our observations demonstrate that a novel type of contribution to the SHE (magnetic SHE) and the inverse SHE (MISHE) can be dominant in some magnetic materials, including antiferromagnets. We attribute this magnetic mechanism in Mn₃Sn to the momentum-dependent spin splitting produced by the non-collinear magnetic order [4]. This discovery further expands the horizons of antiferromagnet spintronics and motivates a universal outlook on spin-charge coupling mechanisms in spintronics.
[1] S. Nakatsuji, N. Kiyohara, and T. Higo, Nature 527, 212–215 (2015).
[2] J. Kuebler, and C. Felser, EPL 108, 67001 (2014).
[3] K. Kuroda et al. Nat Mater. 16, 1090 (2017)
[4] M. Kimata et al. Nature 565, 627 (2019).