Giant Full-Space Anomalous Hall Effect Induced by Non-Coplanar Spin State in Mn-Rich Mn3Sn

Abstract

Antiferromagnets are promising candidates for next-generation spintronic devices owing to their negligible stray fields and ultrafast spin dynamics. The noncollinear antiferromagnet ${\mathrm{Mn}}_3\mathrm{Sn}$ exhibits a large anomalous Hall effect (AHE). However, its specific noncollinear spin configuration leads to the forbiddance of the anomalous Hall conductivity from the (0001) basal plane, ${\sigma }_{(0001)}$, limiting practical applications. Here, using first-principles density functional theory, we demonstrate that Mn enrichment in ${\mathrm{Mn}}_3\mathrm{Sn}$ drives a magnetic transition from the coplanar $120^{\circ }$ spin configuration to a non-coplanar state with moments tilted toward the $c$-axis. This transition is primarily mediated by four-spin ring exchange interaction in the local triangular lattice, which breaks the time-reversal symmetry and generates a giant intrinsic anomalous Hall conductivity over the full three-dimensional space in ${\mathrm{Mn}}_3\mathrm{Sn}$. We predict that ${\sigma }_{(0001)}$ reaches as high as $\sim -468{\Omega }^{-1}\cdot {\mathrm{cm}}^{-1}$, and an enhanced ${\sigma }_{(01\bar{1}0)}$ of $\sim -229{\Omega }^{-1}\cdot {\mathrm{cm}}^{-1}$ is expected in light Mn self-doping of ${\mathrm{Mn}}_3\mathrm{Sn}$ (${\mathrm{Mn}}_{3.125}{\mathrm{Sn}}_{0.875}$). Unlike previously reported mechanisms relying on external magnetic fields or strain, our approach exploits intrinsic compositional tuning to stabilize a non-coplanar magnetic ground state for realizing a strong full-space AHE in antiferromagnets, providing another viable pathway toward high-performance, low-power spintronic devices.

16 pages, 5 figures