Higher order exchange driven noncoplanar magnetic state and large anomalous Hall effects in electron doped kagome magnet Mn$_3$Sn

TL;DR

This study demonstrates how electron doping in Mn$_3$Sn can induce a tunable noncoplanar magnetic state with large anomalous Hall effects, revealing the role of higher-order exchange interactions and scalar spin chirality.

Contribution

The paper combines theoretical calculations and experimental evidence to show that electron doping stabilizes a noncoplanar magnetic state in Mn$_3$Sn, leading to tunable topological AHE.

Findings

Electron doping induces a noncoplanar magnetic state in Mn$_3$Sn.

Large scalar spin chirality contributes to topological AHE.

AHE sign can be switched independently of magnetic order.

Abstract

Owing to the geometrical frustration, Mn$_3 $Sn exhibits a 120$^{\circ}$ in-plane triangular antiferromagnetic (AFM) order with a large anomalous Hall effect (AHE). Here, we present a combined theoretical and experimental study to demonstrate that the in-plane AFM structure in Mn$_3 $Sn can be significantly modified to a tunable noncoplanar magnetic state by suitable electron doping. With the help of Density Functional Theory calculations we show that the presence of higher-order exchange interactions in the system leads to the stabilization of the noncoplanar magnetic ground state, which is further established by neutron diffraction study in the Fe-doped Mn$_3 $Sn sample. Interestingly, we find a large scalar spin chirality (SSC) induced topological AHE that can be significantly tuned with the degree of non-coplanarity. We carry out 60~T magnetic and Hall resistivity measurements to demonstrate the contribution of SSC to the observed AHE. We also illustrate a simultaneous manipulation of dual order in the system, where the AHE arising from the in-plane 120$^{\circ}$ triangular AFM order can switch its sign without affecting the AHE generated by the SSC. The present study opens up a new direction to explore novel quantum phenomena associated with the coexistence of multiple orders.