Double-$Q$ chiral stripe order in the anomalous Hall antiferromagnet CoNb$_3$S$_6$

TL;DR

This study uncovers a complex non-coplanar double-Q magnetic order in CoNb3S6 using resonant x-ray scattering, revealing its role in enabling anomalous Hall effects and providing insights into unconventional magnetotransport.

Contribution

It reports the discovery of a novel non-coplanar double-Q magnetic order in CoNb3S6 driven by four-spin exchange interactions, explaining its anomalous Hall effect.

Findings

Identified a non-coplanar double-Q magnetic structure in CoNb3S6.

Revealed a staggered scalar spin chirality forming stripe-like patterns.

Linked the magnetic order to the anomalous Hall effect in the material.

Abstract

We present fine momentum space resolution resonant elastic x-ray scattering measurements of the magnetic structure of the metallic antiferromagnet CoNb$_3$S$_6$. Using circular dichroism and full linear polarization analysis of the magnetic scattering, we reveal a non-coplanar double-$Q$ ($2Q$) order, with a non-collinear commensurate component and a long-wavelength incommensurate helical component. This $2Q$ structure exhibits a staggered scalar spin chirality that forms a modulated stripe-like pattern with no uniform component. This novel magnetic order is naturally explained by the presence of four-spin exchange interactions and exhibits a complex domain structure that suggests a lowering of the structural symmetry. A symmetry analysis indicates that the $2Q$ order enables a finite anomalous Hall effect in CoNb$_3$S$_6$. In addition to identifying a novel type of magnetic ordering and its origin, our results provide insight into the mechanism of the unconventional magnetotransport phenomena in CoNb$_3$S$_6$ and thus identifies potential routes for realizing novel electronic phenomena in metallic antiferromagnets.