Large anomalous Hall effect induced by weak ferromagnetism in the noncentrosymmetric antiferromagnet $\mathrm{Co}\mathrm{Nb}_3\mathrm{S}_6$

TL;DR

This study investigates the large anomalous Hall effect in the noncentrosymmetric antiferromagnet CoNb3S6, revealing that weak ferromagnetism and Weyl points near the Fermi level are key to this phenomenon.

Contribution

The paper demonstrates that weak ferromagnetism in CoNb3S6 induces a large AHE, linked to Weyl points, with sulfur deficiency suppressing ferromagnetism and the AHE without altering the band structure.

Findings

Weak ferromagnetism causes large AHE in CoNb3S6.

Sulfur deficiency eliminates ferromagnetism and AHE.

Weyl points near the Fermi level are responsible for the large AHE.

Abstract

We study the mechanism of the exceptionally large anomalous Hall effect (AHE) in the noncentrosymmetric antiferromagnet $\mathrm{Co}\mathrm{Nb}_3\mathrm{S}_6$ by angle-resolved photoemission spectroscopy (ARPES) and magnetotransport measurements. From ARPES measurements of $\mathrm{Co}\mathrm{Nb}_3\mathrm{S}_6$ and its family compounds ($\mathrm{Fe}\mathrm{Nb}_3\mathrm{S}_6$ and $\mathrm{Ni}\mathrm{Nb}_3\mathrm{S}_6$), we find a band dispersion unique to the Co intercalation existing near the Fermi level. We further demonstrate that a slight deficiency of sulfur in $\mathrm{Co}\mathrm{Nb}_3\mathrm{S}_6$ eliminates the ferromagnetism and the AHE simultaneously while hardly changing the band structure, indicating that the weak ferromagnetism is responsible for the emergence of the large AHE. Based on our results, we propose Weyl points near the Fermi level to cause the large AHE.