Anomalous Hall Effect in a Noncentrosymmetric Antiferromagnet CoNb₃S₆

An ordinary Hall effect in a conductor arises due to the Lorentz force acting on the charge carriers. In ferromagnets, an additional contribution to the Hall effect, which is proportional to the magnetization, appears and is termed as the Anomalous Hall effect (AHE). Such an anomalous Hall effect is not seen in a collinear anitferromagnet with zero net magnetization. However, recently it has been shown that intrinsic part of the AHE can be non-zero in non-collinear antiferromagnets as well as in topological materials hosting Weyl nodes near the Fermi energy. We have recently found a large anomalous Hall effect with Hall conductivity of 30 Ω^-1 cm^-1 in a collinear antiferromagnet CoNb₃S₆ with a non-centrosymmetric crystal structure. It orders below 27.5 K with the moments lying in the ab-plane. Magnetization measurement shows the presence of a small ferromagnetic component (0.0013 Bohr magnetons) along c-axis. The large AHE, observed only for H || c, is difficult to reconcile in light of the small ferromagnetic component. Here I will discuss potential alternative explanations of the AHE in CoNb₃S₆ framed in terms of topological band structure features or spin texture.