Understanding the Anomalous Hall effect in Co_1/3NbS₂ with revised crystal and magnetic structures

A large anomalous Hall effect (AHE) has recently been observed in the intercalated transition metal dichalcogenide Co_1/3NbS₂ below a known magnetic phase transition at T_N = 29 K. The magnetically ordered state is widely believed to be a form of collinear antiferromagnetism which preserves parity and time reversal symmetry, and there has been discussion about if and how such a state could lead to an AHE or whether the latter should be associated with a weak ferromagnetic moment seen immediately below the transition temperature. In this talk, I address this controversy by presenting new neutron diffraction data on single crystals of Co_1/3NbS₂ and an analysis which suggests that moments in the ordered phase stabilize in a non-collinear configuration. We further present new transport and magneto-optic Kerr measurements which demonstrate that the AHE persists in this material below T_N to temperatures as low as T = 5 K. Finally, we show that AHE signatures in our sample are accurately reproduced by density functional theory calculations. These collective results firmly associate the anomalous transport signatures with the antiferromagnetically ordered state in this material and lends credence to the crystal Hall effect picture.