Simple yet clear local evidence for the tetrahedral triple-Q magnetic ground state in the triangular antiferromagnet Co1/3NbS2

In this work, we demonstrate a simple yet effective procedure for identifying the exotic tetrahedral triple-Q magnetic ordering over the domain averaged collinear single-Q magnetic state for the triangular antiferromagnet Co1/3NbS2. Our density functional theory (DFT) calculations show that the hyperfine magnetic field exhibits a significant anisotropic dependence on the angle between the spin direction and the c-axis, which means that the atoms with different spin directions in the triple-Q state can be divided into two subgroups with a ratio of 1:3 that can be distinguished by local probing methods. Mossbauer spectroscopy measurements on (Co0.99 57Fe0.01)1/3NbS2 crystals confirm exactly our DFT predictions and thus give possible evidence of the tetrahedral triple-Q magnetic state. These results provide important insights into the magnetic ground state of Co1/3NbS2, which shall shed light on the understanding of the anomalous Hall effect in Co1/3NbS2 and other related materials.