Abstract

We report a comprehensive investigation of the lattice and magnetic structure in van der Waals antiferromagnet ${\mathrm{VBr}}_{3}$, characterized by a ${\mathrm{BiI}}_{3}$-type structure at room temperature. Neutron diffraction experiments were performed on both polycrystalline and single-crystalline ${\mathrm{VBr}}_{3}$ samples, revealing clear magnetic Bragg peaks emerging below the N\'eel temperature of ${T}_{N}=26.5$ K. These magnetic Bragg peaks can be indexed by $\mathbit{k}=(0, 0.5, 1)$ in hexagonal notation. Our refinement analysis suggests that the antiferromagnetic order in ${\mathrm{VBr}}_{3}$ manifests as a zigzag structure. Moreover, we observed peak splitting for nuclear Bragg peaks in the HK plane below the structure transition temperature of ${T}_{S}=90.4$ K, indicating the breaking of threefold symmetry within the $ab$ plane.