Lattice and magnetic structure in the van der Waals antiferromagnet VBr3

Abstract: We report a comprehensive investigation of the lattice and magnetic structure in van der Waals antiferromagnet VBr3, characterized by a BiI3-type structure at room temperature. Neutron diffraction experiments were performed on both polycrystalline and single-crystalline VBr3 samples, revealing clear magnetic Bragg peaks emerging below the N\'eel temperature of TN = 26.5 K. These magnetic Bragg peaks can be indexed by k = (0, 0.5, 1) in hexagonal notation. Our refinement analysis suggests that the antiferromagnetic order in VBr3 manifests as a zigzag structure. Moreover, we observed peak splitting for nuclear Bragg peaks in the HK-plane below the structure transition temperature of Ts = 94 K, indicating the breaking of 3-fold symmetry within the ab-plane.