Two-dimensional (2D) layered magnetic materials are generating a great amount of interest for the next generation of electronic devices thanks to their remarkable properties associated with spin dynamics. The recently discovered layered $\mathrm{V}{\mathrm{I}}_3$ ferromagnetic phase belongs to this family, although a full understanding of its properties is limited by the incomplete understanding of its crystallographic structure. The motivation of this work is to address this issue. Here, we investigate the $\mathrm{V}{\mathrm{I}}_3$ crystal structures at low temperature using both synchrotron x-ray and neutron powder diffraction and provide structural models for the two structural transitions occurring at 76 and 32 K. Moreover, we confirm by magnetic measurements that $\mathrm{V}{\mathrm{I}}_3$ becomes ferromagnetic at 50 K and we question the establishment of a long-range magnetic structure by neutron diffraction. We equally determined the magnetic properties of our recently reported $\mathrm{LiV}{\mathrm{I}}_3$ phase, which is like the well-known $\mathrm{Cr}{\mathrm{I}}_3$ ferromagnetic phase in terms of electronic and crystallographic structures and found an antiferromagnetic behavior with a Néel temperature of 12 K. Such a finding provides extra clues for a better understanding of magnetism in these low-dimension compounds. Finally, the easiness of preparing Li-based 2D magnetic materials by chemical/electrochemical means opens wide the opportunity to design materials with exotic properties.

• Received 2 April 2021
• Revised 14 June 2021
• Accepted 21 June 2021

DOI:https://doi.org/10.1103/PhysRevB.104.014105