After the discovery of magnetism in monolayer $\mathrm{Cr}{\mathrm{I}}_3$, the magnetic properties of different two-dimensional materials from the chromium-trihalide family are intuitively assumed to be similar, yielding magnetic anisotropy from the spin-orbit coupling on halide ligands. Here we reveal significant differences between the $\mathrm{Cr}{\mathrm{I}}_3$ and $\mathrm{Cr}{\mathrm{Br}}_3$ magnetic monolayers in their magnetic anisotropy, resulting Curie temperature, hysteresis in an external magnetic field, and evolution of magnetism with strain, all predominantly attributed to a distinctly different interplay of atomic contributions to spin-orbit coupling in two materials.

• Received 29 November 2020
• Revised 26 January 2021
• Accepted 1 March 2021

DOI:https://doi.org/10.1103/PhysRevB.103.125418