Strong magnetic anisotropy and magnetoelastic coupling in chromium chalcohalide monolayers

Two-dimensional (2D) ferromagnets with controllable magnetic anisotropy hold great promise for quantum information processing and sensing. However, realizing large magnetic anisotropy and strong exchange interactions in stable 2D magnetic materials remains a major challenge. Here, we present the identification of strong in-plane magnetic anisotropy in CrSBr-type chromium chalcohalide monolayers. Importantly, the different easy axes of magnetization can be further controlled by applying mechanical strain. The underlying physics are related to the change in the orbital magnetic moment dependent on the lattice. Furthermore, our investigation demonstrates that the optical properties of the ${\mathrm{Cr}}_{2}{\mathrm{SSeBr}}_{2}$ monolayer are sensitive to the magnetization direction. This study is interesting for achieving new 2D ferromagnets and advancing nanoelectronic devices.