Janus single-layer CoClBr. A direct ferromagnetic semiconductor with controllable bandgap and enhanced magnetic anisotropy under strain

The 2D materials with both ferromagnetism and semiconducting properties are desirable for spintronics applications. Here, inspired by the successful synthesis of single-layer CoCl${}_2$, it predicts that Janus single-layer CoClBr is a 2D intrinsic ferromagnetic semiconductor with a direct bandgap of 3.71 eV by first-principles calculations. Single-layer CoClBr exhibits an in-plane magnetic anisotropic energy (MAE) of 542.25 µeV per Co atom and a Curie temperature (T${}_c$) of 89.49 K. Biaxial strain can effectively modulate its bandgap, MAE, and T${}_c$, but will not change the ferromagnetic ground state. Compressive strain can increase the Curie temperature and switch the spin moment from in-plane direction to out-of-plane direction. Tensile strain can enlarge the bandgap and introduce a direct-to-indirect bandgap transition in CoClBr. The MAE of CoClBr reaches 391.73 µeV per Co atom and 1560.49 µeV per Co atom at a compressive strain of -2% and a tensile strain of 5%, respectively. The tunable electronic and magnetic properties of Janus single-layer CoClBr has potential application in low-dimensional spintronics devices. (© 2024 Wiley‐VCH GmbH)