Magnetic Phases of Semiconducting CrI₂ monolayer

The recently discovered van der Waals magnetic semiconductor CrI₂ shows promise for spintronic applications. Using density functional theory (DFT) calculations, we show that the CrI₂ appears at the low Iodine concentration in the Cr-I phase diagram and possesses excellent magnetic properties, including large magnetic moment (~ 4.0 μB/Cr) and large magneto-crystalline anisotropy ~0.7 meV/Cr and good semiconducting properties including sizeable band gap ~ 2.0 eV with completely spin-polarized valence, and conduction bands with large exchange splitting of 0.44 eV and 1.66 eV respectively. Further, we show that the compound is easily exfoliable with cleavage energy, ~ 0.25 J/m², similar to CrI₃. Using the first and second nearest exchange interactions obtained by mapping DFT and Heisenberg Hamiltonian, we construct a magnetic phases diagram including all phases competing with minimum energy ferromagnetic phase. Our work contributes to understanding the CrI₂ monolayer and its applications in spintronic devices.