First-principles prediction of two-dimensional NiI3 monolayer with adsorbed metal atoms

Monolayer NiI3 is a new two-dimensional (2D) intrinsic ferromagnetic Dirac half-metal material, and has attracted widespread attention due to its high Curie temperature and large magnetic anisotropy. In this work, we use first-principles calculations to study the physical properties of 2D NiI3 monolayer with adatom Y (Y=Li, Al, Mg, Ga). Our calculations show that Mg transforms the NiI3 monolayer from a half-metal to a bipolar magnetic semiconductor with a direct bandgap. While, the Li-NiI3, Al-NiI3, and Ga-NiI3 systems exhibit the band properties of 2D half-metals. In addition, the compressive strain can significantly increase the Curie temperatures of monolayer Li-NiI3 and Ga-NiI3. Especially under 1.5% compressive strain, the Mg-NiI3 system transitions from the ferromagnetic state to the antiferromagnetic state. Our study shows that atomic adsorption can optimize the properties of monolayer NiI3, and provides a theoretical basis for the use of atom adsorbed NiI3 system in experimental and device applications.