Layer-dependent electronic and magnetic properties of Nb3I8

The discovery of intrinsic two-dimensional magnetism has ignited intense research interest due to the several and attractive applications in spintronics. Nb3I8 is a recently investigated van der Waals material, exhibiting ferromagnetism and extraordinary visible light-harvesting ability in monolayer form, besides useful remarkable features for the realization of future high-performance nanodevices. Here we use density functional theory and classical Monte Carlo simulations to investigate the electronic and magnetic properties of Nb3I8 in bulk, monolayer, and some multilayer (bilayer and trilayer) forms. Two suitable vdW exchange-correlation functionals, vdW-DF2-C09 and rev-vdW-DF2, have been chosen to compare the first-principles calculation predictions. The layer number directly influences the ground-state magnetism, indicating the possibility of using the thickness as a parameter to control the magnetic response of the material. In particular, it is possible to switch on the antiferromagnetism by adding one or two layers to the ferromagnetic monolayer. This makes Nb3I8 an excellent platform for spintronics applications. Monte Carlo simulations based on a third-nearest-neighbor Ising model provide a Curie temperature close to room temperature (~ 307 K) for the monolayer. The results on the electronic and magnetic properties render the two-dimensional Nb3I8 an ideal and promising candidate for future research and applications.