Exploring the electronic and magnetic properties of two-dimensional M2X3 (M=V, Cr, Mn, Fe, Co, Ni; X=O, S, Se, Te) compounds

Based on first-principles calculations, the dynamical stability, electronic structures and magnetic properties of two-dimensional (2D) M${}_2$X${}_3$ (M=V, Cr, Mn, Fe, Co, Ni; X = O, S, Se, Te) compounds are investigated. According to the results, we identify a series of dynamically, mechanically and thermally stable materials with different magnetic configurations. V${}_2$O${}_3$, V${}_2$S${}_3$, V${}_2$Se${}_3$, V${}_2$Te${}_3$, Cr${}_2$Se${}_3$, Cr${}_2$Te${}_3$, Fe${}_2$O${}_3$, Fe${}_2$S${}_3$ and Fe${}_2$Se${}_3$ are antiferromagnetic (AFM) insulators, with energy gaps ranging from 0.09 eV to 1.67 eV. Cr${}_2$S${}_3$ is a ferromagnetic (FM) insulator with an indirect energy gap of 0.90 eV. Mn${}_2$S${}_3$, Mn${}_2$Se${}_3$, Mn${}_2$Te${}_3$ and Co${}_2$Se${}_3$ are FM metals. Particularly, we predict several rare AFM metals, including Fe${}_2$Te${}_3$, Co${}_2$Te${}_3$ and Ni${}_2$Se${}_3$. The exchange coupling parameters are obtained by fitting the Ising model to first-principles energies to help understand the magnetic mechanism. Monte Carlo simulations indicate that the magnetic phase-transition temperatures of these materials span a wide range, from approximately 150 K to 1000 K. The electronic structures and the magnetic ground states of these 2D compounds can be effectively tuned by biaxial strain and charge doping. This work enriches the family of 2D magnetic materials, especially the family of rare FM insulators and AFM metals.