Two-Dimensional Transition Metal Boride TMB (TM = V, Cr, Mn, and Fe) Monolayers: Robust Antiferromagnetic Semiconductors with Large Magnetic Anisotropy.

Currently, two-dimensional (2D) materials with intrinsic antiferromagnetism have stimulated research interest due to their insensitivity to external magnetic fields and absence of stray fields. Here, we predict a family of stable transition metal (TM) borides, TMB (TM = V, Cr, Mn, Fe) monolayers, by combining TM atoms and B icosahedra based on first-principles calculations. Our results show that the four TMB monolayers have stable antiferromagnetic (AFM) ground states with large magnetic anisotropic energy. Among them, three TMB (TM=V, Cr, Mn) monolayers display an in-plane easy magnetization axis, while the FeB monolayer has an out-of-plane easy magnetization axis. Among them, the CrB and the FeB monolayers are AFM semiconductors with band gaps of 0.13 eV and 0.35 eV, respectively. In particular, the AFM FeB monolayer is a spin-polarized AFM material with a Néel temperature of 125 K. Moreover, the electronic and magnetic properties of the CrB and the FeB monolayers can be modulated by imposing external biaxial strains. Our findings show that the TMB monolayers are candidates for designing 2D AFM materials, with potential applications in electronic devices.