Two-Dimensional Transition Metal Boride TMB₁₂ (TM = V, Cr, Mn, and Fe) Monolayers: Robust Antiferromagnetic...

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, TMB₁₂ (TM = V, Cr, Mn, Fe) monolayers, by combining TM atoms and B₁₂ icosahedra based on first-principles calculations. Our results show that the four TMB₁₂ monolayers have stable antiferromagnetic (AFM) ground states with large magnetic anisotropic energy. Among them, three TMB₁₂ (TM=V, Cr, Mn) monolayers display an in-plane easy magnetization axis, while the FeB₁₂ monolayer has an out-of-plane easy magnetization axis. Among them, the CrB₁₂ and the FeB₁₂ monolayers are AFM semiconductors with band gaps of 0.13 eV and 0.35 eV, respectively. In particular, the AFM FeB₁₂ monolayer is a spin-polarized AFM material with a Néel temperature of 125 K. Moreover, the electronic and magnetic properties of the CrB₁₂ and the FeB₁₂ monolayers can be modulated by imposing external biaxial strains. Our findings show that the TMB₁₂ monolayers are candidates for designing 2D AFM materials, with potential applications in electronic devices.