Exploring room-temperature anti-ferromagnetism in a newly predicted 2D MBene M₄B₆ (M: Cr, Mn, Fe) monolayer using first-principles calculations

The search for two-dimensional (2D) materials is rapidly expanding. Here, we predict a new series of 2D MBene M₄B₆ monolayers composed of transition metal (M: Cr, Mn, Fe) and boron (B) atoms, thereby extending the family of MBenes. Detailed first-principles calculations demonstrate that the new MBene materials have stable hexagonal crystal structures and an antiferromagnetic ground state. The average magnetic moment per magnetic ion in the antiferromagnetic state is calculated as 2.10<i>μ</i>_B per atom, 2.60<i>μ</i>_B per atom, and 1.38<i>μ</i>_B per atom for Cr₄B₆, Mn₄B₆, and Fe₄B₆ monolayers, respectively. The calculated spin-polarized electronic band structures show the narrow gap semiconducting character in the Cr and Mn-based MBene monolayers under consideration. Furthermore, the stability of magnetization against thermal fluctuations is confirmed by the energy barrier created by the magnetocrystalline anisotropy energy (MAE), which is as high as 0.822 meV per cell with respect to hard axes for the Mn₄B₆ monolayer. The high value of MAE indicated that the spin moments will be aligned out of the plane in a 2D Ising Model fashion. The Néel temperatures for the Cr₄B₆, Mn₄B₆, and Fe₄B₆ MBene monolayers are estimated to be 302.09 K, 393.05 K, and 233.62 K, respectively, by using Monte Carlo (MC) simulations. These results indicate that the newly predicted 2D MBene M₄B₆ monolayers are promising materials for spintronic nanodevices at room temperature.