Exploring Bonding Configurations in MnBi₂Te₄-Type Materials

We perform a systematic investigation of several crystal structures, based on monolayer MnBi₂Te₄, of the form MnBBX₂X₂ using first-principles calculations. Our analysis shows that the most energetically favorable bonding configuration of the constituent elements in monolayer MnBBX₂X₂ is determined by the bond length between the Mn atom and its nearest X-site atoms. Tuning the bonding configuration of the material alters the magnetic, electronic, and topological properties. We also calculate the magnetic exchange parameters and magnetic anisotropy energy of the predicted structures. The calculations show that the elements at the X sites mainly determine the magnetic properties. Finally, we propose a stable phase of monolayer MnBi₂S₂Te₂ (i.e., γ-MnBi₂S₂Te₂) that exhibits the quantum anomalous Hall effect (QAHE). This study demonstrates that the bonding configuration of MnBi₂Te₄-type materials provides avenues for tuning the magnetic, electronic, and topological properties of van der Waals (vdW) materials.