Stability subtlety of layered magnetic topological insulator MnBi₂Te₄

Ab initio description of two dimensional magnetic materials (2DMM) thermodynamics faces great challenges, due to the coexistence of different kinds of chemical bonding, as well as coupling between charge, lattice, and spin degrees of freedom. As an illustration of such challenges, we investigated the metastability of a layered magnetic material MnBi2Te4, which hosts the intrinsic quantum anomalous Hall effect but the crystal itself is hard to synthesize. We calculated the reaction free energy of Bi₂Te₃+MnTe→MnBi₂Te₄, considering electron, vibration and magnetic contributions based on state-of-the-art SCAN+rVV10¹ total energy calculations. We found MnBi₂Te₄ to be stable only within a short high temperature range, consistent with experiments. Fundamental interactions including SOC effect, vdW interaction, 2D weak magnetism and lattice vibration all contribute subtly to the high-temperature stability of MnBi₂Te₄, which exemplify that interplay of topology and magnetism can contribute to the stability of the material hosting it. These findings and methods pave a way for future high throughput discovery of novel 2DMM.


¹H. Peng, Z. Yang, J. P. Perdew, and J Sun Phys. Rev. X 6, 041005 (2016).