under Strain and Temperature Variations: A Combined DMC and DFT Approach*

We investigate the magnetic properties of MnBi₂Te₄ (MBT), a magnetic topological insulator that has attracted considerable interest for its potential applications in spintronics and quantum computing. As a van der Waals material, MBT exhibits both magnetic and nontrivial topological phases. Its magnetic properties vary with the number of layers and can be influenced by external parameters such as temperature and strain. Nevertheless, there remains a gap in our theoretical understanding of MBT due to discrepancies between experimental results and ab initio predictions. To reconcile this, we have employed computational methods including Diffusion Monte Carlo (DMC) and Density Functional Theory (DFT). By adjusting the Hubbard U value in response to applied strain via DMC, we determine the magnetic anisotropy energy under varying strains via DFT. Furthermore, we investigate the effect of prevalent antisite defects on the magnetic properties under different strain scenarios. Our results provide profound insights into the behavior of MBT under various conditions, and shed light on the underlying mechanisms of its magnetic properties and their sensitivity to external influences.