First‐principles investigations of amorphous and crystalline MnSb2Te4

Crystalline Mn1Sb2Te4 (MST), an intrinsic magnetic topological insulator, shows similarity to the ground-state structure of the phase-change alloy Ge1Sb2Te4 (GST). However, the atomic structure and key physical properties of amorphous MST—crucial for phase-change functionality—have not been reported to date. In this work, we investigate the amorphous and crystalline states of MST using density functional theory (DFT) and DFT-based ab initio molecular dynamics (AIMD) simulations. In addition to the ordered trigonal phase, we predict the existence of a metastable cubic rocksalt-like phase with a high concentration of intrinsic cation vacancies, in close analogy with rocksalt-like GST. Structural analysis reveals that the short-range order in amorphous MST resembles that of the rocksalt-like phase, featuring defective octahedra and abundant four-membered rings. Furthermore, MST maintains spin polarization in both amorphous and crystalline phases and exhibits a contrast in magnetic and optical properties. These findings identify MST as a promising candidate for applications combining phase-change functionality with intrinsic magnetic order.