Antiferromagnetic topological insulator MnBi₂Te₄: Synthesis and magnetic properties

Recently, MnBi₂Te₄ has been discovered as the first intrinsic antiferromagnetic topological insulator (AFM TI), and it will become a promising material to discover exotic topological quantum phenomena. In this work, we have realized the successful synthesis of high-quality MnBi₂Te₄ single crystals by solid-state reactions. The as-grown MnBi₂Te₄ single crystal exhibits a van der Waals layered structure, which is composed of septuple Te-Bi-Te-Mn-Te-Bi-Te sequences as determined by X-ray diffraction and high-resolution high-angle annular dark field scanning transmission electron microscopy (HAADF-STEM). The magnetic order below 25 K as a consequence of A-type antiferromagnetic interaction between Mn layers in the MnBi₂Te₄ crystal suggests the unique interplay between antiferromagnetism and topological quantum states. Moreover, the transport measurements of MnBi₂Te₄ single crystals further confirm its magnetic transition. This study on the first AFM TI of MnBi₂Te₄ will guide the future research on other potential candidates in the MBi_xTe_y family (M = Ni, V, Ti, etc.).