Direct evidence of induced magnetic moment in Se and the role of misplaced Mn in MnBi2Se4 -based intrinsic magnetic topological insulator heterostructures

Although intrinsic magnetic topological insulator heterostructures are thought to be an ideal system to examine the interplay of topology and magnetism, unintended disorder can alter their property. In this study, the authors combine atom-resolved characterization as well as theoretical calculation and investigate the structural and magnetic properties of heterostructures formed by MnBi${}_{2}$Se${}_{4}$ and Bi${}_{2}$Se${}_{3}$. They clarify the magnetic coupling between Mn atoms placed at different sites and furthermore, detect a clear magnetic signal in the nonmagnetic element Se, providing direct evidence of its magnetic interaction with Mn. This study highlights the need to examine the magnetism of each atom carefully in these systems.