Intermixing-Driven Surface and Bulk Ferromagnetism in the Quantum Anomalous Hall Candidate MnBi Te.

The recent realizations of the quantum anomalous Hall effect (QAHE) in MnBi Te and MnBi Te benchmark the (MnBi Te )(Bi Te ) family as a promising hotbed for further QAHE improvements. The family owes its potential to its ferromagnetically (FM) ordered MnBi Te septuple layers (SLs). However, the QAHE realization is complicated in MnBi Te and MnBi Te due to the substantial antiferromagnetic (AFM) coupling between the SLs.