Revealing Proximity Effects at Magnetic Topological Insulator / Antiferromaget Interfaces*

Magnetic topological insulators are an exciting new platform for the investigation of exciting time-reversal symmetry-breaking physics such as the quantum anomalous hall effect, inverse spin galvanic effect, axion electrodynamics, and spin orbit torque. These materials systems also have great potential for spintronic device applications, but practical development has so far been inhibited by the extremely low (around 30 K) Curie temperature of these materials. Interfacial proximity coupling to other magnetically ordered compounds has been suggested as a mechanism by which this challenge may be addressed. However, separating interfacial exchange coupling from less-desirable effects such as intermixing presents significant challenges. In this work, we use neutron and magnetic X-ray spectroscopy to assemble an depth and element-resolved picture of magnetism within topological insulator/antiferromagnet heterostructures. Our results support true proximity-induced magnetization in (Bi,Sb)₂Te₃ films interfaced with CrSb and MnTe, with enhanced ordering temperature and chiral magnetic structures. We show that the topology and magnetism of the (Bi,Sb)₂Te₃ may be readily controlled through exchange coupling with the adjacent antiferromagnet.