Exchange-biased Quantum Anormalous Hall Effect in Magnetic Topological Insulator and Antiferromagnetic Insulator Heterostructure*

The integration of topological and (anti)ferromagnetic layers has attracted wide interest, to introduce ferromagnetism into nonmagnetic topological insulators (TIs) or to enhance the Curie temperature of magnetically doped topological insulators (MTIs). In addition, the exchange coupling between the layers provides an additional degree of freedom through which the topological surface states can be manipulated. Here, we report on exchange coupling between the quantum anomalous Hall (QAH) state of MTI and an antiferromagnetic insulator with a net parasitic magnetization, Al-doped Cr₂O₃. Polarized neutron reflectometry (PNR) measurements reveal a strong exchange coupling between the two magnetic layers pinning the moments at the interface to point out-of-plane, which leads to the observation of an exchange-biased QAH on the transport signal for the first time.