  The experimental observation of quantum anomalous Hall effect (QAHE) in
magnetic topological insulators has stimulated enormous interest in
condensed-matter physics and materials science. For the purpose of realizing
high-temperature QAHE, several material candidates have been proposed, among
which the interface states in the CdO/ferromagnetic insulator heterostructures
are particularly interesting and favorable for technological applications.
Here, we report the experimental observation of the interfacial ferromagnetism
and anomalous Hall effect in the Fe3O4/CdO/Fe3O4 heterostructures grown via
oxide molecular-beam epitaxy. Systematical variation of the CdO thickness
reveals the interface ferromagnetism as the major cause for the observed planar
magnetoresistance and anomalous Hall effect. Our results might pave the way to
engineer oxide interface states for the exploration of QAHE towards exotic
quantum-physical phenomena and potential applications.
