Probing Interfacial Magnetism and Magnetic Coupling Phenomena in Antiferromagnet - Nanocrystalline Topological Insulator Heterostructures

Topological electronics makes use of novel quantum degrees of freedom, as they are encountered in topological insulators (TIs). One of the most remarkable properties of a TI is the dissipationless carrier transport through its surface states. In magnetically doped TIs, the quantum anomalous Hall effect (QAHE) was observed; a zero-field version of the ordinary quantum Hall effect. However, due to defects associated with the doping, the useful temperature range is rather small. Proximity induced magnetisation is a promising method to create ferromagnetic order in TI. Using an antiferromagnet as magnetic adlayer reduces stray fields that can interfere with the QAH states. We recently discovered that diffusion of magnetic constituents in heterostructures of Mn-based magnetic materials and TI can mimic the elusive proximity induced magnetisation effect at the interface. To address this problem, we propose to utilise NiO/nanocrystalline Bi2Te3-heterostructures grown using sputtering to substantially reduce diffusion and to achieve high-quality interfaces. This should facilitate the observation of proximity induced magnetisation using polarised neutron reflectometry.