Study of proximity induced magnetism in nanocrystalline antiferromagnet-topological insulator heterostructures

Magnetic topological insulators (MTIs) have been at the centre of condensed matter research due to the wealth of quantum effects they harbour. One example is the quantum anomalous Hall effect (QAHE), resembling the quantum Hall effect without the requirement for large applied magnetic fields, and, in principle, cryogenic cooling. To take advantage of the outstanding properties of topological insulators, such as dissipationless and fully spin-polarised transport, and to raise interest for their commercial utilisation, their industry-compatible fabrication has to be demonstrated. Sputtering is one of the fabrication methods of choice for data storage and information processing applications, due to the fast turnaround times, acceptance of large wafer sizes, and high reproducibility. The wider goal of this project is to fully fabricate an MTI heterostructure using sputtering, with the MTI consisting of the topological insulator Cr-doped Sb2Te3 coupled to the antiferromagnet NiO. In the past, we investigated similar heterostructures grown by molecular beam epitaxy (MBE). MBE is widely used in academia due to its high level of control over the growth parameters and as it is ideally suited for research into novel materials of high crystalline quality. However, MBE-grown MTI films are characterised by island growth, which effectively results in poor layer thickness control. This makes MBE-grown samples less suitable for the study of confinement-driven quantum effects. In contrast, sputter deposition leads to extremely smooth films. Here, we plan to investigate the proximity-induced magnetism in sputtered Cr-doped Sb2Te3/NiO heterostructures as a function of MTI thickness.