Growth Control of Magnetic Perovskite/2D Topological Insulator Heterostructures—Towards Tailoring Interfacial Magnetic Interactions

Quantum materials gain an increasing interest in the field of electronics research. One exciting opportunity is heterostructures of magnetic oxides (MO) and topological insulators (TI) exhibiting unique combined properties and emergent interfacial properties. Recent studies on the topological insulating chalcogenide systems, forming heterostructures with magnetic compounds reveal that such systems exhibit emergent interface ferromagnetism, quantum anomalous Hall effect, enhancement of magnetic order, and ordering temperatures and topological surface states extending into the magnetic material. For the materials possessing inherently different crystal structures, an important first step is to ensure high-quality interfaces and the proper connectivity. In this work, we focus on structural engineering of TI Bi₂Te₃ (BT) grown on (001) & (111) oriented magnetic perovskites, as well as the importance of the interface analysis for understanding the origins of the emergent magnetic properties. The aim of the research is to establish a precise BT growth control towards a thorough understanding of magnetic interactions at magnetic perovskite-2D topological insulator interfaces. BT thin films are deposited by pulsed laser deposition (PLD) directly onto (001) and (111)-oriented SrTiO₃ (STO), La_0.7Sr_0.3MnO₃ (LSMO) and LaFeO₃ (LFO). In structural analysis with SEM/AFM, XRD and TEM, we show that BT films can be grown by PLD on high lattice mismatch substrates, yielding high quality plane stacking and surface morphology. We employ Raman spectroscopy to confirm the proper BT stoichiometry. Vibrating sample magnetometry (VSM) is used to investigate the effect on macroscopic magnetism of ferromagnetic LSMO, and x-ray magnetic circular/linear dichroism is used to probe element specific magnetic features. The magnetization analysis indicates a possible magnetic proximity effect in the BT/LSMO(111) system. By utilizing different substrate orientations, as well as magnetic characteristics, heterostructure interactions can be tuned. This tunability can be used to further probe systematically how the oxide spin axis couples to the van der Waals material, and what is the effect on the topological insulator properties.