Topological Insulator Interfaced With Ferromagnetic Insulators: Bi2te3 Thin Films On Magnetite And Iron Garnets

We report our study about the growth and characterization of Bi2Te3 thin films on top of Y3Fe5O12 (111), Tm3Fe5O12 (111), Fe3O4 (111), and Fe3O4 (100) single-crystal substrates. Using molecular-beam epitaxy, we were able to prepare the topological insulator/ferromagnetic insulator heterostructures with no or minimal chemical reaction at the interface. We observed the anomalous Hall effect on these heterostructures and also a suppression of the weak antilocalization in the magnetoresistance, indicating a topological surface-state gap opening induced by the magnetic proximity effect. However, we did not observe any obvious x-ray magnetic circular dichroism (XMCD) on the Te M-45 edges. The results suggest that the ferromagnetism induced by the magnetic proximity effect via van der Waals bonding in Bi2Te3 is too weak to be detected by XMCD, but still can be observed by electrical transport measurements. This is in fact not inconsistent with reported density-functional calculations on the size of the gap opening.