Topological insulator interfaced with ferromagnetic insulators: <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML"><mml:mrow><mml:mi mathvariant="normal">B</mml:mi><mml:msub><mml:mi mathvariant="normal">i</mml:mi><mml:mn>2</mml:mn></mml:msub><mml:mi mathvariant="normal">T</mml:mi><mml:msub><mml:mi mathvariant="normal">e</mml:mi><mml:mn>3</mml:mn></mml:msub></mml:mrow></mml:math> thin films on magnetite and iron garnets
V. M. Pereira, S. G. Altendorf, C. E. Liu, Shu‐Hang Liao, A. C. Komarek, Mengxin Guo, H. J. Lin, C. T. Chen, Minghwei Hong, J. Kwo, L. H. Tjeng, C. N. Wu
Abstract
We report our study about the growth and characterization of $\mathrm{B}{\mathrm{i}}_{2}\mathrm{T}{\mathrm{e}}_{3}$ thin films on top of ${\mathrm{Y}}_{3}\mathrm{F}{\mathrm{e}}_{5}{\mathrm{O}}_{12}$(111), $\mathrm{T}{\mathrm{m}}_{3}\mathrm{F}{\mathrm{e}}_{5}{\mathrm{O}}_{12}$(111), $\mathrm{F}{\mathrm{e}}_{3}{\mathrm{O}}_{4}$(111), and $\mathrm{F}{\mathrm{e}}_{3}{\mathrm{O}}_{4}$(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 $\mathrm{B}{\mathrm{i}}_{2}\mathrm{T}{\mathrm{e}}_{3}$ 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.