Abstract
In this study, we investigate the proximity effect in topological insulator (TI) and magnetic insulator bilayer system. (Bi1−xSbx)2Se3/CoFe2O4 (CFO) heterostructure was fabricated using molecular beam epitaxy and pulsed laser deposition system respectively. As revealed from the magnetoresistance measurement, the weak anti-localization (WAL) is strongly suppressed by proximity effect in (Bi1−xSbx)2Se3/CFO interface. Modified Hikama-Larkin-Nagaoka equation was used to fit the WAL results so that the size of surface state gap can be extracted successfully. The temperature-dependent resistance of the heterostructures at small and large perpendicular magnetic fields were also measured and analyzed. The results indicate that the surface band gap can be induced in TI and continuously enlarged up to 9 T, indicating the gradual alignment of the magnetic moment in CFO under perpendicular magnetic field. The approaches and results accommodated in this work show that CFO can effectively magnetize (Bi1−xSbx)2Se3 and the heterostructures are promising for TI-based spintronic device applications.
Highlights
Interface between topological insulator (TI) and magnetic insulator layers
The results indicate that the slopes κ reveal two different behaviors in small and large perpendicular magnetic field
We can observe α1 ∼ −0.44 and α0 ∼ 0.08, revealing again that TI has been magnetized by CFO because α1 and α0 are more than −0.5 and 0, respectively. These results indicate that the proximity effect can slightly suppress weak anti-localization (WAL), which is consistent with the above-proposed scenario
Summary
Interface between TI and magnetic insulator layers For this reason, the angle-resolved photoemission spectroscopy is not an appropriate way to observe the proximity effect since only the electronic structure of top surface (a few nanometers thickness) can be measured. The angle-resolved photoemission spectroscopy is not an appropriate way to observe the proximity effect since only the electronic structure of top surface (a few nanometers thickness) can be measured Another method to observe the surface gap opening is magnetoresistance (MR) measurement. In large magnetic fields, the κ decreases with increasing magnetic field These results are significantly different with single layer results, which can be attributed to the continual enhancement of the surface gap size in the large magnetic field. Our findings should be useful for the future studies of magnetic TI and TI-based spintronic devices
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