Proximity effects between topological insulators and insulating ferromagnets
- Qi Yang.
- [Stanford, California] : [Stanford University], 2018.
- Copyright notice
- Physical description
- 1 online resource.
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|3781 2018 Y||In-library use|
- To investigate the effects due to proximity between a three-dimensional topological insulator (TI) and an insulating ferromagnet (IF), TI-IF thin film bilayers were fabricated with pulsed laser deposition. Either bismuth(III) selenide (Bi2Se3) or bismuth-antimony(III) telluride (BST) was used for the TI layer, whereas the IF layer was formed by the Heisenberg ferromagnet EuS. While a positive magnetoresistance was observed above the Curie temperature of EuS, as ubiquitously observed in high-quality TI thin films, an unusual negative magnetoresistance was observed below the Curie temperature in the variable-range hopping regime. The angular dependence of such negative magnetoresistance indicates an orbit origin. Specific to BST-EuS bilayers, when the bulk conduction is minimized, magnetic anomalies in AC susceptibility were observed concurrently with resistive anomalies at the same temperatures, suggesting an interface magnetic order. These phenomena together suggest two-stage proximity effects between the topological insulators and the insulating ferromagnet, and provide first steps to realize the half-integer quantum anomalous Hall effect.
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- Submitted to the Department of Physics.
- Thesis Ph.D. Stanford University 2018.
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