This thesis explores the use of 2D materials (graphene and hBN) for spintronics. Interest on these materials in spintronics arose from theoretical predictions of high spin filtering in out-of-plane transport through graphene and hBN sandwiched by ferromagnets. Similarly, 5-layer graphene was forecast to be a perfect spin filter. In the case of in-plane spin transport, graphene was expected to be an excellent material due to its low spin-orbit coupling and low number of defects. Although there already exist experimental works that attempted to explore the aforementioned predictions, they have failed so far to comply with the expected results. Earlier experimental works in graphene and hBN out-of-plane spin transport achieved low spin filtering on the order of a few percent; while spin relaxation parameters in graphene for in-plane spin transport remained one or two orders of magnitude below the predicted values. In the case of vertical devices, the failure to meet the theoretical expectations was attributed to the oxidation of the ferromagnets and the lack of an epitaxial interface between the later and the graphene or hBN. Similarly, the exact mechanisms that lead to high spin relaxation for in-plane spin transport in graphene are not completely understood, in part due to the low-quality of the explored devices. In this thesis we analyze new architectures and procedures that allowed us to fabricate ultraclean and oxidation-free interfaces between ferromagnets and graphene or hBN. In these devices we encountered negative and reversible magnetoresistance, that could not be explained with the previous theoretical models. We propose a new model based on a thorough characterization of the devices and well-known properties of graphene that were not taken into account in the previous model. We also employed a novel type of contact to graphene (1D-contacts) and applied it for the first time to achieve spin-injection in graphene. The main advantage of this type of contact is the full encapsulation of graphene with hBN, which leads to high quality graphene spintronic devices.
| Identifer | oai:union.ndltd.org:bl.uk/oai:ethos.bl.uk:764511 |
| Date | January 2017 |
| Creators | Sambricio Garcia, Jose Luis |
| Contributors | Grigorieva, Irina |
| Publisher | University of Manchester |
| Source Sets | Ethos UK |
| Detected Language | English |
| Type | Electronic Thesis or Dissertation |
| Source | https://www.research.manchester.ac.uk/portal/en/theses/graphenehybrid-devices-for-spintronics(e552a341-6af9-45fb-ba16-d9c43c3412c8).html |
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