Field effect controlled magnetism and magnetotransport in low dimensions

Lei Liang

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Ionic gating is a technique that provides a simple method to access two-dimensional electrical transport systems by forming an electric double layer. It is possible to effectively tune the conductance of semiconductors and even metals. In this thesis, a new type of magnetic ionic liquid has been applied widely as the gating medium. Carrier density variation in proximity of magnetic moments from the anions drives the quantum phase transition in platinum, resulting in a ferromagnetic ground state as revealed by the hysteretic anomalous Hall effects. It is related to both the strong spin orbit interaction and the Stoner instability of platinum. The field-effect induced ferromagnetic state is confined at the platinum|paramagnetic insulating ionic liquid interface with a strong perpendicular anisotropy, which mimics the Ising type of two-dimensional ferromagnetism. Applying an in-plane magnetic field generates both modulations in longitudinal and transverse resistivities that has been successfully interpreted by the spin Hall magnetoresistance theory. In the presence of a strong ferromagnetic state on the surface of platinum, a coexisting Kondo effect emerges that is spatially separated from the top-most surface. Another system studied in this thesis is transition metal dichalcogenides with magnetic intercalants is. Few layer thick Mn1/4TaS2 films are achieved by mechanical exfoliation of bulk crystals. This material shows ferromagnetic easy planes and inter-plane antiferromagnetic interactions, allowing the smallest giant magnetoresistive devices to be fabricated with field controllable magnetization orientations between two neighboring layers. In summary, low dimensional magnetic systems stabilized by significant anisotropy are investigated in this thesis.
Original languageEnglish
QualificationDoctor of Philosophy
Awarding Institution
  • University of Groningen
  • Ye, Justin, Supervisor
  • Palstra, Thomas, Supervisor
  • Blake, Graeme, Co-supervisor
Award date17-Nov-2017
Place of Publication[Groningen]
Print ISBNs978-94-034-0290-1
Electronic ISBNs978-94-034-0289-5
Publication statusPublished - 2017

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