"Integration of magnetic functionalities into electronic circuits requires the use of low cost, scalable methods focusing on the manipulation of magnetic moments by electric fields, as opposed to external magnetic fields. Spin polarized carriers can exert a torque to control the magnetization orientation. These carriers can be injected from ferromagnets (FM). They can also originate from the spin-orbit interaction, by using the Rashba, Dresselhaus and spin Hall effects. Ultimately, one may take advantage of the spin-textured states at the surface of topological insulators (TIs), a recently discovered new state of matter. The later ""spin-orbit torques"" (SOTs) were recently observed in heavy-metal/FM and semiconducting structures. However, the mechanisms in play are under fierce debate, which is hindering technological progress.
The aim of this project is primarily to perform a pioneering investigation of SOTs in TIs, opening new avenues for magnetization control and next-generation spintronic devices. In addition, information on the magnitude, symmetry and origin of the SOTs will be gathered with commonly studied heavy metals. A further objective is to investigate new magnetoresistive effects mediated by TIs surface states.
We will fabricate layered FM/TI and FM/metal structures by molecular beam epitaxy and implement electrical transport and magnetic resonance measurements. The helical nature of surface states in TIs is expected to provide alternative mechanisms to produce SOTs that are currently unexplored. We will also investigate the influence of the magnetic state on the charge transport in FM/FM junctions on top of TIs, in particular current quantization which should be associated with large magnetoresistance.
If successful, the outcomes of this work will include new understanding of the mechanisms by which spin-orbit coupling can lead to SOTs, new materials with optimized effects and novel devices for Information and Communication Technologies based on them."
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