Electrical control of magnetism in oxide films and devices

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One of the most promising routes towards a new generation of fast, low-power electronics is the electrical control of magnetism in insulators. This approach exploits the ability to switch the antiferromagnetic state in several classes of oxides by applying a small writing voltage. The spin polarisation can then be transferred to a ferromagnetic material through an interface, and then read in a conventional way, e.g., using a Tunnelling MagnetoResistance junction as in hard-disk reading heads. This scheme could be employed to produce fast and efficient non-volatile memories, with no writing current to produce Joule heating and therefore dissipate energy. We have recently developed a suite of techniques for simultaneous imaging of antiferromagnetic/ferromagnetic domains and their electrical switching in epitaxial oxide films and devices. We use a combination of synchrotron X-ray diffraction and microscopy, in-house Magnetic Force Microscopy (MFM) and neutron diffraction, which give us access to domains over length scales from 1 cm to < 100 nm. In the past two years, we obtained some very exciting results on thin films and devices of BiFeO3, grown by our collaborators at the University of Madison. In very recent experiments, we directly imagined the process of electrical switching in BiFeO3 and demonstrated the coupling of the BiFeO3 domains with the ferromagnetic domains of a thin metal over-layer. Even more recently, we demonstrated similar effects in epitaxial films of Fe2O3, grown by one of our students in our lab.This EPSRC-funded DPhil project will give the successful candidate the opportunity to develop this line of research in different directions:Identify and grow new materials with electrically controllable domainsExperiment with novel methods to switch the magnetic state of the domains, e.g., through the piezoelectric effect.Build and test prototype devices using electron beam lithography and other clean room processes.This project is likely to involve a combination of experimental techniques, such as:Elastic neutron scattering. We will perform experiments on bulk and films samples predominantly at the ISIS facility at Rutherford Appleton Laboratory.X-ray scattering, including resonant and non-resonant magnetic X-ray diffraction with hard and soft X-rays. We run state-of-the-art laboratory instrumentation in the Clarendon Laboratory, but we perform most of our high-end experiment at the Diamond Light source.Dielectric and transport measurements. One of our specialities is to perform measurements of ferroelectricity in extremely high magnetic fields (up to 65 T - a record in the UK), using the pulsed-magnetic-field facility in the Clarendon Laboratory, but a complete set of more standard measurements is also available.Advanced microscopy. We employ spectral microscopy (PEEM) at Diamond, Magnetic Force Microscopy (MFM) and the Magneto-Optical Kerr Effect to image multi-functional domains, which are the fundamental unit of information storage in oxides.Nanofabrication. We will be using electron beam lithography and other clean-room methods to design and build prototype oxide quantum materials devices.Depending on the candidate's interests, the project may also include a computational element. In collaboration with the Materials Modelling Group in the Department of Materials, we employ Density Functional Theory methods and other computational techniques to model the functional properties of oxides and to predict their behaviour in different architectures.This project falls within the 'Energy', 'Physical Sciences' and 'Quantum Technology' EPSRC themes.