Electric field control of magnetism in artificial multiferroics
Several routes to the electric field control of magnetism are currently being investigated: charge modulation to manipulate the preferred direction of magnetization, ionic diffusion and strain coupling to piezoelectrics. A further possibility is to use exchange coupling between domains in ferroelectrics and ferromagnets. The electric field control of domain walls in an Fe film via coupling to domains in a barium titanate (BTO) substrate has recently been demonstrated and may offer a route to low power memory/logic/sensor devices. However, ferromagnetic films such as Co/Pt with preferred direction of magnetization out-of-plane are more promising technologically because the domain walls are very narrow (a few nm wide) and furthermore the interfacial Dzyaloshinskii-Moriya interaction can lead to nm-scale topologically stable skyrmion bubbles.
This project will investigate the coupling between ferroelectric materials and ferromagnetic layers with perpendicular anisotropy. Available ferroelectric crystals are lead-magnesium niobate-lead titanate (PMN-PT), bismuth ferrite (BFO), BTO and BFO-PTO. The first task will be to obtain perpendicular anisotropy in the magnetic layer: the archetypal thin film is Co/Pt. We will then study the imprinting of ferroelectric domains into the ferromagnet using polarising and magneto-optical microscopy as well as scanning probe techniques. We shall investigate the response of the ferromagnet to electric-field reorientation of the ferroelectric polarisation and apply structural and magnetic characterisation methods including synchrotron techniques to understand the interface physics.
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FTE Category A staff submitted: 24.00
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