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Graham Kimbell

Research Interests

Supervisor: Prof Jason Robinson

Research area: Superconducting spintronics

My work focuses on thin film magnetism and superconductivity. I use pulsed laser deposition to grow ultra-thin epitaxial single crystal films of complex oxide materials, which I then characterise using x-ray techniques, electrical transport measurements, and magnetometry to study phenomena arising from interfaces.

Much of my PhD has been concerned with the controversial reports of skyrmions in several-unit-cell thick SrRuO3 films. Skyrmions are topologically protected nanometer-scale magnetic whirls which are of great interest for their potential use in future generation computing devices as information carriers. Detection of a topological Hall effect is one of the signature Hallmarks (please pardon the pun) of skyrmions. However I have shown that the apparent topological Hall effect in SrRuOcould instead arise from thickness inhomogeneity and not skyrmions [1].

I have also worked on exchange coupling at magnetic perovskite interfaces, and collaborated in thin film growth and characterisation for unconventional superconducting Sr2RuO4 [2] and magnetic insulating YFe5O12 films [3].

Key Publications

[1] Kimbell, G., Sass, P.M., Woltjes, B., Ko, E.K., Noh, T.W., Wu, W. and Robinson, J.W., 2020. Two-channel anomalous Hall effect in SrRuO3Physical Review Materials4(5), p.054414.

[2] Garcia, C.M.P., Di Bernardo, A., Kimbell, G., Vickers, M.E., Massabuau, F.C., Komori, S., Divitini, G., Yasui, Y., Lee, H.G., Kim, J. and Kim, B., 2020. Pair suppression caused by mosaic-twist defects in superconducting Sr2RuO4 thin-films prepared using pulsed laser deposition. Communications Materials1(1), pp.1-8.

[3] Li, Y., Amado, M., Hyart, T., Mazur, G.P., Risinggård, V., Wagner, T., McKenzie-Sell, L., Kimbell, G., Wunderlich, J., Linder, J. and Robinson, J.W., 2020. Transition between canted antiferromagnetic and spin-polarized ferromagnetic quantum Hall states in graphene on a ferrimagnetic insulator. Physical Review B101(24), p.241405.