Unveiling topological magnetic structures with advanced X-ray vector imaging

There is increasing excitement about the prospects of three-dimensional magnetic systems to provide a rich playground for fundamental physics [1,2]. Indeed, the move from planar, two dimensional systems to truly three-dimensional systems offers a host of exciting properties, whether through the introduction of effects such magnetochirality and complex energy landscapes, or the realisation of topological textures that wind in 3D such as skyrmion tubes [3], magnetisation singularities [4], or the recently predicted, but as yet experimentally elusive, topologically non-trivial hopfion [5]. Not only are these objects interesting from a fundamental point of view: their typical sizes – on the nanoscale – and topological stability, have inspired new concepts for technological devices [6].

The surroundings of magnetisation singularities – a circulating Bloch point (left) and an anti-Bloch point (right) – visualised with X-ray magnetic nanotomography. Reproduced from [4].

When it comes to enhancing our understanding, and long term: control, of these topological objects, visualisation is key. Indeed, recent developments in X-ray magnetic 3D imaging [4,7], which have made the direct visualisation of 3D magnetic configurations possible, have led to first observations of the surroundings of magnetisation singularities [4], 3D vortex domain walls [4,7] – and their motion! [7] – along with the very recent discovery of magnetic vortex rings [8]. Now, armed with the necessary experimental capabilities, we find ourselves on the brink of an avalanche of new physics and exciting discoveries.

In this PhD project, you will exploit X-ray magnetic 3D imaging techniques to understand the physics of topological 3D magnetic textures, leading to insights into their formation, stability and behaviour. Using state-of-the-art experimental and analysis techniques, we will push the frontiers of the experimental capabilities, and physical understanding, of these exciting physical systems.


[1] A. Fernández-Pacheco, R. Streubel, O. Fruchart, R. Hertel, P. Fischer, and R.P. Cowburn
Three-dimensional nanomagnetism
Nature Communications 8, 15756 (2017)
[3] C. Donnelly and V. Scagnoli
Imaging three-dimensional magnetic systems with x-rays
J. Phys. Cond. Matt. 32, 21 (2020)
[2] R. Streubel, P. Fischer, F. Kronast, V.P. Kravchuk, D.D. Sheka, Y. Gaididei, O.G. Schmidt and D. Makarov
Magnetism in curved geometries
J. Phys. D: Appl. Phys. 49, 363001 (2016)
[7] C. Donnelly, M. Guizar-Sicairos, V. Scagnoli, S. Gliga, M. Holler, J. Raabe, and L.J. Heyderman
Three-dimensional magnetization structures revealed with X-ray vector nanotomography
Nature 547, 328–331(2017)
[5] P. Sutcliffe
Skyrmion Knots in Frustrated Magnets
Phys. Rev. Lett. 118, 247203 (2017)
[6] A. Fert, V. Cros, and J. Sampaio
Skyrmions on the track
Nature Nanotechnology 8, 152–156 (2013)
[8] C. Donnelly, S. Finizio, S. Gliga, M. Holler, A. Hrabec, M. Odstrčil, S. Mayr, V. Scagnoli, L.J. Heyderman, M. Guizar-Sicairos, and J. Raabe
Time-resolved imaging of three-dimensional nanoscale magnetization dynamics
Nature Nanotechnology 15, 356–360 (2020)
[8] C. Donnelly, K.L. Metlov, V. Scagnoli, M. Guizar-Sicairos, M. Holler, N.S. Bingham, J. Raabe, L.J. Heyderman, N. Cooper, S. Gliga
Experimental Observation of Vortex Rings in a Bulk Magnet
accepted for publication in Nature Physics

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