IMX Seminar Series - Exploring three dimensional spin systems – and beyond

Three dimensional magnetic systems promise significant opportunities for applications, for example providing higher density devices and new functionalities associated with complex topology and greater degrees of freedom [1,2]. Extending to three dimensions allows for the formation of new topologies of spin textures, for example containing defects in 3D such as Bloch point singularities, or truly three-dimensional topological structures such as magnetic hopfions.
In this talk, I will address two main questions: first, can we observe and understand such three-dimensional topological magnetic textures, and second, can we control them?
For the observation and understanding of these three-dimensional textures, we have developed magnetic X-ray tomographic techniques, that open the possibility to map both the three-dimensional magnetic structure [3], and its dynamical response to external excitations [4,5].  In this way, we observe 3D magnetic solitons which we identify as nanoscale magnetic vortex rings, as well as torons that contain Bloch point singularities [6,7].
However, while X-ray magnetic tomography is now a relatively well-established technique, high resolution imaging of extended magnetic systems has so far been limited to rare-earth containing materials. To this end, I will present recent results of soft X-ray dichroic ptychography where the phase dichroism offers a route to imaging magnetic systems that until now have not been accessible [8].
As well as naturally existing within the bulk, 3D spin textures can be introduced and controlled via the patterning of 3D curvilinear geometries [9]. In this way, not only can new states be realized [10], but the energy landscape of topological defects can be designed through the local patterning of curvature induced chirality [11].
This new understanding and control of topological textures in 3D magnetic systems paves the way not only for enhanced understanding of these systems, but also towards the next generation of technological devices.


References

[1] Fernández-Pacheco et al., Nature Communications 8, 15756 (2017).
[2] C. Donnelly and V. Scagnoli, J. Phys. D: Cond. Matt. 32, 213001 (2020).
[3] C. Donnelly et al., Nature 547, 328 (2017).
[4] C. Donnelly et al., Nature Nanotechnology 15, 356 (2020).
[5] S. Finizio et al., Nano Letters (2022)
[6] C. Donnelly et al., Nat. Phys. 17, 316 (2020)
[7] N. Cooper, PRL. 82, 1554 (1999).
[8] J. Neethirajan et al., Phys. Rev. X 14, 031028 (2024)
[9] D. Sheka et al., APL 118, 230502 (2021)
[10] C. Donnelly et al., Nature Nanotechnology 17, 136 (2022)
[11] S. Ruiz Gomez et al., arXiv:2404.06042 [cond-mat.mes-hall]

Bio: Following her MPhys at the University of Oxford, Claire went to Switzerland to carry out her PhD studies at the Paul Scherrer Institute and ETH Zurich. She was awarded her PhD in 2017 for her work on 3D systems, in which she developed X-ray magnetic tomography, work that was recognised by a number of awards.
After a postdoc at the ETH Zurich, she moved to the University of Cambridge and the Cavendish Laboratory as a Leverhulme Early Career Research Fellow, where she focused on the behaviour of three dimensional magnetic nanostructures.
Since September 2021 she is a Lise Meitner Group Leader of Spin3D at the Max Planck Institute for Chemical Physics of Solids in Dresden, Germany. Her group focuses on the physics of three dimensional magnetic and superconducting systems.