XRM2024 - Thu07K - "Three Dimensional Magnetisation and Orientation Fields revealed with Dichroic Ptychographic Tomography"

Three dimensional magnetic systems promise significant opportunities for both fundamental physics, and technological applications, for example providing higher density devices and new functionalities associated with complex topology and greater degrees of freedom[1,2].

One of the main challenges comes with characterising complex three dimensional magnetic systems. Here I will discuss the advances in X-ray magnetic tomographic imaging making use of dichroic X-ray ptychography. Using hard X-ray magnetic tomography, we have been able to map both the static configuration[3,5] , and dynamical behaviour[4,6], of topological magnetic structures[3–8]. Understanding these complex configurations is challenging: recent advances in analytical techniques[7] have provided new capabilities to locate and identify 3D magnetic solitons, leading to the first observation of nanoscale magnetic vortex rings[7,9].

While hard X-ray imaging offers high resolution imaging of extended magnetic systems, the weak magnetic dichroism limits the variety of materials that can be imaged. 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.

Finally, beyond the imaging of magnetization vector fields with X-ray magnetic circular dichroism, we can harness linear dichroism to measure orientation fields in a sample. To this end, we have developed X-ray linear dichroism orientation tomography (XL-DOT), with which we map the c-axis of a polycrystalline V2O5 sample with nanoscale resolution[11]. A key advantage of XL-DOT is that the technique is not limited to crystalline materials, but can be applied to alternative sources of linear dichroism, such as antiferromagnetic and ferroelectric order.

These new capabilities for the high spatial resolution imaging of three dimensional magnetization and orientation fields opens the door to the exploration of both fundamental and technologically relevant systems.

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. K. Witte, et al., Nano Letters 20, 1305 (2020).
6. S. Finizio et al., Nano Letters (2022)
7. C. Donnelly et al., Nat. Phys. 17, 316 (2020)
8. C. Donnelly et al., Nature Nanotechnology 17, 136 (2022)
9. N. Cooper, PRL. 82, 1554 (1999).
10. J. Neethirajan et al., Phys. Rev. X 14, 031028 (2024)
11. A. Apseros et al., Nature 636, 354 (2024)