Measuring Topological Materials and Skyrmions on I16

Topologically nontrivial magnetic states, such as skyrmions, are promising candidates for realising ultralow power spintronic devices, such as racetrack memories. Besides their technological relevance, there has been concerted effort within the scientific community to understand the physical mechanisms stabilising these objects within magnetic materials.  Recently the discovery of skyrmions in centrosymmetric systems, has expanded the range of materials in which skyrmions can be stabilised and prompted further theoretical and experimental studies to determine their physical origin. The centroskymmetric skyrmion hosts that have been discovered to data are all Gd and Eu based intermetallics that have L₃ energy edges, making them candidate materials to study using resonant elastic x-ray scattering (REXS) on I16.  

I16 is well suited to the study and characterisation of skyrmions. Magnetic skymrions give rise to non-collinear magnetic structures, which are described by complex magnetic interaction vectors. The imaginary component in the density matrix description of circularly polarised light gives rise to interference terms that are different for left and right circularly polarised light. In contrast no different in the structure factor for left and right circularly polarised light is present for collinear magnetic structures and hence one can determine the collinearity of the magnetic structure by changing the incident polarisation of light and measuring if a difference in the scattered signal from a magnetic reflection is observed with the right and left circular light.  

Furthermore, topological phases often give rise to charge and or magnetic satellites at specific points in reciprocal space associated with the propagation of the magnetic ordering, which can be easily searched for using the high reciprocal space access provided by I16. Topological phases are often found at cryogenic temperatures and sometimes under an applied magnetic field, which are accessible through our suite of cryogenic equipment and magnets available on the beamline.

Below we list some important papers highlighting the use of REXS in the field of topological materials:

1. Takagi, R., Matsuyama, N., Ukleev, V., Yu, L., White, J. S., Francoual, S., ... & Seki, S. (2022). Nature communications, 13(1), 1472.
2. Khanh, N. D., Nakajima, T., Yu, X., Gao, S., Shibata, K., Hirschberger, M., ... & Seki, S. (2020). Nature Nanotechnology, 15(6), 444-449.
3. Kurumaji, T., Nakajima, T., Hirschberger, M., Kikkawa, A., Yamasaki, Y., Sagayama, H., ... & Tokura, Y. (2019). Science, 365(6456), 914-918.
4. Hirschberger, M., Nakajima, T., Gao, S., Peng, L., Kikkawa, A., Kurumaji, T., ... & Tokura, Y. (2019). Nature communications, 10(1), 5831.