Speaker
Description
Transmission electron microscopes (TEMs) are versatile instruments providing a wealth of information about materials, such as their elemental composition, local crystal structure, defects or strains and more. Electrons as moving charged particles are also influenced by magnetism in the samples, however, this interaction is typically $3-4$ orders of magnitude weaker than the interaction of electrons with the charge distribution in the sample.
In the last approximately two decades, the microscope hardware went through enormous improvements. Notably, in the context of this work, direct electron detectors have vastly improved the signal to noise ratios in the measurements [1]. Consequently, measuring effects of the atomic scale distribution of magnetic fields in the sample on the scattering of electron beam is becoming more feasible. Recently, experiments using differential phase contrast imaging detected atomic scale magnetic fields [2] and holographic experiments reached atomic scale detection of magnetic fields using a high-voltage microscope [3].
The most commonly used method in simulations of elastic electron scattering in TEMs is so called multislice method [4]. However, this method doesn’t include effects of magnetic fields on the electron beam. We have extended the multislice method to include these effects starting from Pauli equation [5]. We have used this method to simulate magnetic differential phase contrast imaging [6,7] and recently even scattering on magnons [8].
Acknowledgements
We acknowledge financial support of the Swedish Research Council, the Olle Engkvist’s Foundation, and the Knut and Alice Wallenberg Foundation.
References
[1] B. D. A. Levin, “Direct detectors and their applications in electron microscopy for materials science,” Journal of Physics: Materials, vol. 4, no. 4. IOP Publishing, p. 042005, Jul. 28, 2021. https://doi.org/10.1088/2515-7639/ac0ff9
[2] Y. Kohno et al., “Real-space visualization of intrinsic magnetic fields of an antiferromagnet,” Nature, vol. 602, no. 7896. Springer Science and Business Media LLC, pp. 234–239, Feb. 09, 2022. https://doi.org/10.1038/s41586-021-04254-z
[3] T. Tanigaki et al., “Electron holography observation of individual ferrimagnetic lattice planes,” Nature, vol. 631, no. 8021. Springer Science and Business Media LLC, pp. 521–525, Jul. 03, 2024. https://doi.org/10.1038/s41586-024-07673-w
[4] J. M. Cowley and A. F. Moodie, “The scattering of electrons by atoms and crystals. I. A new theoretical approach,” Acta Crystallographica, vol. 10, no. 10. International Union of Crystallography (IUCr), pp. 609–619, Oct. 01, 1957. https://doi.org/10.1107/s0365110x57002194
[5] A. Edström et al., “Elastic Scattering of Electron Vortex Beams in Magnetic Matter,” Physical Review Letters, vol. 116, no. 12. American Physical Society (APS), Mar. 24, 2016. https://doi.org/10.1103/physrevlett.116.127203
[6] A. Edström et al., “Quantum mechanical treatment of atomic-resolution differential phase contrast imaging of magnetic materials,” Physical Review B, vol. 99, no. 17. American Physical Society (APS), May 28, 2019. https://doi.org/10.1103/physrevb.99.174428
[7] F. Krizek et al., “Atomically sharp domain walls in an antiferromagnet,” Science Advances, vol. 8, no. 13. American Association for the Advancement of Science (AAAS), Apr. 2022. https://doi.org/10.1126/sciadv.abn3535
[8] J. Á. Castellanos-Reyes et al., “Dynamical Theory of Angle-Resolved Electron Energy Loss and Gain Spectroscopies of Phonons and Magnons in Transmission Electron Microscopy Including Multiple Scattering Effects,” Physical Review Letters, vol. 134, no. 3. American Physical Society (APS), Jan. 22, 2025. https://doi.org/10.1103/physrevlett.134.036402
