# Regensburg 2022 – wissenschaftliches Programm

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# KFM: Fachverband Kristalline Festkörper und deren Mikrostruktur

## KFM 30: Skyrmions 3 (joint session MA/KFM)

### KFM 30.13: Vortrag

### Freitag, 9. September 2022, 12:30–12:45, H37

**Magnetoelastic surface states of skyrmion textures** — •Lars Franke and Markus Garst — Institute for Theoretical Solid State Physics, Karlsruhe Institute for Technology, Germany

At the surface of chiral magnets uncompensated Dzyaloshinskii-Moriya interaction modifies the boundary conditions for the magnetization resulting in a so-called a surface twist. Consequently, skyrmions are expected to change their helicity from Bloch-like within the bulk of the chiral magnet to Néel-like close to the surface [1]. Resonant elastic X-ray scattering experiments [2] have confirmed this predicted change of helicity close to the surface, but the experimentally observed penetration depth was found to be an order of magnitude larger than theoretically expected. In order to account for this discrepancy, we investigate theoretically the influence of a magnetoelastic coupling on the surface twist. Analytical calculations are complicated by broken translational invariance and nontrivial boundary conditions at the surface. However, as in the uncoupled system the length scale for helicity variations is already encoded in the bulk equation. We demonstrate how to extract the length scale from a perturbative approach. The validity of these calculations is checked using micromagnetic simulations, extended with magnetoelastic coupling, of the complete surface state including boundary conditions.

[1] Three-dimensional skyrmion states in thin films of cubic helimagnets, F. N. Rybakov et al. Phys. Rev. B 87, 094424 (2013).

[2] Reciprocal space tomography of 3D skyrmion lattice order in a chiral magnet, S. Zhang et al. PNAS 201803367 (2018).