Reciprocal space tomography of 3D skyrmion lattice order in a chiral magnet

It is commonly assumed that surfaces modify the properties of stable materials within the top few atomic layers of a bulk specimen only. Exploiting the polarization dependence of resonant elastic X-ray scattering to go beyond conventional diffraction and imaging techniques, we have determined the de...

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Bibliographic Details
Published in:Proceedings of the National Academy of Sciences - PNAS 2018-06, Vol.115 (25), p.6386-6391
Main Authors: Zhang, Shilei, van der Laan, Gerrit, Müller, Jan, Heinen, Lukas, Garst, Markus, Bauer, Andreas, Berger, Helmuth, Pfleiderer, Christian, Hesjedal, Thorsten
Format: Article
Language:English
Subjects:
Dependence
Elastic scattering
Hypothetical particles
Imaging techniques
Lattice theory
Magnetic fields
Magnetic properties
Material properties
Particle physics
Particle theory
Physical Sciences
Spin structure
Territory
Three dimensional imaging
Tomography
Twisting
X-ray scattering
X-rays
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Summary:It is commonly assumed that surfaces modify the properties of stable materials within the top few atomic layers of a bulk specimen only. Exploiting the polarization dependence of resonant elastic X-ray scattering to go beyond conventional diffraction and imaging techniques, we have determined the depth dependence of the full 3D spin structure of skyrmions—that is, topologically nontrivial whirls of the magnetization—below the surface of a bulk sample of Cu₂OSeO₃. We found that the skyrmions change exponentially from pure Néel- to pure Bloch-twisting over a distance of several hundred nanometers between the surface and the bulk, respectively. Though qualitatively consistent with theory, the strength of the Néel-twisting at the surface and the length scale of the variation observed experimentally exceed material-specific modeling substantially. In view of the exceptionally complete quantitative theoretical account of the magnetic rigidities and associated static and dynamic properties of skyrmions in Cu₂OSeO₃ and related materials, we conclude that subtle changes of the materials properties must exist at distances up to several hundred atomic layers into the bulk, which originate in the presence of the surface. This has far-reaching implications for the creation of skyrmions in surface-dominated systems and identifies, more generally, surface-induced gradual variations deep within a bulk material and their impact on tailored functionalities as an unchartered scientific territory.
ISSN:0027-8424
1091-6490
DOI:10.1073/pnas.1803367115