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Depth profiling of 3D skyrmion lattices in a chiral magnet—A story with a twist

DOI: 10.1063/9.0000072 DOI Help

Authors: Gerrit Van Der Laan (Diamond Light Source) , S. L. Zhang (University of Oxford; ShanghaiTech University) , T. Hesjedal (University of Oxford)
Co-authored by industrial partner: No

Type: Journal Paper
Journal: Aip Advances , VOL 11

State: Published (Approved)
Published: January 2021
Diamond Proposal Number(s): 11784 , 12943 , 12958

Open Access Open Access

Abstract: From the perspective of surface science, only the topmost atomic layers usually exhibit physical properties that are different to those of the bulk material, whereas the deeper layers are assumed to be bulk-like and remain largely unexplored. Going beyond conventional diffraction and imaging techniques, we have determined the depth dependence of the full 3D spin structure of magnetic skyrmions below the surface of a bulk Cu2OSeO3 sample using the polarization dependence of resonant elastic x-ray scattering (REXS). While the bulk spin configuration showed the anticipated Bloch type structure, it was found that the skyrmion lattice changes to a Néel twisting (i.e., with a different helicity angle) at the surface within a distance of several hundred nm. The exact surface helicity angle and penetration length of this twist have been determined, revealing the detailed internal structure of the skyrmion tube. It was found that the experimental penetration length of the Néel twisting is 7× longer than the theoretical value given by the ratio of J/D. This indicates that apart from the considered spin interactions, i.e., the Heisenberg exchange interaction J and the Dzyaloshinskii-Moriya interaction D, as well as the Zeeman interaction, other effects must play an important role. The findings suggest that the surface reconstruction of the skyrmion lattice is a universal phenomenon, stemming from the breaking of translational symmetry at the interface.

Journal Keywords: Magnetic circular dichroism spectroscopy; X-ray scattering; Depth profiling techniques; Skyrmion dynamics; Heisenberg exchange interaction; Surface physics; Magnetism; Antisymmetric exchange; Chirality

Subject Areas: Materials, Physics


Instruments: I10-Beamline for Advanced Dichroism

Documents:
9.0000072.pdf