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Direct observation of twisted surface skyrmions in bulk crystals

DOI: 10.1103/PhysRevLett.120.227202 DOI Help

Authors: S. L. Zhang (University of Oxford) , G. Van Der Laan (Diamond Light Source) , W. W. Wang (Ningbo University) , A. A. Haghighirad (University of Oxford; Karlsruhe Institute of Technology) , T. Hesjedal (University of Oxford)
Co-authored by industrial partner: No

Type: Journal Paper
Journal: Physical Review Letters , VOL 120 , PAGES 227202

State: Published (Approved)
Published: May 2018
Diamond Proposal Number(s): 12958 , 12943

Abstract: Magnetic skyrmions in non-centrosymmetric helimagnets with Dn symmetry are Bloch-type magnetization swirls with a helicity angle of 90°. At the surface of helimagnetic thin films below a critical thickness, a twisted skyrmion state with an arbitrary helicity angle has been proposed; however, its direct experimental observation has remained elusive. Here, we show that circularly polarized resonant elastic x-ray scattering is able to unambiguously measure the helicity angle of surface skyrmions, providing direct experimental evidence that a twisted skyrmion surface state also exists in bulk systems. The exact surface helicity angles of twisted skyrmions for both left- and right-handed chiral bulk Cu2OSeO3, in the single as well as in the multidomain skyrmion lattice state, are determined, revealing their detailed internal structure. Our findings suggest that a skyrmion surface reconstruction is a universal phenomenon, stemming from the breaking of translational symmetry at the interface.

Journal Keywords: REXS; skyrmions; surface; Cu2OSeO3; dichroism

Subject Areas: Physics, Materials, Information and Communication Technology


Instruments: I10-Beamline for Advanced Dichroism