Internal structure of hexagonal skyrmion lattices in cubic helimagnets Article Swipe
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· 2016
· Open Access
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· DOI: https://doi.org/10.1088/1367-2630/18/9/095004
· OA: W2432704051
We have utilised a high spatial resolution imaging method, Differential Phase\nContrast (DPC) performed in a scanning transmission electron microscope (STEM),\nfor precise measurement of the magnetic induction distribution in skyrmion\nstates in noncentrosymmetric magnetically ordered materials. Applied to\ninvestigate the internal structure of hexagonal skyrmion lattice cells,\nstabilised by an out-plane applied magnetic field in an FeGe nanowedge\nspecimen, mapping of the in-plane component of magnetic induction has yielded\n"average" skyrmion profiles and observation of internal six-fold symmetry. With\nincreasing field strength, the diameter of "average" skyrmion cores was\nobserved to decrease accompanied by a non-linear variation of the lattice\nperiodicity. Variations in structure for individual skyrmions were studied\nutilising an advanced DPC detection scheme with a variety of symmetry lowering\ndistortions being observed. Our observations are consistent with a theoretical\nphenomenological model, which has predicted the structure of hexagonal skyrmion\nlattice cells and also that twisting states near to the material surfaces\nprovide a basis for energetic stabilisation of the skyrmion lattice over the\nconical phase. There was good agreement with experiment for predictions of bulk\nskyrmion structure and their response (core-size & lattice periodicity\nvariation) to an applied field.\n
