Real-space observation of individual skyrmions in helimagnetic nanostripes
Jin Chi-Minga),b),c), Du Hai-Feng†a),b)
       
Comparison of Fresnel fringes at PtC x /FeGe and FeGe/vacuum interfaces: (a), in-focus case; (b), over-focus case with the defocus value 96 μm; (c), under-focus case with the same defocus value 96 μm. It is clearly shown that the range of Fresnel fringes extends above ∼ 100 nm at the FeGe/vacuum interface in the over-focus or under-focus conditions, while it is below ∼ 50 nm at the PtC x /FeGe interface [(b) and (c)]. Moreover, compared with the FeGe/vacuum interface, the strength of Fresnel fringes at the FeGe/PtC x interface is also significantly weakened. This advance enables the Lorentz TEM to directly image the edge state with less influence by the Fresnel fringes. (d) The artificial in-plane magnetic components constructed by the TIE analysis based on the image of panels (a)–(c). The significantly reduced Fresnel effect at the FeGe/PtC x interface is clearly observed. The red dotted lines indicate the position of the FeGe/PtC x and FeGe/vacuum interfaces. For clarity, the corresponding strength of Lorentz TEM images under different focus conditions is plotted as green lines. The white arrows in panel (d) represent the direction of lateral magnetization. Images are taken from Ref. [ 26 ].