Fig. 3.

Magnetic structures of MnSi_1−xGe_x revealed by small-angle neutron scattering (SANS) and Lorentz transmission electron microscopy (LTEM) under magnetic field. a The SANS setup with magnetic field H perpendicular to the incident neutron beam. b Schematic illustration of LTEM observation with H parallel to the incident electron beam (orange lines), where the blue arrows represent the in-plane magnetic moment configuration of a skyrmion. c The over-focused LTEM image (T = 6 K, μ₀H = 0.3 T) in (001) crystal plane and its Fourier transform pattern. d–f The SANS measurement points (gray dots) and sequences (blue arrows) are shown in the magnetic phase diagrams of x = 0.2 (d), x = 0.6 (e), and x = 0.8 (f), where the blue stars represent the data points shown in g–i. The SANS intensity patterns of x = 0.2 (T = 25 K, μ₀H = 0.5 T) (g), x = 0.6 (T = 50 K, μ₀H = 1 T) (h), and x = 0.8 (T = 2 K, μ₀H = 3 T) (i). The small white circles emphasize the characteristic peak intensities for each composition. The candidate multiple-q structures explaining the observed SANS intensity patterns are shown in h–l, where the yellow rings represent the rotation degrees of freedom of q-vectors due to randomly oriented crystal domains in the polycrystalline samples and the yellow dots represent the scattering intensities on the detector plane