Figure 2. Fresnel-mode L-TEM images of the Pt/Co/AlO_x sample.

(a) At normal incidence, θ=0°, the DWs generate no contrast and are invisible. Scale bar, 10 μm. (b) For a sample tilted around the rotation axis indicated by the white arrows by θ=30°, the DWs appear. That the same area has been imaged is confirmed by the pattern of dark spots, which correspond to defects or dust particles. (c) Contrast linetraces: the experimental contrast was obtained at the position of the white line in b. The calculated Bloch and Néel wall contrast was extracted from Fig. 1c. Note that the apparent wall width is far higher than the actual wall width owing to the convolution of the wall profile with the resolution of the Lorentz-defocussed microscope.