Fig. 3

Magnetic force microscopy (MFM) imaging of individual skyrmions and manipulation by local field gradients. Sequence of MFM images illustrating individual skyrmion manipulation by MFM in Pt/CoFeB/MgO multilayer under an applied perpendicular field \({H}_{{\rm{z}}}\) = 71 mT. b, d, f, h Skyrmions are imaged in single pass MFM mode at a lift height \(\Delta z\) = 145 nm, with the topography acquired separately at \({H}_{{\rm{z}}}\) = 50 mT. The dashed arrows are guides for the eye indicating skyrmion motion between consecutive steps. c, e, g Skyrmions are moved by the probe stray field during the topography line scans of a standard two pass MFM scan (also with \(\Delta z\) = 145 nm), which reveal the trajectory followed by skyrmions in the form of actual skyrmion footprints. These scans were stopped before reaching the end only to prevent skyrmions from moving outside of the selected region. The directions of fast (with trace and retrace line scans) and slow MFM scan axes are marked in the individual images. The spacing between consecutive line scans along the slow scan axis is \(\delta\) \(\sim\) 20 nm. As indicated by the sketch in (a), the tip is magnetised along the external field direction for all MFM images, thus opposing the skyrmions core magnetisation