Figure 3
3D analysis of transport dynamics for 4 µm sized SPPs within a dynamically transformed MFL. (a) Sketch of one transport step for the SPP above a hh/tt magnetic stripe pattern (black arrows) after changing the external magnetic field in z-direction. The blue arrow indicates the expected “hopping” like motion of the SPP. Reference positions for the normalization of the experimentally determined vertical movement (zexp) and the theoretically estimated equilibrium distance (zsim) are indicated. Relevant forces for the estimation of zsim were calculated along the indicated vertical axes z and z’ (see Supporting Information S5). (b) Applied external magnetic fields as a function of time for one pulse sequence. Black solid line: field in z-direction, grey dashed line: field in x-direction. (c) Plot of an exemplary SPP trajectory: determined x- (blue circles) and y- (green squares) SPP-center coordinates as functions of time. (d) Experimentally determined z-SPP center coordinates, relative to the equilibrium position of the SPP before the z-field change, superposed on the lateral movement (red circles). The initial z-position before the z-field change has been normalized to zero. Red shaded areas indicate the fit uncertainty for the used z-coordinate calibration function. For comparison, theoretical equilibrium distances between SPP and the substrate surface were computed (cyan triangles). The insets show background-subtracted microscopic images of the SPP at the indicated time. Changes in SPP sharpness and thereby z-position are observable. (e) Plot of determined z-positions in dependence on the x-positions for an SPP during a transport step. Again, red circles represent normalized experimental data (with the red shaded area as the uncertainty), while the cyan triangles depict simulated equilibrium distances. The data normalization was performed as described for (d). Data points of x-, y-position, and the simulated z-distance were connected to provide a guide to the eye.
