Fig. 4: Manipulation of topological number and skyrmionium dynamics.

The magnetic field dependence of MFM images for the Fe₃GaTe₂ nanoflakes with 8.5% Fe^int (a–d) and 65.3% Fe^int (e–h) were obtained at room temperature. The MFM contrast in Fig. a becomes uniform under the magnetic field in panels b–d, indicating that the antiferromagnetic domains transition into the ferromagnetic domains. i, Schematics of current-induced skyrmion and skyrmionium motion. j Sequential MFM images showing skyrmionium displacement after injecting 1 current pulse with 10 GA/m² amplitude. The orange dashed lines are included as visual guides of skyrmionium motion. k Skyrmionium trajectories of the current-induced motion. The red arrows refer to the motion direction, which is along the current pulse direction. l The current pulse-dependent motion distance indicates the velocity of the skyrmionium is ~0.42 mm/s at room temperature under a current density of 10 GA/m².