fig4

Figure 4. Current-driven hopfion motion by STT in a nanostripe. (A-D) Current-driven motions of a hopfion at J = -10 × 10¹¹ A·m^-2 under a magnetic field of 0.34 T. The size of the simulated region is 900 × 600 × 100 nm³. The midplane (z = 50nm) cross-sections of m are shown. (E-H) Simulated under-focused LTEM images corresponding to structures in (A-D). (I) Trajectory of the spin texture driven by STT during a period of 16 ns. (J) The hopfion motion velocity along the x-axis v_x and 2D topological number N_s as a function of time t. The v_x and N_s are calculated based on spin textures in the midplane. (K) The demagnetizing energy density in the z = 50 nm plane at 0 ns.