Spin torques' effects on topological defects and transitions of magnetic domain phases in Ta/CoFeB/MgO

We experimentally study the spin current-driven transitions of magnetic domain patterns in a prototypical multilayer stack of Ta/CoFeB/MgO. The transition processes are demonstrated to be greatly related to responses of topological defects to the spin orbit torque. A moderate perpendicular magnetic field favors stripe domains in the ferromagnetic layer; however, the stripes are cut into dense skyrmions with applying current pulses, where half-skyrmions at the ends of stripes have been proposed to be important. More types of topological excitations are observed in labyrinthine domain patterns at a zero magnetic field. The topological defects can be deleted/generated by spin current with lower/higher current densities. The current-induced deletion/generation of topological defects leads labyrinthine domains to transform into phases with a strong/weak orientational order. We conclude from a derived Thiele equation and micromagnetic simulations that both the current-driven motion of topological defects and magnetization manipulations at domain walls are of significance in current-induced transitions.