Alternating Motion of Single-Domain Walls in Uniaxial Magnetic Wire

Fe-Si-B microwires with strong uniaxial anisotropy reverse magnetization under homeogeneous driving magnetic field, H_dr, by the nucleation at one end and propagation of a single standard domain wall, DW_st, resulting in a giant Barkhausen jump between two stable remanent states with opposite magnetization. Under the additional presence of local field, H_loc, a local reverse domain is nucleated, generating a pair of head-to-head and tail-to-tail injected walls, DW_inj, that propagate in opposite directions. We performed designed experiments to control the motion of the DW_st and DW_inj under the action of both fields. The amplitude and frequency of square-shaped in-phase H_dr and H_loc ac fields are tuned to achieve controlled motion of the DW_inj domain wall. By properly selecting the amplitude of H_dr and H_loc ac fields (i.e., double or multiple frequencies), we experimentally confirm the DW_inj alternating motion between stable local positions/magnetic states, where H_loc plays the role of a magnetic valve and H_dr is the driving field.