Metastable magnetic domain wall dynamics

The dynamics of metastable magnetic domain walls in straight ferromagnetic nanowires under spin waves, external magnetic fields, and current induced spin transfer torque are studied by micromagnetic simulations. It is found that in contrast to a stable wall, it is possible to displace a metastable domain wall in the absence of any external excitation. In addition, independent of the domain wall excitation method, the velocity of a metastable wall is much smaller than a stable wall and their displacement direction could be different from the stable wall depending on the structure of metastable walls. Under the current induced spin transfer torque excitation, the direction of domain wall displacement is directly related to the intensity of nonadiabatic spin transfer torque. In a rough nanowire, it is found that the displacement of a metastable wall could happen much below the critical excitation of a stable wall. Furthermore, we show that it is possible to have either a forward or backward displacement of a metastable domain wall by changing the pulse width of the excitation.