Metastable magnetic domain wall dynamics

Abstract

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 means of 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 external excitation. In addition, independent of the domain wall excitation method, the velocity of a metastable wall is much smaller than that of a stable wall and its displacement direction could be different from that of the stable wall depending on the structure of metastable walls. Under current-induced spin-transfer torque excitation, the direction of domain wall displacement is directly related to the intensity of non-adiabatic 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 a backward displacement of a metastable domain wall by changing the pulse width of the excitation.