The Role of the Oersted Field on the Current-Driven Domain Wall Dynamics Along Wires With Square Cross Section

Current-driven domain wall dynamics in long Permalloy strips with square cross section, taking into account the influence of the Oersted field and the nonadiabatic spin-torque term, are studied in this work. Depending on the size of the square cross section two types of domain wall configurations can be nucleated, transverse or Bloch-point walls. The transverse wall dynamics showed a linear relation between the wall velocity and the applied current density. Also seen for this type of wall is that its dynamic is practically unaffected by either the presence of the Oersted field or the value of the nonadiabatic parameter, and its behavior resembles the one seen in cylindrical wires as it also does not have a Walker breakdown. In the case of the Bloch-point wall there is a threshold current density in order to promote the wall movement and it also depends on the value of the nonadiabatic parameter. The effect of the Oersted field for some values of the nonadiabatic parameter is the increase of the wall’s velocity and reduction of its width. For values above the wall transforms into complex unstable structures.