Asymmetric driven dynamics of Dzyaloshinskii domain walls in ultrathin ferromagnetic strips with perpendicular magnetic anisotropy

摘要

The dynamics of domain walls in ultrathin ferromagnetic strips withperpendicular magnetic anisotropy is studied from both numerical and analyticalmicromagnetics. The influence of the interfacial Dzyaloshinskii-Moriyainteraction associated to a bi-layer strip arrangement has been considered,giving rise to the formation of Dzyaloshinskii domain walls. Such walls possessunder equilibrium conditions an inner magnetization structure defined by acertain orientation angle that make them to be considered as intermediateconfigurations between Bloch and N\'eel walls. Two different dynamics areconsidered, a field-driven and a current-driven dynamics, in particular, theone promoted by the spin torque due to the Spin-Hall effect. Results show aninherent asymmetry associated with the rotation of the domain wallmagnetization orientation before reaching the stationary regime, characterizedby a constant terminal speed. For a certain initial DW magnetizationorientation at rest, the rotation determines whether the reorientation of theDW magnetization prior to reach stationary motion is smooth or abrupt. Thisasymmetry affects the DW motion that can even reverse for a short period oftime. Additionally, it is found that the terminal speed in the case of thecurrent-driven dynamics may depend on either the initial DW magnetizationorientation at rest or the sign of the longitudinally injected current.