Stabilizing Current-driven Steady Flows Of 180° Domain Walls In Spin Valves By Interfacial Dzyaloshinskii-Moriya Interaction

In the past two decades,the great progress of nonvolatile memory preparation technology has led to the revolution of modern information industry.In these nanodevices,magnetic domains with different orientations constitute 0 and 1 in the bit world.The middle region between them is the domain wall.The movement of the domain wall leads to the transmission and operation of data.Generally speaking,domain walls can be driven by external stimuli such as magnetic field,polarization current,spin wave or temperature gradient.Among them,the current driven case is the most valuable in experiment and practical application.In this work,modulations of interfacial Dzyaloshinskii-Moriya interaction(i DMI)on current-driven dynamics of 180 domain walls(180DWs)in long and narrow spin valves(LNSVs)with heavy-metal caplayers are systematically investigated.We focus on LNSVs with in-plane magnetic anisotropy in their free layers.For planar-transverse polarizers(pinned layers of LNSVs),the Walker breakdown can be postponed considerably(practical infinity)by i DMI.More interestingly,the originally unstable traveling mode is also stabilized by i DMI with high saturation velocity thus serves as fast carrier of information.For parallel polarizers,the Walker limit is increased and the corresponding modifications of i DMI to wall velocity in both steady and precessional flows of 180 DWs are provided.For perpendicular polarizers,precessional flow of 180 DWs is absent due to the stability of stationary mode beyond the modified Walker limit.For LNSVs with perpendicular magnetic anisotropy in their free layers,similar results are obtained.Our findings open new possibilities for developing magnetic nanodevices based on 180 DW propagation with low energy consumption and high robustness.