Dynamics Of The Chiral Domain Walls Driven By Spin-orbit Torques

The research of the current-driven domain wall motion has attracted more and more people's attention.In 2008 IBM's Parkin proposed the concept of racetrack memory,because of its potential application value,many researchers engaged in this research,the research on the racetrack memory is now shifting from domain wall motion by the spin transfer torques,to domain wall motion by spin-orbit torques.Due to the spin-orbit torques for the importance of the magnetic device in the future,this paper mainly studied from the following three aspects:The role of higher-order spin-orbit torques in magnetic domain wall motion;Chiral magnetic domain wall motion driven by spin-orbit torques under the titled current;Chiral magnetic domain wall motion driven by spin-orbit torques under in-plane anisotropy structure.This paper adopts the method of collective coordinates,based on Landau-Lifshitz-Gilbert-Slonczewski equation,using the Walker trial solution,systematically analyzed the process of magnetic domain wall motion.First of all,in the study of the higher-order spin-orbit torques,we found under condition about the current along the plane of easy axis or current perpendicular to the easy axis and easy axis perpendicular to the film,the direction of domain wall motion depends on the configuration and chiral of domain wall.In particular,the direction of the domain wall motion controlled by the chiral of original domain wall.So long as the spin-orbit mechanism involved,we can use this scheme of current along the plane of easy axis to improve the speed of domain wall motion and control the direction of the domain wall motion,at the same time,we also found in the some parameters region of the spin-orbit torques,the Walker breakdown can be avoided.Second,in the study of chiral domain wall motion driven by spin-orbit torques under the tilted,we discovered the tilted current can control the direction of domain wall motion is more flexible.Finally,in the research of chiral magnetic domain wall motion driven by spin-orbit torques under in-plane anisotropy structure,we discovered the polarization of domain wall exists a transformation in low current region,and the speed of domain wall motion increase in proportional to the strength of the Dzyaloshinskii-Moriya(DM)interaction in the high current region;The existence of DM interaction maintains the domain wall the sustainability of the precession.Furthermore,we found that the DM interaction makes the adjacent domain wall has the same chiral and the same direction.