The Acceleration Effect Of Current-driven Transverse Domain Walls In Biaxial Nanowires Under Uniform Transverse Magnetic Fields

With the development of nanofabrication teachniques,ferromagnets at the mesoscopic scale exhibit novel properties,which guarantee their extensive applications in modern information industry,thus provide them broad prospects in the modern information industry,especially magnetic storage devices.All these facts make magnetization dynamics of magnetic materials become a hot spot of nowaday's research of condense matter physics.A deep understanding of the microscopic processes occurring in magnetic medias is crucial for effective design of magnetic storage devices,such as magnetic tape,magnetic hard disk and magnetic random access memory.In 1996,J.Slonczewski and L.Berger independently predicted that when a spin-polarized electron current flows through a nanometer-sized spin valve,a spin transfer torque(STT)will be exerted onto the magnetization in the ferromagnetic free layer hence changes its direction.After adding STT to the LLG equation,the modified LLG equation can be obtained.Based on it,in this thesis we investigate the statics and current-driven dynamics of transverse domain walls in quasi-one-dimensional nanowires under uniform transverse magnetic fields in two configurations: "current in the easy-plane(CIP)" and "current perpendicular to the easy-plane(CPP)".For statics,when a uniform transverse magnetic field is applied,the azimuthal distribution of the transverse domain wall is twisted around the wall center.An approximate analytical solution can be obtained by decoupling the azimuthal and polar degrees of freedom.When drive currents are present,the transverse domain walls start to move.With the help of leading-order expansion approach,In CIP configuration,we found that transverse magnetic fields have no acceleration effect on DWs.While in CPP configuration,a finite transverse magnetic field can effectively increase the velocity of the transverse domain walls.