The domain wall motion in a magnetic nanowire is examined theoretically in the regime where the domain wall driving force is weak and its competition against disorders is assisted by thermal agitations. Two types of driving forces are considered; magnetic field and current. While the field induces the domain wall motion through the Zeeman energy, the current induces the domain wall motion by generating the spin transfer torque, of which effects in this regime remain controversial. The spin transfer torque has two mutually orthogonal vector components, the adiabatic spin transfer torque and the nonadiabatic spin transfer torque. We investigate separate effects of the two components on the domain wall depinning rate in one-dimensional systems and on the domain wall creep velocity in two-dimensional systems, both below the Walker breakdown threshold. In addition to the leading order contribution coming from the field and/or the nonadiabatic spin transfer torque, we find that the adiabatic spin transfer torque generates corrections, which can be of relevance for an unambiguous analysis of experimental results. For instance, it is demonstrated that the neglect of the corrections in experimental analysis may lead to incorrect evaluation of the nonadiabaticity parameter. Effects of the Rashba spin-orbit coupling on the domain wall motion are also analyzed.
Spin-orbit torques for current parallel and perpendicular to a domain wall
我们报告了场和电流诱导的磁畴壁（DW）的脱钉实验在Ta/Co20 Fe 60 B20/MgO纳米线通过霍尔交叉几何。虽然纯场诱导的脱钉没有显示出对面内场的角度依赖性，但电流的影响主要取决于内部DW结构，我们通过外部磁面内场来操纵该结构。我们首次展示了平行于DW发送的电流的脱钉测量，并将其脱钉效率与垂直于DW流动的电流的常规情况进行比较。我们发现，最大效率是类似的两个电流方向内的误差条，这是符合一个占主导地位的阻尼类自旋轨道扭矩（SOT），并表明没有大的额外的扭矩出现平行于DW的电流。最后，我们发现了不同的依赖性的最大脱钉效率角为不同的DW和钉扎水平。这强调了我们的全角度扫描的重要性相比，以前使用的测量只有两个场方向（平行和垂直的DW），并显示了精确的DW结构和钉扎位点的自旋轨道扭矩的灵敏度。
Geometrical dependence of domain wall propagation and nucleation fields in magnetic domain wall sensor devices
我们研究了用于畴壁传感器的分段纳米线环基结构中的关键畴壁特性。利用磁光克尔效应（MOKE）和巨磁电阻效应（GMR）测量方法，对器件失效的两个原因，即畴壁传播场（退钉扎）和成核场的分布进行了研究，得到了有意义的统计数据。沉积Ni $_{81}$ Fe $_{19}$的单层、具有Co $_{90}$ Fe $_{10}$ /Ni $_{81}$ Fe $_{19}$作为自由层的完整GMR叠层和Co $_{90}$ Fe $_{10}$的单层，并在工业上图案化，以确定形状各向异性、磁晶各向异性和制造工艺的影响。我们表明，传播场的几何形状的影响很小，但显着的材料参数。磁畴壁形核场可以用与测量的线的几何参数相关的典型Stoner-Wohlfarth模型来描述，并通过考虑工艺参数来拟合。随后在大量器件（3000）中测量GMR效应，以便精确地测量器件之间的变化。这揭示了传感器的成核场的校正上限，其可用于工作元件的快速表征。
