Investigation and control of domain walls and their interaction with spin-polarized currents in nanoscale ferromagnets

在这个项目中，磁畴壁和自旋极化电流之间的相互作用将使用一系列的实验进行研究。畴壁准粒子在畴壁与自旋极化载流子发生相对运动时表现出新颖的物理效应。自旋极化电流可以从畴壁散射，大电流密度可以取代和改变畴壁（由于自旋转移扭矩而引起的电流诱导畴壁运动）。为了理解自旋扭矩效应和验证目前相互矛盾的理论，动态和低温实验提出，允许第一次明确确定的非绝热的载流子输运和探测电流诱导的本征模和微波激发。相反的效应，即当畴壁沿导线沿着移动时产生的电压（自旋动力），仅在理论上预测，并将在实验上进行测试。最后，实验将从众所周知的NiFe合金扩展到激发其他材料，预计会产生更大的效应，例如掺杂的3d金属，稀土化合物合金和其他高度自旋极化的材料类别。这将产生自旋极化电流和磁化之间的相互作用的细节，这在许多材料中迄今为止还没有很好地理解，并且将测试目前使用的s-d交换模型的有效性和限制。

In this project the interplay between magnetic domain walls and spin-polarized currents will be investigated using a range of experiments. Domain Wall quasi particles exhibit novel physical effects when a relative movement between the domain wall and the spin-polarized charge carriers occurs. Spin-polarized currents can be scattered from domain walls and large current densities can displace and transform the walls (current-induced domain wall motion due to spin transfer torque). To understand the spin torque effect and validate the present contradicting theories, dynamic and low temperature experiments are proposed that allow for the first time the unambiguous determination of the non-adiabaticity of the carrier transport and to probe current-induced eigenmodes and microwave excitations. The inverse effect, namely a voltage that occurs when a domain wall moves along a wire (spin motive force) has only been predicted theoretically and it will be tested for experimentally. Finally the experiments will be extended from the well-known NiFe alloys to exciting other materials, where larger effects are expected, such as doped 3d metals, alloys of rare earth compounds and other highly spin-polarized materials classes. This will yield the details of the interaction between the spin - polarized currents and the magnetization, which in many materials is not so far well understood and the validity and limits of the presently used s-d exchange model will be tested.