In situ resistance and magnetoresistance experiments on spin orbit torque systems

在这个项目中，我们一方面想要建立一个蒸发室和溅射室中的电阻、磁阻和反常霍尔效应的现场测量。测量将在单层薄膜和被称为自旋轨道扭矩系统的多层薄膜的生长过程中进行。自旋轨道扭矩使用由例如自旋霍尔效应驱动的自旋累积来切换由非磁体和铁磁或亚铁磁体制成的非对称多层膜的磁化。这项技术在未来的电子设备中非常有希望。此外，这是一个基本的兴趣，因为所使用的系统显示了电荷载流子的动量和它们的自旋之间的锁定。另一方面，我们想要详细地评估已经通过原位测量表征的样品的自旋霍尔角和自旋轨道扭矩转换。从这些现场实验中，可以确定各层的电阻率为第一量。此外，可以分析金属A被金属B覆盖时的电阻增加，并得出关于A和B界面上载流子散射强度的结论。这些信息目前还不能用于解释自旋轨道扭矩的实验。各层的电阻率通常取自块状材料的数据，通常误差较大。此外，自旋霍尔角的大小与载流子在界面上的散射之间的关系是一个开放的非常重要的问题。我们希望，我们在这个项目中的研究可以为以下科学问题做出贡献：-哪些电流在各个层中流动？-电子在界面上的散射有多强？-如何影响(自旋霍尔，自旋轨道扭矩，反常霍尔效应，SMR，USMR，.)取决于各层的厚度和界面的质量？-自旋轨道扭矩的强度和电荷载流子的界面散射之间是否存在关联？

In this project, we want on the one hand to establish in-situ measurements of the electric resistance, the magnetoresistance and the anomalous Hall effect in an evaporation- and a sputter-chamber. The measurements will be done during the growth of single layer films and of multilayers that are known as spin orbit torque systems. The spin orbit torque uses the accumulation of spins driven by, e.g., the spin Hall effect to switch the magnetisation of non-symmetric multilayers made from non-magnets and ferro- or ferrimagnets. This technique is extremely promising for future electronic device. In addition, it is of basic interest because the systems used show a locking between the momentum of the charge carriers and their spin.On the other hand, we want to evaluate in detail the spin Hall angle and the spin orbit torque switching for the samples that have been characterised by the in-situ measurements. From these in-situ experiments, the resistivities of the individual layers can be determined as first quantity. Moreover, it is possible to analyse the resistance increase when a metal A is covered by a metal B and to draw conclusions on the strength of the scattering of the charge carriers at the interface between A and B.These informations are at present not available for the interpretation of experiments on spin orbit torque. The resistivities of the individual layers are often taken from data of bulk materials, and large errors are commonly accepted. Moreover, the relation between the size of the spin Hall angle and the scattering of the charge carriers at the interfaces is an open and very important question. We hope, that our research in this project can contribute to the following scientific questions:- Which current flows in the individual layers?- How strong is the scattering of the electrons at the interfaces?- How do the effects (spin Hall, spin orbit torque, anomalous Hall effect, SMR, USMR, ..) depend on the thicknesses of the individual layers and the quality of the interfaces?- Is there a correlation between the strength of the spin orbit torque and the interface scattering of the charge carriers?