Direct and inverse spin orbit torques

自旋电子学领域的目标是利用电子自旋和电荷自由度的相互作用为未来的信息技术。这种相互作用可以通过自旋-轨道转矩来实现，使得充电电流可以用于产生自旋动力学，反之亦然。该原理对应用具有巨大的吸引力，因为它承诺与传统电子器件兼容，同时通过引入自旋自由度来添加新功能。然而，导致自旋轨道扭矩的微观过程至今还没有得到很好的理解，这使得难以调整效率，甚至难以预测基于该方案的实际设备的定性行为。该项目旨在深入了解自旋轨道扭矩的物理概念，并确定有前途的材料组合和自旋电子学的新概念。实验研究将使用与具有高自旋轨道相互作用的非磁性金属材料接触的非磁性薄膜进行。将使用具有金属或绝缘磁性成分的微米和纳米图案化装置。由于铁磁体和正常金属的界面处固有的对称性破缺，电荷电流可以被用来在这样的系统中对磁矩施加自旋轨道转矩。此外，由于界面反对称交换相互作用，铁磁体中磁矩的非平凡空间有序性可以随之发生，这有利于相邻自旋的倾斜排列。因此，一种特殊的手性磁有序，称为Skyrmion，具有特别的基础和技术意义，因为Skyrmion应该允许通过电流诱导的自旋轨道转矩进行特别有效的操纵。在这个项目中，自旋轨道相互作用，即，将在GHz频率范围内对电荷电流对自旋动力学的作用以及相应的逆效应进行实验研究。因此，感应和光学技术，能够解决在微米和纳米级的磁激发将被利用来感测的磁动力学。所获得的结果将有直接的后果，实际实现的自旋电子器件，这需要小的结构尺寸和GHz频率的操作。最后，所研究的自旋轨道和交换相互作用是磁学中最深刻的机制之一，因此所获得的见解将产生远远超出自旋电子学领域的根本影响。

The field of spintronics aims to exploit the interaction of electronic spin and charge degrees of freedom for future information technology. This interaction can be enabled by spin-orbit torques such that a charge current can be used to generate spin dynamics and vice versa. This principle has tremendous appeal for applications as it promises compatibility with conventional electronics while adding new functionality by incorporating the spin degree of freedom. However, the microscopic processes causing spin-orbit torques are not well understood to date, making it difficult to tune the efficiency or even predict the qualitative behavior of practical devices based on this scheme. This project aims to gain insight into the physical concepts of spin-orbit torques and to identify promising material combinations and new concepts for spintronics. The experimental studies will be carried out using ultrathin magnetic films in contact with nonmagnetic metallic materials with high spin orbit interaction. Micro- and nanopatterned devices with metallic or insulating magnetic constituents will be used. Due to the inherent symmetry breaking at the interface of the ferromagnet and the normal metal, charge currents can be used to exert spin-orbit torques on the magnetic moments in such systems. Moreover, a nontrivial spatial ordering of the magnetic moments in the ferromagnet can ensue due to the interfacial antisymmetric exchange interaction, which favors a canted alignment of neighboring spins. A special kind of chiral magnetic ordering, known as a Skyrmion, is thereby of particular fundamental and technological interest, as Skyrmions should permit a particularly efficient manipulation via current-induced spin-orbit torques. In this project, spin-orbitronic interactions, i.e., the action of charge currents on the spin dynamics, and the respective inverse effects, will be experimentally studied in the GHz-frequency range. Thereby, inductive and optical techniques that are capable of resolving magnetic excitations at the micro- and nanoscale will be exploited to sense the magnetodynamics. The obtained results will have direct consequences for the practical realization of spintronic devices, which require small structure size and GHz-frequency operation. Finally, the studied spin-orbit and exchange interactions are amongst the most profound mechanisms in magnetism, such that the gained insights will have a fundamental impact far beyond the field of spintronics.