Direct and inverse spin orbit torques

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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.