Investigation of the propagation of isolated magnetic skyrmions

• Applicant: Professor Dr. Felix Büttner
• Subject Area: Experimental Condensed Matter Physics
• Term: from 2015 to 2019
• Project identifier: Deutsche Forschungsgemeinschaft (DFG) - Project number 288444881

Skyrmions are promising candidates for future solid state magnetic information storage devices, with perspective realization in particular in racetrack-like nanowire geometries. However, due to the lack of experimental data, the GHz dynamics of skyrmions is still not fully understood, let alone the control of such dynamics. Therefore, in this project, I aim to investigate the translational motion of magnetic skyrmions in a nanowire driven by spin-polarized electrical currents.A large number of theoretical studies predict intriguing phenomena in the propagation of skyrmions, for instance a variation of inertia with the frequency of the excitation and a very low sensitivity of skyrmions to pinning. The experimental verification is an open task and the increased complexity of a real system, e.g., the stray field of the magnetic configuration, variable temperature, or the atomically inhomogeneous material, may strongly affect the physical behavior and reveal further interesting physics.The proposed study has three objectives: (A) Investigation of the material-specific interaction of spin currents with local magnetic moments in materials in which skyrmions exist, (B) development and growth of a material that is suitable for pump-probe imaging of skyrmion propagation with billions of repetitions, and (C) investigation of the quasi-particle behavior of magnetic skyrmions and its relation to the material parameters and to the driving force. A large variety of scientific approaches will be applied to pursue these objectives, including magneto-electrical transport measurements and local magnetometry as well as quasi-static and true dynamic magnetic imaging. The experimental work will be complemented by micromagnetic simulations.Electrical measurements are ideal for high throughput characterizations. Even the mass of the skyrmions can be determined by measuring their resonance frequencies. Furthermore, such measurements provide direct information on the details of the electrical excitations, which can be used to improve the effectiveness and efficiency of these excitations. Imaging experiments will be used to confirm that the investigated structure is indeed a skyrmion. Furthermore, true dynamic imaging reveals the entire two dimensional trajectory of the skyrmion, from which one can directly infer its quasi-particle equation of motion and in particular the magnitude of the parameters of this equation.

• DFG Programme: Research Fellowships
• International Connection: USA
• Host: Professor Dr. Geoffrey S. D. Beach