Dresden 2020 – scientific programme

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MA: Fachverband Magnetismus

MA 55: Non-Skyrmionic Magnetic Textures

MA 55.7: Talk

Thursday, March 19, 2020, 16:45–17:00, POT 6

Few-nm tracking of vortex orbits in the presence of disorder using Ultrafast Lorentz Microscopy — •Marcel Möller, John H. Gaida, Sascha Schäfer und Claus Ropers — 4th Physical Institut, Goettingen, Germany

Static Lorentz Transmission Electron Microscopy presents itself as a viable method for the mapping of nanoscale magnetic textures, offering a resolution down to one nanometer. In this contribution, we demonstrate its adaptation to time-resolved imaging, offering fascinating prospects for studying ultrafast magnetization dynamics. The Göttingen Ultrafast Transmission Electron Microscope (UTEM) is a newly developed instrument, which allows for studies of ultrafast magnetization and demagnetization dynamics induced by radio-frequency currents or optical pulses. This is facilitated with an electron source which can deliver electron pulses with a duration down to 200 fs.

Here, we focus on the investigation of the gyrotropic motion of a magnetic vortex confined within a 26 nm thick 2.1μm x 2.1μm permalloy nanoisland [1]. We demonstrate that we can track the vortex core position with an accuracy below 5 nm, measured by the deviation form an ideal elliptical trajectory and the deviation between identical acquisitions, respectively. Furthermore, using a sinusoidal current pulse which only lasts for a cycles, we can trace the build-up and relaxation of the vortex gyration, which reveals a temporal hardening of the free oscillation frequency and an increasing orbital decay rate attributed to local disorder in the vortex potential.

[1] M. Möller, et al., arXiv:1907.04608 (2019)