Berlin 2018 – wissenschaftliches Programm
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MA: Fachverband Magnetismus
MA 6: Ultrafast magnetism I
MA 6.9: Vortrag
Montag, 12. März 2018, 11:45–12:00, EB 407
Ultrafast magnetization dynamics probed by Lorentz microscopy — •Marcel Möller1, John H. Gaida1, Nara Rubiano da Silva1, Armin Feist1, Sascha Schäfer1,2, and Claus Ropers1 — 14th Physical Institute University of Göttingen, Göttingen, Germany — 2Physical Institute University of Oldenburg, Oldenburg, Germany
Lorentz microscopy is a widely applied technique for the nanoscale mapping of magnetization structures. Its adaptation to time-resolved imaging offers 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 either deliver a continuous electron beam or electron pulses with a duration down to 200 fs at a 0.6 eV spectral width and a sub-nm focal spot size. In this contribution, we investigate the gyrotropic motion of a magnetic vortex confined within a 20 nm thick 2µm x 2µm permalloy nanoisland. Exciting the magnetic vortex with an in-plane spin current near the resonance frequency of 101MHz, we are able to track the gyration of the vortex core with 20 nm resolution. Furthermore, we investigate the response of the vortex to non-periodic excitations. Using a sinusoidal current pulse which only lasts for a few cycles, we can trace the build-up and relaxation of the vortex gyration, which yields the damping and the spectral characteristics of our sample system.