SKM 2021 – wissenschaftliches Programm

Bereiche | Tage | Auswahl | Suche | Aktualisierungen | Downloads | Hilfe

MA: Fachverband Magnetismus

MA 15: Posters Magnetism IV

MA 15.7: Poster

Donnerstag, 30. September 2021, 13:30–16:30, P

Wavelength dependency in ultrafast magnetization dynamics of Nickel — •Martin Stiehl, Marius Weber, Christopher Seibel, Jonas Hoefer, Bärbel Rethfeld, Hans Schneider, Benjamin Stadtmüller, and Martin Aeschlimann — Department of Physics and Research Center OPTIMAS, University of Kaiserslautern, Kaiserslautern, Germany

We revisit the problem of the influence of optical excitation conditions on ultrafast magnetization dynamics. In this contribution, we combined a theoretical analysis of the excitation and electron dynamics with time-resolved magneto-optical Kerr effect (tr-MOKE) studies to uncover the role played by the different pump-photon energies for ultrafast demagnetization in thin Ni films (10nm) on the insulating substrate MgO. We use a time-dependent Fermis Golden Rule approach to model the absorption and the temperature-based µ-T model for the subsequent incoherent electron dynamics. For a fixed absorbed energy one obtains rather different minority and majority carrier distributions for pump photon energies in the range from 0.5eV to 2.5eV. In contrast, we find identical tr-MOKE dynamics for all corresponding pump photon energies. The shape and fluence dependence of these photon energy dependent traces can be described well by our theoretical model. Our observations suggest a negligible influence of the details of the excited hot carrier distributions on the ultrafast demagnetization. Rather, the photon energy dependence of ultrafast demagnetization of Ni seems to be dominated by the deposited energy and quasi-thermal behavior of the electron system.