SKM 2023 – wissenschaftliches Programm
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MA: Fachverband Magnetismus
MA 8: Ultrafast Magnetization Effects I
MA 8.7: Vortrag
Montag, 27. März 2023, 16:45–17:00, HSZ 04
Finite-size effects in [Fe/MgO]n heterostructures on ultrafast timescales — •Moumita Kundu1, Nico Rothenbach2, Tobias Lojewski2, Andrea Eschenlohr2, Markus Gruner2, Katharina Ollefs2, Carolin Schmitz-Antoniak3, Klaus Sokolowski-Tinten2, William Windsor4, Laurenz Rettig4, Rossitza Pentcheva2, Heiko Wende2, Ulrich Nowak1, and Uwe Bovensiepen2 — 1University of Konstanz, Konstanz, Germany — 2University of Duisburg-Essen, Duisburg, Germany — 3TH Wildau, Wildau, Germany — 4FHI Berlin, Berlin, Germany
The analysis of magnetization dynamics on ultrafast timescales provides insight into microscopic interactions of magnetic moments with the charge and lattice degrees of freedom in solids. Here we analyze the finite size effect of ferromagnets on ultrafast timescales for [Fe/MgO]n heterostructures. Using femtosecond time-resolved XMCD, measured at the Femtoslicing facility, BESSY II, we observe an increasing laser-induced demagnetization at time delays > 0.5ps as the Fe layers get thinner, and it can be clearly distinguished from the primary ultrafast demagnetization occurring at < 0.5ps. Atomistic spin simulations are used to investigate the thickness dependence of the ultrafast magnetization dynamics in iron thin films, modeled using an extended Heisenberg-type Hamiltonian in the stochastic Landau-Lifshitz-Gilbert equation, coupled with the 2-temperature model. Comparing with our measurements, we conclude that finite size effects are the dominating factor for the different demagnetization rates due to a reduced spin-spin coordination at the interfaces.