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MA: Fachverband Magnetismus

MA 43: Magnetization Dynamics II of 3

MA 43.1: Vortrag

Donnerstag, 14. März 2013, 15:00–15:15, H22

Ultrafast spin transport as key to femtosecond demagnetization — •Andrea Eschenlohr¹, Marco Battiato², Pablo Maldonado², Niko Pontius¹, Torsten Kachel¹, Karsten Holldack¹, Rolf Mitzner¹, Alexander Föhlisch¹, Peter M. Oppeneer², and Christian Stamm¹ — ¹Institut für Methoden und Instrumentierung der Forschung mit Synchrotronstrahlung, Helmholtz-Zentrum Berlin für Materialien und Energie GmbH, Albert-Einstein-Str. 15, 12489 Berlin, Germany — ²Department of Physics and Astronomy, Uppsala University, Box 516, SE-75120 Uppsala, Sweden

Ultrafast demagnetization of ferromagnetic metals is typically triggered by excitation with a femtosecond laser pulse. Here we demonstrate that hot electrons transported into a ferromagnetic layer can induce demagnetization as fast and efficient as direct laser excitation. We investigate a layered structure consisting of a Ni film covered by a Au layer, with the thickness of the Au layer chosen such that the incident laser pulse is completely absorbed. Magnetization dynamics in the buried Ni film is measured with x-ray magnetic circular dichroism in transmission geometry at the BESSY II Femtoslicing source, finding sub-picosecond demagnetization of equal magnitude as in a directly excited Ni film. Simulations show that the observed demagnetization is due to spin-dependent transport of non-equilibrium electrons from the Au layer through the ferromagnetic layer into the substrate.