Berlin 2012 – scientific programme

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MA: Fachverband Magnetismus

MA 4: Spin-dependent Transport Phenomena

MA 4.7: Talk

Monday, March 26, 2012, 11:00–11:15, H 1012

Ultrafast Transport of Laser-Excited Spin-Polarized Carriers in Metallic Multilayers — •Alexey Melnikov¹, Alexandr Alekhin¹, Tim O. Wehling², Vladimir V. Roddatis³, Damian Bürstel⁴, Detlef Diesing⁴, Alexander I. Lichtenstein², and Uwe Bovensiepen⁵ — ¹Fritz-Haber-Institut der MPG, Abt. Phys. Chemie — ²Universität Hamburg, Theor. Phys. Institut — ³CIC Energigune, Spain — ⁴Universität Duisburg-Essen, Institut für Phys. Chemie — ⁵Universität Duisburg-Essen, Fakultät für Physik

The ultrafast spin dynamics (SD) induced by a transport of spin polarized carriers is a hot topic motivated by the fundamental interest in magnetic excitations and applications like spintronics and data storage. To understand underlying elementary processes typically occurring on femtosecond time scales, we have developed a time-of-flight-like approach that probes SD induced by hot carriers (HC) and demonstrated a spin polarized HC transport through an epitaxial Au/Fe/MgO(001) structure. Using a back pump-front probe configuration, we establish that HC induced in Fe by the pump laser pulse can form a nearly ballistic spin current in Au: optical second harmonic (SH) generated at the Au surface by the probe pulse monitors the transient surface HC density and spin polarization formed by predominantly ballistic/diffusive spin-down/up carriers. Comparing the SH response of Fe to the direct optical excitation with that to the excitation by hot carriers generated in Au, we rule out coherent effects of the pump pulse and show that the HC-induced SD is the main origin of the ultrafast demagnetization. Financial support by the DFG through ME 3570/1-1 is acknowledged.