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

MA: Fachverband Magnetismus

MA 15: Magnetization / Demagnetization Dynamics I

MA 15.1: Topical Talk

Dienstag, 27. März 2012, 09:30–10:00, H 1012

Probing the timescale of exchange interaction in a ferromagnetic alloy — •Stefan Mathias — University of Kaiserslautern and Research Center OPTIMAS — JILA, University of Colorado and NIST

Rapid progress in ultrafast X-ray science worldwide, both in high-harmonic generation (HHG) and X-ray free-electron laser sources, has paved the way for a completely new generation of experiments investigating ultrafast magnetic processes in complex materials with ultrahigh time-resolution and element-specificity. In the presented work, we use extreme ultraviolet (XUV) pulses from a femtosecond HHG as an element-specific probe of ultrafast, optically driven, demagnetization in a ferromagnetic alloy (Permalloy). We show that on femtosecond timescales, the demagnetization dynamics of the constituent elements Fe and Ni in Permalloy are delayed with respect to each other, despite the strong exchange coupling that aligns their magnetic moments in thermodynamic equilibrium. We can further enhance this effect by lowering the exchange energy by diluting the Permalloy with Cu. Our measurement explores the consequences of the fundamental exchange interaction on femtosecond magnetic dynamics in strongly coupled 3d-ferromagnetic systems, showing that distinct magnetization dynamics of the individual elements can be observed on timescales corresponding to the characteristic exchange time.