Berlin 2012 – wissenschaftliches Programm
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MA: Fachverband Magnetismus
MA 15: Magnetization / Demagnetization Dynamics I
MA 15.4: Vortrag
Dienstag, 27. März 2012, 10:30–10:45, H 1012
Momentum dependent ultrafast electrondynamics in antiferromagnetic EuFe2As2 — Laurenz Rettig1,2, Rocio Cortés1,3, Setti Thirupathaiah4, Philipp Gegenwart5, HiraleS. Jeevan5, Martin Wolf3, Jörg Fink4, and •Uwe Bovensiepen1,2 — 1Freie Universität Berlin, FachbereichPhysik — 2Universität Duisburg-Essen,Fakultät für Physik — 3Fritz-Haber-Institut der MPG — 4IFW Dresden — 5UnversitätGöttingen, I. Physikalisches Institut
The response and relaxation dynamics of magnetically ordered materials upon optical excitation is highly interesting from a scientific and an application point of view. Up to now most studies have focussed on ferro- or ferrimagnetic ordered materials. Fe pnictides are metallic, present antiferromagnetic order below the Néel temperature TN, and become superconducting upon doping. Here, we present results obtained for antiferromagnetic EuFe2As2 by femtosecond time- and angle-resolved photoelectron spectroscopy. Employing the momentum-sensitivity of the technique we separate the electron-phonon mediated relaxation from transient changes of the magnetic order. We assign the relaxation time of 200 fs observed at 30 K in a single particle region of the electronic band structure at k||=0.25 Å−1 to relaxation mediated by e-ph scattering. Antiferromagnetic order is established by backfolding bands from X to Γ. Relaxation monitored at Γ occurs with a time constant of 800 fs and is assigned to the transient magnetic order. The merging of these different times for T>TN evidences our conclusion.
This work was supported by the DFG through SPP 1458 and the Alexander von Humboldt Foundation.