Stuttgart 2012 – wissenschaftliches Programm

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MO: Fachverband Molekülphysik

MO 20: Atomic clusters (with A)

MO 20.1: Hauptvortrag

Donnerstag, 15. März 2012, 14:00–14:30, V57.05

X-ray magnetic circular dichroism spectroscopy of size-selected free cluster ions: spin coupling, orbital angular momentum quenching, and magnetic dopants — •Tobias Lau — Helmholtz-Zentrum Berlin für Materialien und Energie GmbH, Institut für Methoden und Instrumentierung der Forschung mit Synchrotronstrahlung, Albert-Einstein-Straße 15, 12489 Berlin

X-ray magnetic circular dichroism (XMCD) spectroscopy is a local and element specific probe to study spin and orbit contributions to the total magnetic moment. With a 5 T and 15 K linear ion trap setup we have sucessfully applied XMCD of size selected cluster ions to study fundamental magnetic properties of transition metals in the molecular limit. Recent results include the observation of ferromagnetic spin coupling in small clusters of archetypical bulk antiferromagnets, as well as antiferromagnetic spin coupling in iron, the most typical 3d bulk ferromagnet. We could also show that the orbital angular momentum is largely quenched already for the smallest iron clusters. Furthermore, magnetization curves recorded at fixed ion trap temperature can be used to determine the cluster ion temperature. As an outlook, first results of XMCD spectroscopy of single impurity atoms in size selected clusters ions will be presented.