title: Spin coupling and orbital angular momentum quenching in free iron clusters.
abstract: Magnetic spin and orbital moments of size-selected free iron cluster ions Fe{n}{+} (n=3-20) have been determined via x-ray magnetic circular dichroism spectroscopy. Iron atoms within the clusters exhibit ferromagnetic coupling except for Fe{13}{+}, where the central atom is coupled antiferromagnetically to the atoms in the surrounding shell. Even in very small clusters, the orbital magnetic moment is strongly quenched and reduced to 5%-25% of its atomic value while the spin magnetic moment remains at 60%-90%. This demonstrates that the formation of bonds quenches orbital angular momenta in homonuclear iron clusters already for coordination numbers much smaller than those of the bulk.
authors.affiliation: Institut für Methoden und Instrumentierung der Forschung mit Synchrotronstrahlung, Helmholtz-Zentrum Berlin für Materialien und Energie GmbH, Albert-Einstein-Straße 15, 12489 Berlin, Germany.
authors.forename: M
authors.initials: M
authors.lastname: Niemeyer
authors.forename: K
authors.initials: K
authors.lastname: Hirsch
authors.forename: V
authors.initials: V
authors.lastname: Zamudio-Bayer
authors.forename: A
authors.initials: A
authors.lastname: Langenberg
authors.forename: M
authors.initials: M
authors.lastname: Vogel
authors.forename: M
authors.initials: M
authors.lastname: Kossick
authors.forename: C
authors.initials: C
authors.lastname: Ebrecht
authors.forename: K
authors.initials: K
authors.lastname: Egashira
authors.forename: A
authors.initials: A
authors.lastname: Terasaki
authors.forename: T
authors.initials: T
authors.lastname: Möller
authors.forename: B V
authors.initials: BV
authors.lastname: Issendorff
authors.forename: J T
authors.initials: JT
authors.lastname: Lau