title: Pinned orbital moments - A new contribution to magnetic anisotropy.
abstract: Reduced dimensionality and symmetry breaking at interfaces lead to unusual local magnetic configurations, such as glassy behavior, frustration or increased anisotropy. The interface between a ferromagnet and an antiferromagnet is such an example for enhanced symmetry breaking. Here we present detailed X-ray magnetic circular dichroism and X-ray resonant magnetic reflectometry investigations on the spectroscopic nature of uncompensated pinned magnetic moments in the antiferromagnetic layer of a typical exchange bias system. Unexpectedly, the pinned moments exhibit nearly pure orbital moment character. This strong orbital pinning mechanism has not been observed so far and is not discussed in literature regarding any theory for local magnetocrystalline anisotropy energies in magnetic systems. To verify this new phenomenon we investigated the effect at different temperatures. We provide a simple model discussing the observed pure orbital moments, based on rotatable spin magnetic moments and pinned orbital moments on the same atom. This unexpected observation leads to a concept for a new type of anisotropy energy.
authors.affiliation: Max Planck Institute for Intelligent Systems, Heisenbergstr. 3, D-70569 Stuttgart, Germany.
authors.forename: P
authors.initials: P
authors.lastname: Audehm
authors.affiliation: Max Planck Institute for Intelligent Systems, Heisenbergstr. 3, D-70569 Stuttgart, Germany.
authors.forename: M
authors.initials: M
authors.lastname: Schmidt
authors.affiliation: Physikalisches Institut, Universität Würzburg, Am Hubland, D-97074 Würzburg, Germany.
authors.forename: S
authors.initials: S
authors.lastname: Brück
authors.affiliation: Max Planck Institute for Intelligent Systems, Heisenbergstr. 3, D-70569 Stuttgart, Germany.
authors.forename: T
authors.initials: T
authors.lastname: Tietze
authors.affiliation: Max Planck Institute for Intelligent Systems, Heisenbergstr. 3, D-70569 Stuttgart, Germany.
authors.forename: J
authors.initials: J
authors.lastname: Gräfe
authors.affiliation: Quantum Matter Institute and Department of Physics and Astronomy University of British Columbia 2355 East Mall, Vancouver, V6T 1Z4, Canada.|Max Planck Institute for Solid State Research, Heisenbergstraße 1, D-70569, Stuttgart, Germany.
authors.forename: S
authors.initials: S
authors.lastname: Macke
authors.affiliation: Max Planck Institute for Intelligent Systems, Heisenbergstr. 3, D-70569 Stuttgart, Germany.
authors.forename: G
authors.initials: G
authors.lastname: Schütz
authors.affiliation: Max Planck Institute for Intelligent Systems, Heisenbergstr. 3, D-70569 Stuttgart, Germany.
authors.forename: E
authors.initials: E
authors.lastname: Goering