title: Complex Magnetic Exchange Coupling between Co Nanostructures and Ni(111) across Epitaxial Graphene.
abstract: We report on the magnetic coupling between isolated Co atoms as well as small Co islands and Ni(111) mediated by an epitaxial graphene layer. X-ray magnetic circular dichroism and scanning tunneling microscopy combined with density functional theory calculations reveal that Co atoms occupy two distinct adsorption sites, with different magnetic coupling to the underlying Ni(111) surface. We further report a transition from an antiferromagnetic to a ferromagnetic coupling with increasing Co cluster size. Our results highlight the extreme sensitivity of the exchange interaction mediated by graphene to the adsorption site and to the in-plane coordination of the magnetic atoms.
authors.affiliation: Istituto di Struttura della Materia (ISM), Consiglio Nazionale delle Ricerche (CNR) , I-34149 Trieste, Italy.
authors.forename: Alessandro
authors.initials: A
authors.lastname: Barla
authors.affiliation: S3-Istituto di Nanoscienze-CNR , Via Campi 213/A, I-41125 Modena, Italy.
authors.forename: Valerio
authors.initials: V
authors.lastname: Bellini
authors.affiliation: Institute of Condensed Matter Physics (ICMP), Ecole Polytechnique Fédérale de Lausanne (EPFL) , Station 3, CH-1015 Lausanne, Switzerland.
authors.forename: Stefano
authors.initials: S
authors.lastname: Rusponi
authors.affiliation: Institute of Theoretical Physics and Astrophysics, University of Kiel , D-24098 Kiel, Germany.
authors.forename: Paolo
authors.initials: P
authors.lastname: Ferriani
authors.affiliation: Institute of Condensed Matter Physics (ICMP), Ecole Polytechnique Fédérale de Lausanne (EPFL) , Station 3, CH-1015 Lausanne, Switzerland.
authors.forename: Marina
authors.initials: M
authors.lastname: Pivetta
authors.affiliation: Institute of Condensed Matter Physics (ICMP), Ecole Polytechnique Fédérale de Lausanne (EPFL) , Station 3, CH-1015 Lausanne, Switzerland.
authors.forename: Fabio
authors.initials: F
authors.lastname: Donati
authors.affiliation: Institute of Condensed Matter Physics (ICMP), Ecole Polytechnique Fédérale de Lausanne (EPFL) , Station 3, CH-1015 Lausanne, Switzerland.
authors.forename: François
authors.initials: F
authors.lastname: Patthey
authors.affiliation: Department of Materials, ETH Zurich , CH-8093 Zurich, Switzerland.
authors.forename: Luca
authors.initials: L
authors.lastname: Persichetti
authors.affiliation: Istituto di Struttura della Materia (ISM), Consiglio Nazionale delle Ricerche (CNR) , I-34149 Trieste, Italy.
authors.forename: Sanjoy K
authors.initials: SK
authors.lastname: Mahatha
authors.affiliation: Dipartimento di Fisica, Università della Calabria , I-87036 Arcavacata di Rende (Cs), Italy.
authors.forename: Marco
authors.initials: M
authors.lastname: Papagno
authors.affiliation: Swiss Light Source, Paul Scherrer Institut , CH-5232 Villigen PSI, Switzerland.
authors.forename: Cinthia
authors.initials: C
authors.lastname: Piamonteze
authors.affiliation: Institute of Theoretical Physics and Astrophysics, University of Kiel , D-24098 Kiel, Germany.
authors.forename: Simon
authors.initials: S
authors.lastname: Fichtner
authors.affiliation: Institute of Theoretical Physics and Astrophysics, University of Kiel , D-24098 Kiel, Germany.
authors.forename: Stefan
authors.initials: S
authors.lastname: Heinze
authors.affiliation: Department of Materials, ETH Zurich , CH-8093 Zurich, Switzerland.
authors.forename: Pietro
authors.initials: P
authors.lastname: Gambardella
authors.affiliation: Institute of Condensed Matter Physics (ICMP), Ecole Polytechnique Fédérale de Lausanne (EPFL) , Station 3, CH-1015 Lausanne, Switzerland.
authors.forename: Harald
authors.initials: H
authors.lastname: Brune
authors.affiliation: Istituto di Struttura della Materia (ISM), Consiglio Nazionale delle Ricerche (CNR) , I-34149 Trieste, Italy.
authors.forename: Carlo
authors.initials: C
authors.lastname: Carbone
keywords: X-ray magnetic circular dichroism (XMCD); density functional theory (DFT); graphene; magnetic exchange interaction; scanning tunneling microscopy (STM)