title: Beyond the Heisenberg model: anisotropic exchange interaction between a Cu-tetraazaporphyrin monolayer and Fe3O4(100).
abstract: The exchange coupling of a single spin localized at the central ion of Cu-tetraazaporphyrin on a magnetite(100) surface has been studied using x-ray magnetic circular dichroism (XMCD). Sum rule analysis of the XMCD spectra results in Cu spin and orbital magnetic moments as a function of the applied external field at low temperatures (20 K). The exchange coupling is positive for magnetization direction perpendicular to the surface (ferromagnetic) while it is negative for in-plane magnetization direction (antiferromagnetic). We attribute the anisotropy of the Heisenberg exchange coupling to an orbitally dependent exchange Hamiltonian.
authors.affiliation: Institut für Anorganische Chemie und Analytische Chemie, Johannes Gutenberg-Universität Mainz, D-55099 Mainz, Germany.
authors.forename: J
authors.initials: J
authors.lastname: Klanke
authors.forename: E
authors.initials: E
authors.lastname: Rentschler
authors.forename: K
authors.initials: K
authors.lastname: Medjanik
authors.forename: D
authors.initials: D
authors.lastname: Kutnyakhov
authors.forename: G
authors.initials: G
authors.lastname: Schönhense
authors.forename: S
authors.initials: S
authors.lastname: Krasnikov
authors.forename: I V
authors.initials: IV
authors.lastname: Shvets
authors.forename: S
authors.initials: S
authors.lastname: Schuppler
authors.forename: P
authors.initials: P
authors.lastname: Nagel
authors.forename: M
authors.initials: M
authors.lastname: Merz
authors.forename: H J
authors.initials: HJ
authors.lastname: Elmers