title: 2D to 3D crossover of the magnetic properties in ordered arrays of iron oxide nanocrystals.
abstract: The magnetic 2D to 3D crossover behavior of well-ordered arrays of monodomain γ-Fe(2)O(3) spherical nanoparticles with different thicknesses has been investigated by magnetometry and Monte Carlo (MC) simulations. Using the structural information of the arrays obtained from grazing incidence small-angle X-ray scattering and scanning electron microscopy together with the experimentally determined values for the saturation magnetization and magnetic anisotropy of the nanoparticles, we show that MC simulations can reproduce the thickness-dependent magnetic behavior. The magnetic dipolar particle interactions induce a ferromagnetic coupling that increases in strength with decreasing thickness of the array. The 2D to 3D transition in the magnetic properties is mainly driven by a change in the orientation of the magnetic vortex states with increasing thickness, becoming more isotropic as the thickness of the array increases. Magnetic anisotropy prevents long-range ferromagnetic order from being established at low temperature and the nanoparticle magnetic moments instead freeze along directions defined by the distribution of easy magnetization directions.
authors.affiliation: Department of Material and Environmental Chemistry, Arrhenius Laboratory, Stockholm University, Stockholm, Sweden.
authors.forename: Bertrand
authors.initials: B
authors.lastname: Faure
authors.forename: Erik
authors.initials: E
authors.lastname: Wetterskog
authors.forename: Klas
authors.initials: K
authors.lastname: Gunnarsson
authors.forename: Elisabeth
authors.initials: E
authors.lastname: Josten
authors.forename: Raphaël P
authors.initials: RP
authors.lastname: Hermann
authors.forename: Thomas
authors.initials: T
authors.lastname: Brückel
authors.forename: Jens Wenzel
authors.initials: JW
authors.lastname: Andreasen
authors.forename: Florian
authors.initials: F
authors.lastname: Meneau
authors.forename: Mathias
authors.initials: M
authors.lastname: Meyer
authors.forename: Alexander
authors.initials: A
authors.lastname: Lyubartsev
authors.forename: Lennart
authors.initials: L
authors.lastname: Bergström
authors.forename: German
authors.initials: G
authors.lastname: Salazar-Alvarez
authors.forename: Peter
authors.initials: P
authors.lastname: Svedlindh
mesh_terms: D016880:Anisotropy; D003198:Computer Simulation; D060526:Magnetic Fields; D058185:Magnetite Nanoparticles / Q000737:chemistry* / Q000648:ultrastructure*; D008956:Models, Chemical; D008958:Models, Molecular; D008968:Molecular Conformation
chemical_list: D058185:Magnetite Nanoparticles