title: Spacing-dependent dipolar interactions in dendronized magnetic iron oxide nanoparticle 2D arrays and powders.
abstract: Self-assembly of nanoparticles (NPs) into tailored structures is a promising strategy for the production and design of materials with new functions. In this work, 2D arrays of iron oxide NPs with interparticle distances tuned by grafting fatty acids and dendritic molecules at the NPs surface have been obtained over large areas with high density using the Langmuir-Blodgett technique. The anchoring agent of molecules and the Janus structure of NPs are shown to be key parameters driving the deposition. Finally the influence of interparticle distance on the collective magnetic properties in powders and in monolayers is clearly demonstrated by DC and AC SQUID measurements. The blocking temperature T(B) increases as the interparticle distance decreases, which is consistent with the fact that dipolar interactions are responsible for this increase. Dipolar interactions are found to be stronger for particles assembled in thin films compared to powdered samples and may be described by using the Vogel Fulcher model.
authors.affiliation: Institut de Physique et de Chimie des Matériaux de Strasbourg, UMR CNRS-UdS 7504, 23, rue du Loess, BP 43, 67034 Strasbourg Cedex 2, France.
authors.forename: Solenne
authors.initials: S
authors.lastname: Fleutot
authors.forename: Gareth L
authors.initials: GL
authors.lastname: Nealon
authors.forename: Matthias
authors.initials: M
authors.lastname: Pauly
authors.forename: Benoit P
authors.initials: BP
authors.lastname: Pichon
authors.forename: Cédric
authors.initials: C
authors.lastname: Leuvrey
authors.forename: Marc
authors.initials: M
authors.lastname: Drillon
authors.forename: Jean-Louis
authors.initials: JL
authors.lastname: Gallani
authors.forename: Daniel
authors.initials: D
authors.lastname: Guillon
authors.forename: Bertrand
authors.initials: B
authors.lastname: Donnio
authors.forename: Sylvie
authors.initials: S
authors.lastname: Begin-Colin
mesh_terms: D003198:Computer Simulation; D050091:Dendrimers / Q000737:chemistry; D060526:Magnetic Fields; D058185:Magnetite Nanoparticles / Q000737:chemistry* / Q000648:ultrastructure*; D008422:Materials Testing; D008956:Models, Chemical; D011208:Powders
chemical_list: D050091:Dendrimers; D058185:Magnetite Nanoparticles; D011208:Powders