title: Non-conductive ferromagnets based on core double-shell nanoparticles for radio-electric applications.
abstract: Two fabrication schemes of magnetic metal-polymer nanocomposites films are described. The nanocomposites are made of graphene-coated cobalt nanoparticles embedded in a polystyrene matrix. Scheme 1 uses non-covalent chemistry while scheme 2 involves covalent bonding with radicals. Preservation of the net-moment of cobalt and electrical insulation are achieved by means of a core double-shell structure of cobalt-graphene-polystyrene. The graphene shell has two functions: it is a protective layer against metal core oxidation and it serves as the functionalization surface for polymer grafting as well. The polystyrene shell is used as an insulating layer between nanoparticles and improves nanoparticles dispersion inside the polystyrene matrix. The theoretical maximum volume filling ratio estimated at ~30 % is almost reached. The nanocomposites are shown to undergo percolation behavior but retain low conductivity (<1 S/m) at the highest filling ratio reached ~25 % leading to extremely low losses (10(-3)) at high frequency. Such low conductivity values are combined with large magnetization, as high as 0.9 T. Ability for radiofrequency applications is discussed in regards to the obtained magnetization.
authors.affiliation: LETI, CEA, MINATEC Campus, 17 rue des Martyrs, 38054 Grenoble Cedex 9, France ; LTM, CNRS-UJF, MINATEC Campus, 17 rue des Martyrs, 38054 Grenoble Cedex 9, France.
authors.forename: Hélène
authors.initials: H
authors.lastname: Takacs
authors.affiliation: LETI, CEA, MINATEC Campus, 17 rue des Martyrs, 38054 Grenoble Cedex 9, France.
authors.forename: Bernard
authors.initials: B
authors.lastname: Viala
authors.affiliation: LETI, CEA, MINATEC Campus, 17 rue des Martyrs, 38054 Grenoble Cedex 9, France.
authors.forename: Vanessa
authors.initials: V
authors.lastname: Hermán
authors.affiliation: LTM, CNRS-UJF, MINATEC Campus, 17 rue des Martyrs, 38054 Grenoble Cedex 9, France.
authors.forename: Jean-Hervé
authors.initials: JH
authors.lastname: Tortai
authors.affiliation: INAC, CEA, 17 rue des Martyrs, 38054 Grenoble Cedex 9, France ; INAC, Univ. Grenoble Alpes, 17 rue des Martyrs, 38054 Grenoble Cedex 9, France.
authors.forename: Florence
authors.initials: F
authors.lastname: Duclairoir
authors.affiliation: LETI, CEA, MINATEC Campus, 17 rue des Martyrs, 38054 Grenoble Cedex 9, France.
authors.forename: Juvenal
authors.initials: J
authors.lastname: Alarcon Ramos
authors.affiliation: INAC, CEA, 17 rue des Martyrs, 38054 Grenoble Cedex 9, France.
authors.forename: Pierre-Henri
authors.initials: PH
authors.lastname: Jouneau
authors.affiliation: INAC, CEA, 17 rue des Martyrs, 38054 Grenoble Cedex 9, France.
authors.forename: Hanako
authors.initials: H
authors.lastname: Okuno
authors.affiliation: Visualization Sciences Group, FEI, 3 Impasse Rudolf Diesel, 33700 Mérignac, France.
authors.forename: Gwenolé
authors.initials: G
authors.lastname: Tallec
keywords: Core double-shell; Ferromagnetism; Nanocomposites; RF properties