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This article reports non-conductive ferromagnetic properties of metal/polymer nanocomposite films intended to be used for RF applications. The nanocomposite arrangement is unique showing a core double-shell structure of metal-carbon-polystyrene: M/C//P1/P2, where M=Co, Ni is the core material, C=graphene or carbon is the first shell acting as a protective layer against oxidation, P1=pyrene-terminated polystyrene is the second shell for electrical insulation, and P2=polystyrene is a supporting matrix (// indicates actual grafting). The nanocomposite formulation is briefly described, and the film deposition by spin-coating is detailed. Original spin-curves are reported and analyzed. One key outcome is the achievement of uniform and cohesive films at the wafer scale. Structural properties of films are thoroughly detailed, and weight and volume fractions of M/C are considered. Then, a comprehensive overview of DC magnetic and electrical properties is reported. A discussion follows on the magnetic softness of the nanocomposites vs. that of a single particle (theoretical) and the raw powder (experimental). Finally, unprecedented achievement of high magnetization (~0.6 T) and ultra-high resistivity (~1010µΩ cm) is shown. High magnetization comes from the preservation of the existing protective shell C, with no significant degradation on the particle net-moment, and high electrical insulation is ensured by adequate grafting of the secondary shell P1. To conclude, the metal/polymer nanocomposites are situated in the landscape of soft ferromagnetic materials for RF applications (i.e., inductors and antennas), by means of two phase-diagrams, where they play a crucial role. [ABSTRACT FROM AUTHOR]

This paper describes the two routes with grafting schemes (covalent or not covalent) for producing non-conductive ferromagnetic films of core double-shell cobalt–graphene–polystyrene nanocomposites. Films present high moment (103 emu/g) and high resistivity ( 10^10~\mu \Omega \cdot cm) leading to a constant permeability of 1.9 with a magnetic loss tangent of 10^\mathrm -3 at 10 GHz. [ABSTRACT FROM AUTHOR]