Magnetic negative permittivity with dielectric resonance in random Fe3O4@graphene-phenolic resin composites

Abstract

Magnetic Fe 3 O 4 @graphene-phenolic resin (FGR-PR) composites with negative permittivity were prepared by chemical coprecipitation and pressing method. Alternating current conductivity, permittivity, and permeability of the FGR-PR composites were investigated. An obvious percolation phenomenon was observed with the increase of FGR content from 84 to 91 vol%. Two types of negative permittivity attributed to the Lorentz and the Drude model, respectively, w e r e o b s e r v e d i n t h e c o m p o s i t e s . D u e t o t h e magnetocrystalline anisotropy and saturation magnetization, the real permeability enhanced from 1.17 to 4.1 with the increasing FGR content from 6 to 98 vol%. In addition, the frequency dispersion of permeability was attributed to the domain wall and the gyromagnetic spin resonance. The magnetic loss decreased firstly in the low frequency, attributing to the natural resonance, and then increased in the high frequency from the eddy current.

Modification of structural and dielectric properties of polycrystalline Gd-doped BFO–PZO

“…37 Similar behavior of dielectric loss was also observed by Wu et al and was shown to be dependent on the dopant concentration in the solution. 47 This type of peaking behavior is observed when the jumping frequency of the Fe 2þ and Fe 3þ ions is exactly equal to the frequency of the applied field. 48 In the present case, the abrupt increase in the dielectric loss can be related to similar type of concentration-dependent behavior.…”

Preparation and application synthesis of magnetic nanocomposite using waste toner for the removal of Cr(vi)

“…21 Recently, iron-bearing materials have been applied to various elds such as drug delivery, sensors, electromagnetic interference shielding, and adsorbents for environmental remediation. [22][23][24] In the environmental eld, iron-bearing materials such as magnetite, 25,26 iron suldes, 27,28 goethite, 29 and zerovalent iron 30 can remediate Cr(VI). It has also been reported that fabric-and cellulose-derived magnetic carbon-iron nanomaterials possess high efficiency for Cr(VI) removal, 31,32 where Cr(VI) is reduced to Cr(III) by the reductive intermediates generated from ZVI such as Fe(II).…”

Recent Progress on the Metacomposites with Carbonaceous Fillers

“…38 composites. 63 The transition of dielectric constant from positive to negative (75 to -75) was observed in the FGR-PR composites when the FGR content reached 91 vol%. According to the Lorentz model, the negative permittivity appeared when the frequency of applied electromagnetic field exceeded the resonance frequency, and the resonance frequency for FGR91 was about 460 MHz.…”