Model design on calculations of microwave permeability and permittivity of Fe/SiO2 particles with core/shell structure

Broadband metamaterials and metasurfaces: a review from the perspectives of materials and devices

“…However, the spin of the electrons and magnetic moments in solid state materials cannot easily keep up with the oscillation of the electromagnetic waves at frequencies above a few gigahertz and magnetism from electronic spin almost disappears at higher infrared and optical frequencies [41,44,45]. Although studies to overcome this limitation have been carried out [46,47], lowdispersion magnetic materials above the microwave regime are yet to be realized [4]. This absence of intrinsically-magnetic building blocks at high frequencies presents predicaments for constructing broadband magnetic metamaterials using similar mixing formulae as in dielectric composites because, in strict quasi-static assumptions (i.e.∇ ñ E 0 and ∇ ñ H 0) [48], where the electric and magnetic fields are decoupled, effective permeability other than unity is theoretically prohibited if only non-magnetic constituent materials are available.…”

Synthesis, microstructure and magnetic properties of Fe3Si0.7Al0.3@SiO2 core–shell particles and Fe3Si/Al2O3 soft magnetic composite core

“…Besides, silica coating techniques have been also used to prepared soft magnetic composites [14][15][16]. SiO 2 is commonly used as surfaced shell of magnetic core-shell nanoparticles because of its good chemical inertness, high suspension stability and non-toxicity [16][17][18][19][20][21][22][23][24]. In recent years, silica-coated iron particles have also been investigated as a novel kind of SMCs by many researchers [9,14,15], while few studies have been carried out for the FeSiAl-based soft magnetic materials.…”

Low Weight Hollow Microspheres of Iron with Thin Dielectric Coating: Synthesis and Microwave Permeability

“…An effective way to protect these metals from oxidation is to encapsulate chemically-active particles into an inorganic protective shell. A core-shell structure is therefore formed [20,21]. Silica, SiO 2 , may be used as a protecting material [21,22].…”