Negative permeability spectra in Permalloy granular composite materials

Kasagi, Teruhiro; Tsutaoka, Takanori; Hatakeyama, Kenichi

doi:10.1063/1.2198113

Cited by 102 publications

(50 citation statements)

References 15 publications

Supporting

Mentioning

Contrasting

Order By: Relevance

“…The ''lower'' negative permittivity in the PEI nanocomposites should be induced by dilute effect from the ether groups and higher free volume of phenylene ether groups that usually account for the lower positive permittivity of PEI compared with that of PI. [17] This meaningful result suggests that, when constructing metamaterials with polymer hosts/substrates, the polymer component should not only be considered as an insulating medium, as in most research, [11,12,16,17,27] but its chemical structure can also exert great influence on the negative permittivity, and possibly negative permeability. The fact that negative permittivity appears in organic polymer/non-metallic CNFs composites and epoxy/nanopolyaniline hybrids [18] also reveals that a metallic element (in metals and ceramics) is not indispensable to the single negative-permittivity materials.…”

mentioning

confidence: 88%

“…For the polymers involved in a metamaterial system, they were usually only applied as insulating hosts/substrates. [11,12,16,17] Moreover, their negative permittivity and/or negative permeability were considered to be caused solely by those inorganic inclusions, and were independent of the polymer properties. In a recent study, on nanopolyanilne/ epoxy hybrids obtained by a special absorption-transferring process, [18] the occurrence of negative permittivity was considered to have resulted from the formation of a continuous conductive network of conductive polymer, polyaniline.…”

mentioning

confidence: 99%

See 1 more Smart Citation

Single Negative Metamaterials in Unstructured Polymer Nanocomposites Toward Selectable and Controllable Negative Permittivity

2009

View full text Add to dashboard Cite

Negative permittivity is one of the key characteristics of the unique metamaterials, a novel class of artificial materials with special structures that simultaneously exhibit negative permittivity and permeability. In metamaterials, adherence to the right-hand rule, which is obligatory for all other materials working in an electromagnetic field (electric field E, magnetic field H), does not apply. The wave vector k in metamaterials is consistent with a left-handed rule, and, hence, this special class of materials is also called left-handed materials (LHM), first theoretically proposed by Veselago in 1960s.[1] The negative permittivity and negative permeability endow LHM with several special properties, such as negative refractive index, reversed Doppler Effect, and reversed Cherenkov radiation, [2] none of which exist in natural materials. Metamaterials can be applied in sub-wavelength imaging, cloaking, wave filter, super lens, and band-gap design. [3][4][5] Since 2000, when investigations of metamaterials were experimentally performed by double-slit-ring resonator and linear vibrator, [6] research on the construction and application of metamaterials in optical and microwave frequencies range have attracted great interest, and much theoretical work has been published; however, the realization of their promise still requires great effort.It is well recognized that the unusual properties of metamaterials are determined by their specially designed structures, rather than their compositions. In other words, the permittivity and/or permeability are not, or are just weakly, dependent on chemical structures and constituent compositions, or interactions among different components in the materials. Various structures have been designed by physicists and electrical engineers to obtain negative permittivity and negative permeability, including double-split-ring resonators, [3] S-shaped resonators, [7] multilevel dendritic structures, [2] nano/small apertures, [8,9] metallic nanoclusters, [5] among others. In all of these, resonance was considered to be the main mechanism of the realization of both negative permittivity and negative permeability, while the phase changes close to the resonant frequency.[10] In contrast, the exploration of metamaterials from the point of view of materials (chemistry and properties) has not attracted substantive attention from material researchers. Among the very limited work reported, almost all research in this field focused on metals and ceramics, which contain metallic elements and can consequentially realize negative permittivity and/or permeability under certain conditions. In particular, ferromagnetic materials were the subject of considerable interests in realization of metamaterials, owing to the resultant negative permittivity of metallic materials below plasma frequency as well as negative permeability of some ferromagnetic metals and metallic alloys in the vicinity of the ferromagnetic resonance frequency. [11][12][13] However, to the best of our knowledge, research has been rarely...

show abstract

mentioning

confidence: 88%

mentioning

confidence: 99%

Single Negative Metamaterials in Unstructured Polymer Nanocomposites Toward Selectable and Controllable Negative Permittivity

2009

View full text Add to dashboard Cite

show abstract

“…The maximum μ r ″ value is lower than that of the sample with 60 wt% CNTs/Co@C (0.17), due to the decreased addition amount of CNTs/Co@C. Notably, the μ r ″ values are less than zero in the 8.9-20 GHz range, denoting that the Co/CNTs nanocomposites could be used as a left-hand material. Notably, the μ r ″ values are less than zero in the 8.9-20 GHz range, denoting that the Co/CNTs nanocomposites could be used as a left-hand material [47][48][49]. For a further investigation, the dielectric loss tangent (tanδ E = ε ″ /ε ′ ) and magnetic loss tangent (tanδ M = μ ″ /μ ′ ) were calculated for two samples and are displayed in Fig.…”

Section: Em Absorption Performancesmentioning

confidence: 99%

Strengthened electromagnetic absorption performance derived from synergistic effect of carbon nanotube hybrid with Co@C beads

Qiao

Liu

et al. 2017

Adv Compos Hybrid Mater

View full text Add to dashboard Cite

The composite structure of Co beads (200-300 nm) threaded by carbon nanotubes has been synthesized through a facile solvothermal method followed by a carbon reduction process. A carbon layer of ca. 5 nm was coated on the surface of Co beads to form a coreshell structure (CNTs/Co@C), in favor of the antioxidation of Co nanoparticles. The CNTs/Co@C hybrid showed a saturation magnetization (M s ) of 82.5 emu g −1 and a larger H c value of 258.8 Oe than bulk Co (ca. 10 Oe). Served as an EM wave absorption material, the epoxy resin composites consisting of 60 wt% and 40 wt% CNTs/Co@C hybrid exhibited effective EM absorption (RL < − 10 dB) over the frequency ranges of 1.5-15 and 1.6-20 GHz with the matching thicknesses of 1.0-7.5 and 1.0-10.0 mm, respectively. The superior EM absorption performances of CNTs/Co@C hybrid containing strong absorption, wide frequency range, thin thickness, and light weight are mainly attributed to the synergy of magnetic loss from Co beads and dielectric loss from carbon nanotubes, as well as remarkable impedance matching.

show abstract

“…LHM has changed the range of what are acceptable electric and magnetic material properties. In particular, a negative permeability in Permalloy has been recently reported (Kasagi et al 2006) above 5 GHz. This is however not surprising, as the low values of permeability (zero or negative) in the higher portions of the spectrum were just not of any practical interest a decade or two ago.…”

mentioning

confidence: 99%

“…According to equation (1), for some particular set of parameters, the permeability can assume negative values over some frequency range. In particular, we will consider a ferrite with the following parameters μ DC = 39, μ ∞ = 1, f 0 = 1.82 GHz, G = 3.2 GHz, conductivity σ = 0.006, and ε ≈ 11 over the 2-10 GHz range (these parameters for an unbiased ferrite are representative in view of the data reported in Kasagi et al 2006). The magnetic properties of this lossy ferrite are shown in figure 1, where at 7.5 GHz we observe, μ ≈ −1 + 0.9i, which is to be compared with Ag in the optical where ε ≈ −1 + 0.4i.…”

mentioning

confidence: 99%

A non-structured subwavelength near-field microwave lens

Monzón

2009

Proc. R. Soc. A.

View full text Add to dashboard Cite

This paper proposes a super resolution near-field radio frequency focusing device consisting of a thin planar layer of a particular ferrite characterized by negative permeability. Radiation focusing is investigated and it is established that the resulting non-structured lens is characterized by a resolving power 2-3 times the lens thickness, regardless of the wavelength. The resulting near field lens can be used as a magnetic field device for imaging inside non-magnetic objects.

show abstract

Negative permeability spectra in Permalloy granular composite materials

Cited by 102 publications

References 15 publications

Single Negative Metamaterials in Unstructured Polymer Nanocomposites Toward Selectable and Controllable Negative Permittivity

Single Negative Metamaterials in Unstructured Polymer Nanocomposites Toward Selectable and Controllable Negative Permittivity

Strengthened electromagnetic absorption performance derived from synergistic effect of carbon nanotube hybrid with Co@C beads

A non-structured subwavelength near-field microwave lens

Contact Info

Product

Resources

About