Search

A review of natural materials that exhibit negative permittivity or permeability, including gaseous plasma, metals, superconductors, and ferromagnetic materials, is presented. It is shown that samples made of such materials can store large amount of the electric (magnetic) energy and create plasmonic resonators for certain values of permittivity, permeability, and dimensions. The electric and the magnetic plasmon resonances in spherical samples made of such materials are analyzed using rigorous electrodynamic methods, and the results of the analysis are compared to experimental data and to results obtained with other methods. The results of free oscillation and Mie scattering theories are compared. Similarities and differences between permittivity and permeability tensors for magnetized plasma and magnetized ferromagnetic materials are underlined. Several physical phenomena are explained on the grounds of rigorous electrodynamic analysis and experiments. These phenomena include unequal electric and magnetic energies stored in plasmonic resonators, the small influence of dielectric losses on the Q-factors of magnetic plasmon resonances, the role of radiation and dissipation losses on the properties of plasmonic resonators, and the theoretical possibility of the existence of lightning plasma balls. [ABSTRACT FROM AUTHOR]

Double-negative performance has played a significant role in electronic applications owing to its both permeability and permittivity negative values. Microwave absorption material has a substantial role in electromagnetic shielding, radar absorption, stealth applications, etc. Herein, a novel double-negative metacomposite, SrFe 12 O 19 /rGO, was designed by a simple one-pot hydrothermal method, and the microwave absorption properties of the material were studied in the microwave region from 2 to 18 GHz using VNA analysis. The structural and morphological studies were analysed using XRD, FT-IR, and SEM instrumentation techniques and the magnetic property of the material was studied using VSM analysis. Both studies confirmed the hard magnetic nature of the material. The particle sizes of SrFe 12 O 19 and SrFe 12 O 19 /rGO measured from XRD are 55.60 nm and 41.55 nm, respectively. Hexagonal plate-like morphology were observed from FESEM images. The coercivity of SrFe 12 O 19 /rGO increased, and the magnetocrystalline anisotropy was changed due to the decrease in particle size. The magnetic saturation value decreases due to the presence of non-magnetic rGO. The resultant SrFe 12 O 19 /rGO metacomposite shows negative permittivity and permeability values. The minimum reflection loss values observed for pure and rGO-decorated strontium ferrites are −28.49 dB at 7.76 GHz and −23.78 at 11.04 GHz, respectively. In addition to experimental results, simulation studies were also performed to study the reflection loss with matching thickness using a quarter wavelength mechanism. The results show that this composite can be employed as a left-handed metamaterial that finds applications in absorption, antennas, sensors, wireless power transfer systems, etc. The left-handed metamaterial can shift the frequency region from a lower to a higher frequency region. The rGO decorated metacomposite is a promising material for microwave absorption at higher frequency regions. [ABSTRACT FROM AUTHOR]

Since the electromagnetic metamaterials are artificial materials with subwavelength‐scale periodic architectures, they can manipulate electromagnetic waves by exhibiting unusual properties of characteristic negative permittivity ε and permeability μ. However, their fabrication toward reducing the anisotropy for the realization of practical metamaterials is still a challenge. A homogeneous La0.5Sr0.5MnO3 with negative properties synthesized by a facile method consisting of the sol–gel method and pressure‐less sintering is proposed in this paper. By appropriately tuning eg electrons concentration, lattice symmetry, and magnetic resonance, the La0.5Sr0.5MnO3 can simultaneously achieve negative ε and μ at the frequency range of 575–650 MHz. Experimental results and theoretical simulation suggest that negative ε is attributed to the plasma oscillation of eg electrons and high lattice symmetry, whereas the magnetic resonance causes the negative μ. The enhancement is due to the reduction of the eddy current and the effective magnetic anisotropy. An important step toward the development of natural compound metamaterials is represented in this paper. [ABSTRACT FROM AUTHOR]

In this paper, the resonance behavior of LaFeO 3 in the GHz range was investigated. Synthesis of LaFeO 3 , by solid state reaction between Fe 2 O 3 and La 2 O 3 , was confirmed by X-ray diffractometry. LaFeO 3 exhibited dielectric resonance and magnetic resonance, which can lead to negative permittivity and negative magnetic permeability. By controlling sample synthesis parameters, specifically sintering temperature, the peak in negative permeability can be tuned between 2.6 and 2.8 GHz, while the peak in negative permittivity can be tuned between 0.8 and 1.2 GHz. This material can be applied to fields such as electromagnetic metamaterials, where it could be used to increase the gain of an antenna, or to control the transmission of microwaves. [ABSTRACT FROM AUTHOR]

This paper introduces a 3-D spherical spiral expansion of the split ring resonator (SRR) commonly used to achieve negative permeability. The spherical spiral unit cell is shown to produce negative permeability over a much wider bandwidth than the traditional SRRs, and also to be capable of producing wideband negative permittivity or a double-negative response, depending on the orientation of the unit cell with respect to the incident electric field. The current structures leading to this phenomenon are discussed. Simulated and measured results are presented. [ABSTRACT FROM AUTHOR]

ABSTRACT Carbon nanofibers (CNFs)/polypyrrole (PPy) nano metacomposites are prepared by in situ polymerization in this article. The negative permittivity and negative permeability of CNFs/PPy nano metacomposites are achieved simultaneously. CNFs/PPy composites form different morphologies with the increase in CNFs content. Complex conductive networks formed by overlapped CNFs are present in CNFs/PPy composites with 30 and 50 wt % CNFs. The negative permittivity of the CNFs/PPy composites is attributed to the plasma oscillation of delocalized electrons, and the negative permeability results from a large number of conductive loops. The appearance of negative permeability is accompanied by the decrease in resistivity, which reflects that a large number of conductive loops are derived from complex conductive networks. Double negative property appears in the frequency range 845-1000 MHz in CNFs/PPy composites with 30 wt % CNFs content and 825-1000 MHz in CNFs/PPy composites with 50 wt % CNFs content. CNFs/PPy composites present double negative property in a wider frequency range compared with MWCNTs/PPy nanocomposites. © 2017 Wiley Periodicals, Inc. J. Polym. Sci., Part B: Polym. Phys. 2017, 55, 1724-1729 [ABSTRACT FROM AUTHOR]

Multi-walled carbon nanotubes(MWCNTs)/polypyrrole(PPy) nanocomposite particles were synthesized by in-situ polymerization. Negative permittivity and negative permeability appeared simultaneously in MWCNTs/PPy nanocomposites with different content of MWCNTs. It was found from SEM analysis that MWCNTs/PPy nanocomposite particles were randomly packed with a large number of micropores, and formed a lot of conductive loops around the micropores, some MWCNTs could be cross the micropores and increase the number of conductive loops. In the meantime, MWCNTs themselves in MWCNTs/PPy composite also formed many conductive networks. The negative permittivity behavior stem from the plasma oscillation of delocalized electrons in the conductive networks, and the negative permeability was attributed to the diamagnetic response of ring currents in the plentiful conductive loops. This study should initially find a double negative metamaterial in polymer composites. [ABSTRACT FROM AUTHOR]

This article presents the design, simulation, and fabrication of a new planar left-handed metamaterial (LHM), which consist of a combination of a modified square rectangular split ring resonator and strip wire. Both structures are on the same plane. The structure is simulated and measured with the microstrip antenna operating at frequency 5.8 GHz. The LHM has been analyzed using Nicolson-Ross-Weir approach to obtain the negative permeability and permittivity at 5.8 GHz. The fabrication of the LHM is on FR-4 board substrate. From the simulation and measurement results, the gain of the microstrip antenna with LHM has increased by 4.0 dB. The return loss of the antenna with LHM is improved to 15.7 dB compare without LHM structure. © 2012 Wiley Periodicals, Inc. Microwave Opt Technol Lett 54:2828-2832, 2012; View this article online at wileyonlinelibrary.com. DOI 10.1002/mop.27186 [ABSTRACT FROM AUTHOR]

The focusing behavior and optimal design of lossy double-negative (DNG) metamaterial slabs are thoroughly explored in this paper via an efficient technique. To this aim, the novel scheme embodies the signal processing notions of the cross-correlation coefficient and mean square error (mse) to treat structures with convoluted attributes. Furthermore, an enhanced formulation of the latter indicator, devoid of its conventional weaknesses, is introduced. In particular, by neglecting the phase term due to wave propagation in the vacuum/metamaterial space, the modified mse attains far more accurate outcomes without any contrived assumptions. The effectiveness of the prior criteria is successfully examined through the infinite slab case. Next, analysis proceeds to finite-length slabs which are modeled by means of a frequency-dependent finite-difference time-domain algorithm. Numerical verification, addressing diverse complicated DNG arrangements, reveals the advantages of the proposed methodology, indicating its competence to reliably explore the operational characteristics of such demanding media. [ABSTRACT FROM AUTHOR]

The resonant frequencies of five different ring resonators are measured with the aid of a network analyser within the frequency range of about 1.5 to 2.8 GHz. The resonant frequencies for those configurations are also determined from numerical calculations using the commercially available MICRO-STRIPES package. The experimental and numerical results are shown to be very close to each other. Analytical results from various authors, available for three of the configurations, are also compared with the experimental results; one of them leads to a large discrepancy, but the other analytical approximations are shown to be not too far off. © 2005 Wiley Periodicals, Inc. Microwave Opt Technol Lett 46: 473–476, 2005; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/mop.21021 [ABSTRACT FROM AUTHOR]

Here, we analyze the transverse-magnetic (TM) wave interaction with a pair of slabs, one being an epsilon-negative (ENG) layer in which the real part of permittivity is assumed to be negative while its permeability has positive real part, and the other being a mu-negative (MNG) layer that has the real part of its permeability negative but its permittivity has positive real part. Although wave interaction with each slab by itself has predictable features, we show that the juxtaposition and pairing of such ENG and MNG slabs may, under certain conditions, lead to some unusual features, such as resonance, complete tunneling, zero reflection and transparency. The field distributions inside and outside such paired slabs are analyzed, and the Poynting vector distributions in such structures are studied. Using equivalent transmission-line models, we obtain the conditions for the resonance, complete tunneling and transparency, and we justify and explain the field behavior in these resonant paired structures. Salient features of the tunneling conditions, such as the roles of material parameters, slab thicknesses, dissipation, and angle of incidence are discussed. The analogy and correspondence between the ENG-MNG pair and the pair of a slab of conventional material juxtaposed with a "double-negative" medium is also discussed. Finally, a conceptual idea for a potential application of such a "matched" lossless ENG-MNG pair in "ideal" image displacement and image reconstruction is proposed. [ABSTRACT FROM AUTHOR]

Gaussian beam propagation in structures containing meta-materials with negative permittivity and negative permeability is numerically studied by using a bidirectional wide-angle finite-difference beam propagation method. Illustrative and quantitative views are given for various anomalous behaviors, such as the negative angle of refraction, beam refocusing, arbitrarily thin distributed Bragg reflector, and negative lateral shift of the reflected beam from a grounded slab, by a Gaussian beam propagating in some meta-material structures. © 2003 Wiley Periodicals, Inc. Microwave Opt Technol Lett 37: 292–296, 2003; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/mop.10898 [ABSTRACT FROM AUTHOR]

In this paper, double negative performance of GdFeO 3 in GHz range was investigated. Double negative performance generally occurs in ceramic/metal composites or artificial metamaterials. Therefore, this behavior of single phase ABO 3 perovskites is very interesting. Conventional solid phase method was used for synthesis of GdFeO 3 ceramics. Double negative performance of GdFeO 3 occurred, with negative permeability at 2.6–2.8 GHz and negative permittivity at 0.9–1.4 GHz. The reason for the resonance was also analyzed. Furthermore, resonance frequency could be easily adjusted by varying sintering temperature. Results showed that GdFeO 3 can be applied in new field of metamaterials for antennas. By placing a double negative metamaterial lens in front of antenna source, the gain and directivity of the antenna can be increased. The material can be placed in front of antenna source as a zero-refractive metamaterial lens. Therefore, it is necessary to study the properties of metamaterials based on GdFeO 3. • GdFeO 3 exhibits double negative performance in the GHz range. • The resonance frequency of GdFeO 3 can be adjusted by sintering temperature. • GdFeO 3 can be applied in new field of metamaterials for antennas. [ABSTRACT FROM AUTHOR]

Effects of the frequency-dependence of the permeability and permittivity of a left-handed material (LHM), when used as one of the components of a Bragg reflector, are investigated. It is found that typical broad Bragg reflectivity peaks appear in the frequency range in which the material is not left-handed. Inside the LHM range, the Bragg peaks are very narrow and of low intensity. © 2003 Wiley Periodicals, Inc. Microwave Opt Technol Lett 38: 494–495, 2003; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/mop.11100 [ABSTRACT FROM AUTHOR]