scholarly journals Symmetrized Maxwell–Garnett Approximation as an Effective Method for Studying Nanocomposites

2019 ◽  
Vol 7 (4) ◽  
pp. 92-100 ◽  
Author(s):  
M. M. Yashin ◽  
H. B. Mirzokulov
Keyword(s):  
Kerr Effect ◽  
Effective Permittivity ◽  
Effective Medium ◽  
Magnetic Nanocomposites ◽  
Optimal Method ◽  
Dielectric System ◽  
Effective Dielectric Permittivity ◽  
Granular Alloys ◽  
Classical Size ◽  
Nanocomposite Structures

The symmetrized Maxwell-Garnett (SMG) approximation is considered as the most optimal method of an effective medium for the description of nanocomposite structures. This approximation takes into account the microstructure of the sample, which makes it possible to calculate the metal-dielectric system. Thus, SMG describes with good accuracy the structure of the nanocomposite. Besides, this approximation is applicable for granular alloys consisting of metal components. As a result, this technique can be considered as a universal approximation to describe a wide class of nanostructured materials. At the same time, this article discusses various methods of effective environment. In these methods, the metal component of nanocomposites and the dielectric matrix are replaced by an effective medium with effective permittivity εeff. It is necessary that the particles (granules) in such structures be small in comparison with the wavelength of electromagnetic radiation incident on the sample. Based on this, the spectral dependences of the transverse Kerr effect (TKE) in magnetic nanocomposites were calculated with (CoFeZr)(Al2O3) structure as an example at different concentrations of the magnetic component. The simulation was carried out at small and large concentrations (below and above the percolation threshold). The spectral dependences were obtained taking into account the form factor of nanoparticles and the quasi-classical size effect. Besides, the authors note and discuss in this paper the contribution of various mechanisms that affect the type of spectra of the transverse Kerr effect. Using the symmetrized Maxwell-Garnett approximation, the effective values of the granule size of the nanocomposites under study were found, and the tensor of effective dielectric permittivity (TEDP) was calculated. The obtained TEDP values allowed to simulate the spectral dependences of the magneto-optical transverse Kerr effect. The authors discuss and draw conclusions about the features of the obtained spectral dependences in both the visible and infrared regions of the spectrum. In addition, the practical and fundamental importance of the obtained results is noted. The importance of effective medium methods for the study of optical, transport and magneto-optical properties of magnetic nanocomposites is shown.

Effect of Grain Size on Effective Permittivity of Ferroelectric Films Based on Effective Medium Theory

2014 ◽  
Vol 619 ◽  
pp. 188-192
Author(s):  
Jatuporn Thongsri
Keyword(s):  
Effective Medium Theory ◽  
Effective Permittivity ◽  
Effective Medium ◽  
Ferroelectric Film ◽  
Dead Layer ◽  
Core Radius ◽  
Ferroelectric Films ◽  
Medium Theory ◽  
Effective Dielectric Permittivity ◽  
The Relationship

Based on effective medium theory, the temperature dependence of effective dielectric permittivity, εe(T), on core radius (a) and thickness (t) of non-ferroelectric dead layer (DL) on the surface of inhomogeneous grains of ferroelectric film made up of cylindrical ferroelectric grains was theoretically investigated. It was found that εe(T) increases with increasing core radius but decreases with increasing DL thickness. In this work, an equation expressing the relationship among εe, a and t was derived. This equation is very useful for the preparation of a ferroelectric film to desired properties.

scholarly journals Effective medium concept in temporal metamaterials

Nanophotonics ◽  
2020 ◽  
Vol 9 (2) ◽  
pp. 379-391 ◽  
Author(s):  
Victor Pacheco-Peña ◽  
Nader Engheta
Keyword(s):  
Scientific Community ◽  
Effective Permittivity ◽  
Step Function ◽  
Effective Medium ◽  
Electromagnetic Response ◽  
Multilayered Structures ◽  
Filling Fraction ◽  
Time Harmonic ◽  
Matter Interaction ◽  
Materials Used

AbstractMetamaterials are mostly designed in the time-harmonic scenario where wave propagation can be spatially manipulated. Tailoring the electromagnetic response of media in time has also gained the attention of the scientific community in order to achieve further control on wave-matter interaction both in space and time. In the present work, a temporally effective medium concept in metamaterial is theoretically investigated as a mechanism to create a medium with a desired effective permittivity. Similar to spatially subwavelength multilayered metamaterials, the proposed “temporal multilayered”, or “multistepped” metamaterial, is designed by alternating in time the permittivity of the medium between two values. In so doing, the temporally periodic medium can be modeled as an effective metamaterial in time with an effective permittivity initiated by a step function. The analogy between the temporal multistepped and the spatial multilayered metamaterials is presented demonstrating the duality between both domains. The proposed temporal metamaterial is analytically and numerically evaluated showing an excellent agreement with the designed parameters. Moreover, it is shown how the effective permittivity can be arbitrarily tailored by changing the duty cycle of the periodic temporal metamaterial. This performance is also connected to the spatial multilayer scenario in terms of the filling fraction of the different materials used to create the multilayered structures.

Effective-medium theory for nonlinear magneto-optics in magnetic granular alloys: cubic nonlinearity

2003 ◽  
Vol 258-259 ◽  
pp. 103-105 ◽  
Author(s):  
Alexander B. Granovsky ◽  
Michail V. Kuzmichov ◽  
Jean-Pierre Clerc ◽  
Mitsuteru Inoue
Keyword(s):  
Effective Medium Theory ◽  
Effective Medium ◽  
Cubic Nonlinearity ◽  
Medium Theory ◽  
Granular Alloys

scholarly journals Forest dielectric characteristics for navigation satellites signals in L 1 range

2019 ◽  
Vol 75 ◽  
pp. 01011
Author(s):  
Аnatoly Sorokin ◽  
Vladimir Podoprigora ◽  
Evgenii Ponomarev
Keyword(s):  
Effective Permittivity ◽  
Dielectric Characteristics ◽  
Anisotropic Dielectric ◽  
Spatial Anisotropy ◽  
Multi Scale ◽  
Dielectric Media ◽  
Effective Dielectric Permittivity ◽  
The Individual ◽  
Individual Trees ◽  
Birch Forests

A structural dielectric model of the forest is presented taking into account the wood Biomass distribution. The multi-scale structural formations of the individual trees and the stand as a whole as a hierarchical system of non-interacting components of the mixed dielectric are discussed. Layers of crowns and trunks are distinguished as anisotropic dielectric media with gradient boundaries. The possibility of using the orientation parameter of the order of branches in the crown layer to estimate the gradients of the effective permittivity of the inhomogeneous distribution and its spatial anisotropy is analyzed. A comparative analysis of the features of the effective dielectric permittivity of pine and birch forests is carried out. The possibilities of using a layered anisotropic dielectric forest model to describe the transformation of GPS and GLONASS signals in order to restore the biometric characteristics of the forest are considered.

Growth and Metrology of Silicon Oxides on Silicon Carbide

2004 ◽  
Vol 815 ◽  
Author(s):  
Andrew M. Hoff
Keyword(s):  
Film Growth ◽  
Electronic Device ◽  
Effective Permittivity ◽  
Contact Potential Difference ◽  
Oxide Films ◽  
Silicon Substrates ◽  
Contact Potential ◽  
Charge Voltage ◽  
Device Development ◽  
Effective Dielectric Permittivity

AbstractThermal oxidation of SiC by the afterglow method has opened new pathways of opportunity to address both thin film growth and defects that hinder electronic device development with this important semiconductor material. Oxide growth, with rates up to 700Å per hour, on SiC has been demonstrated using this technique over a temperature range from 400°C to 1100°C at 1 Torr total pressure. Electrical and physical properties of oxide films grown by conventional means or by the afterglow method were obtained with a novel, non-contact charge-voltage (Q-V) metrology approach. This instrument employs a combination of incremental contact potential difference values obtained in response to applied corona charge generated from air. The slope of the Q-V characteristic within a bias range corresponding to accumulation of the semiconductor provides an effective dielectric permittivity value for the grown film. Effective permittivity values for afterglow oxides grown on SiC approach that of SiO2 grown on silicon substrates whereas the values for oxides grown on SiC in an atmospheric steam oxidation process are always depressed relative to SiO2 on silicon, indicating that the latter process always produces low-k oxides. A mechanistic discussion regarding these observed differences between the two oxidation methods is presented along with suggestions for an integrated process and metrology approach to reduce defects in oxide films on SiC.

Effective Medium Calculations of the Electromagnetic Behavior of Single Walled Carbon Nanotube Composites

2002 ◽  
Vol 739 ◽  
Author(s):  
John W. Schultz ◽  
Rick L. Moore
Keyword(s):  
Carbon Nanotubes ◽  
Carbon Nanotube ◽  
Dielectric Properties ◽  
Volume Fraction ◽  
Metal Layer ◽  
Effective Permittivity ◽  
Effective Medium ◽  
Dielectric Constants ◽  
Single Walled Carbon Nanotube ◽  
Single Walled Carbon

ABSTRACTDielectric properties of single walled carbon nanotube assemblies were calculated with an effective medium approximation at frequencies from 200 MHz to 200 GHz. The model treats the carbon nanotubes as layered cylinders, each with a core, a graphene layer and an outer layer, to investigate the dielectric properties of coated and filled nanotubes. The graphene and metal layer properties were modeled with a Drude approximation based on literature data. A generalized Bruggeman model was then used to determine the macroscopic behavior of the modified carbon nanotubes in a composite structure as a function of volume fraction, frequency, and aspect ratio. The depolarization factors in this model were scaled by the normalized effective permittivity to better account for percolation behavior. The model showed a wide variety of frequency dependent dielectric properties. Uncoated tubes were calculated to form highly conductive materials at volume fractions of just a few percent and metal-coated tubes enhanced the conductivity by an order of magnitude. Calculations of nanotubes with insulating coatings showed that high dielectric constants with moderate to low dielectric loss were possible.

scholarly journals Simulation of the Spectra of the Transverse Kerr Effect of Magnetic Nanocomposites FeCoZr−Al2O3

2019 ◽  
pp. 63-72 ◽  
Author(s):  
M.M. Yashin ◽  
A.N. Yurasov ◽  
E.A. Ganshina ◽  
V.V. Garshin ◽  
D.V. Semenova ◽  
...  
Keyword(s):  
Kerr Effect ◽  
Ion Beam ◽  
Quantitative Agreement ◽  
Magnetic Nanocomposites ◽  
Ion Beam Sputtering ◽  
Qualitative And Quantitative ◽  
Low Concentrations ◽  
Beam Sputtering ◽  
Transverse Effect ◽  
Experimental Preparation

The magneto-optical properties of magnetic nanocomposites have been studied in the study of spectral dependences of the transverse Kerr effect (TKE). Experimental preparation of nanocomposites formed from FeCoZr and Al2O3 alloys at different component concentrations by ion-beam sputtering is discussed. Discuss various methods of the theoretical study of nanocomposites depending on the concentration of ferromagnetic components. The spectral dependences of TKE at low concentrations of the metal component are investigated. Spectral dependences of the Kerr transverse effect are simulated in the framework of the TKE are compared taking into account the size effect at different values of the nanocomposite granule size. There is a good qualitative and quantitative agreement between experimental and theoretical spectral dependences of TKE. In addition, in this paper, we note both practical and fundamental importance of the results. The possibilities of using such nanocomposite materials are discussed.

Simplified Core-Shell Model of Biochar - Iron Ore Mixture for Calculation of Effective Permittivity and Permeability

2018 ◽  
Vol 279 ◽  
pp. 240-244
Author(s):  
Anton P. Anzulevich ◽  
Igor V. Bychkov ◽  
Vasiliy D. Buchelnikov ◽  
Zhi Wei Peng ◽  
Zhu Cheng Huang ◽  
...  
Keyword(s):  
Shell Model ◽  
Iron Ore ◽  
Volume Fraction ◽  
Effective Permittivity ◽  
Effective Medium ◽  
Simplified Model ◽  
Effective Medium Approximation ◽  
Core Shell ◽  
Permittivity And Permeability ◽  
Shell Particles

The simplified model of biochar-bearing iron ore with binder was studied. It was considered a mixture of two types of core-shell particles, ‘iron ore – binder’ particles and ‘biochar – binder’ particles. The expressions to calculate complex effective permittivity and permeability was derived by effective medium approximation (EMA). The corresponding dependencies on volume fraction of iron ore in the mixture are provided.

Magneto-optical properties of two-layer film systems based on Fe and Cr

2020 ◽  
Vol 34 (27) ◽  
pp. 2050251
Author(s):  
Oleksandr Bezdidko ◽  
Shkurdoda Yuriy ◽  
Olena Fedchenko ◽  
Iryna Cheshko ◽  
Serhiy Protsenko
Keyword(s):  
Kerr Effect ◽  
Room Temperature ◽  
Thermal Evaporation ◽  
Spin Valve ◽  
Protective Layer ◽  
Optical Kerr Effect ◽  
Multilayer Systems ◽  
Magneto Optical Kerr Effect ◽  
Kerr Angle ◽  
Granular Alloys

The results of the investigation of two-layer Fe/Cr systems using the magneto-optical Kerr effect (MOKE) are presented in this paper. The samples were obtained by thermal evaporation in a vacuum with a thickness of individual layers from 2 nm to 50 nm. It was found that the presence of the Cr layer significantly affects the values of the coercivity and the Kerr angle. At a substrate temperature of 450 K, the value of the coercivity is almost half that of the same sample obtained at room temperature of the substrate. In addition, the influence of the order of deposition of layers, as well as the effect of a thin gold protective layer on the parameters measured by the Kerr method, is shown. These studies have shown that the MOKE can be used as an additional method for studying the composition of multilayer systems, granular alloys and spin-valve systems, using specific software methods.

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