Magnetic Permittivity Research Articles

Effect of Ferrimagnetic Resonance on Conversion of Electromagnetic Standing Wave Energy into Mechanical Energy

In this paper by means of physical modeling method we obtain the algorithms for calculation of magnetic permittivity in ferrite in case of arbitrary values of magnetic intensity of electromagnetic wave and force of standing electromagnetic wave impact on ferrite cylinder of arbitrary diameter which is placed into constant magnetic field. A value of constant magnetic field intensity provides appearance of ferrimagnetic resonance. It is researched a dependence of a force dependently on distance between metallic shield and ferrite cylinder for ferrimegnetic and spatial resonances. Standing wave forming in a free space with power flow density of 622 kW/m2 and wavelength of 3.2 cm reflects from metallic shield placed at a distance of λ0/8 + nλ0/2, n = 0, 1, 2, … measured from the center of ferrite cylinder and it impacts with force of 10.6 N on ferrite cylinder with a length of 0.64 m with resonance radius of 2.808 mm. Application of spatial resonance and standing electromagnetic wave allows to increase of energy conversion factor of microwave energy conversion into mechanic one 58 times in compare to application of ferrimagnetic resonance only in known papers.

Обратная волна Ценнека вдоль плоской границы раздела сред

We consider the surface Zennek wave along the plane boundaries of the vacuum-medium interface with isotropic permittivity, and the vacuum-medium described by isotropic dielectric and magnetic permittivity. In the latter case, we also consider the H-wave and the possibility of negative real parts of the permeability. Forward and backward waves at the boundary of a material with an inhomogeneous permittivity profile are considered. The conditions for the existence of forward and backward surface and volume waves, as well as fast and slow surface waves, are studied.

Spontaneous isotropy breaking for vortices in nonlinear left-handed metamaterials

We explore numerically and analytically the pattern formation and symmetry breaking of beams propagating through left-handed (negative) nonlinear metamaterials. When the input beam is a vortex with topological charge (winding number) $Q$, the initially circular (isotropic) beam acquires the symmetry of a polygon with $Q$, $2Q$, or $3Q$ sides, depending on the details of the response functions of the material. Within an effective field-theory model, this phenomenon turns out to be a case of spontaneous dynamical symmetry breaking described by a Landau-Ginzburg functional. Complex nonlinear dependence of the magnetic permittivity on the magnetic field of the beam plays a central role, as it introduces branch cuts in the mean-field solution, and permutations among different branches give rise to discrete symmetries of the patterns. By considering loop corrections in the effective Landau-Ginzburg field theory we obtain reasonably accurate predictions of the numerical results.

Characterization of Electromagnetic Properties of In Situ Soils for the Design of Landmine Detection Sensors: Application in Donbass, Ukraine

To design holographic and impulse ground penetrating radar (GPR) sensors suitable for humanitarian de-mining in the Donbass (Ukraine) conflict zone, we measured critical electromagnetic parameters of typical local soils using simple methods that could be adapted to any geologic setting. Measurements were recorded along six profiles, each crossing at least two mapped soil types. The parameters selected to evaluate GPR and metal detector sensor performance were magnetic permeability, electrical conductivity, and dielectric permittivity. Magnetic permeability measurements indicated that local soils would be conducive to metal detector performance. Electrical conductivity measurements indicated that local soils would be medium to high loss materials for GPR. Calculation of the expected attenuation as a function of signal frequency suggested that 1 GHz may have optimized the trade-off between resolution and penetration and matched the impulse GPR system power budget. Dielectric permittivity was measured using both time domain reflectometry and impulse GPR. For the latter, a calibration procedure based on an in-situ measurement of reflection coefficient was proposed and the data were analyzed to show that soil conditions were suitable for the reliable use of impulse GPR. A distinct difference between the results of these two suggested a dry (low dielectric) soil surface, grading downward into more moist (higher dielectric) soils. This gradation may provide a matching layer to reduce ground surface reflections that often obscure shallow subsurface targets. In addition, the relatively high dielectric deeper (10 cm–20 cm) subsurface soils should provide a strong contrast with plastic-cased mines.

بإستخدام المحلل الشبكي Ca1-xNixFe2O4 دراسة الخصائص الكهربائية والمغناطسية والإمتصاصية لفيرايت السبينل نوع

In this work, the spinal ferrite has been prepared where , used. as radar absorbing materials (RAM). Conventional ceramic techniques method was used to prepare these materials at microwaves with the range of frequencies (8-12) GHz. The absorption for microwaves was examined by the utilized the network analyzer. The relationship between reflectivity, absorption and attenuation coefficient were plotted as a function of frequency, and sintered at a temperature . The results showed the emergence of several resonance peaks at , samples showed high Absorbency in contrast low reflectivity and high values of attenuation coefficient at the same frequencies, this is due to domain rotation as well domain wall motion of the ferrite. The values of the real and imaginary parts of relative magnetic Permeability and relative electric permittivity were measure for all samples. The results revealed the apparent resonance peaks at same frequencies that apparent at absorption and reflectivity curves of the same samples. X-ray diffraction tests were made for one sample and result showed the structure of the sample is polycrystalline. في.هذا البحث تحضير سلسلة من فيرايت السبينل نوع حيث تأخذ القيم بزيادة مقدارها كمواد ماصة للأشعة الرادارية. تم إستخدام الطريقة السيراميكية التقليدية في تحضير العينات والتي تم تلبيدها بدرجة حرارة واحدة درست إم تصاصية العينات ضمن النطاق السيني حيث مدى التردد بإستخدام جهاز المحلل الشبكي. رسمت العلاقة بين ألإمتصاصية، الإنعكاسية، معامل التوهين، النفاذية المغناطيسية و السماحية الكهربائية كدوال للتردد عند النطاق السيني. بينت النتائج ظهور عدة قمم رنينية عند ترددات النطاق السيني, أظهرت العينات إمتصاصية عالية وقيم معامل التوهين عالية في المقابل إنعكاسية قليلة والسبب هو دوران الحقل المغناطيسي نتيجة حركة جدار الحقل المغناطيسي للفيرايت. من قياسات النفاذية المغناطيسية وثابت العزل وضحت النتائج وجود القمم الرنينية عند نفس الترددات التي ظهرت عند منحنيات الإمتصاصية والإنعكاسية. تم فحص حيود الأشعة السينية للعينة حيث أظهرت النتائج أن تركيب العينة هو متعدد التبلور.

Boundary element analysis of 3D shell‐like rigid electrically conducting inclusions in anisotropic thermomagnetoelectroelastic solids

AbstractThe paper presents general boundary element approach for analysis of thermomagnetoelectroelastic solids containing shell‐like electrically conducting inclusions with high magnetic permittivity. The latter are modeled with opened surfaces with certain boundary conditions on their faces. Rigid displacement and rotation, along with constant electric and magnetic potentials of inclusions are accounted for in these boundary conditions. Formulated boundary value problem is reduced to a system of singular boundary integral equations, which is solved numerically by the boundary element method. Special attention is paid to the field singularity at the front line of a shell‐like inclusion. Special shape functions are introduced, which account for this square‐root singularity and allow accurate determination of field intensity factors. Approaches for fast and accurate numerical evaluation of anisotropic thermomagnetoelectroelastic kernels are discussed, which are crucial in derivation of fast and precise boundary element approach. Numerical examples are presented.

Material equations and Maxwell’s equations for isotropic media; waves with negative group velocity and negative values of ε (ω) and μ(ω)

The frequently used Maxwell’s equations that contain E, B, D, and H fields are only substantiated in the framework of linear material equations and for isotropic media alone. We have shown that accounting for the deviation of magnetic permittivity μ (ω) from unity in the usually employed dispersion equation implies a false precision. Therefore, if spatial dispersion is disregarded, transverse waves only exist in the energy region where ε(ω) > 0 and have a positive group velocity.

Bi2O3 adjusting equivalent permeability and permittivity of M-type barium ferrite for antenna substrate application

In this paper, Co-Ti doped M-type barium ferrite [Ba(CoTi)1.22Fe9.56O19] was prepared at low temperature (925 °C) in O2 atmosphere with different amounts of Bi2O3 sintering additive (x = 5–14 wt%). XRD showed superfluous Bi2O3 additive led to BiFeO3 phase formation, which is the important factor to adjust properties of material. SEM revealed that the grain size diminished gradually. For magnetic and dielectric properties, with different amounts of Bi2O3, saturation magnetization (Ms) decreased and coercivity (Hc) gradually increased. Complex magnetic permeability and dielectric permittivity presented excellent regularity, and the equivalent permeability and permittivity were obtained when x = 5 wt%. At x = 5 wt%, the real part of permeability (μ′) and permittivity (ε′) were about 18.3 at a range of 10 MHz–1.0 GHz, the magnetic loss (tan δμ) was about 3.4 × 10−2, and the dielectric loss (tan δε) was about 2.8 × 10−3. It showed that Bi2O3 not only lowered the sintering temperature of ferrite, but also adjusted the magnetic and dielectric properties, and the material has potential to apply for miniaturizing efficient antennas at high frequency.

Magnetooptics in Cylindrical Structures

Understanding magnetooptics in cylindrical structures presents interest in the development of magnetic sensor and nonreciprocal devices compatible with optical fibers. The present work studies wave propagation in dielectric circular cylindrical structures characterized by magnetic permeability and electric permittivity tensors at axial magnetization. The Helmholtz equations deduced from the Maxwell equations in transverse circularly polarized representation provide electric and magnetic fields. With the restriction to terms linear in off-diagonal tensor elements, these can be expressed analytically. The results are applied to magnetooptic (MO) circular cylindrical waveguides with a step refractive index profile. The nonreciprocal propagation is illustrated on waveguides with an yttrium iron garnet (YIG) core and a lower refractive index cladding formed by gallium substituted yttrium iron garnet (GaYIG) at the optical communication wavelength. The propagation distance required for the isolator operation is about one hundred micrometers. The approach may be applied to other structures of cylindrical symmetry in the range from microwave to optical frequencies.

4D Printing of Complex Structures with a Fast Response Time to Magnetic Stimulus.

A poly(dimethylsiloxane)/Fe (PDMS/Fe) composite ink was developed for reversible four-dimensional (4D) printing to create magnetically responsive three-dimensional (3D) structures with a fast response time for their structure evolvements under external magnetic field. These 3D structures could obtain or lose high magnetization immediately by the on or off of an external magnetic field due to the low magnetic coercive force and the high magnetic permittivity of soft magnetic Fe particles in this composite ink, whereas PDMS in this composite ink served as the flexible matrix component to ensure their shape recovery. As exampled by a 3D butterfly with the fast flapping of its wings under an external magnetic field, complex 3D structures created by 4D printing with this PDMS/Fe ink could have the reversible magnetically stimulated structure evolvement property and develop designed magnetically induced motions with a fast response time for various magnetomechanical applications. Furthermore, structure evolvements of these 3D structures could also induce structure-related property changes, as demonstrated by a 3D terahertz photonic crystal (3D-TPC) device with remotely tunable terahertz properties, which could create novel functionalities for various functional devices created by 4D printing from this kind of ink through external magnetic field stimulation.

Peculiarities of electromagnetic field oscillations of a charged particle rotating about a conductive ball

Abstract. The paper investigates some characteristic features of the electromagnetic field of a relativistic charged particle that uniformly rotates about a conductive ball in its equatorial plane. It is assumed that the braking of the particle due to radiation is compensated by an external influence (e.g. the electric force) that compels the particle to turn uniformly in a circle. The magnetic permittivity of the ball is assumed to be one. The work is based on the corresponding exact analytic solutions of Maxwell’s equations. The generalized Drude-Lorentz-Sommerfeld formula for the dielectric function of the conductive ball is used in numerical calculations. It is shown that localized oscillations of a high-amplitude electromagnetic field can be generated at a given harmonic inside the ball at a certain (resonant) particle rotation frequency at a small distance from the surface of the ball. Herewith, at large distances from the trajectory of the particle, these localized oscillations are accompanied by intense radiation at the same harmonic, which is many times more intense than the analogous radiation in the case when the ball is absent. The possibilities of using this phenomenon to develop sources of quasi-monochromatic electromagnetic radiation in the range from giga- to terra hertz frequencies are discussed.

Peculiarities of electromagnetic field oscillations of a charged particle rotating about a conductive ball

Abstract. The paper investigates some characteristic features of the electromagnetic field of a relativistic charged particle that uniformly rotates about a conductive ball in its equatorial plane. It is assumed that the braking of the particle due to radiation is compensated by an external influence (e.g. the electric force) that compels the particle to turn uniformly in a circle. The magnetic permittivity of the ball is assumed to be one. The work is based on the corresponding exact analytic solutions of Maxwell’s equations. The generalized Drude-Lorentz-Sommerfeld formula for the dielectric function of the conductive ball is used in numerical calculations. It is shown that localized oscillations of a high-amplitude electromagnetic field can be generated at a given harmonic inside the ball at a certain (resonant) particle rotation frequency at a small distance from the surface of the ball. Herewith, at large distances from the trajectory of the particle, these localized oscillations are accompanied by intense radiation at the same harmonic, which is many times more intense than the analogous radiation in the case when the ball is absent. The possibilities of using this phenomenon to develop sources of quasi-monochromatic electromagnetic radiation in the range from giga- to terra hertz frequencies are discussed.

Study on wave absorption properties of carbonyl iron and SiO2 coated carbonyl iron particles

Because of the excellent properties, carbonyl iron powder particles and their surface modified products are often used as radar absorbers. The electromagnetic wave attenuation mechanism of the carbonyl iron powders and SiO2 coated carbonyl iron particles were analyzed on the basis of the studies of scholars from all over the world and compared with the solutions calculated by the COMSOL software. The results obtained through the analytical solution and COMSOL simulated calculation values tend to be consistent; the ratio of the complex magnetic permittivity to the complex permittivity of the nano-SiO2 coated carbonyl iron powder particles tend to be 1, and the impedance matching performance of nano-SiO2 coated carbonyl iron powder particles is improved. Compared with the carbonyl iron particles, SiO2 coated carbonyl iron particles have lower electromagnetic wave absorptivity.

Magnetoelectric properties of Co-doped BiFeO3 nanoparticles

The magnetoelectric (ME) properties of sol–gel grown BiFe[Formula: see text]Co[Formula: see text]O3 (BFCO) nanoceramics, with different sizes, were investigated at room-temperature. X-ray diffraction (XRD) measurement was performed to investigate structural properties of the samples understudy. Magnetic field-dependent dielectric permittivity has been systematically investigated in the frequency range of 20 Hz to 1 MHz. To ensure the origin of magnetodielectric response, the magnetoimpedance (MI) spectroscopy was adopted using equivalent circuit model. The a.c. conductivity was found to obey the Jonscher’s universal power law. The modifications in spiral spin structure in the BFCO nanoparticles with size less than [Formula: see text]62 nm significantly affect the ME coupling parameters.

TMOKE as efficient tool for the magneto-optic analysis of ultra-thin magnetic films

Ultra-thin magnetic dielectric films are of prime importance due to their applications for nanophotonics and spintronics. Here, we propose an efficient method for the magneto-optical investigation of ultra-thin magnetic films which allows one to access their state of magnetization and magneto-optical properties. It is based on the surface-plasmon-polariton-assisted transverse magneto-optical Kerr effect (TMOKE). In our experiments, sub-100 nm-thick bismuth-substituted lutetium iron-garnet films covered with a plasmonic gold grating have been analyzed. The excitation of surface plasmon-polaritons provides resonance enhancement of TMOKE up to 0.04 and makes it easily detectable in the experiment. For films thicker than 40 nm, the TMOKE marginally depends on the film thickness. A further decrease in the film thickness diminishes TMOKE since for such thicknesses the surface plasmon-polariton field partly penetrates inside the non-magnetic substrate. Nevertheless, the TMOKE remains measurable even for few-nm-thick films, which makes this technique unique for the magneto-optical study of ultra-thin films. Particularly, the proposed method reveals that the off-diagonal components of the magnetic film permittivity tensor grow slightly with the reduction of the film thickness.

Nuclear magnetic relaxation and Knight shift due to orbital interaction in Dirac electron systems

We study the nuclear magnetic relaxation rate and Knight shift in the presence of the orbital and quadrupole interactions for three-dimensional Dirac electron systems (e.g., bismuth–antimony alloys). By using recent results of the dynamic magnetic susceptibility and permittivity, we obtain rigorous results of the relaxation rates (1/T1)orb and (1/T1)Q, which are due to the orbital and quadrupole interactions, respectively, and show that (1/T1)Q gives a negligible contribution compared with (1/T1)orb. It is found that (1/T1)orb exhibits anomalous dependences on temperature T and chemical potential μ. When μ is inside the band gap, (1/T1)orb∼T3log(2T/ω0) for temperatures above the band gap, where ω0 is the nuclear Larmor frequency. When μ lies in the conduction or valence bands, (1/T1)orb∝TkF2log(2vFkF/ω0) for low temperatures, where kF and vF are the Fermi momentum and Fermi velocity, respectively. The Knight shift Korb due to the orbital interaction also shows anomalous dependences on T and μ. It is shown that Korb is negative and its magnitude significantly increases with decreasing temperature when μ is located in the band gap. Because the anomalous dependences in Korb is caused by the interband particle-hole excitations across the small band gap while (1/T1)orb is governed by the intraband excitations, the Korringa relation does not hold in the Dirac electron systems.

The effects of magnetic field and polarization on the permeability and permittivity of (1 – x)Ni0.4Zn0.6Fe2O4+xPb(Zr0.53Ti0.47)O3 composites at high frequency

(1 – x)Ni0.4Zn0.6Fe2O4+xPb(Zr0.53Ti0.47)O3 (x = 0–1) multiferroic composite materials were prepared by a conventional sintering process. The magnetic permeability and permittivity were researched at high frequency in detail. The permittivity ε′ decreases slightly with the frequency and the permittivity ε″ shows a peak in the 3 MHz–1 GHz range. The permeability displays a relaxation resonance within the 3 MHz–1 GHz frequency range. The magnetic resonances of the domain wall and spin rotation were excited by the external dc magnetic field in the microwave frequency. The resonance peaks in the imaginary permeability move to high frequency with the magnetic field, but shift to low frequency in the composite samples. The permittivity spectra exhibit two resonance peaks after polarization. The changes of the permittivity and permeability under magnetic field or/and after polarization confirm the interaction between ferromagnetism and ferroelectricity in the microwave frequency. The observed phenomena were understood by employing a resonance equation for the domain wall motion and a Landau–Gilbert equation for the spin rotation. The results indicate that permittivity and permeability can be adjusted by the magnetic field or electric field.

High-selective band-reject FSS with dual-band near-zero refractive index based on complementary dual-layer symmetry resonator-ring

A new band-reject frequency-selective surface (FSS) based on dual-band near-zero refractive index metamaterial (ZIM) design is presented in this paper. Consisting of a planar array of complementary dual-layer symmetry resonant ring, the proposed FSS exhibits a high-selective band-reject filtering response. From the viewpoint of effective medium, the subwavelength FSS is characterized by near-zero effective magnetic permeability and near-zero effective electric permittivity in two different operational bands, respectively. The corresponding resonant behavior and E-field distributions are analyzed in detail. A prototype of the proposed FSS working in X-band is fabricated and measured. The simulation and experiment results verify the effectiveness and correctness of the ZIM-based design method.

Low loss, enhanced magneto-dielectric properties of Bi2O3 doped Mg-Cd ferrites for high frequency antennas

Mg1-xCdxCo0.05Fe1.95O4 ferrites are proposed for high frequency radar antennas, where x varies with the value of 0.0, 0.2, 0.3 and 0.4. With 5 wt% Bi2O3 added for low temperature co-fired ceramic (LTCC) application, the spinel ferrites synthesized at 930 °C reveal fairly excellent magnetic and dielectric properties. X-ray diffraction indicates the processed samples present normal spinel peaks and Bi24Fe2O39 (BFO) peaks. The existing BFO tailors the real part of magnetic permeability (ε′) and dielectric permittivity (μ′) to be approximately equal (x = 0.4, ε'≈μ'≈26) at a wide frequency range from 1 MHz to 100 MHz. Meanwhile, the LTCC-processed samples have ultra low dielectric loss tanδε and magnetic loss tanδμ (tanδε≈0.0008, tanδμ≈0.03, x = 0.3). In addition, the high saturation magnetization and appropriate coercivity mean enhanced magnetization. These eminent magneto-dielectric characteristics enable the materials to possess a farther study-worthy necessarity.

A combination dielectric and acoustic laboratory instrument for petrophysics

Laboratory testing of rock samples is the primary method for establishing the physics models which relate the rock properties (i.e. porosity, fluid permeability, pore-fluid and saturation) essential to evaluating a hydrocarbon reservoir, to the physical properties (resistivity, nuclear magnetic resonance, dielectric permittivity and acoustic properties) which can be measured with borehole logging instrumentation. Rock samples usually require machining to produce a suitable geometry for each test as well as specific sample preparation, e.g. multiple levels of saturation and chemical treatments, and this leads to discrepancies in the condition of the sample between different tests. Ideally, multiphysics testing should occur on one sample simultaneously so that useful correlations between data sets can be more firmly established. The world’s first dielectric and acoustic combination cell has been developed at CSIRO, so that a sample may be machined and prepared, then measured to determine the dielectric and acoustic properties simultaneously before atmospheric conditions in the laboratory affect the level of hydration in the sample. The dielectric measurement is performed using a conventional three-terminal parallel plate capacitor which can operate from 40 Hz up to 110 MHz, with modified electrodes incorporating a 4 MHz P-wave piezo crystal. Approximately 10 (acoustic P-) wavelengths interact with a typical (10 mm thick) sample so that the user may reliably ‘pick’ the P-wave arrival times with acceptable resolution. Experimental evidence indicates that the instrument is able to resolve 0.25 mm thickness in a Teflon sample test piece. For a number of engineering materials including Teflon and glass and also for a geological samples (Donnybrook sandstone from Western Australia) there is a perfectly linear relationship between both capacitance and P-wave arrival time with sample thickness. Donnybrook sandstone has a consistently linear increase in dielectric permittivity and P-wave velocity with saturation consistent with the Gassmann–Hill prediction. Both the dielectric permittivity and P-wave velocity are faster parallel to the bedding plane than orthogonal to the bedding plane in a shale from the Cooper Basin, Australia.