Imaginary Part Of Permeability Research Articles

Electrospinning of PVP-based multilayered graphene oxide/BiFeO3/SrFe12O19 composite nanofibers

Four composite nanofibers with specific concentrations of PVP and BiFeO3, GO, and SrFe12O19 reinforcements were synthesized separately, which were named G, S, B, GBS: G (PVP + GO), S (PVP + SrFe12O19), B (PVP + BiFeO3), and GBS (PVP + GO + BiFeO3 + SrFe12O19). The structural, magnetic, and dielectric properties of the composite successfully prepared by the electrospinning method were investigated to absorb electromagnetic waves in the frequency range of 8–12.5 GHz. Negative values observed in imaginary parts of permeability and permittivity in a large frequency range can be explained by new structures called left-handed. The maximum amount of reflection loss in the X-Band range around the frequency of 11.66 GHz for G, S, B, and GBS samples are obtained at −36.8, −37.66, −39.3, and −39.5 dB, respectively, which shows relatively good potential in military applications.

Tunable and broad-band electromagnetic wave absorption using W-type Hexaferrites in 1–40 GHz range

W-type Sr-hexaferrites, Sr0.75Ca0.25Zn2-xCoxFe16O27 (0.0 ≤ x ≤ 2.0), were synthesized, and their magnetic and electromagnetic (EM) wave absorption properties were investigated. As x increased from 0.0 to 2.0, the saturation magnetization value increased and reached a maximum at x = 1.25, followed by a decrease, while the magnetic anisotropic field (Hani) decreased and showed a minimum at x = 1.0, then increased again. The variation in Hani could be controlled by adjusting the value of x, which also changed the ferromagnetic resonance (FMR) frequency and enabled control over the frequency band of EM wave absorption. It is demonstrated that the EM wave absorption is primarily controlled by imaginary part of permeability (μ") induced by FMR. Composite of the W-type hexaferrite-epoxy (10 wt%) with x = 0.75–2.0 showed a broad-band EM wave absorption in the 1–18 GHz range, while the composites with x = 0–0.4 showed it in the 26.5–40 GHz. The x = 1.25 sample satisfied RL < − 10 dB in the 7–17 GHz range with a thickness of 2.1 mm, while x = 0.3 sample satisfied RL < − 10 dB in the 27–39 GHz with a thickness of 0.8 mm. Sr0.75Ca0.25Zn2-xCoxW is a very promising material for tunable wideband EM wave absorbers in 1–40 GHz range.

Electric-dipole and magnetic absorption in TbFeO3 single crystals in the THz–IR range

Various mechanisms of absorption including both electric-dipole excitations and magnetic ones in a broadband (5–5000 cm−1) polarized transmission and reflection spectra were studied in orthoferrite TbFeO3 using a coherent submillimeter, pulsed THz, and IR Fourier transform spectroscopy. The classical oscillator model and generalized four-parameter model were used to analyze the spectra obtained, and the parameters of the models were determined. We analyzed main absorption processes, which include contributions of both phonons and multi-phonon processes as well as electron transitions in Tb3+ ions and two antiferromagnetic resonance modes in the Fe subsystem. As a result, the spectra of real and imaginary parts of permeability and permittivity were obtained. A distinctive feature of the studied electrodynamic response in TbFeO3 is a significant absorption in the THz range due to multi-phonon processes, which exceeds optical phonon contribution by an order of magnitude at room temperature.

Enhancement of magnetic properties in FeCoNiCr0.4CuX high entropy alloys through the cocktail effect for megahertz electromagnetic wave absorption

Electromagnetic wave absorption materials for megahertz (MHz) frequency range remains a key core issue that the poor effective attenuation performance and impedance mismatch. Based on previous research and theoretical analysis, an effective solution is to improve the real and imaginary parts of the complex permeability. In addition, the absorbents are also required to have excellent temperature stability and oxidation resistance due to exposure to harsh environments such as air and high temperature. Herein, the FeCoNiCr0.4CuX high entropy alloys powders (HEAs) with planar anisotropy are prepared by mechanical alloying method. Relying on the “cocktail effect” of HEAs, the addition of appropriate Cu element can increase the aspect ratio of the particles and the shape-dependent anisotropy field to further improve the permeability. Experimentally, the real part of the permeability for the FeCoNiCr0.4Cu0.2 HEAs ranges from 2.7 to 7.5 and the imaginary part of the permeability can reach 2.7 in the MHz frequency range. The maximum reflection loss can reach −33.6 dB at 484 MHz and the effective absorption bandwidth (reflection loss<−10 dB) can almost cover the entire MHz frequency range. Furthermore, the FeCoNiCr0.4Cu0.2 HEAs have stable electromagnetic wave absorption performance and superior oxidation resistance with increasing temperature. This research exploits the characteristics of HEAs to further break the inherent magnetic limit by adjusting the morphology and provides a new pathway for solving the matter of MHz electromagnetic wave absorption.

On the Study of Surface Fluorinated α-Fe₂O₃ for Microwave Absorption

This article involves microwave (MW) absorption characteristic investigation of surface fluorinated iron oxide, synthesized via the hydrothermal method and compared with pristine $\alpha $ -Fe2O3. The MW absorption characteristics are studied by measuring real and imaginary parts of both permittivity ( $\varepsilon$ ) and permeability ( $\mu $ ) for pristine $\alpha $ -Fe2O3 and surface fluorinated Fe2O3 in the frequency range of 5.85–18 GHz. The imaginary part of permeability ( $ {\mu }_{\mathrm {r}}^{''}$ ) and the magnetic loss tangent value ( ${\tan} {\delta }_{ {\mu }}$ ) of surface fluorinated Fe2O3 are found to be superior to pristine $\alpha $ -Fe2O3. The maximum reflection loss (RL) in surface fluorinated Fe2O3 is observed at different frequencies as a function of sample’s thickness, for example, RLs −18 dB at 7.5 GHz ( $t = 3.5$ mm) and −12 dB at 9 GHz ( $t = 3$ mm), respectively. These characteristics make this material a potential candidate as radar absorbing material (RAM) both in $C$ -band and $X$ -band. For the first time, the MW absorption characteristics of fluorinated $\alpha $ -Fe2O3 have been demonstrated, which are the novel study in itself.

Hardened Glass Particle and Carbon Black Using Resin for Potential Electromagnetic Shielding in Biomedical Electronic Equipments

This study aims to investigate the electromagnetic properties of a composite of hardened glass particle and carbon using resin in determining the absorbability of the composite for electromagnetic interference (EMI). The electromagnetic absorption measurement was conducted using T-R method (transmission-reflection) by measuring the dielectric constant, loss factor, real and imaginary part of permeability, reflection coefficient and transmission coefficient. The measurement is taken for X band frequency and Ku band frequency within the frequency range from 8.2GHz to 12.4GHz and 12.4GHz to 18GHz, respectively. Dielectric constant of sample decrease when frequency increases. The high dielectric constant of material implies that the material has high absorbability of field energy, resulting in high attenuation of the applied field.

Electrical tuning of skyrmion dynamics in multiferroic composite thin films

A lack of space-inversion symmetry along with broken time-reversal symmetry at ferromagnetic/ferroelectric interfaces gives rise to the electric field control of the effective magnetic field and the Dzyaloshinskii-Moriya interaction, thus allowing for the formation of multiferroic skyrmions at room temperature. The electric-field-driven evolution of spin textures at the ferromagnetic/ferroelectric interface is investigated by means of Monte Carlo simulations. It is demonstrated that the skyrmion lattice can be stabilized by the moderate interfacial magnetoelectric couplings. The chirality, radius, position, and numbers of skyrmions are found to be tunable by an external the electric field. The nonequilibrium dynamics of skyrmions, however, strongly depends on the frequency of the applied time-oscillating electric field. With the increase of the frequency of the ac electric field, multiferroic skyrmions become unstable and after several periods they are, ultimately, damping down to the helimagnetic phase. Under microwavelike electric fields, the dynamic multiferroic response of the skyrmion lattice is anisotropic and inhomogeneous. The electric-field-induced resonance spectrum of the magnetic skyrmion with a distinct peak in the imaginary part of permeability is successfully simulated by the Fourier transformation of magnetization.

Room-temperature multiferroicity in magnetic field-poled polyaniline and its enhancement via Cu2+-complexation

We report on the discovery of room-temperature multiferroicity in camphorsulfonic acid-doped polyaniline synthesized under an applied magnetic field of 0.5 T, increasingly enhanced via Cu2+-doping up to 8 wt%, probably as a nitrogen-coordinated square planar-like complex revealed by electron paramagnetic resonance spectra. Room-temperature switchable magnetization and polarization hysteresis cycles are presented, reaching saturated magnetization (polarization) of 0.019 emu/g (4.369 μC/cm2) and coercivity (remanence) of 0.051 kOe (2.089 μC/cm2) and revealing strong electric exchange bias. Both real and imaginary parts of permeability and permittivity exhibit resonance feature enhanced by Cu2+-doping, peaking at about the same position in the microwave range of 2–18 GHz and strongly suggesting magnetoelectricity. The proposed model picture, which accounts for both ferroelectricity and exchange bias, assumes ferromagnetic and ferroelectric orders within the same domain represented by crystalline polyaniline islands immersed within the amorphous polyaniline template. Modified Landau-Lifshitz-Gilbert equations account for the matching of permeability and permittivity resonance features.

Effect of heat-treatment on LiZn ferrite hollow microspheres prepared by self-reactive quenching technology

Lithium-zinc ferrite hollow microspheres (LiZn FHMs) containing special surface crystals were synthesized by self-reactive quenching technology. The samples were heat-treated at 1200 °C and held for 4 h. The influence of the heat-treatment on LiZn FHMs was studied. The results show that the surface of hollow microspheres is smooth without heat-treatment. The phase components are Fe2O3, Fe3O4, Li0.435Zn0.195Fe2.37O4, and Li0.5Fe2.5O4. The minimum reflectivity is −13.5 dB, and the corresponding frequency is 7.5 GHz. The effective absorption band lower than −10 dB is 6.2–8.5 GHz, and the bandwidth is 2.3 GHz. After heat-treatment, crystals on the surface of hollow microspheres grow significantly. Multiple-shape micro-nano crystals containing triangular, polygonal, and irregular crystal are generated. However, the phase composition does not change. The real part of the permittivity (e′), the imaginary part of permittivity (e″), the real part of permeability (μ′), and the imaginary part of permeability (μ″) all increase, and the microwave absorption properties at low frequency are significantly increased, with the absorption peak moving to a lower frequency range. The minimum reflectivity is −26.5 dB, and the corresponding frequency changes to 3.4 GHz. The effective absorption band is 2.6–4 GHz, and the bandwidth is 1.4 GHz.

Hexagonal Co/C/BaZn0.2Co0.8TiFe10O19 ternary hybrids: Synthetic method and microwave absorption properties

Through a simple method, hexagonal Co/C/BaZn0.2Co0.8TiFe10O19 ternary hybrids have been successfully prepared. The method can be used to prepare a variety of metal/ferrite. The saturation magnetization value gradually decreases with increasing content of BaZn0.2Co0.8TiFe10O19 (BZCTM). The coercivity value relates to particle size and content of BZCTM. The μ″-μ′ (μ′ and μ″ is the real and imaginary part of permeability respectively) curve can be used to infer the magnetic loss. For the materials mainly with magnetic loss, it can be used to infer the reflection loss. With d = 1.9 mm, the reflection loss (RL) of S1 (containing 0.1 g BZCTM) achieves minimum (−47.23 dB) at 9.95 GHz. For S4 (containing 0.7 g BZCTM), the bandwidth of RL below −10 dB is from 11 to 17.82 GHz (d = 1.9 mm). What's more, the μ″-μ′ curve can indicate the direction to improve magnetic loss, which is significance for studying the reflection loss of materials.

Loss enhanced spin Hall effect of transmitted light through anisotropic epsilon- and mu-near-zero metamaterial slab.

Spin Hall effect of light (SHEL) is prosperous in precision metrology and quantum information processing. In normal situations, the inevitable loss of material will greatly weaken SHEL, which is a major constraint to its potential applications. We first report the loss enhanced SHEL through epsilon and mu-near-zero (EMNZ) metamaterial slab by anisotropic configuration of epsilon and mu tensors. It is verified that the loss of EMNZ metamaterial can effectively enlarge the splitting between right-circularly polarized (RCP) and left-circularly polarized light (LCP) components of linear polarized light even when the incident angle is much larger than critical angle. Calculation results show that when the imaginary part of permeability's vertical component is equal to 0.1, a flat-top transverse shift peak can be observed which remains unchanged for different vertical component of permeability and thickness of EMNZ metamaterial. In this case the maximum transverse shift of left-circularly polarized light can be increased to 24.676 micrometers by EMNZ metamaterial loss without any amplification method. Meanwhile, the transverse shifts of RCP (LCP) light can be modulated flexibly by EMNZ metamaterial loss. Therefore the loss enhanced SHEL makes quantum devices applicable which paves the way towards on-chip and inter-chip optical circuitry.

Enhanced magnetic domain relaxation frequency and low power losses in Zn2+ substituted manganese ferrites potential for high frequency applications

Nowadays electronic industries prerequisites magnetic materials, i.e., iron rich materials and their magnetic alloys. However, with the advent of high frequency applications, the standard techniques of reducing eddy current losses, using iron cores, were no longer efficient or cost effective. Current market trends of the switched mode power supplies industries required even low energy losses in power conversion with maintenance of adequate initial permeability. From the above point of view, in the present study we aimed at the production of Manganese–Zinc ferrites prepared via solution combustion method using mixture of fuels and achieved low loss, high saturation magnetization, high permeability, and high magnetic domain relaxation frequency. The as-synthesized Zn2+ substituted MnFe2O4 were characterized by X-ray diffractometer (XRD) and transmission electron microscopy (TEM). The fractions of Mn2+, Zn2+ and Fe2+ cations occupying tetrahedral sites along with Fe occupying octahedral sites within the unit cell of all ferrite samples were estimated by Raman scattering spectroscopy. The magnetic domain relaxation was investigated by inductance spectroscopy (IS) and the observed magnetic domain relaxation frequency (fr) was increased with the increase in grain size. The real and imaginary part of permeability (μ′ and μ″) increased with frequency and showed a maximum above 100MHz. This can be explained on the basis of spin rotation and domain wall motion. The saturation magnetization (Ms), remnant magnetization (Mr) and magneton number (µB) decreased gradually with increasing Zn2+ concentration. The decrease in the saturation magnetization was discussed with Yafet–Kittel (Y–K) model. The Zn2+ concentration increases the relative number of ferric ions on the A sites, reduces the A–B interactions. The frequency dependent total power losses decreased as the zinc concentration increased. At 1MHz, the total power loss (Pt) changed from 358mW/cm3 for x=0–165mW/cm3 for x=0.9. Pt for all the Zn doped samples exhibited the temperature stability up to 100°C.

Improved microwave absorption properties of TiO2 and Ni0.53Cu0.12Zn0.35Fe2O4 nanocomposites potential for microwave devices

Nanostructured xTiO2+(1-x) Ni0.53Cu0.12Zn0.35Fe2O4 nanocomposites (where 0 ≤ x ≤ 1) were prepared by a low temperature microwave-hydrothermal (M-H) method at 165 °C/45 min. Microwave sintering (MS) technology has been applied in the preparation of nanocomposites. Several kinds of such systems have been fabricated by MS technology. The sintering time and temperature were reduced from 22 h to 1100 °C for conventional sintering process to 30 min and 500 °C for MS process, respectively. The addition of TiO2 to Ni0.53Cu0.12Zn0.35 ferrite increased the dielectric properties (ε′ and ε″). The imaginary part of permeability (μ″) was found to increase with an increase of TiO2. The complex permittivity and permeability were collected by the vector network analyser and the absorbing properties were calculated according to transmission theory. The absorption peak shifted to higher frequencies with the substitution. The highest reflection coefficient value of −28 dB at 10.26 GHz was observed for the x = 0.5 sample. The microwave absorption band width of −10 dB with xTiO2+(1-x) Ni0.53Cu0.12Zn0.35Fe2O4 nanocomposites is effectively broadened compared with other ferrites. Based on the magnetic and microwave measurements xTiO2+(1-x) Ni0.53Cu0.12Zn0.35Fe2O4 may be a good candidate for electromagnetic materials and other practical applications like military and civil applications.

Effect of Zn2+ Substituted on Structural and Magnetic Properties of Manganese Ferrite Synthesized via Combustion Route

Solution combustion method was successfully used for the synthesis of nanocrystalline Mn1-xZnxFe2O4 with stoichiometry (x = 0, 0.1, 0.3, 0.5, 0.7, 0.9 and 1.0). The room temperature dielectric studies real and imaginary part of permittivity (epsilon' and epsilon `') were undertaken in the vide frequency range 1 MHz to 1 GHz. It was found that the real part of permittivity (epsilon') is increases with increasing in frequency and it shows a resonance behavior above 1 GHz and at much higher frequencies there is a significant decrease in the loss factor (epsilon `'). The magnetic domain relaxation was investigated by inductance spectroscopy (IS) and the observed magnetic domine relaxation frequency (f(r)) was increased with increase of grain size. It was observed that the real and imaginary part of permeability (mu' and mu `'), saturation magnetization (M-s), remnant magnetization (M-r) and magneton number decreases gradually with increasing Zn2+ concentration. The decrease in the saturation magnetization may be explained as the Zn2+ concentration increases, the relative number of ferric ions on the A sites diminishes and this reduces the A-B interaction.

Structural and magnetic properties of manganese zinc ferrite nanoparticles prepared by solution combustion method using mixture of fuels

The structural analysis and magnetic investigation Mn1−xZnxFe2O4 with stoichiometry (x=0, 0.1, 0.3, 0.5, 0.7, 0.9 and 1.0) were synthesized by solution combustion method using mixture of fuel this is first of its kind. As synthesized Mn–Zn nanoferrites were characterized by X-ray Diffractometer (XRD), Transmission electron microscopy (TEM) at room temperature. The magnetic domain relaxation was investigated by inductance spectroscopy (IS) and the observed magnetic domain relaxation frequency (fr) was increased with the increase in grain size. The Room temperature magnetic properties were studied using vibrating sample magnetometer (VSM). It was observed that the real and imaginary part of permeability (μ′ and μ″), saturation magnetization (Ms), remanance magnetization (Mr) and magneton number (Mr/Ms) were decreases gradually with increasing Zn2+ concentration. The decrease in the saturation magnetization may be explained as, the Zn2+ concentration increases the relative number of ferric ions on the A sites diminishes and this reduces the A–B interaction. Hence synthesized materials are good for high frequency applications.

Dynamic magnetic characteristics of Fe78Si13B9 amorphous alloy subjected to operating temperature

The operating temperature dependence of dynamic magnetic characteristics of the annealed Fe78Si13B9 amorphous alloy core was systematically investigated. The core loss, magnetic induction intensity and complex permeability of the amorphous core were analyzed by means of AC B–H loop tracer and impedance analyzer. It is found that the operating temperature below 403K has little impact on core loss when the induction (B) is less than 1.25T. As B becomes higher, core loss measured at high temperature becomes higher. For the cores measured at power frequency, the B at 80A/m and the coercivity (Hc) at 1T decline slightly as the temperature goes up. Furthermore, the real part of permeability (μ′) increases with the rise of temperature. The imaginary part of permeability (μ″) maxima shifts to lower frequency side with increasing temperature, indicating the magnetic relaxation behavior in the sample. In addition, with the rise in the operating temperature of the annealed amorphous core, the relaxation time tends to increase.

Structural and Magnetic Properties of Mn-Zn Ferrites Synthesized by Microwave-Hydrothermal Process &lt;sup&gt;&lt;/sup&gt;

Nanocrystalline Mn1-xZnxFe2O4 (x=0, 0.2, 0.4, 0.6, 0.8 and 1.0) ferrites have been successfully synthesised using microwave–hydrothermal method for high frequency applications. The nanopowders were characterised using X-ray diffraction (XRD) and sintered using microwave furnace at 900°C and the total time taken for sintering is 30 min. The frequency dependence of real and imaginary part of permeability were measured in the range 1 MHz to 1.8 GHz. The saturation magnetisation and coercive force were obtained using a vibration sample magnetometer (VSM) in the field of 1.5 T. The temperature dependence of initial permeability (μi) was measured in the temperature range of 300K to 600K at 10 kHz. The high values of permeability and saturation magnetization enables these materials to be the potential candidates for a number of applications, for example, in transformers, choke coils, noise filters and recording heads.

Effect of NaNO3 foaming agent on barium ferrite hollow microspheres prepared by self-reactive quenching technology

Al+Fe2O3+BaO2 and NaNO3 as the reactive system and the foaming agent, respectively, are used to prepare barium ferrite hollow microspheres (BFHMs) by self-reactive quenching technology based on flame spraying technology, self-propagating high-temperature synthesis (SHS) technology and quick chilling technology. Effects of NaNO3 on the particle size, morphology, phase structure and microwave absorption properties of BFHMs are investigated through SEM, XRD, particle size analyzer, high-speed camera and vector network analyzer. The results show that, after adding 10wt.% NaNO3, the average particle size of BFHMs decreases initially from 28μm to 6μm, as well as the particle distribution gets narrower. Micro-nano lamellar crystals appear on the surface of BFHMs, with the dimension ranging from 500nm to 2μm. BaFe2O4 and Fe3O4, which have spinel structures, can be seen in XRD, and they are beneficial for microwave absorption properties. The real part (ɛ′), imaginary part (ɛ″) of permittivity, and the imaginary part of permeability (μ″) increases in 0.5–18GHz. The real part (μ′) of permeability increases in 0.5–10.3GHz, while decreases in 10.3–18GHz. The microwave absorption properties are improved greatly, and the minimum reflectivity decreases from −3.1dB to −9.8dB. The reasons for improvement of microwave absorption properties after adding NaNO3 foaming agent may be the decreasing of the particle size of BFHMs, the appearance of ferrites (BaFe2O4 and Fe3O4) with spinel structure and special micro-nano tabular crystals. Magnetoplumbite-type barium ferrites (BaFe12O19) hollow microspheres are obtained after heat-treatment and the microwave absorption properties are further improved.

Structural, Magnetic and Electrical Properties of Cu-Mg Ferrites

Cu1-xMgxFe2O4 ferrites with (x = 0.2, 0.4, 0.6, 0.8 and 1.0) has been synthesized by double sintering ceramic technique at 11500C for 2hr and investigated for their structure, microstructure, complex permeability behaviour, DC and AC resistivity, dielectric constant measurements. X-ray analysis indicated the formation of single-phase cubic spinel structure for all samples and the lattice parameter was found to decrease with increasing Mg content. Grain size was found to decrease from 34.36 to 4.16 mm with the increase of Mg contents. The real part of initial permeability (??) remained constant up to certain lower range of frequency after it decreased slightly to lower value of permeability at which imaginary part of permeability (?²) showed a maximum value. The decrease of ?? is observed with the increase of Mg content which is attributed to a decrease of grain size. DC electrical resistivity and dielectric constant decreased with increasing Mg content and AC resistivity decreased with increasing frequency, exhibiting normal ferrimagnetic behaviour. The observed variation of electrical and dielectric properties has been explained on the basis of the electronic hopping frequency between Fe2+ and Fe3+ ions in present samples. Keywords: Ferrites; XRD; Micrographs; Complex permeability; DC resistivity. © 2014 JSR Publications. ISSN: 2070-0237 (Print); 2070-0245 (Online). All rights reserved. doi: http://dx.doi.org/10.3329/jsr.v6i2.17351 J. Sci. Res. 6 (2), 205-215 (2014)

Effect of multilayer structure on high-frequency properties of FeCo/(FeCo)0.63(SiO2)0.37 nanogranular films on flexible substrates

The high-frequency properties of the FeCo-SiO2 monolayer nanogranular films and FeCo/(FeCo)0.63(SiO2)0.37 multilayer nanogranular films which were elaborated on flexible substrates by magnetron sputtering system were studied. Compared to the monolayer films with the same FeCo content, the multilayer structures comprised of FeCo/(FeCo)0.63(SiO2)0.37 exhibit more excellent properties that the real and imaginary parts of permeability, more than the double value of the monolayer, increase to 250 and 350, respectively. The variation was considered owing to the reduction of the anisotropy field.