Magnetic Permeability Spectra Research Articles

Exploring novel magnetic behaviors in cobalt-doped magnetite synthesized by plasma arc discharge method

Magnetite, a naturally occurring iron oxide, has been widely studied due to its potential applications in various fields. Doping magnetite with foreign ions can significantly alter its structural and magnetic properties. This study aimed to investigate the effects of Co2+ ion doping on the structural and magnetic properties of magnetite. The work introduces cobalt-substituted iron ferrites synthesized using a novel plasma arc discharge (PAD) method and systematically explores how cobalt content affects magnetic properties, aiming to optimize the material for enhanced performance. A series of CoxFe1-xFe2O4 (x=0, 0.1, 0.2, 0.3, and 0.5) ferrites with varying Co2+ concentrations (x=0, 0.1, 0.2, 0.3, and 0.5) were synthesized using a PAD method. The synthesized materials were characterized using X-ray diffraction (XRD) and field emission scanning electron microscopy (FESEM). Magnetic properties were evaluated through magnetic hysteresis loops and permeability spectra. XRD analysis confirmed the formation of a nanostructured spinel-type oxide in all samples. FESEM images revealed ultra-fine particles with a homogeneous composition and narrow size distribution. The optimal combination of magnetic properties was achieved at a Co2+ concentration of x=0.1, which exhibited a high saturation magnetization, low coercivity, moderate effective anisotropy constant, and a relatively high magnetic permeability at 5 MHz. The results demonstrate that Co2+ ion doping can effectively tailor the structural and magnetic properties of magnetite. The optimized composition (x=0.1) offers promising potential for applications requiring a balance of high magnetization and low coercivity.

Tailoring the in-plane magnetic anisotropy and permeability spectra of obliquely deposited Fe40Co40B20 films for 5G communications

Ferromagnetic films are widely used in magnetic devices owing to their high saturation magnetization, high magnetic permeability, and low coercivity. However, it is extremely challenging to apply ferromagnetic films to high-frequency communication applications due to the low resonant frequency of permeability spectra. Here, ferromagnetic Fe40Co40B20 films are prepared using oblique magnetron sputtering deposition and the static and dynamic magnetic properties are comprehensively investigated. The self-shadowing effect caused by the tilted growth of columnar grains introduces in-plane magnetic anisotropy to the films, thereby increasing the natural resonant frequency. As the sputtering angle increases from 24° to 30°, the resonant frequency increases from 4.09 to 4.87 GHz, resulting in an approximate liner tunability of 0.13 GHz/degree. Compared to the normally sputtered films, the figure of merit in regard to the microwave magnetic performance of the obliquely sputtered films is significantly enhanced by more than 50%. These results reveal the effectiveness of the oblique sputtering deposition to tailor the in-plane magnetic anisotropy and permeability spectra of ferromagnetic films for the high-frequency film inductor application of 5G communications.

Radar absorbing and shielding characteristics in ferrite-polymer composites Mn-Zn ferrite/P (TFE-VDF)

The article discusses the electromagnetic absorbing and shielding properties of ferrite-polymer composites of the composition Mn-Zn ferrite/fluoroplast-42, obtained by pressing a mixture of powders with heating. The measurement of the complex magnetic and dielectric permittivity spectra, as well as the reflection coefficient spectra was carried out in the frequency range 0.1-7 GHz. Using the obtained spectra, a comprehensive analysis of the absorbing characteristics of the composites was carried out, and the factors responsible for the absorption were determined. Fitting of the composites magnetic permeability spectra show that the process of natural ferromagnetic resonance prevails over the resonance of domain walls, and a decrease in the concentration of ferrite inclusions leads to a significant shift in the frequency of natural ferromagnetic resonance to high frequencies. It was found that for composites with a thickness of 5-10 mm, compositions with a mass fraction of ferrite ≤0.4 show radio-absorbing properties, while compositions with a fraction of ≥0.6 show shielding properties. Keywords: polymer composite, magnetic properties, radio absorption, feromagnetic resonance, polyvinylidene fluoride, manganese-zinc ferrite.

Радиопоглощающие и радиоэкранирующие характеристики феррит-полимерных композитов Mn-Zn феррит/П (ТФЭ-ВДФ)

The article discusses the electromagnetic absorbing and shielding properties of ferrite-polymer composites of the composition Mn-Zn ferrite/fluoroplast-42, obtained by pressing a mixture of powders with heating. The measurement of the complex magnetic and dielectric permittivity spectra, as well as the reflection coefficient spectra was carried out in the frequency range 0.1 - 7 GHz. Using the obtained spectra, a comprehensive analysis of the absorbing characteristics of the composites was carried out, and the factors responsible for the absorption were determined. Fitting of the composites magnetic permeability spectra show that the process of natural ferromagnetic resonance prevails over the resonance of domain walls, and a decrease in the concentration of ferrite inclusions leads to a significant shift in the frequency of natural ferromagnetic resonance to high frequencies. It was found that for composites with a thickness of 5 - 10 mm, compositions with a mass fraction of ferrite ≤ 0.4 show radio-absorbing properties, while compositions with a fraction of ≥ 0.6 show shielding properties.

Frequency dispersion model of the complex permeability of soft ferrites in the microwave frequency range

AbstractThe complex permeability of Cu‐doped nickel‐zinc polycrystalline ferrites is strongly dependent on microstructure, particularly, on relative density () and average grain size (). In this study, a mathematical model, able to fit the measured magnetic permeability spectra from 106 to 109 Hz, is proposed and validated for a width range of average grain sizes (3.40–23.15 μm) and relative densities (0.83–0.96). To the authors’ knowledge, domain‐wall motion and spin rotation contributions to magnetic permeability have been integrated jointly with the microstructure for the first time in the proposed model, highlighting the relative influence of each magnetizing mechanism and microstructure on the magnetic permeability at different angular frequencies.

The effect of long time exposure to light of a water-based ferrofluid on its low frequency complex magnetic permeability

The paper reports on the effect of prolonged exposure to light of a water-based ferrofluid, with magnetite particles, double stabilized with oleic acid, on its low frequency complex magnetic permeability.The investigated ferrofluid was divided into three samples and placed in identical transparent glass vials. The reference sample, denoted by SR was kept in dark (in the laboratory), other sample, denoted by SL, was exposed to the light of a table lamp, with LED bulb (in the laboratory) and the third sample, denoted by SG, was exposed to natural sunlight, in a garden (subjected to the succession of days and nights as well as to the weather conditions). The duration of exposure to light was 80 days, during the summer.Complex magnetic permeability measurements over the frequency range 1 kHz–2 MHz show that after exposure to light both SL and SG samples exhibit Brownian maxima, unlike the reference sample, which has no maximum.Dynamic light scattering measurements show that in all three ferrofluid samples, the magnetic nanoparticles are mainly organized in condensed phase droplets and after exposure to light, the diameter of agglomerations increases.The change in the magnetic permeability spectrum of the investigated samples is explained based on the change in the local structure of ferrofluids, due to the electron-hole pairs resulted by photoelectric effect in magnetite, which affect the electrochemical balance of the colloidal system.

X-Band Electromagnetic Characterization of Fe<sub>72</sub>Al<sub>23</sub>V<sub>5</sub> Based Nanocomposites

Determination of the electromagnetic parameters is an important tool to evaluate the microwave-absorbing characteristic of a novel material. In this context, our research was carried out to investigate the electromagnetic parameters of nanocomposites samples obtained by inclusion of nanostructured Fe72Al23V5 powders in a resin matrix. Nanostructured Fe72Al23V5 powders were synthesized by high-energy mechanical alloying (MA) route and characterized using a scanning electron microscopy (SEM). The nanostructured Fe72Al23V5 powders were dispersed in an epoxy resin matrix. Nanocomposites bulk samples of rectangular section and given thickness were shaped for electromagnetic characterization in an X-band metallic rectangular waveguide. Electromagnetic characterization was performed in terms of measured Sij scattering parameters. Dielectric permittivity and magnetic permeability spectra were extracted over the microwave X-band via the transmission/reflection technique. Obtained results exhibit how the nature and size of the inclusions affect the electromagnetic parameters in the X-band frequencies.

Composition dependence of amorphous forming, crystallization behavior, magnetic and electronic properties of silicon-rich FeSiBCuNb alloys

Fe-Si-B-Cu-Nb nanocrystalline alloys have been commercially applied at higher frequencies. However, few research works are focused on improving high-frequency magnetic properties for these alloys. In this paper, we reported crystallization behavior, soft magnetic properties and permeability spectra for silicon-rich Fe72.5Si16B7 Cu1Nb3.5-xMx (where × = 1.5 and M = Nb, P, Mo, V) nanocrystalline alloys prepared by crystallization from amorphous precursors. Through the copper roller melting spinning technique, we can attain complete amorphous alloy ribbons when M is 1.5 at.% Nb, P or Mo. After annealing at appropriate temperatures, by comparison with the alloy of M = 1.5 at.% Nb, the alloy with addition of 1.5 at.% P shows a lower coercivity (Hc = 0.8 ~ 1.5 A/m), and a higher effective permeability (µe) at 1 kHz–20 kHz (µe = 116,600 at 1 kHz) while the µe gets much lower at 30 kHz–200 kHz; the alloy with addition of 1.5 at.% Mo exhibits a larger Hc (Hc = 2.9 ~ 3.4 A/m), and a lower µe at 1 kHz − 20 kHz but then the µe becomes higher at 30 kHz–200 kHz (µe = 31,000 at 100 kHz).

Electromagnetic Properties and Absorption Evaluation of Processed Carbonyl Iron and MWCNT at PANI Nanocomposites in the <inline-formula> <tex-math notation="LaTeX">$X$ </tex-math> </inline-formula>-Band

Composites loaded with various carbonyl iron-based (CI) materials are fabricated and characterized with regards to their electromagnetic properties and absorption in the X-band (8–12 GHz). The combination of inclusion CI particles and multiwalled carbon nanotubes (MWCNT) is also explored. To this effect, CI micropowder has been successively processed to get the form of flaked, porous, and nanosized TiO2-coated particles, whereas MWCNT has been coated with polyaniline (PANI). The processed fillers were primarily characterized to verify their structural consistency and large variations in the microstructure. The static magnetic properties of the CI-based powders have been analyzed via the vibrating sample magnetometry. Finally, complex dielectric permittivity and magnetic permeability spectra along with the return loss (RL) maps of composites loaded with the powders under study have been extensively investigated. Among the studied samples, the multicomponent composite with core-shell-structured CI-TiO2 and MWCNT-PANI exhibits the maximum magnetic and dielectric losses, which yields high RL peaks (>20 dB) tuned within the X-band for layer thickness from 2.5 to 3.5 mm. Particularly for thickness from 2.85 to 3 mm, this quarter-wavelength absorber displays the broadband operation potential as RL values larger than 10 dB can be achieved throughout the X-band.

Enhanced Microwave Absorption Properties of Doped M-Type Barium Hexagonal Ferrites in Ka-band Frequencies

The present study reports the microwave absorption characteristics of La3+-Na+ substituted barium hexaferrites with chemical composition: Ba(1−2x)LaxNaxFe10CoTiO19 and Ba(1−2x)LaxNaxFe10Co0.5TiMn0.5O19 (0.00 ≤ x ≤ 0.25) respectively in Ka-band frequencies. The electromagnetic characteristics such as complex permittivity, complex permeability, and microwave absorption properties were studied using Vector Network Analyzer in 26.5–40.0 GHz frequency band. Dielectric properties showed almost constant variation with increase in frequency. Magnetic permeability spectra observed wavy variation with frequency. Comparing the electromagnetic properties of two series, it is observed that Co–Ti–Mn series observes higher values of electromagnetic properties in comparison to Co–Ti series. For composition x = 0.15 of Ba(1−2x)LaxNaxFe10Co0.5TiMn0.5O19 series, −55.33 dB reflection loss at 30 GHz frequency with −10 dB absorption bandwidth around 3.51 GHz has been observed. Thus, these materials can be employed as effective absorbers for Ka-band microwave absorbers.

Metastable magnetic bubble in [Co/Pd]4/Py multilayers

Magnetic bubbles are topological spin textures that offer interesting physics and great promise for next-generation information storage technologies. The main obstacles so far are that magnetic bubbles are generated with no field stimuli in new material systems at room temperature. Here, we report the observation of individual magnetic bubbles and its high-frequency measurement at room temperature in an exchange-coupled [Co/Pd]4/Py multilayers. We demonstrate that the emergence of magnetic bubbles at remanence can be tuned by the in-plane tilted magnetic field (roughly 3°) along the film plane at room temperature. High frequency results indicate that the presence of magnetic bubbles leads to broadening of the magnetic permeability spectrum lines (due to the non-uniformity of the magnetic moments). Our findings may help to facilitate the application of bubble-based devices at room temperature in exchange-coupled magnetic multilayers.

Effect of Powder Grain Size on Microstructure and Magnetic Properties of Hexagonal Barium Ferrite Ceramic

Compact hexagonal barium ferrite (BaFe12O19, BaM) ceramics with excellent magnetic properties have been prepared from powder with the optimal grain size. The dependence of the microstructure and magnetic properties of the ceramics on powder grain size was studied in detail. Single-phase hexagonal barium ferrite powder with grain size of 177 nm, 256 nm, 327 nm, and 454 nm was obtained by calcination under different conditions. Scanning electron microscopy revealed that 327-nm powder was beneficial for obtaining homogeneous grain size and compact ceramic. In addition, magnetic hysteresis loops and complex permeability spectra demonstrated that the highest saturation magnetization (67.2 emu/g) and real part of the permeability (1.11) at 1 GHz were also obtained using powder with grain size of 327 nm. This relationship between the powder grain size and the properties of the resulting BaM ceramic could be significant for development of microwave devices.

Influence of cold isostatic pressing on the magnetic properties of Ni-Zn-Cu ferrite

In power electronics, there is the need to develop solutions to increase the power density of converters. Interleaved multicellular transformers allow interleaving many switching cells and, as a result, a possible increase in the power density. This converter is often composed of a magnetic core having the function of an intercell transformer (ICT) and, depending on the complexity of the designed architecture, its shape could be extremely complex. The switching frequencies (1-10 MHz) for the new wide band gap semiconductors (SiC, GaN) allow to interleave switching cell at higher frequencies than silicon-based semiconductors (<1 MHz). Intercell transformers must follow this increase in frequency times-fold the number of switching cells. Current applications for ICT transformers use Mn-Zn based materials, but their limit in frequency drive raises the need of higher frequency magnetic materials, such Ni-Zn ferrites. These materials can operate in medium and high power converters up to 10 MHz. We propose to use Ni0,30Zn0,57Cu0,15Fe2O4 ferrite and to compress it by cold isostatic pressing (CIP) into a a green ceramic block and to machine it to obtain the desired ICT of complex shape prior sintering. We compare the magnetic permeability spectra and hysteresis loops the CIP and uniaxially pressed ferrites. The effect of temperature and sintering time as well as high-pressure on properties will be presented in detail. The magnetic properties of the sintered cores are strongly dependent on the microstructure obtained.

Effect of lanthanum substitution on structural and magnetic properties of nickel zinc ferrites

The purpose of the presented research is to investigate the effect of La3+ ions substitution for Fe3+ ions in Ni0.42Zn0.58LaxFe2-xO4 (x = 0, 0.02, 0.04, 0.06, 0.08, 0.10) ferrite compositions prepared by the innovated glycine-nitrate process based on auto-combustion method. Structural and magnetic properties of examined samples were estimated by the analysis of X-ray spectra, EDAX spectrum, SEM micrographs, thermomagnetic characteristics, magnetic hysteresis loops and complex permeability spectra.

Complex permeability and permittivity spectra of percolated Fe50Co50/Cu granular composites

Complex permeability and permittivity spectra of Fe50Co50/Cu hybrid granular composite materials have been studied in the RF to microwave frequency range. At low Cu particle content, the Fe50Co50/Cu hybrid sample shows a metallic percolative property with the electrical conductivity value about 0.1S/cm. However, the low frequency plasmonic (LFP) state with negative permittivity (ENG) spectrum was not observed. An abrupt increase of electrical conductivity takes place at 14 to 16vol% Cu content where the conductivity becomes above 1.0S/cm; the Fe50Co50/Cu composite possesses the LFP state with negative permittivity spectrum below a characteristic frequency. The complex permittivity spectra in the LFP state can be described by the Drude model. Magnetic permeability spectrum in the LFP state showed a broad frequency dispersion above 10MHz; a small negative permeability (MNG) dispersion was observed from 2 to 10GHz. Consequently, the double negative (DNG) electromagnetic property with MNG and ENG was realized in the microwave range for the Cu content of 26 and 30vol%.

Analysis and reoperation of the magnetic permeability spectra of textured composite based on Z-type hexaferrite by using Cramers-Kronig relations

The frequency dependences of the magnetic permeability of textured composite based on Ba3Co2,4Fe23,2O41 ferrite are given. The magnetic permeability spectra were obtained by coaxial method in the frequency range 0.01–18 GHz. The expert judgement on the spectra was made by using Cramers – Kronig relations. It was shown, that the Cramers – Kronig relations can be used to correct magnetic permeability measurements by reciprocal recalculation of the frequency dependences of the real and imaginary parts.

Effect of Zn substitution on structural, dielectric and magnetic properties of nanocrystalline Co1−xZnxFe2O4 for potential high density recording media

Co1−xZnxFe2O4 (0 ≤ x ≥ 1) nanopowders were synthesized using microwave hydrothermal method. The synthesized powders were characterized by X-ray diffraction and transmission electron microscope (TEM). The average particle size was obtained from TEM and it is found to be 17 nm. Then powders were sintered using microwave sintering method at 900 °C/15 min. The real part of permittivity varies as Zn concentration increases and the resonance frequency was observed at much higher frequencies (>1 GHz) and there is a significant decrease in the loss factor. The dielectric parameters were observed to decrease with the increased Zn contents. The frequency dependent dielectric properties of all these nanomaterials have been explained qualitatively in accordance with Koop’s phenomenological theory. The magnetic permeability spectra exhibit resonance and anti-resonance type behaviour. Lower reduced remnant magnetization (Mr/Ms) values (x < 0.5) suggest that all the samples have uniaxial anisotropy. The increasing trend of magnetic parameters (coercivity and retentivity) is consistent with crystallinity. The moderate magnetization and high coercivity are enough to attain considerable signal to noise ratio in high density recording media.

Microwave and millimeter wave dielectric permittivity and magnetic permeability of epsilon-gallium-iron-oxide nano-powders

In millimeter wave frequency range, hexagonal ferrites with high uniaxial anisotropic magnetic fields are used as absorbers. These ferrites include M-type barium ferrite (BaFe12O19) and strontium ferrite (SrFe12O19), which have natural ferromagnetic resonant frequency range from 40 GHz to 60 GHz. However, the higher frequency range lacks suitable materials that support the higher frequency ferromagnetic resonance. A series of gallium-substituted ε-iron oxides (ε-GaxFe2−xO3) are synthesized, which have ferromagnetic resonant frequencies appearing over the frequency range of 30 GHz to 150 GHz. The ε-GaxFe2−xO3 is synthesized by the sol-gel method. The particle sizes are observed to be smaller than 100 nm. In this paper, in-waveguide transmission and reflection method and the free space magneto-optical approach have been employed to study these newly developed ε-GaxFe2−xO3 particles in millimeter waves. These techniques enable to obtain precise transmission spectra to determine the dielectric and magnetic properties of both isotropic and anisotropic ferrites in the microwave and millimeter wave frequency range from single set of direct measurements. The complex dielectric permittivity and magnetic permeability spectra of ε-GaxFe2−xO3 are shown in this paper. Strong ferromagnetic resonances at different frequencies determined by the x parameter are found.

The complex initial reluctivity, permeability and susceptibility spectra of magnetic materials

Abstract The HF complex permeability spectrum of a magnetic material is deduced from the measured impedance spectrum, which is then normalized to a series permeability spectrum. However, this series permeability spectrum has previously been shown to correspond to a parallel magnetic circuit, which is not appropriate. Some of the implications of this truth are examined. This electric/magnetic duality has frustrated efforts to interpret the shape of the complex magnetic permeability spectra of materials, and has hindered the application of impedance spectroscopy to magnetic materials. In the presence of magnetic loss, the relationship between the relative magnetic permeability and the magnetic susceptibility is called into question. The use of reluctivity spectra for expressing magnetic material properties is advocated. The relative loss factor, tan δ m / μ i is shown to be an approximation for the imaginary part of the reluctivity. A single relaxation model for the initial reluctivity spectra of magnetic materials is presented, and its principles are applied to measurements of a high permeability ferrite. The results are presented as contour plots of the spectra as a function of temperature.

Calculation of the energy loss in giant magnetic impedance elements using the complex magnetic permeability spectra

The giant magnetic impedance (GMI) effect in ferromagnetic materials has been investigated for sensing applications. The GMI properties were evaluated via numerical solution of the complex magnetic permeability of the material. MATLAB® simulation was carried out to study the frequency dependence of magnetic permeability via obtaining solutions of the Landau–Lifshitz–Gilbert (LLG) and the Maxwell’s equations. The results indicate that the complex magnetic permeability peaks at a frequency of 6 GHz, corresponding to the ferromagnetic resonant (FMR) frequency, where the energy loss is maximum. A variation of the Gilbert damping parameter (α ) associated with the LLG equation inversely affects this peak value. The area under the curve of complex magnetic permeability, calculated through counting the number of pixels within the image, provides an estimate of the average energy loss density within the material and appears to be consistent with the variation of the peak intensity.