Initial Magnetic Permeability Research Articles

Microwave assisted cobalt nickel ferrite as exhaust thrust sensor and EMI shield

Spinel ferrites have garnered an increasing share of attention in recent decades. The fact that these substances are employed in a wide range of applications, such as electromagnetic interference interference (EMI) shielding and sensor technology. Exhaust thrust sensors have an increasing demand in exhaust air circulator of automobile engine. In the present article Co0.5Ni0.5Fe2O4 (CNF) is synthesized by ceramic route and are sintered using microwaves. The structural, optical, magnetic and morphology are studied using X-ray diffraction, Ultraviolet (UV) visible, Vibrating sample magnetometer (VSM) and scanning electron microscopy (SEM). The magnetic initial permeability as a function of temperature has exhibited quasi single domain grain behaviour. Large stress response and exhaust pressure sensitivity are noticed for the bulk as well as micro inductor fabricated suggesting a plausible application as exhaust thrust sensor applications. The CNF exhibits a high total shielding effectiveness of 55.96 dB, suggesting that almost 99.999% of incoming electromagnetic radiation is effectively reduced by this material. Spinel ferrite CNF have excellent electromagnetic shielding in microwave region and making it very useful for military (radar and stealth) and electronic industries.

In-plane magnetic properties and anisotropy of scandium substituted thulium iron garnet thin films for fluxgate magnetometer

In-plane easily magnetized scandium substituted thulium iron garnet films(Tm3Fe5-xScxO12) with soft magnetic properties have recently attracted attention for fluxgate magnetometer applications. In this paper, thin Tm3Fe5-xScxO12 films were prepared on gadolinium gallium garnet substrates by liquid phase epitaxial(LPE) method. Microstructural properties, composition, magnetic properties and the in-plane anisotropy of the films were discussed. We found that the films turned from tensile stress to compressive stress as the Sc3+ substitution decreased, and the in-plane anisotropy was mainly caused by stress reducing as Sc3+ declined. By analyzing the in-plane magnetic hysteresis loops, the magnetic performance was the best when x = 0.75. Tm3Fe4.25Sc0.75O12 film had the lowest in-plane coercive field(0.006 Oe) and the highest initial magnetic permeability(378), which was more beneficial to realize fluxgate magnetometers.

Analysis of the electromagnetic properties of 2000NN/2000NM composites with ferroelectric and polymer matrices

The results of studying the electrical properties of ferrite-dielectric composites containing inclusions of Mn-Zn and Ni-Zn spinel ferrites with the same initial magnetic permeability (grades 2000NM and 2000NN, respectively) and different electrical resistance are presented. Four matrix materials, polymer and ceramic dielectrics with a different dielectric permittivity were used in the experiments: polystyrene (PS525), polyvinylidene fluoride (grade F2MB), lead zirconate titanate (ZTS-21), and barium titanate (TBK-3). Experimental samples of composites were obtained by hot (for a polymer matrix) or cold pressing with a binder (in case of ferroelectric ceramic matrix). It has been shown that the microwave-absorbing properties of the resulting composites significantly depend on the electrical properties of the dielectric matrix and the electrical resistivity of the filler. The highest attenuation of electromagnetic waves of 25 – 27 dB in the frequency range 4 – 5 GHz is observed for ferrite-polymer composites with a semiconductor filler of 2000NM with a thickness of microwave-absorbing material of 6 mm. For composites with Mn-Zn ferrite filler, a pronounced shift in the dispersion region of magnetic permeability is also observed, which in turn changes the frequency position of peak radio absorption. For the composites with a ferroelectric matrix, the operating frequency range for both fillers shifted to the low-frequency region 1 – 4 GHz with a maximum attenuation of up to 22 dB at the same thickness. It was experimentally confirmed that at a concentration of ferrite Cm = 40 % wt., the value of the frequency of absorption peal center fc and the minimum value of the reflection loss Kref for a filler with high electrical resistance of 2000NN decrease with an increase in the dielectric constant of the matrix. As for the composites with a 2000NM filler, the (ε’ of the matrix) dependence passes through a minimum. The obtained composites can be considered as effective microwave-absorbing materials for the frequency range 1 – 6 GHz with peak attenuation of the electromagnetic wave in the range 14 – 27 dB and frequency band (less than 10 dB) in the range 1.1 – 2.5 GHz.

Influence of the powders phase composition and sintering atmosphere on the structure and magnetic properties of Mn-Zn ferrites

The magnetic properties of Mn-Zn ferrites depend strongly on the microstructure, chemical and phase composition. In this paper the effect of synthesis and sintering conditions on the structure, phase composition and properties of Mn-Zn ferrites is investigated. The specimens for the study were obtained by pressureless sintering. The magnetic properties were measured on a B-H analyzer. The structure was investigated by XRD and SEM. Materials with an average grain size of 2.2 μm were obtained by sintering at a temperature of 1265 °C. It was found that an increase in the synthesis temperature from 700 to 1000 °C promotes the growth of the initial magnetic permeability of these materials from 1100 to 1370. The rapid cooling of the powders synthesized at 1000 °C allows maintaining a high content of the spinel phase. In the structure of materials obtained by sintering powders with initially high spinel content at 1300 °C, grains of abnormally large size are formed. This leads to an increase in the initial permeability, magnetic induction at Hm = 1200 A/m, f = 10 kHz and magnetic losses at high frequencies (up to 500 kHz). A material with fine-grained structure was obtained by using air at the heating stage of pressureless sintering. This contributed to the reduction of magnetic losses without a significant decrease in Bm.

TUDY OF THE INITIAL MAGNETIC PERMEABILITY OF LiTiZnMnFERRITES OBTAINED BY LIQUID-PHASE SINTERING UNDER RADIATION-THERMAL AND THERMAL CONDITIONS

The measuring the temperature dependence of the initial permeability was used to study the features of phase and structural transformations in lithium-titanium ferrites as a function of time, heating and cooling rates, and the temperature of liquid-phase sintering under thermal and radiation-thermal heating. Ferrite was synthesized from powder mixture by solid-phase synthesis. A low-melting additive bismuth dioxide was used to obtain the ferrite ceramics by liquid-phase sintering. RT sintering was carried out by heating the samples with a pulsed (1.5–2.0) MeV electron beam. It was established that the additive leads to a less defective state of sintered ferrites, while the action of radiation enhances this effect in the early stages of sintering. The regularities of the influence of the heating and cooling rates of compacted samples on the change in the initial magnetic permeability of sintered ferrites are established.

Effect of plastic deformation on the phase composition and electromagnetic characteristics of the 321N austenitic steel (08Kh18N10T)

The changes in the phase composition and electromagnetic properties of the 321N chromium-nickel austenitic steel under plastic deformation by uniaxial tension are studied. As strain increases from 0 to 0.37, the content of ferromagnetic α′-martensite in the steel increases monotonically to 60%. The electrical resistivity and the initial magnetic permeability increase monotonically by factors of 1,25 and 18, respectively. To monitor the strain state and the content of α'-martensite in products made of the 321N steel, it is preferable to use initial magnetic permeability rather than electrical resistance. The skin layer thickness of the deformed 321N steel for frequencies from 5 to 1000 kHz is calculated from the experimental values of initial magnetic permeability and electrical resistivity. Eddy current diagnostics of the state of the surface of products made of this steel, hardened by surface plastic deformation, is proposed to be performed at frequencies ranging between 100 and 200 kHz.

Spark Plasma Sintered Soft Magnetic Composite Based on Fe-Si-Al Surface Oxidized Powders.

Soft magnetic composites (SMCs) need a stable matrix to apply heat treatments for enhancing their magnetic characteristics. A stable matrix can be offered by alumina, but the densification of the ferromagnetic particles covered by this oxide (by sintering) can be very difficult. This paper proposes a feasible synthesis route for obtaining alumina matrix SMCs. An Fe-Si-Al alloy with nominal composition Fe85Si9Al6 was obtained by mechanical alloying of elemental Fe, Si, and Al powders, and further, the as-milled powders were superficially oxidized by immersion in HCl solution. The oxide layer was composed of iron, silicon, and aluminum oxides, as the Fourier-transform infrared spectroscopy technique revealed. The Fe-Si-Al@oxide powder was densified by the spark plasma sintering technique-SPS. Upon sintering, a continuous matrix of oxide (mainly alumina) was formed by the reaction of the Fe-Si-Al powder coreswith their oxide layer. The main part of the composite compacts after sintering consisted of an Fe3Si-ordered phase dispersed in an oxide matrix. The DC and AC tests of magnetic composite compacts showed that upon increasing the sintering temperature, the density, magnetic induction, and magnetic permeability increased. The initial magnetic permeability was constant in the entire range of testing frequencies and the magnetic losses increased linearly. The stability of the magnetic characteristics in frequency is promising for developing further such types of magnetic composite.

Modified copper zinc ferrite nanoparticles doped with Zr ions for hyperthermia applications

The problem of the present work is to synthesize a nanomagnetic material with low TC below 45 °C and its particle size below 30 nm to be appropriate material for convert magnetic loss into heat energy. A series of Cu0.4Zn0.6+yZryFe2–2yO4 nanoparticles compositions where y = (0.05, 0.1) were synthesized via citrate sol–gel method. The prepared samples were characterized by X-ray diffraction (XRD) and transmission electron microscopy (TEM). The grains were observed from SEM confirming the crystalline structure of the ferrite which was detected by X-ray diffraction. Magnetic hysteresis loop measurements illustrate that materials exhibit soft magnetic properties at low Zr content, while at higher Zr content all materials behave as superparamagnetically without any saturation magnetization Ms. The initial magnetic permeability ({mu }_{i}) at frequency 10 kHz as a function of temperature was measured. A sudden change in {mu }_{i} appears around Curie temperature, making our samples good candidates for magnetic temperature transducer (MTT) devices. The DC resistivity for sample at y = 0.05, 0.1 was studied. The resistivity decreases linearly with increasing temperature within the given range of temperature up to 666 K for all samples. The dielectric constant of all samples is nearly independent on temperature through the range of 450 to 600 K which is a common character of ferrites. The dielectric loss was found to increase by increasing temperature, which may be related to the increase in AC conductivity. Hyperthermia measurements show the maximum specific power loss and temperature increase were 26 w/gr and 43 °C, respectively, for sample containing Zr = 0.05, after 2 min of measurements. One of the real applications of the material is that it is used as an effective method in tumor treatment by exposing the patient to external magnetic field.

Effect of Bi2O3 contents on magnetic and electromagnetic properties of LiZnMn ferrite ceramics

Soft LiZnMn ferrites with low coercive force values and small grain sizes were developed by the solution combustion synthesis and low temperature sintering technique for microwave applications at a high frequencies. Bismuth oxide was used as an additive to lower the sintering temperature. The examination covered the influence of Bi2O3 on the crystal structure, microstructure, primary magnetic and dielectric characteristics of lithium-zinc-manganese ferrites. The most promising sample designed for using in microwave devices was produced by sintering at 1075 ℃ temperature for 8 h with added 1.5 wt% Bi2O3. These production conditions have yielded 2.98 µm average grain size in a ceramic product, the density is 4.84 cu cm/g, and the coercive force, residual induction, and saturation induction are 58 A/m, 2078.4 G, and 3439.1 G, respectively. In addition, this sample demonstrates a high initial magnetic permeability (μi = 168), Curie temperature (Tc = 437.5 ℃), high values of the dielectric loss tangent (tan δɛ = 6.32⸱10−3), ferromagnetic resonance line width (ΔH = 280 Oe) and the resonance line of spin waves (ΔHk = 1.87 Oe). Further increase in the bismuth oxide content allows observing a change in the ceramics microstructure, accompanied by a deterioration in the magnetic and electromagnetic characteristics. Here, the discussion covers the mechanism of change in the functional properties of lithium-zinc-manganese ferrites produced in the conditions of solution combustion with added bismuth oxide. Thus, synthesizing of initial pre-ceramic powder by glycine-nitrate combustion and subsequent low-temperature sintering with added bismuth oxide is a novel efficient technique of producing advanced soft high-frequency LiZnMn ferrites.

Analysis of stress influence and plastic strain on magnetic properties during the forming process

The aim of this paper is to analyze the relation between magnetic and mechanical properties during and after forming processes. For this purpose, several tensile tests were carried out on sheet metal samples up to a defined plastic strain. The specimens were left in the clamping device in order to relieve the force in several steps until the specimen was completely relieved. As a consequence, the gradual relief leads to a reduction of internal stress states. During the forming process, the initial magnetic relative permeability and magnetic anisotropy of the sample were measured several times. Both properties are related to the mechanical states in the material through the effects of magnetic embrittlement and magneto-elasticity. The plastic strain of the specimens was determined by optical measurements and the stresses in the measurement range during the tensile test was determined with the help of a subsequent numerical simulation. This made it possible for the first time to measure the magnetic properties of samples with different plastic strain and different stress states. The evaluation shows that there is a strong correlation between permeability and plastic strain as well as anisotropy and stress. Based on these findings, it has been confirmed, that the determination of the plastic strain by a soft sensor is possible.

Thermal Hysteresis Control in Fe49Rh51 Alloy through Annealing Process

We report the results of studies of the magnetic and transport properties of Fe49Rh51 alloy prepared by different sequences of quenching and the annealing process. The temperature dependences of the relative initial magnetic permeability and resistivity are analyzed. An optimal regime consisting of annealing at 1300 K for 440 min and quenching from 1300 K to 275 K is found to observe the desired narrow antiferromagnetic–ferromagnetic transition in Fe49Rh51 alloy under cyclic conditions. This has the potential to increase the efficiency of cooling devices based on the magnetocaloric effect of magnetic materials with a first-order field-induced phase transition.

Measuring And Computing System for Studying the Magnetic Characteristics of Soft Magnetic Materials

Non-destructive eddy current diagnostics of the structure, composition, physical and mechanical properties of ferromagnetic materials, as well as eddy current monitoring of the operational parameters of products manufactured from them, requires knowledge of the magnetic characteristics of these materials. In eddy current measurements, the results obtained are influenced by a significant number of factors — magnetic and electrical properties of materials, geometric characteristics of products, measurement conditions, design features of an eddy current sensor, etc. Also, the magnetic properties themselves have high structural sensitivity. Thus, identification of the diagnosed parameters puts great importance on the tasks to separate the influencing factors and isolate the contribution of the magnetic properties.
 This paper describes the measuring and computing system that allows automatic determination of the magnetic permeability of soft magnetic ferromagnetic materials at various values of the strength of the external magnetizing field. The system has been tested using soft magnetic ferrites samples. An experimental dependence of the magnetic permeability on the magnitude of the magnetic field for the initial section of the main magnetization curve is presented. The obtained initial magnetic permeability is compared with the data of independent indirect measurements.
 The proposed system provides an increase in the reliability and accuracy of the results of the experimental determination of magnetic characteristics and can be used for non-destructive diagnostics of products made of soft magnetic ferromagnetic materials.

Rietveld refinement, cation distribution, morphological and magnetic study of NiAlxFe2-xO4 nanoparticles

NiAlxFe2-xO4 (where x = 0.00, 0.20, 0.40, 0.60, 0.80, and 1.00) nanoparticles (NPs) are synthesized using the flash auto combustion method where CO (NH2)2 is used as a fuel. NiAlxFe2-xO4 nanostructure is characterized by X-ray diffraction (XRD) and Rietveld refinement by using FULLPROF Suite. SEM and TEM analysis are used to study the morphology of the samples, the size and the shape of the crystallites respectively. The morphology of the samples showed the creation of uniform and spherical structural with a narrow size distribution. The XRD results and Rietveld refinement show that the lattice contains single phase spinel structure with Fd3m space group. The average crystallite size is calculated by two methods, the Debye-Scherer formula and it is found to decrease from 23.9 to 14.3 nm, while using Williamson–Hall (W–H) method, it is found to decrease from 18.89 to 10.1 nm. Magnetic properties are studied at room temperature. Theoretical and experimental magnetic moments are decreased with increasing Al content. Also, the magnetic measurements show that the samples exhibited ferrimagnetic behavior and the initial magnetic permeability, the saturation magnetization, the remnant magnetization, the coercivity, and the magnetic anisotropy constant are decreased with increasing the non-magnetic Al content.

Spectral, electrical, magnetic and radiation shielding studies of Mg-doped Ni–Cu–Zn nanoferrites

Nanoferrites of Ni0.1Cu0.2MgxZn(0.7−x)Fe2O4 (x = 0.0, 0.15, 0.25, 0.35, 0.45, 0.55 and 0.70 wt%) system fabricated using flash auto combustion technique. All investigated samples annealed for 2 h at 600 °C. XRD, FTIR and TEM were utilized to evaluate the structural characterization of as-prepared samples. The electrical DC resistivity of the investigated samples is evaluated as a function of frequency and temperature. The initial magnetic permeability (μi) is dependent on the temperature and was measured at constant frequency 1 kHz and 10 kHz of the sinusoidal wave. A single-phase of spinel structure was formed and with increasing Mg content the peak (311) of 100% intensity decreases, which demonstrates the presence of Mg, which slows down the growth of the crystal as X-ray result. The FTIR spectra of the prepared ferrite samples are distinguished by the presence of two strong absorption bands (ν1 = 554 cm−1) and (ν2 = 449 cm−1). The morphological observation is determined by the transmission electron microscopy (TEM) and shows that the particles size ranged between 26 and 39 nm. It can notice shifted Curie temperature (Tc) to a higher temperature by increasing Mg content. Mass attenuation coefficient (μm), mean free path (λ), half value layer (X1/2), tenth value layer (X1/10) and effective atomic numbers (Zeff) for the studied samples, have been simulated using FLUKA (2020.0beta.2), while energy change from 15 × 10–3 to 153+ keV with increasing Mg concentration, both μm and Zeff decrease. The largest value of μm and Zeff when x = 0% while sample x = 0.35% has a minimum value of λ, X1/10 and X1/2.

Fabrication and characterization of novel soft magnetic [(Fe0.7Co0.3)71.2B24Y4.8]96Nb4/V2O5 bulk metallic glassy/composite cores with excellent magnetic permeability and low core losses

In the present work, fabrication, characterization and magnetic properties of novel soft magnetic composites (SMCs) based on V2O5 insulated [(Fe0.7Co0.3)71.2B24Y4.8]96Nb4 glassy particles are investigated. The uncoated glassy particles, consolidated at an optimized temperature of 893 K, yield bulk metallic glasses (BMGs) exhibiting a high relative density of 99.5%, a wide supercooled liquid region (SLR) of 92 K, a high initial magnetic permeability of 4310, and a notably low coercivity of 35 A/m. The Fe-based glassy particles in the SMCs are uniformly coated by V2O5 insulation, with negligible interfacial reaction or decomposition of the insulation upon hot consolidation. Additionally, the composite samples, particularly with 5 vol% V2O5, display a high thermal stability comparable to monolithic glassy cores. The V2O5 coated glassy particles preserve their excellent thermoplastic formability and densification behavior upon consolidation, resulting in formation of SMCs with a high relative density (98.5–99%). The prepared composites present a low coercivity (79–100 A/m) and a considerably higher initial permeability (425–475) at 1 kHz compared to most other SMCs prepared before. Furthermore, the performed V2O5 insulation enhances the frequency stability of the initial permeability and increases the relaxation frequency from 700 Hz for glassy cores up to 18 kHz for the composites. Magnetic loss separation analysis reveals negligible excess losses of the samples, while larger hysteresis losses are found for the composite cores up to 2 kHz. The composites with 5 vol% V2O5 exhibit about 55% smaller eddy current losses and 47% lower total core losses at 2 kHz than that of glassy cores. The obtained results suggest that the new composite cores are promising soft magnetic materials for medium frequency range electromagnetic applications.

Technological scheme for lithium-substituted ferrite production under complex high-energy impact

The paper presents technological schemes developed for synthesis of lithium-zinc ferrite powders and sintering of ferrite ceramics, including mechanical activation of the initial mixtures of reagents in a planetary ball mill and subsequent radiation-thermal heating of powders by pulsed or continuous electron beams. Their structural and electromagnetic properties, such as density, porosity, average grain size, Curie temperature, saturation magnetization, initial magnetic permeability, and electrical resistivity, are studied. The technological scheme developed for synthesis of lithium-substituted ferrites using complex effects can be used to produce ferrite powders of homogeneous phase composition with high saturation magnetization at a significantly lower temperature and synthesis time without preliminary compaction of samples. The technological scheme for sintering ferrite ceramics through single-stage radiation-thermal heating of press samples from mechanically activated reagents increases the sample density by ~5%, initial magnetic permeability by ~10%, and electrical resistivity by (2.5–3) times, decreases porosity by ~60% and reduces the duration of ferrite production as compared to that of the two-stage production of ferrite ceramics.

Effect of compressive mechanical stress on the magnetic properties of LiTiZn ferrite ceramics

In the article, it was experimentally determined that compressive mechanical stress affects the parameters of the temperature dependence of the initial permeability. LiTiZn ferrite ceramics were sintered at 1010 °C for 2 h in air. The experimental curves were mathematically processed using the phenomenological expression to describe the initial magnetic permeability according to the Smith-Wijn model. It is shown that the change in the shape of the experimental curves correlates with the calculated data of the increase in the demagnetizing factor with an increase in mechanical stress. It is hypothesized that the change in the shape of the temperature curves is due to the magnetoelastic effect and the temperature dependence of the magnetostriction constant. Also, it was found that mechanical stress does not affect the X-ray microstructural parameters, including the true physical broadening of the reflexes. At the same time, the growth of mechanical stress to the maximum possible level for such type of ferrite ceramics leads to an increase in the coercive force by 10%. The character of the impact of mechanical stress on the shape of the temperature dependence curve of the initial permeability differs from the effect of non-magnetic Al2O3 additives. Thus the character of the change in the shape of the temperature dependence curve of the initial permeability allows monitoring nonmagnetic phases or mechanical stress in a LiTiZn ferrite ceramics production.

Magnetocrystalline Anisotropy and Spinorientation Phase Transitions of Co2z Hexaferrite Doped With Ti4+ and Zn2+ Ions

The paper presents the methodology for calculation of ferromagnetic resonance spectra of polycrystalline and powder hexaferrites with easy magnetization plane. Magnitudes of magnetocrystalline anisotropy fields and magnetomechanical ratios of the hexaferrites of Ba3Co1.5+хTiхFe24.5–2хO41 (0.0 ≤ х ≤ 1.0) and Ba3Co2.5–хZnxTi0.5Fe23O41 (0.0 ≤ х ≤ 1.2) (0.0 ≤ х ≤ 1.2) systems were determined from an experimental study of the parameters of ferromagnetic resonance at room temperature. The study of temperature dependences of initial magnetic permeability was used to determine the temperatures of spin-orientation phase transitions of these materials. It was shown that substitution of Co2+Ti4+ complex for Fe3+ ions leads to the widening of the temperature region of existence for the magnetic ordering of the easy magnetization plane type with high magnetic permeability in the microwave frequency region. Substitution of Zn2+ ions for some of the Co2+ ions increases the saturation magnetization.

Effect of particle size and size distribution on the permeability of soft magnetic liquid silicone rubber composites

Magnetic composites made of LSR (Liquid Silicone Rubber) and a magnetic filler have been investigated with respect to magnetic field guidance for transcutaneous energy transport. Effects of particle size and size distribution on the effective initial magnetic permeability are analyzed. A simple model is presented to describe the permeability as a function of the degree of filling, particle size and size distribution. From this, a calculus for the relevant size average of the filler was developed at 20 vol% of magnetic filler. The calculus showed self-consistency and can be used to tailor optimized powders for better field guidance.

Torque Analysis in Coaxial Magnetic Gears Considering Nonlinear Magnetic Properties and Spatial Harmonics

A coaxial magnetic gear (CMG) consisting of an inner ring, outer ring, and flux modulator exhibits relatively large torque density at low operating cost and low noise level. To guide the selection of soft magnetic materials for the flux modulator, this paper first incorporates the Jiles–Atherton model within a finite-element (FE) framework. The influence of nonlinear magnetic properties on end-effect losses (magnetic flux leakage and fringing) is then investigated with the objective of maximizing the pullout torque. For flux modulators whose initial magnetic permeability and saturation flux density exceed certain threshold value, the pullout torque of a CMG becomes insensitive to magnetic properties and end-effect losses can be efficiently calculated from a 2-D FE model together with a constant torque reduction ratio. This paper presents a systematic torque surface method that can decouple the analysis of average torque and torque ripples. This method has been implemented to evaluate load dependence and rotation speed fluctuation of a CMG.