Magnetic Properties Of Ferrites Research Articles

Influence of calcination temperature and particle size distribution on the physical properties of SrFe12O19 and BaFe12O19 hexaferrite powders

The paper deals with the economic optimisation of ferrite powder preparation during producing hard ferrite magnets. The magnetic properties of ferrites are investigated by replacing feedstock and reducing calcination temperature and particles in the order of tens of microns. The granulates about 8–10 mm in size were calcined for 2 h in the temperature range from 1100 °C to 1300 °C and additionally crushed and milled to an average particle size of about 80–90 µm. The scanning electron microscopy images confirmed the agglomerates of particles with different shapes and sizes in tens of µm. The X-ray diffraction measurements revealed that, besides the SrFe12O19 and BaFe12O19 phases, there was also the presence of 2–39% hematite. The highest values of maximum energy product (BH)max = 930 J/m3 and remanent magnetic induction Br = 72.8 mT were obtained at a calcination temperature of 1300 °C. The Henkel plots confirmed the presence of exchange-coupling and dipolar magnetic interactions at lower and higher magnetic fields, respectively. The strength of interactions was also dependent on the calcination temperature. Replacing strontium with barium led to a deterioration of the magnetic parameters, which were optimal at a lower calcination temperature (1100 °C). This phenomenon was partly overcome by reducing the mean particle size of Ba-based hexaferrites to 45–50 µm.

Radio-Absorbing Magnetic Polymer Composites Based on Spinel Ferrites: A Review.

Ferrite-containing polymer composites are of great interest for the development of radar-absorbing and -shielding materials (RAMs and RSMs). The main objective of RAM and RSM development is to achieve a combination of efficient electromagnetic wave (EMW) absorption methods with advantageous technological and mechanical properties as well as acceptable weight and dimensions in the final product. This work deals with composite RAMs and RSMs containing spinel-structured ferrites. These materials are chosen since they can act as efficient RAMs in the form of ceramic plates and as fillers for radar-absorbing polymer composites (RAC) for electromagnetic radiation (EMR). Combining ferrites with conducting fillers can broaden the working frequency range of composite RAMs due to the activation of various absorption mechanisms. Ferrite-containing composites are the most efficient materials that can be used as the working media of RAMs and RSMs due to a combination of excellent dielectric and magnetic properties of ferrites. This work contains a brief review of the main theoretical standpoints on EMR interaction with materials, a comparison between the radar absorption properties of ferrites and ferrite-polymer composites and analysis of some phenomenological aspects of the radar absorption mechanisms in those composites.

Rare earth Ce-doped W-type barium ferrites for tunable electromagnetic waves absorption performance

W-type ferrites possessing low cost and high chemical stability, show high potential in electromagnetic wave (EMW) absorption field. However, due to the low dielectric loss, developing high EMW absorption performance of W-type ferrites remains desired. Here, rare earth (RE) cerium (Ce)-doped W-type barium ferrites (Ba1-yCeyNi2Fe15.4O27, y = 0.1, 0.2, 0.3, 0.4, 0.5, 0.6) are prepared by a sol-gel approach. The influences of Ce doping are detailed analyzed. Ce ions with unpaired 4f electrons and strong spin-orbit coupling of angular momentum enhance the dielectric and magnetic properties of ferrites. Ba0.7Ce0.3Ni2Fe15.4O27 achieves the minimum reflection loss (RLmin) value of -52 dB while Ba0.6Ce0.4Ni2Fe15.4O27 showcases the widest effective absorption bandwidth (EAB) of 1.36 GHz associated with the RLmin reaching -38 dB, significantly outperforming the undoped ferrites. This work thus demonstrates a high-efficiency utilization of Ce for enhancing the EMW absorption performance of widely employed W-type barium ferrites, efficiently advancing the application field of RE elements.

Modification of the local structure and properties of zinc-substituted hexagonal barium ferrites for microwave devices under magnetic pulsed processing

The results of studies of the effect of magnetic pulse treatment on the local structure and magnetic properties of substituted ferrite for microwave devices are presented. The change in the magnetic properties of ferrites as a result of exposure to them by pulses of a weak magnetic field indicates the possibility of controlling the parameters of ferrites by means of a magnetic field and thereby influence the resonant characteristics of microwave devices based on them.

Metamagnetic effect in selected MnMg ferrite

A few studies are available on MnMg ferrites, but there is missing information about these ferrites from the point of view of metamagnetic nature. Therefore, in the present study, we have focused on metamagnetic properties of selected MnMg ferrite. The magnetic properties of ferrites having the formula Mn0·894Mg0·347Fe1·758O3.88 prepared by the ceramic technique have been studied. Magnetic measurement has been carried out for examined compound from low magnetic field up to critical field intensity 580 A/m. The composition indicated metamagnetic nature below critical field intensity. In adequate low applied field the formation and increasing of magnetic induction with temperature is caused by changes from canted triangular model to two sublattices model of ferrimagnetic spinel structure. This suggests the existence of canted spin structure in the MnMg ferrite system. Ferrimagnetic properties have been measured by hysteresis loop tracer technique for wide scale of temperatures. Barkhausen noise analysis demonstrated that the magnetizing is prevalently possessed with mechanism of the domain walls motion.

Influence of different complexing agents on structural, morphological, and magnetic properties of Mg–Co ferrites synthesized by sol–gel auto-combustion method

In the preparation process of magnesium-cobalt nano-ferrite powder (Mg0.1Co0.9Fe2O4) by sol–gel self-propagation method, the effect of complexing agent on the nanostructure and magnetic properties of ferrite is studied by changing the type of complexing agent (the complexing agent includes citric acid, oxalic acid, tartaric acid, glucose, and egg white). The XRD pattern of each sample has eight distinct characteristic peaks, and the number of the strongest peak in each map is one [i.e., (311) peak]. All these evidences can preliminarily indicate that the sample has a spinel structure. In addition, in the FTIR of the sample, it can be seen that there are several distinct characteristic peaks at 580 cm−1 (i.e., Fe–O peak, etc.) which can also prove the structural characteristics of the sample. In the SEM map, the sample can be seen to have an elliptical shape with a crystalline grain size between 28 and 50 nm. From this, we can guess that the complexing agent participates in the reaction and has a certain influence on the particle size of the sample. Elemental analysis showed that all the six samples prepared contained magnesium, cobalt, iron, and oxygen, and then we quantitatively analyzed the sample to find that the prepared sample was the target product. The BET test shows that a sample is prepared with glucose as the complexing agent, the specific surface area of it can be increased. The VSM data show that magnesium–cobalt ferrite powder with high saturation magnetization, residual magnetization, and coercivity can be prepared by selecting glucose as the complexing agent.

Microstructure, magnetic, and dielectric properties of Co–Zr co-doped hexagonal barium ferrites based on the sintering temperature and doping concentration

In this work, M-type hexagonal barium ferrites co-doped with Co and Zr atoms were prepared by a solid-phase method based on the sintering temperature and doping concentration. First, the influences of the sintering temperature on the crystal structure, microstructure, and magnetic properties of ferrites were studied. The crystallinity of the materials increases with the sintering temperature and obtaining high density and uniform grain size at 1300 °C, which promotes grain-boundary diffusion and suppresses grain-boundary migration. Second, the dependence of the crystal structure, microstructure, magnetic, and dielectric properties of Ba(CoxZrx)Fe12−2xO19 on the doping concentration (x = 0, 0.2, 0.4, 0.6) was investigated at sintering temperature of 1300 °C. The increase of the crystal parameter c with x value reveals that the ions of Co2+ and Zr4+ successfully replace the Fe3+ ions. Additionally, the co-doping ions of Co2+–Zr4+ promote the grain-boundary migration and result in some large size grain (> 20 mm) that appeared and increased with the doping concentration. The magnetic hysteresis loops reveal the saturation magnetization increases from 60.45 to 68.6 emu/g, and the coercivity decreases from 1800 to 190 Oe with the x increased to 0.6. The dielectric properties measurement displays the Co–Zr co-doping can improve the dielectric and reduce the dielectric loss. The highest value of the real part of permittivity (e′) and the lowest value of the imaginary part of permittivity (e″) can be obtained at a doping concentration of x = 0.4.

Influence of Mg2+ replacement on the structure and magnetic properties of MgxZn1−xFe2O4 (x = 0.1–0.5) ferrites

In this study, the Mg–Zn polycrystalline ferrites with the chemical formula MgxZn1−xFe2O4 (x = 0.1, 0.2, 0.3, 0.4, 0.5) were prepared by standard solid-phase reaction method at the optimal sintering temperature of 1573 K. The structure and magnetic properties of ferrites were characterized by advanced technologies such as XRD, SEM, EDX, FTIR, XPS, and SQUID-VSM. The XRD and FTIR spectra confirmed that all samples had a spinel structure, and the lattice constant and volume decreased gradually. The SEM, EDX, and XPS spectra were used to characterize the microstructure, ion concentration and element valence of the sample. For the obtained sample, as the amount of Mg2+ ions doping increases, the competition between antiferromagnetic (AFM) and ferromagnetic (FM) causes the transition temperature to increase from 19 to 383 K, making it have a broader application prospect. Under the proper doping amount, the saturation magnetization (MS) and coercivity (HC) of all samples were ameliorated at ultra-low temperature and normal temperature. Experimental results show, with the continuous doping of Mg2+ ions, the values of MS and HC continue to increase, the maximum value of Ms can reach 43.6 emu/g (at 300 K) and 96.8 emu/g (at 5 K), and the maximum value of Hc can reach 38.5 Oe (at 300 K) and 99.6 Oe (at 5 K) in the series, which has just reached the use requirements of inductors, transformers and other magnetic components.

Synthesis of Ni0.5Zn0.5Fe2O4-reinforced E-glass/epoxy nanocomposites for radar-absorbing structures

ABSTRACT The development of new radar-absorbing structures (RASs) with strong microwave absorption, fine thickness and adequate structural performance is imperative. Herein, nanocrystalline Ni0.5Zn0.5Fe2O4 was synthesised by a facile and effective sol–gel autocombustion technique. The structural and magnetic properties of ferrite were determined by various characterisation techniques, and E-glass/epoxy-based nanocomposites with different weight percentages of ferrite were fabricated by in-situ polymerisation. Further, electromagnetic properties were investigated to elucidate the possible absorption mechanism of the fabricated structures. The 4-mm-thick double-layered E-glass/epoxy/nickel–zinc ferrite composites exhibited reflection loss (RL) of <−10 dB for a bandwidth of 2.4 GHz and a maximum RL of −33 dB at 9.6 GHz. This performance was attributed to the larger magnetic loss and sufficient matching of electromagnetic parameters. This study provides a unique insight into the utilisation of Ni0.5Zn0.5Fe2O4 for producing lightweight and relatively thin RASs in the X-band at a low cost.

Effect performance of the nanomagnetic properties of Ni–Cu–Co ferrites by Al3+ ions adulteration

In this paper, aluminum-doped Ni–Cu–Co ferrite nanomagnetic material powder was prepared by sol–gel technique using citric acid as a complexing agent and high-purity nitrate as raw material. The effect of doping amount of different Al[Formula: see text] ions on the structure and magnetic properties of ferrites has been studied. The X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FTIR), Transmission electron microscopy (TEM), Energy dispersive X-ray (EDX) and Vibrating sample magnetometer (VSM) were used to characterize the structural and magnetic properties of ferrite. The XRD analysis showed that all samples of Ni–Cu–Co ferrites have a single-phase cubic spinel structure. Average crystallite size was calculated by the Debye–Scherrer formula and it was found that the average crystallite size of the sample was affected by the doping concentration. As the amount of Al[Formula: see text] ion doping increases, the crystallite size decreases from 54.88 nm to 46.09 nm. The absorption peak of Fourier transform infrared spectroscopy (FTIR) at 590 cm[Formula: see text] further indicates the formation of cubic spinel structure of Ni–Cu–Co ferrite. Transmission electron microscopy (TEM) images show the presence of particles which are spherically cubic-shaped particles. The constituent elements of the samples were analyzed by EDX spectroscopy. In addition, the ferromagnetism of the samples was confirmed by VSM measurements. The saturation magnetization (Ms) and remanent magnetization (Mr) first increase and then decrease when the aluminum ion concentration increases. Compared with pure samples and other doped samples, they have the best magnetic properties when the doping amount of Al[Formula: see text] ions is [Formula: see text]. It also shows that the prepared samples are suitable for magnetic recording materials.

RESEARCH OF MAGNETIC FIELD DISTRIBUTION IN THE WORKING AREA OF DISK SEPARATOR, TAKING INTO ACCOUNT AN INFLUENCE OF MATERIALS OF PERMANENT MAGNETS

Based on the results of a numerical-field analysis of the distribution of the magnetic force field in the working area of the disk magnetic separator, designed to clean bulk substances from ferromagnetic inclusions, the influence of the magnetic material of the poles of the magnetic system on the field distribution is determined. A consistent study of two magnetic systems assembled on the basis of magnetic materials of different classes is carried out. The finite element method implemented in the COMSOL Multiphysics software environment is used to calculate the distribution of magnetic induction in a disk magnetic separator with rare-earth and ferrite magnets. Due to the complexity of the spatial geometry of the force field in the working area of the disk magnetic separator, a three-dimensional model of the magnetic system is developed. A comparative analysis of the distribution of the magnetic force field in the working area of the disk separator with a highly coercive magnetic system and with a magnetic system based on ferrite blocks is carried out. As a result of the analysis, it is found that the indicators of the intensity and heterogeneity of the magnetic field for a highly coercive magnetic system significantly exceed the corresponding parameters of a ferrite magnetic system. It is proved that when choosing magnets for the magnetic system of a disk separator, preference should be given to highly coercive alloys, the magnetic properties of which significantly exceed the magnetic properties of ferrite magnets. To reduce the cost of the magnetic system of the disk separator, the use of a combined magnetic system assembled from magnetic materials of different classes is proposed. Studies of combined magnetic systems with various mass fractions of magnetic materials are done. The ratio of the mass fractions of magnets of various properties in the poles of the magnetic system is determined, at which sufficiently high magnetic characteristics are provided in the working area. It is shown that the presence of a ferrite fraction in the magnetic poles not only reduces the cost of the magnetic system of the separator, but also reduces the mass of the system. The tasks of further research are justified

Effect of Co2Y additive on power loss of Ni0.8Zn0.2Fe2O4 ferrites

Ba2Co2Fe12O22 (Co2Y, 0 wt%, 2 wt%)-added Ni0.8Zn0.2Fe2O4 polycrystalline ferrites are prepared by solid-state reaction method, and the magnetic properties of ferrites are investigated. Magnetic measurements show that the magnetic loss is obviously decreased with Co2Y addition. Loss separation reveals that both hysteresis loss and eddy current loss reduce significantly after Co2Y addition. The mechanism of magnetic loss decreasing due to Co2Y additive is discussed, and the decrease of magnetic hysteresis loss and eddy current loss caused by Co2+ cation doping was regarded as the main reason for the observed power loss decrease in ferrites and insulating grain boundary composed by barium compound which plays a role in decreasing eddy current loss. The Q value of Co2Y-added Ni0.8Zn0.2Fe2O4 ferrite was much higher than that of Ni0.8Zn0.2Fe2O4 sample which can be used as inductors for high-frequency applications.

A comparison study of the Structural and magnetic properties of pure Ni metal and NiZnMn ferrite

The magnetic properties of a pure Nickel metal and Nickel-Zinc-Manganese ferrites having the chemical formula Ni0.1(Zn0.4Mn0.6)0.9Fe2O4 were studied. The phase formation and crystal structure was studied by using x-ray diffraction which confirmed the formation of pure single spinel cubic phase with space group (Fd3m) in the ferrite. The samples microstructure was studied with scanning electron microstructure and EDX. The magnetic properties of the ferrite and nickel metal were characterized by using a laboratory setup with a magnetic field in the range from 0-500 G. The ferrite showed perfect soft spinel phase behavior while the nickel sample showed higher magnetic loss and coercivity.

Magnetic properties of indium doped Ni0.4Zn0.6InxFe2−xO4

The effect of indium ions doped Ni0.4Zn0.6InxFe2-xO4(x = 0∼0.20 in step of 0.05) prepared through solid-state reaction has been investigated. The structure and magnetic properties of ferrites are characterized by x-ray diffraction, SEM and BH analyzer. X-ray diffraction results reveal that the samples have cubic spinel structure and the lattice constant slightly increases with In doping content increase. SEM images show that average grain size grows with indium doping and EDS spectral confirm the composition of ferrites. Magnetic measurement indicated that permeability of ferrites decreases as indium doping content increases, but power loss increases with In3+ doping. Hysteresis loss shows a novel decrease at low frequency in heavily indium doped ferrites.

Structure and magnetic properties of Ni0.5Zn0.5Mn0.5-xMoxFe1.5O4 ferrites prepared by sol-gel auto-combustion method

A series of Mo doped Ni-Mn-Zn ferrites compounds with the formula Ni0.5Zn0.5Mn0.5-xMoxFe1.5O4 (x = 0, 0.025, 0.05, 0.075 and 0.1) were first synthesized by sol-gel auto-combustion method. The X-ray diffraction (XRD), field emission scanning electron microscopy (FESEM), Fourier transform infrared spectroscopy (FTIR), and vibrating sample magnetometer (VSM) analysis were carried out to characterize the microstructural and magnetic properties of ferrites. Rietveld refinement of X-ray diffraction data confirmed the formation of cubic spinel structure and the emergence of FeMoO4 phase with the substitution of Mo6+ contents. The grain size increased remarkably due to the formation of the liquid phase. The saturation magnetization (Ms) increased while the coercivity (Hc) decreased from 67.3 to 12.1 Oe due to the decrease of magneto-crystalline anisotropy constant. The initial permeability (μi) increased significantly from 34 (x = 0) to 114 (x = 0.075) and later decreased for x = 0.1. In our experiment, Ni0.5Zn0.5Mn0.425Mo0.075Fe1.5O4 ferrite presented the best microstructure and soft magnetic properties.

Effect of Magnetic Pulse Processing on the Structure and Magnetic Properties of Ferrites

The effect a pulsed magnetic field has on the crystal structure and macroscopic magnetic parameters of hexagonal ferrites BaFe12O19 and SrFe12O19 are studied. It is shown that changes in the physical properties of ferrites are due to the ordering of cation vacancies on the boundaries of hexagonal and spinel blocks that minimize local distortion of the oxygen polyhedrons. Violation of the collinear ordering of the magnetic moments of iron ions in the nonequivalent positions of SrFe12O19 ferrite is observed, due to the selective localization of such vacancies (and thus violations of the magnetic relationships in Fe–O–Fe).

Fabrication of M-type ferrites with high La-Co concentration through Ca2+ doping

Ca2+ doped Sr0.45-xCaxLa0.55Fe11.6Co0.4O19 (x = 0, 0.15, 0.3, and 0.45) ferrites were fabricated through a conventional ceramic process. The influences of Ca2+ doping on the microstructure and magnetic properties of ferrites were investigated. Ca2+ doping could mitigate the presence of impurity phase (CoFe2O4) in ferrites. Single phase M-type ferrites could be fabricated when x ≥ 0.3. Additional Co2+ ions entered the crystal lattice and preferentially occupied the 4f2 site with Ca2+ doping. This effect greatly improved the remanence (Br) and intrinsic coercivity (Hcj) when x increased from 0 to 0.3. The average grain size of sintered ferrites slightly increased with the amount of doped Ca2+ ions. This behavior led to the deterioration of Hcj when x increased from 0.3 to 0.45. Consequently, ferrite prepared with x = 0.3 presented the highest maximum energy product ((BH)max) of 5.24MGOe. This performance is much higher than that of conventional La-Co substituted Sr-ferrites.

Structural, magnetic and hyperfine characterizations of nanocrystalline Zn-Cd doped nickel ferrites

In our present work, we have synthesized a series of Cd-Zn doped nickel ferrite ((Cd0.5−xZnx)Ni0.5Fe2O4; x=0, 0.1, 0.2, 0.3, 0.4 and 0.5) through standard chemical co-precipitation method to study the influence of diamagnetic ions (Cd, Zn) on the magnetic properties of ferrites. XRD and Raman spectroscopy were employed for the structural characterizations. The refinement of the X-ray diffractogram data augmented by the Williamson-Hall plots showed the presence of Cd2+ vacancies and a strained crystal structure. The vibrational spectroscopy indicated the presence of lower space-group symmetry and a distorted crystal structure. Magnetic measurements showed the samples possessed low magnetic anisotropy along with a canted spin structure. The Mössbauer measurements confirmed the cation distribution and gave evidence of super transferred hyperfine interactions arising due to canted spin structure of the system.

Structural and Magnetic Properties of Nickel Substituted Mg Ferrites

Polycrystalline ferrites with general formula NixMg1-xFe2O4 (0.0 ≤ x≤ 0.5) were synthesized by solid state reaction method. The existence of cubic spinel structure of ferrites was confirmed by X-ray diffraction (XRD) measurement which belongs to the space group of Fd3m - Oh7. Crystallite size of ferrites was estimated by using Debye-Scherer formula; it varies from 930 nm to 1.04 μm. The lattice constant, interplanar distances and miller indices were estimated by using X-ray diffraction measurement. The lattice constant increases with increase in Ni content. Porosity of ferrites was estimated by using Hendricks and Adams method; it is found to increase with increase in Ni content and maximum porosity 22.4% was observed for Ni0.5Mg0.5Fe2O4 ferrites. The dielectric constant decreases with increase in frequency shows dielectric dispersion behavior which is predicted by Maxwell-Wagner type interfacial polarization and is in good agreement with Koops phenomenological theory. AC conductivity increases with increase in frequency shows small polarons type of conduction mechanism. The magnetic properties of ferrites were studied by using M-H hysteresis loop and measured saturation magnetization and magnetic moment of the ferrites.

The structure and magnetic properties of NiCuZn ferrites sintered via a two-step sintering process

Fine powders of Ni0.4CuxZn0.6−xFe2O4, where 0≤ x ≤0.25, were prepared by sol–gel auto-combustion method. A two-step sintering process and the traditional final-stage sintering process have been adopted to produce NiCuZn ferrite toroidal specimens. The densification, microstructure, and magnetic properties of the ferrites have been investigated. It has been found that the sample produced by a two-step sintering process has a higher sintered density than the sample produced by the traditional final-stage sintering process, and the former gives rise to a higher initial permeability, especially when x = 0.15. Both the two sintering processes have no impact on Curie temperature which is only dependent on Cu-substituted content. The two-step sintering process is an effective method to produce high-density ferrites with improved soft magnetic properties.