Magnetic Properties Of MnZn Ferrites Research Articles

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.

Ferrite materials with high saturation magnetic induction intensity and high permeability for magnetic field energy harvesting: Magnetization mechanism and Brillouin function temperature characteristics

Manganese-zinc (MnZn) ferrites play an indispensable role in energy transform and harvesting. It is notable to mention that the combined enhancement of initial permeability (μi), saturation magnetic induction (Bs) and Curie temperature (Tc) is conducive to improving the output power and safety of magnetic field energy harvesting devices. In this paper, high permeability MnZn ferrites were synthesized by a conventional oxide ceramic method. The thermomagnetic curves of MnZn ferrites were fitted according to the Néel molecular field theory (NMFT) and the Brillouin function. Then the molecular field coefficient γaa, γab, γbb, and Tc were calculated. Aiming at the magnetization mechanism of permeability, the contributions of domain wall motion and spin rotation were analyzed by fitting the complex permeability spectrum. Furthermore, the temperature characteristics of μi and Bs are analyzed, and we simulated and compared the effect of different magnetic properties of MnZn ferrites on the output of non-invasive magnetic field harvester. The MnZn ferrites with superior comprehensive performance own potential applications for non-invasive magnetic field harvester.

Effect of a YIG nanoparticle additive on the magnetic properties of MnZn ferrites for MHz frequency applications

AbstractIn this study, MnZn ferrites with added YIG nanoparticles were developed for MHz frequency applications. The effect of the magnetic YIG additive on the power loss, initial permeability, and cutoff frequency of MnZn ferrites was investigated. A small quantity of added YIG effectively reduces the power loss and concurrently increases the initial permeability. Compared to the results for the MnZn ferrite with no added YIG, the optimal MnZn ferrite with 600 ppm added YIG exhibits a reduction in the power loss at 25°C of 56.4% and 36.6% at 1 MHz/50 mT and 3 MHz/10 mT, respectively, and a 13.9% increase in the initial permeability. This sample also exhibits a good stability of the power loss against temperature. The power loss remains below 205 kW/m3 over temperatures ranging from 25 to 140°C. The effect mechanism of YIG addition on the magnetic properties of MnZn ferrites was studied. An analysis based on the equivalent circuit model showed that the reduction in the eddy current loss and power loss mainly results from the increase in the grain boundary resistance caused by the addition of highly resistive YIG.

Effect of Ni substitution and annealing temperature on structural and magnetic properties of MnZn-Ferrites: Cytotoxicity study of ZnO and SiO2 coated core shell structures

Magnetic spinel ferrite nanoparticles (NPs) have a broad scope of applications based on their structural properties, including in lithium-ion batteries, catalysts, electrochemical energy storage, drug delivery, magnetic hyperthermia, and photothermia. In this study, we investigated the structure, crystallographic phase formations, and magnetic properties of Ni-substituted MnZn ferrites (MZFs), Mn(0.6-x)Zn(0.4-y)Ni(x+y)Fe2O4 (x = 0–0.6, y = 0; y = 0–0.4, x = 0) compositions of as-prepared (AP) and air annealed (350–1200 °C) samples. All AP NPs exhibited a pure spinel structure. Ni-MZF compositions annealed at 600 °C had high α-Fe2O3 secondary phase content in Ni-MZFs (Ni substituted for Zn), whereas Ni-MZFs with x = 0.4 (Ni substituted for Mn) had no impurities, and its magnetization (50 emu/g) was enhanced compared with that of the other samples. X-ray photoelectron spectroscopy revealed that Fe3+ cations were present in tetrahedral and octahedral sites. The single spinel phase reappeared with improved crystallinity in all Ni-MZFs by annealing at 1200 °C and exhibited superior magnetization (60–73 emu/g) compared with that of MZF (35 emu/g). Additionally, the spinel phase was stabilized in the ZnO- and SiO2-coated Ni-MZF core shell structures annealed at 700 °C with higher magnetization than MZF. Moreover, Ni-MZF core shell structures exhibited biocompatibility and may have biomedical applications.

Evolution of structure and magnetic properties in MnZn ferrite-silica nanocomposites fabricated by sol–gel method

We explore the influence of the silica matrix on size, spinel phase stability, and magnetic properties of MnZn ferrite. For this purpose, Mn0.6Zn0.4Fe2O4 (MZF) nanoparticles (NPs) dispersed in silica (SiO2) matrix [MZF1−x/(SiO2)x x = 0, 10, 30%] synthesized by one-pot sol–gel process. The evolution of a pure spinel phase is apparent from the as-prepared (AP) MZF/SiO2 (30%) amorphous state on annealing in the temperature range 600–900 °C in air, whereas the AP free-standing MZF NPs exhibit a secondary phase of α-Fe2O3 along with spinel structure in this temperature range. The crystallite size is 5 ± 1 nm for a 600 °C annealed sample and increases to 10 ± 1 nm for a 900 °C annealed sample. From the detailed analysis of the temperature and magnetic field-dependent magnetization data, it is found that the AP sample exhibits weak magnetic behavior. However, annealed samples exhibit a maximum in zero-field-cooled magnetization at a certain temperature (TP), which increases with the increase of annealing temperature. The M–H curves above TP indicate the presence of superparamagnetic (SPM)-like behavior. From the present study, we show that the phase stability and magnetic properties of MZF/SiO2 composites have improved compared to bare MZF NPs.

Optimizing the Soft Magnetic Properties of Mn-Zn Ferrite by a Proper Control of Sintering Process

Manganese zinc (Mn-Zn) ferrites were prepared by solid-state reaction. The sintering process was investigated in detail using differential scanning calorimetry/thermogravimetric analysis and x-ray diffraction characterizations. A three-step weight loss was observed and the main Mn-Zn ferrite formation reaction was detected. Two-step heat treatment was employed to achieve high density Mn-Zn ferrite. For sintering temperatures from 1300°C to 1400°C, crystal grains of Mn-Zn ferrite became uniform with larger size and more equiaxed shape. The grain boundaries changed from curved to straight. Such features were believed helpful for the magnetic domain wall movement. In addition, better diffusivity at higher sintering temperature homogenized the distribution of impurities which also facilitated the magnetic domain alignment. Thanks to the microstructure acquired by controlling the sintering process, a high-amplitude permeability of 1151, a low total loss of 411 W/kg and coercivity of 57.63 A/m at 65 kHz were simultaneously achieved on samples sintered at 1400°C.

Effect of Calcination Temperature on Magnetic Properties of MnZn Ferrites for High Frequency Applications

With the development of switching power supplies, miniaturization and high efficiency become hot research issues, and decreasing high-frequency losses is an effective method to achieve it. In this article, the effect of different calcination temperature on the power losses of MnZn ferrites at high frequency (500 kHz) over a broad temperature range is reported. The MnZn ferrites samples were prepared by ceramic process and the effect of calcination temperature was analyzed. The raw materials were calcined at 775 ℃, 800 ℃, 825 ℃, 850 ℃, 875℃, 900 ℃, 925 ℃ and 950 ℃, and the regular fluctuations of particle size (as-calcined), density (as-sintered) and magnetic properties are presented in this work. It is shown that the samples calcined at 850 ℃ exhibit optimal microstructure and magnetic properties. The newly developed MnZn ferrites are characterized by sintered density of 4.61 g/cm³, initial permeability of 1223 (10 kHz/0.1 mT/25 ℃), saturation magnetic flux density of 488 mT (10 kHz/1200 A/m/25 ℃) and power losses of 68 mW/cm³ (500 kHz/50 mT/100 ℃).

Influence of starting powder milling on magnetic properties of Mn-Zn ferrite

In this paper, the influence of additional sieving and milling of starting industrial Mn-Zn powders on magnetic properties was investigated. The starting powder was milled for 60 minutes, followed by sieving through 325 and 400 meshes. The starting and milled powders were used to fabricate toroid shaped samples sintered at 1200?C for 2 hours. Structural parameters of the fabricated samples were analysed by X-ray diffraction and scanning electron microscopy. Complex permeability, core loss density, and hysteresis were measured using the modified watt-meter method. The complex permeability and hysteresis loop were modelled with a new model proposed in the paper. The core loss density was modelled with the Steinmetz empirical equation. The experimental results and calculations show the significance of the additional milling and sieving process on magnetic properties of Mn-Zn ferrite in the frequency range 0.1-10MHz. These processes increase the relative permeability about 3 times and decrease the core loss 4 times by milling of the starting powder.

Effects of heating processing on microstructure and magnetic properties of Mn-Zn ferrites prepared via chemical co-precipitation

The fine powders of Mn-Zn ferrites with uniform size were prepared via chemical co-precipitation method. X-ray diffraction analysis (XRD), scanning electron microscopy (SEM), vibrating sample magnetometer (VSM), frequency dependence of permeability and metallographical microscope were used to investigate the crystal structure, surface topography and magnetic properties of the powders and the sintering samples. The experimental results demonstrate that the precursor powders have formed a pure phase cubic spinel Mn x Zn1−x Fe2O4 while in the reactor and show definite magnetism, which can solve the difficult issue in washing process effectively. When calcined beneath 450 °C, the powders have intact crystal form and the crystallite size is less than 20 nm. Comparison tests of sintering temperatures show that 1 300 °C is the ideal sintering temperature for Mn-Zn ferrites prepared by using the chemical co-precipitation.

Effect of heating rate on densification and magnetic properties of MnZn ferrites sintered by multiphysical fields coupling methodology

This work has provided a novel idea of fabricating MnZn bulk ferrite materials. MnZn ferrite powders with a composition of Zn0·8Mn0·2Fe2O4 (wt-%) were sintered under coupled multiphysical fields applied by Gleeble-1500D thermal simulation instrument. Cylindrical bulk ferrites with a diameter of 2·5 mm and a height of 2·5 mm were prepared, and the effect of heating rate on densification and magnetic properties of MnZn ferrites was studied. The results show that the densification and magnetic properties of MnZn ferrite were directly affected by the heating rates. A relative density of up to 98·5% was achieved when the heating rate of 100°C s−1 was used. Such magnetic properties as maximum energy product and remanence of MnZn ferrite sintered under coupled multiphysical fields are improved when compared to samples produced by conventional sintering. In particular, a 204·39% increase in maximum energy product is obtained. Finally, the densification mechanisms of multiphysical fields sintering method are discussed.

Effect of Oxygen Content during Sintering on the Losses of MnZn Ferrites

The magnetic properties of MnZn ferrites are highly influenced by the partial oxygen pressure during sintering. In this work MnZn ferrites with different chemical compositions were pressed in a toroidal form and sintered at 1290 °C for 6 h at different oxygen pressures. X ray diffraction using K-edge radiation of Fe, Zn and Mn were performed in order to identify the atomic preference in the MnZn ferrite spinel structure, by means of Rietveld analysis. Magnetic losses were measured at 25 °C and 100 °C (200mT, 100 kHz). The high temperature loss decreased with the increase of oxygen content during sintering whereas at room temperature this effect was opposite. The losses behavior as function of frequency was analyzed according the loss separation model.

Effects of Eu<sup>3</sup><sup>+</sup> Substitution on Nanosized Mn-Zn Ferrite Powders Synthesized by Combustion Processing

A series of Eu3+-substituted Mn 0.65 Zn 0.35 Fe 2-x EuxO4 ( x = 0.00-0.04) nanoscaled ferrites were synthesized by a citrate sol-gel combustion processing. The effects of Eu 3+ substitution on the crystalline formation, microstructure and magnetic properties of Mn-Zn ferrite annealing at temperature from 500°C to 800°C were investigated. The results showed that the lattice parameter increased and it contributed to monophase spinel with the addition of Eu 3+ at x≤ 0.03. The remanence and coercive field increased with Eu 3+ substitution but it changed slightly in saturation magnetization when annealing ferrite powders at 700°C.

Soft magnetic properties of MnZn ferrites prepared by powder injection moulding

In this study, properties of soft-magnetic manganese zinc ferrite manufactured by powder injection moulding - PIM technology were presented. A powder consisting of Mn1- xZnxFe2O4 with small addition of hematite ?-Fe2O3 was mixed with an organic binder (wax and thermoplastic) to form ferrite feedstock. The ferrite feedstock was injected in a mould with a cavity shaped like a small cylinder with a hole on the main axis. Injection moulded samples were then solvent, thermally debinded and sintered in air atmosphere. Structure of sintered sample was characterized using X-ray diffractometry, scanning electron microscopy and thermomagnetic measurements. Magnetic properties were measured by hysteresis graph at different frequencies up to 1 kHz. Sintered sample contains a mixture of two phases Mn0.6Zn0.4Fe2O4 (68 wt. %) and ?-Fe2O3 (32 wt. %). The Curie temperature is TC ? 220?C for the green sample but after the heating up to 470?C, TC increase up to about 300?C. The high increase of normalized magnetic permeability of about 800 % was observed due to melting and burning of binder. The hysteresis loop of sintered MnZn ferrite toroidal cores has an R-shape with saturation of 0.44 T and remanence ratio of 0.49. The low value of coercivity (only 47 A/m) was related to the presence of ?-Fe2O3 crystalline phase and attained already optimum density (? ? 4.8 g/cm?) i.e. observed low level of porosity. Attained relative magnetic permeability ?r ? 2000 as well as power losses Ps ? 21 W/kg for sintered sample (at 1 kHz; 0.39 T) is in agreement with the MnZn ferrite commercial samples.

Structure and Magnetic Properties of Mn-Zn Ferrite Synthesized by Glycine-Nitrate Auto-Combustion Process

Manganese-Zinc ferrites belong to the group of soft ferrite materials characterized by high magnetic permeability and low power loses. These materials are mainly used as cores for inductors, transformers, recording heads and noise filters among others. In this study, nanocrystalline Mn-Zn ferrite with the chemical formula Mn1-xZnxFe2O4withx=0.2, 0.4, 0.6, 0.8 has been successfully synthesized by glycine-nitrate auto-combustion process using glycine as a fuel and nitrates as oxidants. The structures and magnetic properties of the resulting powder were investigated by X-ray diffraction (XRD), scanning electron microscopy (SEM) and vibrating sample magnetometer (VSM). It is revealed from the XRD pattern than a significant amount nanocrystalline Mn1-xZnxFe2O4ferrite with average crystallite size in the range 43.25-66.7 nm has been formed. The magnetic measurement gives a typical value of saturation magnetic of 34-69 emu/g and coercivity of 40-60 Oe.

Microstructure and temperature dependence of magnetic properties of CuO-added MnZn ferrites

MnZn ferrites with the chemical formula Mn0.68Zn0.25Fe2.07O4 have been prepared by a conventional ceramic technique. Then, the effects of CuO addition on the microstructure and temperature dependence of magnetic properties of MnZn ferrites were investigated by characterizing the fracture surface micrograph and measuring the magnetic properties over a temperature ranging from 25 to 120°C. The results show that the lattice constant and average grain size increase with the increase of CuO concentration. When the CuO concentration is below 0.07 wt.%, the initial permeability and saturation magnetic flux density increase monotonously, and the temperature of the secondary maximum peak in the curve of initial permeability versus temperature and the lowest power loss shift to a lower temperature with the increase of CuO concentration. However, excessive CuO concentration (>0.07 wt.%) results in abnormal grain growth and porosity increase, which causes the initial permeability and saturation magnetic flux density decrease and the power loss increase at room temperature. Furthermore, the temperature of the secondary maximum peak in the curve of initial permeability versus temperature and the lowest power loss shift to a higher temperature.

Modelling magnetic properties of MnZn ferrites with the modified Jiles–Atherton description

Consideration of temperature and anisotropy effects in hysteresis modelling allows for tailoring the operation point of magnetic circuits. The recently modified Jiles–Atherton model has been extended to describe the hysteresis loops in MnZn ferrites for two temperatures below the Curie point. Anisotropy is modelled by a proper choice of the value of the quantum number J in the Brillouin function.

Preparation and magnetic properties of Mn-Zn ferrites by the Co-precipitation method

Mn-Zn ferrites (Mn1−xZnxFe2O4) with different compositions were prepared by the coprecipitation method, and the influences of such synthesis conditions as pH value, composition and volume ratio (R) of the mixed solution and NH4HCO3 solution on their microstructures and magnetic properties were discussed. The samples were characterized by X-ray diffraction (XRD) and magnetization measurement instrument. Lattice parameters and average crystalline size of the synthesized materials were calculated from the corresponding XRD patterns with the related software Jade.5. For samples of different pH values, only one phase was found when pH values were 7.0, 8.0 and 9.0. The sample with pH value of 7.0 exhibited the highest saturation magnetic induction, the lowest coercive force, and crystallized best. For samples of different R values with pH value of 7.0, only one phase was observed in all samples, and the sample with R value of 2.3 exhibited the highest saturation magnetic induction and the lowest coercive force. The composition has mainly afected the magnetic properties, and the saturation magnetic induction increases with the increase of the content of Zn (x), but decreases when x is beyond 0.6. The trend of coercive force is on the contrary. However, no magnetism is exhibited when the x value is up to 0.8.

Microstructure and magnetic properties of Sn-substituted MnZn ferrites

Sn-substituted MnZn ferrites were prepared by conventional oxide ceramic process. The influences of Sn substitution on microstructure and magnetic properties of MnZn ferrites were investigated. The results indicated that with increase of Sn substitute concentration, the diffraction peaks shifted slightly towards the lower angles and the lattice parameter ( a) increased. And at room temperature, the bulk density ( d m), initial permeability ( μ i), saturation magnetic induction ( B s) and electrical resistivity ( ρ) of Sn-substituted MnZn ferrites all increased initially and then decreased with the further increase of Sn substitute concentration, while the power losses decreased first and then increased subsequently. Meanwhile, the temperature of secondary maximum peak of μ i– T curve and the minimum losses moved to lower temperature while the Sn substitute concentration increased. When the content of Sn substitution was 0.3 mol%, at room temperature, the initial permeability, saturation magnetic induction, density and electrical resistivity reached their maxima, while the hysteresis loss ( P h), eddy current loss ( P e) and total losses ( P cv) achieved their minima. The P h∼ T and μ i– T curves varied contrarily, and due to the contribution of extra eddy current loss ( P e,exc) that was proportional to P h, the P e– T curve did not agree with its classical expression. Finally, MnZn ferrite substituted with 0.3 mol% SnO 2 shows the highest initial permeability (3894) and lowest losses (303 kW/m 3) at room temperature.

Study of Mn 3O 4 doping to improve the magnetic properties of MnZn ferrites

The effect of Mn 3O 4 doping on the magnetic properties of MnZn ferrites is studied. It is found that adding Mn 3O 4 as a dopant after pre-sintering, in contrast with the traditional approach of adjusting Mn 3O 4 content in the main composition, results in different magnetic properties of MnZn ferrites. Compared to its corresponding sample, 500 ppm Mn 3O 4 addtion raises the initial permeability of MnZn ferrite sample by 12.97%, and the saturated magnetic induction by 7.45%, and reduces its power loss by up to 23%. The improvement of magnetic properties will be strengthened with the increase of Mn 3O 4 doping amount before it reaches 0.5 wt%, continue increasing the doping amount, and the improvement will be gradually impaired. It is also found that suitable amount of Mn 3O 4 addition mainly reduces the hysteresis loss of MnZn ferrites at frequencies below 200 kHz, and when it is above 200 kHz, the eddy current loss can be considerably reduced. XRD and SEM data reveal that Mn 3O 4 doping results in no obvious change in the microstructure of MnZn ferrites.

Effects of Ta 2O 5 addition on the microstructure and temperature dependence of magnetic properties of MnZn ferrites

MnZn ferrites with the chemical formula Mn 0.68Zn 0.25Fe 2.07O 4 have been prepared by the conventional ceramic technique. Toroidal cores were sintered at 1350 °C for 4 h in N 2/O 2 atmosphere with 4% oxygen. Then the influence of Ta 2O 5 addition on the microstructure and temperature dependence of magnetic properties of MnZn ferrites was investigated by characterizing the fracture surface micrograph and measuring the magnetic properties over a temperature ranging from 25 to 120 °C. The results show that, when the Ta 2O 5 concentration is not more than 0.04wt%, the grain size has a slight increase with the increase of Ta 2O 5 concentration, the temperature of secondary maximum peak in the curve of initial permeability versus temperature and the lowest power loss shift to lower temperature. However, excessive Ta 2O 5 concentration (>0.04wt%) results in the exaggerated grain growth and porosity increase, which make the initial permeability and saturation magnetic flux density decrease and the power loss increase at room temperature. Furthermore, the temperature of secondary maximum peak in the curve of initial permeability versus temperature and the lowest power loss shift to about 100 °C.