Mn-Zn Ferrite Research Articles

The Effects of Bto with a Ptc Characteristic on the Mnzn Ferrites for Applications in the Frequency Range of 100-300khz

The Effects of Bto with a Ptc Characteristic on the Mnzn Ferrites for Applications in the Frequency Range of 100-300khz

A DNA Nanocomplex Containing Cascade DNAzymes and Promoter-Like Zn-Mn-Ferrite for Combined Gene/Chemo-dynamic Therapy.

Sequential control of exogenous chemical events inside cells is a promising way to regulate cell functions and fate. Herein we report a DNA nanocomplex containing cascade DNAzymes and promoter-like Zn-Mn-Ferrite (ZMF), achieving combined gene/chemo-dynamic therapy. The promoter-like ZMF decomposed in response to intratumoral glutathione to release a sufficient quantity of metal ions, thus promoting cascade DNA/RNA cleavage and free radical generation. Two kinds of DNAzymes were designed for sequential cascade enzymatic reaction, in which metal ions functioned as cofactors. The primary DNAzyme self-cleaved the DNA chain with Zn2+ as cofactor, and produced the secondary DNAzyme; the secondary DNAzyme afterwards cleaved the EGR-1 mRNA, and thus downregulated the expression of target EGR-1 protein, achieving DNAzyme-based gene therapy. Meanwhile, the released Zn2+ , Mn2+ and Fe2+ induced Fenton/Fenton-like reactions, during which free radicals were catalytically generated and efficient chemo-dynamic therapy was achieved. In a breast cancer mouse model, the administration of DNA nanocomplex led to a significant therapeutic efficacy of tumor growth suppression.

A DNA Nanocomplex Containing Cascade DNAzymes and Promoter‐Like Zn‐Mn‐Ferrite for Combined Gene/Chemo‐dynamic Therapy

AbstractSequential control of exogenous chemical events inside cells is a promising way to regulate cell functions and fate. Herein we report a DNA nanocomplex containing cascade DNAzymes and promoter‐like Zn‐Mn‐Ferrite (ZMF), achieving combined gene/chemo‐dynamic therapy. The promoter‐like ZMF decomposed in response to intratumoral glutathione to release a sufficient quantity of metal ions, thus promoting cascade DNA/RNA cleavage and free radical generation. Two kinds of DNAzymes were designed for sequential cascade enzymatic reaction, in which metal ions functioned as cofactors. The primary DNAzyme self‐cleaved the DNA chain with Zn2+ as cofactor, and produced the secondary DNAzyme; the secondary DNAzyme afterwards cleaved the EGR‐1 mRNA, and thus downregulated the expression of target EGR‐1 protein, achieving DNAzyme‐based gene therapy. Meanwhile, the released Zn2+, Mn2+ and Fe2+ induced Fenton/Fenton‐like reactions, during which free radicals were catalytically generated and efficient chemo‐dynamic therapy was achieved. In a breast cancer mouse model, the administration of DNA nanocomplex led to a significant therapeutic efficacy of tumor growth suppression.

Effect of Dy3+ substitution on microwave behaviour of nanocrystalline Mn-Zn Ferrite

Microwave-hydrothermal (M-H) method had been employed to synthesize a series of Dy3+doped Mn-Zn ferrite Mn0.6Zn0.4Fe2–xDyxO4 (x=0, 0.01, 0.03, 0.05, 0.07, 0.09) nanopowders at 160°C/30 min. The prepared samples have been characterized by Fourier Transform Infrared Spectrometer. The grain size of sintered ferrites are in the range of 60-70 nm. Decrease in saturation magnetization and increase in coercivity were observed with an increase of Dy3+ concentration in Mn-Zn ferrites. The complex permeability and complex permittivity of the prepared samples were measured in the frequency range of 2–18 GHz using a using a vector network analyzer. It is observed that small variation of Dy3+ substitution in spinel ferrite tailored microwave absorbing parameters dramatically. The reflection loss (RL) increased with the Dy3+ content upto x ≤ 0.03. The sample with x=0.03 of thickness 2.3 mm showed minimum reflection loss of -20.5 dB with a bandwidth of 3.8 GHz. Thus the present materials exhibit good microwave absorption properties and hence can act as EMI suppressors. Copyright © 2018 VBRI Press.

Effect of sintering temperature on structural, magnetic, dielectric and optical properties of Ni–Mn–Zn ferrites

Spinel ferrite [Formula: see text][Formula: see text][Formula: see text]Fe2O4 was prepared by a conventional ceramic process followed by sintering at three different temperatures (1050[Formula: see text] C, 1100[Formula: see text] C and 1150[Formula: see text] C). X-ray diffraction (XRD) investigations stated the single-phase cubic spinel structure and the FTIR spectra revealed two prominent bands within the wavenumber region from 600 cm[Formula: see text] to 400 cm[Formula: see text]. Surface morphology showed highly crystalline grain development with sizes ranging from 0.27 [Formula: see text]m to 0.88 [Formula: see text]m. The magnetic hysteresis curve at ambient temperature revealed a significant effect of sintering temperature on both coercivity ([Formula: see text] and saturation magnetization ([Formula: see text]. Temperature caused a decrease in DC electrical resistivity, while the electron transport increased, suggesting the semiconducting nature of all samples and that they well followed the Arrhenius law from which their activation energies were determined. The values of Curie temperature ([Formula: see text] and activation energy were influenced by the sintering temperature. Frequency-dependent dielectric behavior (100 Hz–1 MHz) was also analyzed, which may be interpreted by the Maxwell–Wagner-type polarization. The UV–vis–NIR reflectance curve was analyzed to calculate the bandgap of ferrites, which showed a decreasing trend with increasing sintering temperature.

Electron beam sintering of Mn-Zn ferrites using a forevacuum plasma electron source

The article presents the results of electron beam sintering without applying pressure of Mn-Zn ferrites in an oxygen environment. Samples for sintering were made from fine powders and pressed at various pressures into compacts in the form of disks. Measurements of the elemental composition and structure of the sample after sintering are presented. It is shown that the result of sintering depends on the pressing pressure of compacts, time and temperature of sintering.

Preparation and study magnetic properties of the nanosized ferrite Zn0.5Mn0.5Fe1.95Mo0.02Tb0.01Sm0.01Gd0.01O4 with negative magnetization. A new result

ABSTRACT This work, concern the studies of the local atomic structure of the rare-earth doped Zn-Mn ferrite (Zn0.5Mn0.5Fe1.95Mo0.02Tb0.01Sm0.01Gd0.01O4), characterization techniques such as thermogravimetric analysis, X-ray diffraction (XRD), and Magnetic Properties Measurement System (MPMS), allowed us the effect of rare earth and their impacts on the structure, the size of nanocrystals, and the magnetic properties of the formed nano-ferrite. The XRD analysis showed that a single-phase was obtained at a low temperature of 500°C, with an environmentally friendly process, and nanometric size (8 nm). Magnetic measurements show a superparamagnetic behavior at 80 and 300 K and a week ferrimagnetism at 5 K. Furthermore, these measurements showed that this sample exhibits negative magnetization under zero-field cooled measurements (ZFC) with a low applied field (100 Oe), while the magnetization remains positive under field-cooled (FC) measurement conditions for the same applied field, which is a new result never observed in the case of Zn-Mn doped nano-ferrite.

On the modelling of the anhysteretic magnetization of homogeneous soft magnetic materials

The analysis and optimization of devices with soft magnetic cores, such as inductive sensors and electric machines, rely on a simple and precise modelling of their nonlinear anhysteretic magnetization. The Langevin-Weiss equation of state has the advantages of being physically-based and capable of accurately describing isotropic materials. In fact, it has even been adopted as the backbone of the popular Jiles-Atherton model to describe magnetic hysteresis. However, many studies show the difficulty of retrieving the modelling parameters given an experimental anhysteretic curve, for which stochastic optimization methods are generally used.In this work, we present a simple and deterministic method for finding the parameters of the Langevin-Weiss model: the saturation magnetization, the temperature dependent a parameter, and the molecular field constants. To this end, we optimize a problem with a nonlinear solver where the fitting variables are instrinsically bounded. We validated the approach by analyzing three widely used soft magnets; a grain-oriented silicon steel, a Mn-Zn soft ferrite, and a Fe-based nanocrystalline alloy with induced anisotropy.We demonstrate that, contrary to what has previously been assumed, the Langevin-Weiss function can provide a good description of the anhysteretic magnetization of any homogeneous material, even materials with strong transverse uniaxial anisotropy. The key, which seems to have been overlooked, is to allow the Weiss molecular field to be negative.

Synthesis of La-doped Mn0·6Zn0.4LaxFe2-xO4 and the study of its structural, electrical and magnetic properties for high frequency applications

Lanthanum doped Mn–Zn Ferrite nanoparticles, Mn0·6Zn0.4LaxFe2-xO4 (x = 0.00–0.10 in steps of 0.02), employing oxides of raw materials has been prepared by the conventional solid state reaction (SSR) route. The structural characteristics of resulting ferrite products are investigated by powder X-ray diffraction (XRD) confirming the formation of spinal cubic crystal structure of Mn–Zn Ferrite with privileged orientation along (311). The crystallite size, lattice constant, dislocation density, strain and other microstructural parameters have been traced as a function of the La content (x). FTIR results demonstrate the existence of functional groups associated with Mn–Zn ferrite observing the corresponding peaks at 423 cm−1 and 529 cm−1. The Eg values are lying between 1.23 eV and 1.30 eV studied by exploiting UV–Vis absorption. The ferromagnetic behavior of Mn–Zn ferrite products has been found with the help of PPMS. The saturation magnetization (MS) of bare sample is much larger than that of doped ferrites and decreases with the increasing amount of La content. The coercivity (HC) increases with La introduction and the remnant magnetization reduces from 0.8447 emu/gm to 0.1436 for lower La content (x = 0.02), while it increases at higher La content (x = 0.04–0.10). Dielectric properties and AC resistivity have been extracted from the measurement of impedance analyzer at ambient temperature. The values of dielectric constant are found to be higher in bare Mn–Zn ferrite than La doped Mn–Zn ferrite products.

Investigation on the formation, structural and photocatalytic properties of mixed Mn-Zn ferrites nanoparticles embedded in SiO2 matrix

The structure, morphology and photocatalytic features of the Mn-Zn ferrite nanoparticles embedded in SiO2 matrix produced by a modified sol-gel synthesis were investigated. The synthesis consists of mixing the metal nitrates, 1,4-butanediol and tetraethylorthosilicate, formation of the SiO2 matrix by gelation, formation of the metallic succinate precursors by heating the gel up to 200 °C and formation of the ferrite system by thermal treatment at higher temperatures. The formation of Mn-, Zn- and Fe-succinate precursors up to 200 °C and their decomposition into ferrites up to 400 °C was confirmed both by thermal analysis and Fourier-transform infrared spectroscopy. The X-ray diffraction provided information on the crystalline phases, crystallite size and lattice constant, while the morphology of the samples was investigated by transmission electron microscopy. The crystallite size increased (30.5–53.4 nm), while the energy band gap of the samples decreased (2.09−1.33 eV) with the increase of the Mn content in the ferrite; thus, the amount of manganese nitrate used in the synthesis could be an easy tailoring approach of the mixed Mn-Zn ferrites. All samples showed sonophotocatalytic activity, being able to degrade Rhodamine B under visible light irradiation, Mn0.3Zn0.7Fe2O4@SiO2 sample having the best sonophotocatalytic performance.

Correlating the microstructure and magnetic properties of MnZn power ferrites via Co2O3 and MoO3 co-doping for MHz applications

MnZn power ferrites for MHz and wide temperature applications were prepared by ceramic process and effects of Co2O3 and MoO3 co-doping on the microstructure and magnetic properties have been investigated, and MnZn power ferrite with ultra-high cut-off frequency of 14.2 MHz has been prepared. It has been revealed that the grain size of the MnZn ferrite can be homogenize via the co-doping of Co2O3 and MoO3, giving rise to enhanced electrical resistivity, compensated magnetocrystalline anisotropy and reduced domain wall displacement. Effective reduction of the power loss with improved temperature stability and cut-off frequency have been achieved by synergistic function of Co2O3 and MoO3 via liquid-phase sintering increasing the possibility of Co2+ cation entering into the spinel lattice.

PVP Encapsulated Mn0.8Zn0.2Fe₂O₄ Nanoparticles: Synthesis, Microstructure, and Magnetic Characterizations

We report the polyvinylpyrrolidone (PVP) encapsulated MnZn ferrite (MnSUB0.8/SUBZnSUB0.2/SUBFe₂O₄/PVP) nanocomposite for low-temperature magnetic properties prepared by the facile one-pot sol-gel route. The transmission electron microscopy analysis revealed spherical shape ferrite particles in a polymer matrix MnSUB0.8/SUBZnSUB0.2/SUBFe₂O₄/PVP nanocomposite) with an average particle size of 11.6 nm. The Rietveld refinement of X-ray diffraction (XRD) data revealed the pure cubic spinel structure formation. The lattice parameter is 8.3825 Å, and the average crystallite size is 10 nm evaluated from XRD data. Raman spectroscopy analysis is in agreement with XRD results. The temperature-dependent magnetization analysis disclosed the effective anisotropy constant KSUBeff/SUB, the value of 3.0 × 10⁴ J/㎥. The meticulous investigation of magnetic field-dependent magnetic properties from 2 K to 350 K unveiled superparamagnetic (SPM) behavior. From the electron spin resonance (ESR) analysis, the calculated g value and spin-spin relaxation time (T₂) are 2.03 and 2.52 × 10SUP-11/SUP sec, respectively, which confirms the SPM behavior.

Low temperature sintered MnZn ferrites for power applications at the frequency of 1 MHz

The low power loss Mn-Zn ferrites with fine grains were developed by the low-temperature-sintering ceramic process for power applications at a high frequency of 1 MHz. The LiBO2 sintering aid was added to promote the low temperature sintering and densification. The effects of LiBO2 on micromorphology and magnetic properties of the sintered Mn-Zn ferrites were investigated. With the aid of LiBO2, sintering temperature could be reduced as low as 990 °C. The optimum sample was obtained by the addition of 500 ppm LiBO2 sintered at 1020 °C. The average grain size of this sample is 2.78 μm, the density reaches 4.82 g/cm3, and the minimum power loss is 310 kW/m3 at 1 MHz/30 m T and 25 °C. This sample shows good wide-temperature stability of power loss. The mechanism of power loss affected by the LiBO2 addition was also discussed. The ceramic sintering process combining the low temperature sintering and the sintering aid offers a new way to develop high-frequency Mn-Zn ferrites.

A new nano-grain Mn–Zn spinel ferrite smart cores to enhance the efficiency of high-frequency devices

Mn-Zn ferrites are widely interested in the application as current-compensated chokes due to their astounding features. In this study, nanocrystalline Mn-Zn ferrite (Mn0.8Zn0.2Fe2O4) was synthesized using the coprecipitation method. The structures and magnetic properties of the resulting powder were assessed using X-ray diffractometer (XRD), transmission electron micrographs (TEM), magnetic properties at room temperature (AGFM) and Curie temperature measurement. XRD pattern confirmed the formation of nanocrystalline Mn-Zn ferrite with average crystallite sizes in 11.3 nm. The magnetic measurements revealed that they have superparamagnetic behavior. The electromagnetic properties of these cores including the output voltage versus input voltage, quality factor and impedance versus frequency at four sintered temperatures were assessed. The results demonstrated that the fabricated smart core sintered at low temperature (800 °C) could efficiently be appropriate for work in a test frequency of 15 MHz. This encouraging feature suggests that it is worthwhile for application in modern switch-mode power supply modules.

Development of Mn-Zn power ferrite with low losses over a broad temperature range for applications in the high frequency region of 0.5-3 MHz

Due to the rapid development of electronic devices towards high frequency, miniaturization, and high efficiency, it is imperative to develop MHz-frequency power ferrites exhibiting low loss over a broad temperature range. In this work, the broad-temperature low-loss Mn-Zn power ferrites operating in the frequency range of 0.5-3 MHz have been fabricated following the traditional oxide ceramic process. Co3O4 was added and its content was optimized to achieve the broad-temperature characteristics of power loss. The optimal Co3O4 content was determined to be 0.35 wt%. The power losses of this material are less than 30, 120, and 30 kW/m3 in the broad temperature range from 0 to 120 °C under the conditions of 500kHz/50 mT, 1MHz/50 mT, and 3MHz/10 mT, respectively. This material is an ideal material for applications in power conversion electronics at high frequencies (0.5-3 MHz). The effect of Co3O4 addition on power loss is discussed based on the compensation model of magnetocrystalline anisotropy constant. Analysis of the three parts of power loss reveals that the residual loss gradually becomes to be predominant above 1.2 MHz. The addition of Co3O4 reduces the residual loss and increases the cut-off frequency. This is ascribed to the induced uniaxial anisotropy of Co2+.

Core Loss Model for Arbitrary Excitations With DC Bias Covering a Wide Frequency Range

Core loss prediction is quite complex as the excitation of magnetic materials varies depending on the topology and the operating mode of switched-mode power supplies. In particular, the waveform of the magnetic flux density, including its dc bias, affects core losses. This article presents the results of an extensive core loss study performed on Mn-Zn ferrites. The investigation comprises core excitations with, among others, sinusoidal and triangular shapes of the magnetic flux density with and without dc bias. Based on the obtained core loss data, an empirical core loss model has been derived for the prediction of specific core losses in Mn-Zn ferrites that is valid for arbitrary excitations, including dc bias of the magnetic flux density. Multiplying the quasi-static energy losses depending on the swing and the dc bias of the magnetic flux density by an effective frequency yields the core losses. The proposed model covers a wide frequency range and only requires the quasi-static energy losses at low frequencies and two frequency-independent parameters. These parameters can be easily extracted from a limited number of measurements or from the data provided by manufacturers. The verification of the proposed approach demonstrates an adequate accuracy of 15% for all investigated Mn-Zn ferrites and for the broad range of studied waveforms and parameters.

Effect of Mn-substitution on the structure Co0.6Zn0.4Fe2O4

One Ferrite is a ferromagnetic substance where it is ideally used to manufacture devices such as rectifiers, memory devices, and inductors hearts as well as for various applications of microwave waves. The electrical and structural characterization of ferrites depends on preparation methods, nature of dopant, and dopant concentration. For these reasons, the series samples of Co0.6Zn0.4MnxFe2−xO4 ferrites prepared, using a traditional ceramic process, Mn-Zn ferrites were synthesized and sintered up to 1200 °C for 5 hours. We tested the X Ray diffraction (XRD) for different Mn-substitution (where x = 0, 0.2, and 0.4). XRD studies confirmed that the sample’s structural have a cubic spinel phase. The electrical characterization (such as conductivity, real and imaginary dielectric constant) was measured and discussed, as well.

Thermal instabilities of cobalt containing MnZn ferrite cores for medium (500 kHz) frequency applications

MnZn ferrites of the nominal composition (Mn0.81Zn0.19)Fe2.13O4, doped with cobalt, have been studied concerning the evolution of their medium (500 kHz) frequency power losses and initial magnetic permeabilities upon ageing at various temperatures for various times. Thermal ageing results to significant power loss reduction by about 50% at 400 kHz-50 mT (i.e. at 90 °C from initially 58–29 mW cm−3) and about 30% at 500 kHz–100 mT (i.e. at 90 °C from initially 690–480 mW cm−3), accompanied with a simultaneous decrease of the relative initial permeability from initially 1700–1200. The extent of power loss reduction depends on ageing time and temperature and can be described by a thermally activated process, during which Co2+ ions fall from a metastable high energy state to a stable lower energy state with an activation energy 0.33 eV/cation. Addition of TiO2 to an amount of 4000 ppm (wt.%) appears to retard the cobalt-induced ageing process by increasing the activation energy to 0.45 eV/cation, while equal amount additions of SnO2 did not seem to have any effect.

A Free-Standing Electromagnetic Energy Harvester for Condition Monitoring in Smart Grid

Wireless energy harvesting is an effective way to power condition monitoring sensors which are the basis of smart grid. In this paper, a new free-standing I-shaped core is designed to scavenge electromagnetic energy from large alternating current. An I-shaped core can guide more magnetic flux by adding a pair of magnetic flux collector plates at both ends of the rod core. It weakens the core demagnetization field and enables more energy to be collected. Since a magnetic field line can be bent with high-permeability soft magnetic materials, a highly efficient grid-shaped coil is proposed. Compared with the I-shaped coil, its weight is lighter and power density is higher. A Mn-Zn ferrite with high relative permeability and ultralow conductivity can effectively reduce eddy current loss, which proves to be the most suitable material. The measured open circuit voltage agrees well with the theoretical value. The experimental results show that the output power can reach 4.5 mW when the I-shaped coil is placed in a magnetic flux density of 6.5 μTrms. The power density is 7.28 μW/cm3. Therefore, the proposed design can be very effective for supplying condition monitoring sensors.

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.