Mn-Zn Ferrite Research Articles

Highly stable dielectric frequency response of chemically synthesized Mn-substituted ZnFe2O4

The tenacity of the present study was to develop a material using an economical chemical route, having balance between magnetic and dielectric order parameters for maximum transmittance of electromagnetic waves in order to use them in shielding materials. In this context, Mn-Zn ferrites were prepared using a wet chemical based sol-gel auto-combustion technique. X-ray diffraction confirmed the pure phase formation of samples, while some impurity peaks were also present for the higher value of Mn substitution. Field emission scanning electron microscopy revealed a decrease in grain size with increasing Mn substitution. While energy dispersive X-ray spectroscopy confirmed the elemental composition of pure and Mn substituted samples, the dielectric constant, dielectric loss and tangent loss were decreased with increasing frequency and increasing Mn substitution. The complex electric modulus was found to be a function of frequency and values of complex electric modulus were increased with increasing frequency and Mn substitution. The complex impedance of RC series circuit and RC parallel circuit was also decreased with increasing both the parameters while AC conductivity was increased in the series. Dielectric frequency response was also studied for the prepared samples and the best match was found with expected results. The Nyquist and Cole-Cole plots revealed the semi-conductive behavior at higher frequency and Mn substitution also yielded the same results. The relative stability of the samples to be used as dielectric materials was also studied using Bode and Nichols plots, and a comparatively high gain margin was observed, well suitable for potential applications in electromagnetic shielding.

Low loss MnZn ferrites for applications in the frequency region of 1–3 MHz

The purpose of this particular study is the development of a high frequency –1 to 3 MHz – stable MnZn ferrite. The notion under which the study was held was the preliminary investigation of the dissipation mechanisms, and subsequently the hypothesis of the predominance of one. Accordingly the path of enhancement commenced with a selection of high frequency MnZn ferrite as the base – namely one exhibiting high ferromagnetic resonance (FMR) already – and the selective addition of Co2+ and Mg2+. Arguably the offspring of the study was a superb high frequency ferrite, stable throughout the temperature spectrum, 25–115 °C, presenting power losses as low as 87 mW cm−3 (1 MHz, 50 mT, 85 °C) and 319 mW cm−3 (3 MHz, 30 mT, 85 °C). Initial permeability (10 kHz, 0.1 mT) remains higher than the value of 850 (25–115 °C) and FMR appears no earlier than 7.1 MHz. To the authors’ knowledge these values are among the best reported.

The Use of Co-Precipitation to Produce Nano-Mn–Zn Ferrite ([MnxZn1−x]Fe2O4) from Waste Batteries

This study uses pure materials or waste batteries to produce a nanoscale Mn–Zn ferrite. Acid is used to dissolve the battery into solution and then co-precipitation is used to produce nanoscale ferrite. When the calcination temperature in an air atmosphere exceeds 600 °C, α-Fe2O3 is generated and there is a decrease in the saturated magnetization. Using waste batteries to produce [Mn0.54Zn0.46]Fe2O4 at a pH of 10, the saturated magnetization is 62.85 M (emu/g), which is optimal. At a pH of 10, the particulate diameter is largest, at about 40 nm. The stronger the crystal phase of Mn–Zn ferrite, the greater is the saturated magnetization. The ferrite crystal phase is analyzed using X-ray diffraction (XRD), scanning electron microscopy (SEM) and a vibrating sample magnetometer (VSM). The stronger the crystal phase, the larger is the average particulate diameter. The magnetic properties, the particulate diameter and the magnetic flux density of ferrite powders that are prepared under different conditions are studied. [MnxZn1−x]Fe2O4 ferrite powders can be used as an iron core and as resonance imaging materials.

Effects of sol concentration on the structure and magnetic properties of sol-gel MnZn ferrites

ABSTRACTMnZn ferrite films were grown on Si substrate by sol-gel method with different sol concentrations varying from 0.1 to 0.4 M.The dependence of structural and magnetic properties of these films on sol concentrations was deeply investigated. The results show that high sol concentration is favorable for obtaining films with good crystalline quality. Morphology and surface roughness of the thin films depend on sol concentration. With the enhancement of sol concentration, the MnZn ferrite grains gradually increase and surface roughness is also gradually increased which is ascribed to the particle collision and electrostatic force between particles. Magnetic properties measurement indicate that the prepared MnZn ferrite films were typically soft ferrite materials. The Ms increased from 13.90 emu/cm3 to 89.13 emu/cm3 as sol concentration increased from 0.1 mol/L to 0.4 mol/L. The FMR linewidth decreased with the increasing of sol concentration, the film prepared by 0.4 mol/L sol has the FMR linewidth of 5.96 Oe. The mechanism of the improvement of magnetic properties is analyzed.

Modelling of electrical properties of mn-zn ferrites taking into account the frequency of the occurrence of the dimensional resonance

Abstract Besides their magnetic properties, Mn-Zn ferrites are also characterized by appreciable electrical properties. This electro- magnetic nature of Mn-Zn ferrites material properties causes a dimensional resonance to occur in samples. The latter hinders measurements of the frequency dependences of intrinsic permittivity and electrical conductivity. In the paper, we present a sign in measurement results that shows the frequency range in which dimensional resonance has already occurred. Above this range, properties extracted from measurements are not intrinsic any longer. We refer to the sign to determine the last point of the measurement data set that is used as an input for an equivalent circuit modelling of the electrical properties. This “last point” criterion helps to exclude the possibility of modelling apparent properties instead of intrinsic ones. The results obtained show that the frequency dependent electrical properties may be well modeled even if the upper limit of the input frequency range to the curve fitting is below the frequency range in which the dimensional resonance occurs.

A novel method for vanadium slag comprehensive utilization to synthesize Zn-Mn ferrite and Fe-V-Cr alloy

Vanadium slag is a by-product from steelmaking process of vanadium-titanium magnetite, which mainly contains FeO, MnO, V2O3, and Cr2O3, The elements Fe and Mn are major components of Mn-Zn ferrite. The elements V and Cr are major components of V-Cr alloy. In view of the potential application in these study, a Mn0.8Zn0.2Fe2O4 of high saturation magnetization (Ms = 68.6 emu/g) and low coercivity (Hc = 3.3 Oe) was successfully synthesized from the leaching solutions of vanadium slag by adding appropriate chemical reagents, ZnCl2 and MnCl2·4H2O, via roasting at 1300 °C for 1 h. The minor components (CaO and SiO2) in the leaching solution of vanadium slag segregated to the grain boundaries resulting in increasing the resistivity of ferrite. The value of DC resistivity of Mn0.8Zn0.2Fe2O4 at 25 °C reached 1230.7Ω m. The residue containing Fe, V and Cr was chlorinated by AlCl3 and the Fe3+, V3+, and Cr3+ ions were released into the NaCl-KCl eutectic. The current-time curve for the electrolysis of molten salt was investigated. Alloy (Fe, V, and Cr) of granular shape was obtained. The residue can be used to produce the mulite. This process provided a new approach to utilize slag from steelmaking.

Degradation of bisphenol A by electro-enhanced heterogeneous activation of peroxydisulfate using Mn-Zn ferrite from spent alkaline Zn-Mn batteries

Mn-Zn ferrite (Mn0.6Zn0.4Fe2O4) was prepared by a gel method using spent alkaline Zn-Mn batteries as raw materials and employed as catalyst to degrade bisphenol A (BPA) by electro-enhanced heterogeneous activation of peroxydisulfate (PDS). The effects of initial pH, current density, PDS concentration, and Mn-Zn ferrite dosage on BPA removal were investigated. The formation of reactive radicals was verified by electron paramagnetic resonance (EPR) spectroscopy. The results of radical quenching experiments indicate that surface-bound sulfate and hydroxyl radicals played an important role in BPA removal. The stability of Mn0.6Zn0.4Fe2O4 catalyst was investigated by cycling experiments, which indicates Mn0.6Zn0.4Fe2O4 is stable and can be reused. This work also provides an alternative way for the reutilization of spent alkaline Zn-Mn batteries.

Temperature dependence on the mass susceptibility and mass magnetization of superparamagnetic Mn–Zn–ferrite nanoparticles as contrast agents for magnetic imaging of oil and gas reservoirs

ABSTRACTThe mass susceptibility (χmass) and mass magnetization (Mmass) were determined for a series of ternary manganese and zinc ferrite nanoparticles (Mn–Zn ferrite NPs, MnxZn1−xFe2O4) with different Mn:Zn ratios (0.08 ≤ x ≤ 4.67), prepared by the thermal decomposition reaction of the appropriate metal acetylacetonate complexes, and for the binary homologs (MxFe3−xO4, where M = Mn or Zn). Alteration of the Mn:Zn ratio in Mn–Zn ferrite NPs does not significantly affect the particle size. At room temperature and low applied field strength the mass susceptibility increases sharply as the Mn:Zn ratio increases, but above a ratio of 0.4 further increase in the amount of manganese results in the mass susceptibility decreasing slightly, reaching a plateau above Mn:Zn ≈ 2. The compositional dependence of the mass magnetization shows less of a variation at room temperature and high applied fields. The temperature dependence of the mass magnetization of Mn–Zn ferrite NPs is significantly less for Mn-rich compositions making them more suitable for downhole imaging at higher temperatures (>100 °C). For non-shale reservoirs, replacement of nMag by Mn-rich Mn–Zn ferrites will allow for significant signal-to-noise enhancement of 6.5× over NP magnetite.

Concurrent Core Loss Suppression and High Permeability by Introduction of Highly Insulating Intergranular Magnetic Inclusions to MnZn Ferrite

A novel approach entailing the introduction of incongruent insulating magnetic inclusions to the grain boundary region of polycrystalline ferrite cores has been proposed to target the eddy current loss as the major source of core loss at high operating frequency. To demonstrate the efficacy of this approach, highly resistive ferrimagnetic nanoparticles (NPs) of yttrium iron garnet (YIG) were introduced to the grain boundaries of MnZn ferrite. Diamagnetic NPs of barium titanate (BTO) were similarly added as a nonmagnetic insulating grain boundary control additive. A profound decrease was observed in the eddy current loss (up to 79%) by using this approach. For the case of magnetic inclusions, a retained high permeability (24% reduction) was achieved, whereas the samples with nonmagnetic additives experienced a considerable sacrifice to permeability (64% reduction). The sustained high permeability was attributed to the ferrimagnetic YIG NPs maintaining long-range magnetic interactions, whereas the BTO NPs both frustrated the eddy current and long-range intergranular magnetic interactions. These results indicate that low permeability is no longer a necessary constraint for suppression of core power loss.

Influence of Sintering on the Structural, Electrical, and Magnetic Properties of Li–Ni–Mn–Zn Ferrite Synthesized by Citrate Precursor Method

Substituted lithium ferrites having the compositional formula Li0.35−0.5x Nix Mn0.1 Zn0.2 Fe2.35−0.5x O4 where 0.1 ≤ x ≤ 0.3 in steps of 0.05 had been synthesized by the citrate precursor method. The samples were given single sintering at 900 °C and double sintering, second sintering at 900 °C after a pre-sintering or first sintering at 600 °C. Spinel phase structure was confirmed from FTIR spectra and XRD patterns. A study on the structural parameters (lattice constant, density, porosity and crystallize size), electrical parameters (dielectric constant $$ \varepsilon^{'} $$ , dielectric loss tangent $$ tan\delta $$ , dc resistivity ρ dc), and magnetic parameter (initial permeability $$ \mu_{i}^{'} $$ ) of single-sintered (SS) and double-sintered (DS) Li–Ni–Mn–Zn ferrite samples has been investigated. Structural studies reveal that DS samples enhance density and reduce porosity. Electrical studies showed lower value of dielectric constant, and dielectric losses while higher dc resistivity is observed in DS samples. However, in both series, an anomalous high increase in dielectric constant for x = 0.15 is observed. It was found from magnetic studies that the initial permeability is lower in the DS samples. The mechanism that involves in the results obtain above is being discussed.

A Comparative Study of Magnetite and Mn–Zn Ferrite Nanoliquids Flow Inspired by Nonlinear Thermal Radiation

A Comparative Study of Magnetite and Mn–Zn Ferrite Nanoliquids Flow Inspired by Nonlinear Thermal Radiation

Novel applications of magnetic materials and technologies for medicine

We analyze the applications of the magnetocaloric effect (MCE) achieved with advanced magnetic materials and technologies. New results such as the use of MCE-based composite material for ‘smart’ coating of implants, which allows for a controlled release of drugs over time. The material is comprised of two layers: the one manifesting a large MCE and the other made of a temperature-responsive polymer containing the drug. The latter is released by the polymer if the temperature induced by magnetic field (due to MCE) is changed. The polymer undergoes sharp phase transition in response to the slight temperature drop of ∼1–3 °C (down to 34–36 °C in the body). Local cooling is achieved with FeRh alloy, one of the most perspective MCE materials with the first order phase transition. It is critically important to take into account several peculiarities of phase transition and MCE behavior in these series of alloys. Recent studies on high-purity samples showed an ‘irreversible’ effect of MCE indicating that the temperature of FeRh does not return to its initial value after the full cycle of the magnetic field during dynamic MCE measurements. A theoretical explanation based on ab initio calculations has been provided. Magnetic hyperthermia in oncology is rapidly developing therapeutic modality. Recent experiments have shown that Mn-Zn ferrite emerges as a cost-effective material for this method compared with currently used magnetite nanoparticles. We present our achievements on magnetically guided capsule endoscopy. The advances in magnetically guided capsule endoscopy are also discussed. We provide the experimental setup for the computer-controlled system of magnetic field sources that create necessary forces to control the position of the capsule in five degrees of freedom in a given area. The system has the feedback on the position and is designed to monitor the endoscopic capsule during gastrointestinal tract examination.

Magnetic Field Analysis for Dimensional Resonance in Mn–Zn Ferrite Toroidal Core and Comparison With Permeability Measurement

This paper studies the calculation method of core loss and magnetic state in Mn-Zn ferrites under an arbitrary waveform excitation. The effective dielectric constant, which is caused by a thin high-resistive layer at the grain boundary, is treated as a modification of Ohm's law by using an equivalent circuit. This procedure enables us to calculate both the dimensional resonance and eddy-current loss. To confirm the accuracy of the proposed model, the size dependence of the complex permeability and core loss of the toroidal core is analyzed. These results show a good agreement with the experimental measurement in the megahertz region. By using the same model, the core loss mechanism excited by a triangular-wave current is analyzed. In the low-frequency region, the core loss is suppressed by the reduction of a steep change in magnetic flux. However, the core loss near the resonant frequency is increased at the turning point of the current wave, where the time derivative of the current changes discontinuously and a higher harmonic component is induced.

High-Frequency Properties of Fe-4.5 Wt% Si Powders With an Insulating Layer Synthesized by a Modified Dew-Point Treatment

The frequency for wireless power chargers is in the range of 100–205 kHz when using MnZn ferrite and NiZn ferrite. Compared to ferromagnetic metals, these ferrites have higher resistivity, which reduces the eddy loss at high frequencies, though they also have lower magnetization values that limit the distance and the direction between the receiver and transmitter units. Thus, there is a strong demand for the development of a new metallic magnetic sheet that can suppress the eddy-current loss in the high-frequency range. To meet this demand, a modified dew-point insulation coating method for Fe-4.5 wt% Si powders was assessed and the high-frequency properties of green compacts consisting of these powders were investigated. As a result, a thin high-resistivity layer was successfully coated onto the powders. In addition, both eddy-current loss and hysteresis loss of their compacts were dramatically reduced in the high-frequency region.

Impedance spectral analysis and scaling behavior of Mn2+–Si4+ substituted Mn–Zn ferrites

This communication reports complex impedance (Z* = Z′ − iZ″) spectral analysis of polycrystalline spinel ferrite system, Mn0.7+xZn0.3SixFe2−2xO4 (x = 0.0–0.3), synthesized by a solid-state reaction route over the broad frequency (f = 20 Hz–1 MHz) and temperature (T = 300–673 K) ranges. Variation of Z′(f, T) showing a typical negative temperature coefficient of resistant type behavior. Cole-Cole plots (Z″ versus Z′) have been used to determine grain and grain boundary resistances, capacitances, relaxation frequencies and relaxation times. Relaxation time is found to decrease with temperature and it obeys the Arrhenius relationship. The corresponding activation energy values are found to be about ~0.6 eV suggesting conduction due to the polaron hopping based on the electron carriers. Evidence of the components from both localized and delocalized relaxations is observed. The scaling of Z″/Zmax by using fmax as a scaling parameter is more successful as compared to that carried out using σdc as a scaling quantity. The results revealed that the complex dielectric parameters and structure of the ferrite ceramics are strongly coupled properties.

Improving soft magnetic properties of Mn-Zn ferrite by rare earth ions doping

Mn-Zn ferrites doped with different Sm2O3, Gd2O3, Ce2O3 or Y2O3 were prepared by traditional ceramic technology using industrial pre-sintered powders. A small amount of Sm2O3, Gd2O3, Ce2O3 or Y2O3 can significantly improve the microstructure and magnetic properties. The single spinel phase structure can be maintained with the doping amount up to 0.07 wt.%. A refined grain structure and uniform grain size distribution can be obtained by doping. For all rare earth oxides, a small amount of doping can significantly increase the permeability and reduce the coercivity and magnetic core loss. The optimized doping amount for Sm2O3 or Gd2O3 is 0.01 wt.%, while for Ce2O3 or Y2O3 is 0.03 wt.%. A further increase of the doping content will lead to reduced soft magnetic properties. The ferrite sample with 0.01 wt.% Sm2O3 exhibits the good magnetic properties with permeability, loss, and coercivity of 2586, 316 W/kg, and 24A/m, respectively, at 200 mT and 100 kHz. The present results indicate that rare earth doping can be suggested to be one of the effective ways to improve the performance of soft ferrites.

Magnetic loss, permeability, and anisotropy compensation in CoO-doped Mn-Zn ferrites

Mn-Zn ferrite samples prepared by conventional solid state reaction method and sintering at 1325 °C were Co-enriched by addition of CoO up to 6000 ppm and characterized versus frequency (DC – 1GHz), peak polarization (2 mT – 200 mT), and temperature (23 °C – 120 °C). The magnetic losses at room temperature are observed to pass through a deep minimum value around 4000 ppm CoO at all polarizations values. This trend is smoothed out either by approaching the MHz range or by increasing the temperature. Conversely, the initial permeability attains its maximum value around the same CoO content, while showing moderate monotonical decrease with increasing CoO at the typical working temperatures of 80 – 100 °C. The energy losses, measured by a combination of fluxmetric and transmission line methods, are affected by the eddy currents, on the conventional 5 mm thick ring samples, only beyond a few MHz. Their assessment relies on the separation of rotational and domain wall processes, which can be done by analysis of the complex permeability and its frequency behavior. This permits one, in particular, to calculate the magnetic anisotropy and its dependence on CoO content and temperature and bring to light its decomposition into the host lattice and Co2+ temperature dependent contributions. The temperature and doping dependence of initial permeability and magnetic losses can in this way be qualitatively justified, without invoking the passage through zero value of the effective anisotropy constant upon doping.

Synthesis of metal-doped Mn-Zn ferrite from the leaching solutions of vanadium slag using hydrothermal method

Using vanadium slag as raw material, Metal-doped Mn-Zn ferrites were synthesized by multi-step processes including chlorination of iron and manganese by NH4Cl, selective oxidation of Fe cation, and hydrothermal synthesis. The phase composition and magnetic properties of synthesized metal-doped Mn-Zn ferrite were characterized by X-ray powder diffraction, Raman spectroscopy, transmission electron microscopy (TEM), X-ray photon spectra (XPS) and physical property measurement. It was found that Mn/Zn mole ratio significantly affected the magnetic properties and ZnCl2 content significantly influenced the purity of the phase of ferrite. Synthesized metal-doped Mn-Zn ferrite, exhibiting a larger saturation magnetization (Ms=60.01emu/g) and lower coercivity (Hc=8.9Oe), was obtained when the hydrothermal temperature was controlled at 200°C for 12h with a Mn/Zn mole ratio of 4. The effect of ZnCl2 content, Mn/Zn mole ratio and temperature on magnetic properties of the synthesized metal-doped Mn-Zn ferrite were systemically investigated. This process provided a new insight to utilize resources in the aim of obtaining functional materials.

Effect of multiwalled carbon nanotubes on the thermoelectric properties of Mn-Zn ferrites

In this study, Mn-Zn ferrites with three different multiwalled carbon nanotubes (MWNTs) concentration, 1,2,3 wt%, were used to compare the effect of MWNTs on thermoelectric properties of the composites. The dimensionless figure of merit (ZT) of the composites at the low contents (1 and 2 wt%) of MWNTs have shown significantly increased values compared to those of composites at the high contents (3 wt%) in the temperature range of 323–973 K. The maximum ZT of 0.038 was obtained at 2 wt%. It is considered that the improved thermoelectric performance of the composite mainly originated from electrical conductivity that is attributed to the increased carrier concentration or carrier mobility.

MHD forced convection ow and heat transfer of ferro fluids over a moving at plate with uniform heat flux and second-order slip effects

In this study, the problem of two-dimensional forced convection MHD flow and heat transfer of ferro fluids over a moving at plate with the influence of uniform heat flux and secondorder slip eff ects is considered. By applying the similarity transformation, the governing equations are reconstructed into the similarity equations and the resulting equations are solved via shooting technique. Then, we implement a stability analysis in order to verify which solutions are stable and physically realizable. The e ects of the magnetic parameter,moving parameter, mass transfer parameter, rst-order surface slip parameter, second-order surface slip parameter and volume fraction of solid ferroparticles on the dimensionless velocity, temperature, skin friction and Nusselt numbers are discussed in the form of tabular and graphical presentation. For this present study, we consider the results based on three preferred ferroparticles, namely magnetite, cobalt ferrite and Mn-Zn ferrite in water- and kerosene-based fluids. The results display the existence of dual solutions for a plate moving towards the origin in which the rst solution is stable and physically realizable, while the second solution is not. Moreover, it is demonstrated that the magnetic, moving, mass transfer and slip eff ects together with the volume fraction of ferro fluids delay the boundary layer separation.