Fe2O4 Ferrites Research Articles

Synthesis of Mn1-xZnxFe2O4 ferrite powder by co-precipitation method

Ferrimagnetic substances referred to as ferrites are ionic crystals whose chemical composition is of the form XFe2 O4 where X signifies a divalent metal. Magnetic Nano sized ferrites have found a significant potential in many applications, such as magnetic recording media, Ferro fluids and radar absorbing coating. Ferrites are widely used in many industrial applications due to their spontaneous magnetization. Soft ferrites of Mn-Zn, Ni-Zn and Mg-Mn are well known for their high magnetic permeability. In the present research work we have prepared fine Mn1-xZnxFe2O4 ferrite powder with varying x concentrations (0.25-0.75) by metal chloride precursors through a co-precipitation technique by pipette drop method using aqueous NaOH solution for comparing their spontaneous magnetization and particle size. The co-precipitation technique is a high way to produce chemically homogeneous powder with fine particle size in nanometers (22.5nm-74.5nm).The effect of x-concentration on the particle size of the Mn(1-x) Zn(x) ferrite has been discussed on the basis of XRD. The crystalline phases have been identified by X-ray diffraction with Cu-Kα radiations. The XRD patterns have verified that the specimen has spinal type structure. The observable peaks are broad since the size of the particles is small. We have concluded that at constants temperature particle size increases with increasing x-concentrations. Effect of different concentrations of x (Zn+2) on the spontaneous magnetization of different Mn(1-x) Zn(x) Fe2O4 sample is determined. We have reached the conclusion that all the samples of Mn(1-x) Zn(x) Fe2 O4 ferrites were magnetic either of low or high magnetization. The maximum spontaneous magnetization and minimum particle size is obtained at x=0.25 (at digestion temperature=65°C).

Electromagnetic and microwave absorbing properties of SmCo coated single-wall carbon nanotubes/NiZn-ferrite nanocrystalline composite

The electromagnetism and microwave absorption properties of SmCo coated single-wall carbon nanotubes (SmCo@SWCNTs) and Ni0.5Zn0.5Fe2O4 ferrite (NiZn-ferrite) nanocrystalline composites with different ingredient weight ratios were investigated in the frequency range of 2–18 GHz. SmCo@SWCNTs were prepared by a direct current arc discharge method. NiZn-ferrite nanocrystalline was synthesized by a sol-gel method. The electromagnetic properties of the nanocomposites in the paraffin matrix were measured by a vector network analyzer. The Debye equation and Bruggeman symmetric medium equation were introduced to explain the dielectric properties of the nanocomposites, and the mechanisms for the dielectric and magnetic losses were discussed. The experiment results reveal that the absorbing properties of the nanocomposites could be improved by tuning for a suitable weight ratio between SmCo@SWCNTs and NiZn-ferrite nanocrystallines. The reflection loss simulation calculations demonstrated that the nanocomposite could be excellent materials for microwave absorption.

Ferroelectric–Ferromagnetic Ceramic Composites Based on PZT with Added Ferrite

The study presents a ferroelectric–ferromagnetic composite based on a doped PZT‐type and ferrite powders. Ferroelectric powder (in amount of 90 wt‐%) was based on multicomponent PZT‐type materials, while nickel–zinc ferrite Ni1–xZnxFe2O4 (in amount of 10 wt‐%) served as the magnetic component of the composite. The syntheses of the ferroelectric–ferromagnetic composite's components were performed using solid‐phase sintering, while final densification of the synthesized powder was achieved using free sintering. X‐ray analysis of the composite confirmed the presence of strong maxima originating from particular PZT‐type material phases, as well as weak peaks from the Ni0.64Zn0.36Fe2O4 ferrite, without foreign phases. The microstructure of the fracture of the ferroelectric–ferromagnetic composites shows that the ferrite grains on the surface of the ferroelectric component are distributed heterogeneously. Magnetic studies have characterized composite as a soft ferromagnetic material. The study indicated the influence of the magnetic subsystem on the electrical properties. In the two‐phase PBZTMC–NZF ceramic composite, the magnetic component causes the decrease in electric permittivity and increased value of the dielectric losses.

Structural, magnetic, and elastic properties of nanocrystalline Al-substituted Mn0.5Zn0.5Fe2O4 ferrite

Structural, elastic, and magnetic properties have been investigated for Mn0.5Zn0.5Fe2−xAlxO4 (x=0.0, 0.1, 0.3, 0.5) prepared by sol–gel method. X-ray diffraction pattern (XRD) beside Fourier-transform infrared spectra proves the formation of a pure cubic spinel phase for the whole samples with nanosized crystals of size ranging from 4.5 to 10.1nm. TEM images confirmed the extremely fine size of the prepared samples. XRD and FTIR analyses clarified that Al substitution has improved the elastic properties of the Mn–Zn ferrites. Superparamagnetic behavior has been recorded for the prepared samples through vibrating sample magnetometry (VSM), whose data were used to suggest a cation distribution supported by the experimental data of the lattice parameter and absorption peaks of IR spectra.

Scandium substituted nickel–cobalt ferrite nanoparticles for catalyst applications

Nanograined Ni0.5Co0.5ScxFe2−xO4 (x=0, 0.05, 0.1 and 0.2) spinel ferrites were prepared by sol–gel self-combustion method and heat treatment at 900°C for 4h. Their structure and surface properties were investigated by X-ray diffraction, scanning electron microscopy, EDX spectroscopy and BET analysis. The catalyst properties of the ferrite nanopowders were tested in the catalytic combustion of acetone, propane and benzene. The results revealed that the partial substitution of Fe3+ by Sc3+ ions on the octahedral sites of spinel structure of Ni0.5Co0.5Fe2O4 ferrite has a favorable effect on the catalytic activity of this ferrite. The Ni0.5Co0.5Sc0.2Fe1.8O4 ferrite composition was found to be the most active catalyst and can be a good candidate for catalytic combustion of propane and acetone at moderate temperatures. The acetone conversion over this catalyst exceeds 90% at 400°C. The enhancement of the catalytic activity of the Sc doped Ni–Co ferrites may be ascribed to smaller crystallite sizes (35–39nm), larger specific surface areas (29–32m2/g) and the presence of Sc cations in spinel structure.

Effects of copper content on the structural and magnetic properties of spinel (Co,Cu)Fe2O4 ferrites

Spinel Co–Cu ferrites with the nominal composition Co1−xCuxFe2O4 ferrites (x = 0.0–0.4 with steps of 0.1) were prepared by a chemical coprecipitaiton and sintering process, and their structural and magnetic properties were studied by using XRD, TGA–DTA, FTIR, SEM and VSM analyses. All the specimens prepared are single phase after sintering at 900 °C for 5 h, and nearly no change of lattice parameter is found. The study of grain size shows that suitable amount of Cu substitution is favorable for the growth of grains, while too much Cu substitution inhibits the growth of grains instead. Also found is that with the increase of x, the saturation magnetization decreases continuously from 76.6 (x = 0.0) to 59.0 emu/g (x = 0.4), while the coercivity exhibits a first decreasing but then increasing tendency.

Infrared spectral studies of nanostructured Co2+-substituted Li-Ni-Zn ferrites

Polycrystalline Li0.5Ni0.25–0.5xCo0.5xZn0.5Fe2O4 ferrites (x = 0.0, 0.1, 0.2, 0.3, 0.4, and 0.5) were prepared by standard auto-combustion method and characterized by XRD and IR spectra. The XRD results suggest that all samples were single-phase with a cubic spinel-type structure. The lattice constant, particle size, metal-oxygen bond length (RA and RB), cation radii (rA and rB) on A and B-sub lattices were found to increase while the X-ray density and porosity, decrease with increasing x. The IR spectra show two absorption bands, at ν1 about 600 cm−1 and ν2 at about 425 cm−1, which were attributed to tetrahedral (A) and octahedral (B) sites of the spinel structure, respectively. The band positions were found to depend on x. The force constants, Kt and Ko, were calculated and plotted against cobalt concentration x. Compositional dependence of the force constants is explained in terms of cation-oxygen bond distances and redistribution of cations.

The Cobalt Zinc Spinel Ferrite Nanofiber: Lightweight and Efficient Microwave Absorber

To solve the heavy mass problem of the traditional spinel ferrite using as the microwave absorber, the CoxZn(1−x)Fe2O4 (x = 0.2, 0.4, 0.6, 0.8) ferrite nanofibres were synthesized by electrospinning method. The phase composition, morphology, and electromagnetic properties were analyzed. The results showed that all the as‐prepared CoxZn(1−x)Fe2O4 ferrites exhibited the homogeneous nanofibrous shape. The saturation magnetization and coercivity were enhanced by tuning the Co2+ content. The electromagnetic loss analysis indicated that the Co0.6Zn0.4Fe2O4 ferrite nanofiber performed the strongest microwave attenuation ability. The microwave absorbing coating containing 15 wt% of Co0.6Zn0.4Fe2O4 ferrite nanofiber showed the reflection loss less than −10 dB in the whole X‐band and 80% of the Ku‐band frequencies. Meanwhile, the surface density was only 2.4 Kg/m2.

Synthesis and soft magnetic properties of Zn0.8−xNixMg0.1Cu0.1Fe2O4 (x = 0.0−0.8) ferrites prepared by sol–gel auto-combustion method

Single phase nanocrystalline Zn0.8−xNixMg0.1Cu0.1Fe2O4 (x=0.0−0.8), were synthesized by sol–gel auto-combustion method without post-preparation treatment and, effect of Ni content on structural and magnetic properties is studied by X-ray diffraction (XRD), magnetic measurements and cation distribution. Scherrer’s grain diameter range between 23.5 and 35.1nm. Experimental and theoretical lattice parameter values suggest that the estimated cation distribution is close to the real distribution. Change in Ni-content leads to variation in cation distribution at site A and B. Ni2+ ions occupy both A and B site, but when Zn2+ is fully replaced by Ni2+, it totally goes to A site. Both coercivity measured at 50Hz and quasi static coercivity value is found to increase with nickel content. Same trend is observed for anisotropy constant values. Best magnetization value of 25.04emu/g was obtained for the specimen with x=0.60. Variation of magnetic properties and other parameters (obtained via cation distribution) can be understood in terms of observed changes in distribution of cation(s) on A and B site.

Temperature- and frequency-activated semiconductor-to-metal transition in soft ferromagnetic Li0.5Mn0.5Fe2O4 ferrite

We prepared Li0.5Mn0.5Fe2O4 ferrite through chemical reaction in a highly acidic solution and the subsequent sintering of the chemical routed powder at temperatures ≧̸800 °C. Surface morphology showed a plastoferrite character for a sintering temperature >1000 °C. The mechanical softening of metal–oxygen bonds at higher measurement temperatures stimulated a delocalization of charge carriers, which were strongly localized in the A and B sites of the spinel structure at lower temperatures. The charge delocalization process activated a semiconductor-to-metal transition in the ac conductivity curves, obeyed by the Jonscher power law and Drude equation. A metallic state is also confirmed by the frequency dependence of the dielectric constant curves.

Study of microstructure and semiconductor to metallic conductivity transition in solid state sintered Li0.5Mn0.5Fe2O4−δ spinel ferrite

Li0.5Mn0.5Fe2O4 ferrite has been prepared by solid state sintering route. XRD pattern showed single phased cubic spinel structure. The samples exhibited typical character of plastoferrite with ring shaped surface microstructure. New feature observed in the present ferrite is the frequency activated conductivity transition from semiconductor to metallic state above 800 K. The increase of conductivity with frequency in the semiconducting regime follows Jonscher power law, while decrease of conductivity in metallic regime obeys Drude equation. The conductivity in semiconductor regime has been understood by hopping mechanism of localized charge carriers among the cations in B sites of cubic spinel structure. At higher temperatures, overlapping of electronic orbitals from neighbouring ions and free particle like motion of lighter Li+ ions among interstitial lattices contributed metallic conductivity. The samples provided evidence of localized nature of the charge carriers at lower temperatures and increasing delocalized character with the increase of measurement temperature. From application point of view, such ferrites behave as semiconductor at low temperature and allow electromagnetic wave to pass through, but transform into a metallic reflector with negative dielectric constant at high temperature.

Fabrication and performance optimization of Mn—Zn ferrite/EP composites as microwave absorbing materials

Magnesium-substituted Mn0.8Zn0.2Fe2O4 ferrite is synthesized by the sol—gel combustion method using citrate acid as the complex agent. The electromagnetic absorbing behaviors of ferrite/polymer coatings fabricated by dispersing Mn—Zn ferrite into epoxy resin (EP) are studied. The microstructure and morphology are characterized by X-ray diffraction and scanning electron microscope. Complex permittivity, complex permeability, and reflection loss of ferrite/EP composite coating are investigated in a low frequency range. It is found that the prepared ferrite particles are traditional cubic spinel ferrite particles with an average size of 200 nm. The results reveal that the electromagnetic microwave absorbing properties are significantly influenced by the weight ratio of ferrite to polymer. The composites with a weight ratio of ferrite/polymer being 3:20 have a maximum reflection loss of −16 dB and wide absorbing band. Thus, the Mn—Zn ferrite is the potential candidate in electromagnetic absorbing application in the low frequency range (10 MHz—1 GHz).

Structural, magnetic, and dielectric properties of nanocrystalline Cr-substituted Co0.8Ni0.2Fe2O4 ferrite

The structural, magnetic, and electric properties of Co0.8Ni0.2CryFe2−yO4 (0.00≤y≤0.75; step 0.15) prepared via citrate precursor method are investigated. The structural properties of the produced nano-particles were examined through X-ray diffraction (XRD) and infrared spectroscopy (IR). The XRD pattern revealed a single phase cubic spinel structure for all the samples. The crystallite size decreases with increasing Cr content. Magnetic properties were recorded using vibrating sample magnetometer (VSM). The saturation magnetization increased first with y=0.15 then decreased continuously with further increase of Cr3+ content. Quite reasonable cation distribution was proposed for all the samples relying on the experimental results of lattice parameters, magnetization, and IR spectrum. Theoretically estimated lattice parameters and magnetic moments (using Neel's two sub-lattice model) obtained from the proposed cation distribution are in conformity with those experimentally obtained from XRD and VSM results, respectively. Chromium substitution was found to improve ac electric properties, which was revealed by analyzing frequency-dependent ac conductivity and loss factor.

The magnetostrictive and magnetoelectric characterization of Ni0.3Zn0.62Cu0.08Fe2O4–Pb(FeNb)0.5O3 laminated composite

Magnetoelectric effect in multiferroic materials is widely studied for its fundamental interest and practical applications. The magnetoelectric effect observed for single phase multiferroics is usually small. A much larger effect can be obtained in composites consisting of magnetostrictive and ferroelectric phases. This paper investigates the magnetoelectric effect of multilayer (laminated) structure consisting of 7 nickel ferrite and 8 PFN relaxor layers. It describes the synthesis and tape casting process for Ni0.3Zn0.62Cu0.08Fe2O4 ferrite and relaxor PbFe0.5Nb0.5O3 (PFN). Magnetic susceptibility, hysteresis, ZFC–FC curves and dependencies of magnetization versus temperature for PFN relaxor and magnetoelectric composite were measured with a vibrating sample magnetometer (VSM) in an applied magnetic field up to 85kOe at a temperature range of 10–400K. Parallel and perpendicular magnetostriction of the pure ferrite and bulk and laminated composites were measured at room temperature as a function of the magnetic field (0.3–6.5kOe). Magnetoelectric effect at room temperature was investigated as a function of the static magnetic field (0.3–6.5kOe) and the frequency of the sinusoidal magnetic field (0.01–6.5kHz). At lower magnetic field, the magnetoelectric coefficient increases slightly before reaching a maximum and then decreases. The magnetoelectric coefficient αME increases continuously as the frequency is raised, although this increase is less pronounced in the 1–6.5kHz range. The maximum values of magnetoelectric coefficient attained for the layered composites exceed about 50mV/(Oecm).

The effect of sintering temperature on evolution of structural and magnetic properties of nanostructured Ni0.3Zn0.7Fe2O4 ferrite

Nanocrystalline Ni0.3Zn0.7Fe2O4 ferrite was synthesized by the sol–gel auto-combustion method. The structural, morphological, and magnetic properties of samples, sintered at different temperatures of 350–1,200 °C, have been studied using X-ray diffraction (XRD), field emission scanning electron microscope, Fourier transform infrared (FTIR) spectroscopy, vibrating sample magnetometer (VSM), and AC susceptibility. XRD results indicated that the average crystallite sizes are in the range of ~13 to ~58 nm. The activation energy of crystallization of Ni0.3Zn0.7Fe2O4 ferrite was found to be 12.46 kJ mol−1. Also, the spinel phase formation was further monitored by the FTIR analysis. VSM studies of the samples indicate that magnetization increases with the crystallite size and the maximum magnetization (49.42 emu g−1) observed in the sample sintered at 1,200 °C. The coercivity increases with increasing the crystallite size and reaches a maximum value of 13.82 Oe, then decreases. Also, the low temperature-sintered samples (350 and 400 °C) were superparamagnetic, due to their near-zero coercivity and remanence. AC susceptibility measurements on low temperature-sintered samples show that the interparticle interaction leads to the superspin glass-like behavior in these nanoparticle samples.

Structural analysis and magnetic properties of nanocrystalline NiCuZn ferrites synthesized via a novel gelatin method

In this study, nano-crystalline Ni0.6−xCuxZn0.4Fe2O4 ferrite (0.0⩽x⩽0.5) with grain sizes of 16–38nm have been prepared through a novel method using gelatin. The proper calcination temperature for the precursors which corresponding to the ferrites formation is estimated through thermal analysis measurement. X-ray diffraction patterns confirmed the formation of single phase cubic spinel structure. The grain size was estimated using transmission electron microscopy (TEM) technique. The lattice constant hardly changed with increasing copper concentration while the crystallite size increases. Fourier transform infrared spectra (FT-IR) indicate that the portion of Fe3+ ions at the tetrahedral sites move to the octahedral sites as some of the substituted Cu2+ ions get into the tetrahedral sites. The effect of Cu-substitution on the magnetic properties was studied through the temperature dependence of the molar magnetic susceptibility. The Curie temperatures (TC) were found to decrease with increasing the Cu concentration while molar magnetic susceptibilities remain constant.

Structural phase transformation and hysteresis behavior of Cu-Zn ferrites

A series of Cu1-xZn x Fe2O4 ferrite (with x = 0.0, 0.1, 0.2, 0.3, 0.4, 0.5, 0.6) compositions were synthesized using the standard solid-state reaction technique. X-ray diffraction was used to study the structure of the above investigated samples. The theoretical and experimental lattice parameters (ath and aexp) were calculated for each composition. A significant decrease in density and subsequent increase in porosity were observed with increasing Zn content. Curie temperature, TC, has been determined from the temperature dependence of permeability and found to decrease with increasing Zn content. The anomaly observed in the temperature dependence of permeability was attributed to the existence of two structural phases: cubic phase and tetragonal phase. Low-field hysteresis measurements have been performed using a B-H loop trace from which hysteresis parameters have been determined. Coercivity and hysteresis loss were estimated with different Zn contents.

Characterization and spectral studies of Co3+-doped Cd0.4Mn0.6Fe2O4 ferrites

Abstract A series of the Cd0.4Mn0.6CoxFe2−xO4 ferrites, 0≤x≤1, were prepared and studied by using X-ray patterns and Mossbauer and FMR spectra. The lattice parameter, mean ionic radii and hopping and bond lengths and edges are determined and discussed as functions of Co3+ content x. The obtained value of oxygen positional parameter was 0.397 for all samples. The recorded FMR and Mossbauer spectra indicated a ferrimagnetic nature of all the samples. The spin–spin relaxation time, the Lande factor (g), line width ∆H and the resonance field are affected by the Co3+ additions x. The Mossbauer spectra were analyzed to two sextets attributed to the Fe3+ ions at A- and B-sites. The quadrupole and isomer shift values are found to be independent on x, whereas the hyperfine magnetic fields, HA and HB, and Mossbauer line widths at the A- and B-sites, respectively, showed dependence on x. Also HA and HB were affected by the hopping and bond lengths at these sites.

Microstructure and Magnetic Properties of Microwave Sintered Ni<sub>0.5</sub>Zn<sub>0.5</sub>Fe<sub>2</sub>O<sub>4</sub> Ferrite

Ni0.5Zn0.5)Fe2O4 ferrite has been sintered via microwave irradiation. The structural, component and magnetic properties of NiZn ferrite was determined by SEM, X-ray powder diffraction (XRD) and automatic hysteresis loop magnetometer. Results showed that the material sintered by microwave energy at 1220°C for 20min had a high purity (Ni0.5Zn0.5)Fe2O4 phase. The sample obtained magnetic properties of intrinsic coercivity 222A/m, saturation magnetization 332mT, initial permeability 0.20mH/m and maximum permeability 0.58mH/m. Compared with conventional sintering method, microwave sintering of NiZn ferrite is more efficient and reducing soaking time.

Magnesium-Zinc Ferrite Nanoparticles: Effect of Copper Doping on the Structural, Electrical and Magnetic Properties

In this paper, Mg0.5Zn0.5-Cu(x)Fe2O4 ferrites nanoparticles were synthesized by facile co-precipitation route and characterized in detail in terms of their structural, electrical and magnetic properties as a function of Cu concentration. The prepared samples have cubic spinel phase as confirmed by X-ray diffraction patterns. The decrease of the lattice constant and increase of X-ray density indicate the solubility of Cu ions in the spinel lattice. The AC conductivity measurements between 300 K and 773 K at different frequencies 1 KHz up to 1 MHz, showed two different behaviors as semiconductor-like at high temperature and frequency depending behavior associated with dispersion phenomena at low temperatures. The conduction mechanism in the system is influenced by Cu concentration and the dominant one is the hopping conduction mechanism. Dielectric measurements at the same conditions of temperatures and frequencies exhibited that the dielectric loss increases with increasing the temperature and decreasing the frequency indicating the semiconducting nature of the ferrite compounds. An anomalous behavior of the dielectric loss is observed in samples with high Cu content which explained in terms of resonance between frequency accompanied the electronic hopping and the frequency of the external electric field. The analysis of Mössbauer spectra revealed that copper free compound is super-paramagnetically relaxed in nature and zinc free compound demonstrates ferrimagnetic order. Moreover, hyperfine field spectrum shows the migration of Cu ions from octahedral to tetrahedral site in zinc free compound.