O4 Ferrites Research Articles

The influence of Ga doping on structural magnetic and dielectric properties of NiCr0.2Fe1.8O4 spinel ferrite

A series of spinel ferrites NiCr0.2GaxFe1.8−xO4 (x=0.00, 0.002, 0.04, 0.06, 0.08) was prepared by co precipitation technique. The influence of rare earth element Ga ions the structural dielectric and magnetic properties of NiCr0.2Fe1.8O4 ferrites was investigated. The X-ray diffraction confirmed the phase precipitated out was pure spinel phase with few traces of secondary phases. The crystallite size decreases and density increases with the increases of Ga contents. The magnetic moment, saturation magnetization and remanent magnetization increased with addition of Ga ions in spinel ferrite. The dielectric constant is described that it decreases more suddenly at low frequencies as compare at higher frequencies. The decrease in dielectric loss with frequency follows Deby's relaxation phenomena. Both the variation in tan loss and dielectric loss with frequency shows a similar. AC conductivity increases with the increases of frequency which inversely proportional to concentration of Ga3+ ions follows Jonscher law. These Gallium Chromium doped nickel ferrites are very helpful for high frequency switching devices.

Synthesis and characterization of rare-earth elements substituted Ni-Zn ferrites

ABSTRACTThe spinel Ni0.7Zn0.3RE0.04Fe1.96O4 ferrites with RE˭Ce and Y are fabricated by the polyacrylamide gel method. The effect of rare earth ions substitution for iron ions on the structure, morphology, electromagnetic and microwave-absorbing properties of Ni-Zn ferrites are investigated by X-ray diffraction (XRD), transmission electron microscope (TEM), thermogravimetric and differential thermal analysis (TG-DTA) and HP8510B network analyzer, respectively. The results indicate that Ni0.7Zn0.3RE0.04Fe1.96O4 ferrites form a pure cubic spinel structure, and Ce3+ and Y3+ substitute into the crystal lattice. Both the real ϵ′ and imaginary ϵ″ parts values of complex permittivity for Ni0.7Zn0.3RE0.04Fe1.96O4 ferrites are higher than those for Ni-Zn ferrites in X-band (8.2-12.4 GHz) frequency range. When RE ions substitute for iron ions, the real μ′ and imaginary μ″ parts values of complex permeability for Ni0.7Zn0.3RE0.04Fe1.96O4 ferrites decrease and increase, respectively. The microwave-absorbing properties are better for RE-substituted Ni-Zn ferrites than Ni-Zn ferrites. For Ni0.7Zn0.3Ce0.04Fe1.96O4 ferrites, the minimum loss is −12.5 dB at 18 GHz for an absorber thickness of 2 mm.

Substitution effects on magnetic properties of Mg1.3-xMnxAlyFe1.8-yO4 ferrite

Mg1.3-xMnxAlyFe1.8-yO4 (x = 0.1–0.2, y = 0.15–0.3) spinel ferrites were prepared using conventional ceramic technique. Highly densified Mg–Mn–Al ferrites (with 99% theoretical density) were obtained, and the influence of Mn and Al substitution on the characteristics of these ferrites has been systematically studied. The microstructure, magnetic properties, and ferromagnetic resonance linewidth (ΔH) of the Mg–Mn–Al ferrites have been analyzed by X-ray diffraction, B-H analyzer, and ferromagnetic resonance (FMR) spectrometer. The results showed that all of the samples were single spinel phase. As Mn content increases and Al content decreases, both saturation magnetization (4πMs) and squareness ratio increase, while the coercivity (Hc) first increases and then decreases. In addition, good ferromagnetic resonance linewidth properties were also obtained as 143.8 Oe at 9.3 GHz for the sample with x = 0.17 and y = 0.20. The results imply that Mg1.3-xMnxAlyFe1.8-yO4 ferrites may be applicable for X-band (8–12 GHz) microwave devices.

Low-temperature sintering and ferrimagnetic properties of LiZnTiMn ferrites with Bi2O3-CuO eutectic mixture

The effects of Bi2O3-CuO mixture on the microstructural development and gyromagnetic properties of low-temperature sintered Li0.42Zn0.27Ti0.11Mn0.1Fe2.1O4 (LiZnTiMn) ferrites have been studied in order to adapt the development of low-temperature co-fired ceramics (LTCC) technology and produce gyromagnetic devices with a multilayer process. In this work, a pure spinel phase can be formed with a sintering temperature ranging from 880 °C to 900 °C, which allows them to be co-fired with silver internal electrodes. The addition of Bi2O3-CuO mixture in LiZnTiMn ferrites contributes significantly to the grain growth, densification and improving ferrimagnetic properties through a low-temperature sintering process. Their low-temperature sintering mechanism was proposed and discussed. The results show that the codoping of 0.21 wt% Bi2O3 and 0.29 wt% CuO cannot only double increase the saturation induction, but also drastically reduce the ferromagnetic resonance line width at 9.3 GHz, indicating that Bi2O3-CuO additive is a good candidate for reducing the sintering temperature of LiZnTiMn ferrites.

Remanence Enhancement Effect in Ni0.7Zn0.3Fe2O4/Co0.8Fe2.2O4 Ferrite Multilayer Film**Supported by the National Natural Science Foundation of China under Grant Nos 11274314, 11374304, 51102072, 21201052 and U1632161, the Natural Science Major Foundation of Anhui Provincial Higher Education Institutions under Grant No KJ2012ZD14, the Natural Science Foundation of Anhui Province under Grant No 1508085MA18, the Postdoctoral Science Foundation of China under Grant No

Ni0.7Zn0.3Fe2O4/Co0.8Fe2.2O4 (NZFO/CFO) multilayer films are fabricated on Si(100) substrates by the chemical solution deposition method. The microstructure and magnetic properties are systematically investigated. The results of field-emission scanning electronic microscopy show that the grain size of the NZFO/CFO multilayer film is quite uniform and the thickness is about 300 nm. The remanence enhancement effect of the NZFO/CFO multilayer film can be mainly attributed to the exchange coupling interaction between NZFO and CFO ferrite films, which is in favor of the design and fabrication of modern electronic devices.

Thickness and Composition Tailoring of K- and Ka-Band Microwave Absorption of BaCo x Ti x Fe(12−2x)O19 Ferrites

The goal of this research is to investigate the electromagnetic and microwave absorption properties of M-type barium hexaferrites with chemical formula BaCo x Ti x Fe(12−2x)O19 (x = 0.0, 0.2, 0.4, 0.6, 0.8, 1.0) in K and Ka band. Characterization techniques such as x-ray diffraction analysis and scanning electron microscopy were applied to confirm ferrite formation. The frequency dependence of the complex permittivity and complex permeability was studied for prepared ferrite samples in the frequency range from 18 GHz to 40 GHz. Factors such as the quarter-wavelength condition, impedance matching, high dielectric–magnetic losses, as well as ferromagnetic resonance were investigated to determine their contribution to the absorption characteristics. It was found that the quarter-wavelength (λ/4) model could be successfully applied to predict and understand the position as well as number of reflection peaks in the microwave absorption spectrum. The origin of the reflection loss peaks is explained and verified based on calculations of input impedance, loss tangent, and ferromagnetic resonance. Reflection loss analysis revealed that all six compositions exhibited reflection loss peaks (absorption >90%) at their matching thicknesses and frequencies. Therefore, these ferrites are potential candidates for use in electromagnetic shielding applications requiring low reflectivity in K and Ka band.

Structural and magnetic studies of the Co1+xTixFe2(1−x)O4 ferrites

The cubic spinel Co1+xTixFe2(1−x)O4 ferrites, 0.0≤x≤0.5, were prepared by the standard ceramic technique. The samples were examined using the techniques; XRD, FT-IR, SEM and VSM. The average lattice parameter showed dependence on x, whereas the crystallite and grain size and strain did not. The infrared spectra showed six absorption bands in the range of 200–1000cm−1. They were assigned to the corresponding metallic ion–oxygen bonds among the A- and B-sites. The absorption bands ν1 and ν2 and their intensities and force constants F1 and F2 were increased against x. Using the transmitted and absorbed energy, the IR velocity and refractive index and jump rate of vacancies were determined and discussed as functions of x. The trend of sauration magnetization Ms was decreased with x, whereas that of coercivity and anisotropy constant was increased. The determined Debye temperature and stiffness constant of the samples were discussed as functions of x. The absorption bands ν1 and ν2 proved dependence on the distance between magnetic ions (hopping length) LA-A and LB-B at the A- and B-sites, respectively, whereas F1 and F2 proved dependence on Ms.

Electromagnetic properties of nanocrystalline Al3+ substituted MgCuMn ferrites synthesized by microwave hydrothermal method

The effect of Al3+ substitution on electromagnetic properties has been studied for nanocrystalline Mg0.8Cu0.2Mn0.05Al x Fe1.95−x O4 ferrites, wherein x varies from 0 to 0.4 in steps of 0.1. These ferrites were synthesized by using microwave hydrothermal method and then characterized using X-ray diffractometer (XRD), Fourier transform infrared and transmission electron microscopy. The synthesized powders were densified using microwave sintering method at 950∘C/50 min. Structural and surface morphology of sintered samples were characterized using XRD and atomic force microscopy, respectively. The complex permittivity and permeability properties were measured over a frequency range 100 Hz–1.8 GHz. The temperature variation of magnetic properties were measured in the temperature range of 300–650 K. The electrical and magnetization studies inferred that the values of d.c. resistivity increases by 27%, whereas saturation magnetization decreases linearly from 38.6 to 23.0 emu g−1 and Curie temperature was found to be decreased from 628 to 513 K with an increase of Al3+ ions. The low dielectric, magnetic losses, moderate saturation magnetization and high-temperature stability properties exhibited by Al3+ substituted MgCuMn ferrites make them find applications in microwave devices, such as circulators and isolators etc. The applicability of present samples for microwave devices has been tested by the measurement of ferromagnetic resonance linewidth at Ka band.

Improvement of room temperature electric polarization and ferrimagnetic properties of Co1.25Fe1.75O4 ferrite by heat treatment

We report the improvement of electric and magnetic properties of the chemical routed samples of Co1.25Fe1.75O4 ferrite. Synchrotron X-ray diffraction pattern confirmed the cubic spinel structure in all samples. Raman spectroscopy provided the information of mixed-type cubic spinel structure, where Co2+ and Fe3+ ions order both in octahedral and tetrahedral sites. The thermal heat treatment has brought a systematic change in electric polarization and magnetic parameters. At a critical annealing temperature (TAN) of 800°C, the sample has shown the highest magnetic coercivity ~596Oe and relatively large squareness ~0.5. The electrical conductivity, dielectric loss and dielectric constant have decreased with increase of TAN. The dielectric constant becomes stable for TAN above 800°C. The samples annealed in the temperature range 900–1000°C have shown a good signature of ferroelectric polarization, although it is under saturation value and leakage of polarization due to conductive effect is observed. This work shows the scope of the improvement of electric polarization due to capacitive effect on increasing the annealing temperature of as-prepared Co ferrite sample.

Evidence of structural damage in Sm and Gd co-doped Mn–Zn ferrite ceramics due to high-energy gamma irradiation

We report the evidence of structural changes due to high energy gamma irradiation in Mn0.4Zn0.6SmxGdyFe2−(x+y)O4 (where x=y=0.01, 0.02, 0.03, 0.04 and 0.05) ferrites prepared by self-propagating high temperature synthesis method. The structural properties of the as prepared samples and the structural modifications to the samples after gamma irradiation were studied by X-ray diffraction (XRD), Mössbauer spectroscopy and Fourier Transform Infrared (FTIR) Spectroscopy at room temperature. The XRD patterns of the as prepared samples reveal the formation of mixed cubic spinel phase along with small amounts of α-Fe2O3, SmFeO3 and/or GdFeO3 impurity phases. All samples were exposed to gamma radiation dose of 50kGy originating from a 60Co source. Our results demonstrate that after gamma irradiation the structure and composition of the various phases in the sample were changed and more stable new phases like ZnFe2O4, α-Fe2O3 and MnO2 evolved. As a result the (magnetic) properties of the materials were also altered. Our observation of changes in structural and magnetic properties of the reported ferrites are important for understanding the stability and performance of the materials used in various devices, which are exposed to high energy gamma-rays.

Stress-Induced Anisotropy and Stress Dependence of Saturation Magnetostriction in the Jiles-Atherton-Sablik Model of the Magnetoelastic Villari Effect

Abstract The paper presents the results of the magnetoelastic Villari effect modelling in high-permeability Mn0.51Zn0.44Fe2.05O4 ferrite. Modelling was performed on the basis of measurements of magnetoelastic characteristics of frame-shaped samples. For the modelling, the corrected Jiles-Atherton-Sablik model was used. On the base of modelling results, the stress dependence of parameter k and stress-induced anisotropy were estimated. As a result the changes of saturation magnetostriction of Mn0.51Zn0.44Fe2.05O4 ferrite subjected to stresses were calculated. Such changes were previously observed experimentally. However, the phenomenon of stress-induced sign change of saturation magnetostriction was never previously explained quantitatively

Effect of zinc substitution on Co-Ga and Co-Tl ferrite nanoparticles prepared by hydrothermal route

Nanoparticles of CoFe2O4, Co0.5Zn0.5Fe1.5Tl0.5O4, Co0.5 Zn0.5Fe1.5Ga0.5O4 ferrites were synthesised by hydrothermal method, and the influence of Tl3+ and Ga3+ doping on the properties of Co0.5Zn0.5Fe2-xMxO4 (M = Tl and Ga) was studied. X-ray diffraction studies revealed the formation of single-phase spinel-type cubical structure and the particle sizes of the as-obtained samples were found to be ~42–56 nm. Field Emission Scanning Electron Microscope (FE-SEM) and Tunnelling Electron Microscope (TEM) were used to characterise the microstructure of the samples and particle size determination, which exhibited the formation of spherical nanoparticles. The saturation magnetisation (Ms) and coercivity (Hc) value change due to the addition of nonmagnetic zinc to the CoFe1.5Tl0.5O4 and CoFe1.5Ga0.5O4. The magnetic studies demonstrated that zinc nanoparticles displayed paramagnetic behaviours with thallium cobalt ferrite and gallium cobalt ferrite, while cobalt ferrite with Tl3+ and Ga3+ ions nanoparticles exhibited ferromagnetic behaviours. The addition of zinc had changed the ferromagnetic material to paramagnetic material.

Investigation of microwave absorption and DC electrical properties of Mn2+ and Ti4+ substituted SrMnxTixFe(12−2x)O19 ferrite

The microwave characterization of Mn2+ and Ti4+ ions substituted M-type SrMnxTixFe(12−2x)O19 hexagonal ferrite (x = 0.5, 1.0, 1.5 and 2.0) has been reported as a function of frequency, substitution and thickness in X-band. The static current density (J)-electric field (E) characteristics have been investigated as a function of substitution at an applied field from 4 kV/m to 40 kV/m. The microwave characteristics have been measured using microwave power meter in the rectangular slotted waveguide and the current density has been measured using electrometer. The microwave absorption has been evaluated using the standard model of quarter wavelength criterion. The microwave absorption is enhanced while electrical current density is decreased with the substitution of Mn2+ and Ti4+ ions. The different compositions have scope for microwave or high frequency absorber applications.

Silica-coated manganite and Mn-based ferrite nanoparticles: a comparative study focused on cytotoxicity

Magnetic oxide nanoparticles provide a fascinating tool for biological research and medicine, serving as contrast agents, magnetic carriers, and core materials of theranostic systems. Although the applications rely mostly on iron oxides, more complex oxides such as perovskite manganites may provide a much better magnetic performance. To assess the risk of their potential use, in vitro toxicity of manganite nanoparticles was thoroughly analysed and compared with another prospective system of Mn–Zn ferrite nanoparticles. Magnetic nanoparticles of La0.63Sr0.37MnO3 manganite were prepared by two distinct methods, namely the molten salt synthesis and the traditional sol–gel route, whereas nanoparticles of Mn0.61Zn0.42Fe1.97O4 ferrite, selected as a comparative material, were synthesized by a new procedure under hydrothermal conditions. Magnetic cores were coated with silica and, moreover, several samples of manganite nanoparticles with different thicknesses of silica shell were prepared. The size-fractionated and purified products were analysed using transmission electron microscopy, dynamic light scattering, measurement of the zeta-potential dependence on pH, IR spectroscopy, and SQUID magnetometry. The silica-coated products with accurately determined concentration by atomic absorption spectroscopy were subjected to a robust evaluation of their cytotoxicity by four different methods, including detailed analysis of the concentration dependence of toxicity, analysis of apoptosis, and experiments on three different cell lines. The results, comparing two manganese-containing systems, clearly indicated superior properties of the Mn–Zn ferrite, whose silica-coated nanoparticles show very limited toxic effects and thus constitute a promising material for bioapplications.

Ba(CoTi)1.22Fe9.56O19 ferrites prepared by sol–gel method and solid-state method techniques

In this work, we synthesized the Co–Ti-substituted barium ferrite materials (Ba(CoTi)1.22Fe9.56O19) by sol–gel method (S1) and solid-state method (S2). The phase formation, structural and magnetic properties of both samples were investigated separately. Differential scanning calorimeter and thermo-gravimetric analysis curves showed changes in energy and weight with respect to temperatures during the sintering process—from room temperature to 1200 °C at a rate of 10 °C per min. X-ray diffractometer patterns indicate that both samples, with Co–Ti ions substitution, had single phase of M-type barium ferrite, and no clear structural changes or formation of second phase was observed. Grain size and shape of samples were exhibited in SEM images, from which S1 showed more regular-shaped particles than S2. Magnetic hysteresis loops of the samples were measured using a vibrating sample magnetometer and showed similar saturation magnetization (M s) and coercivity (H c). M s and H c are mainly determined by electron magnetic moment, ion occupation and particle size. Microwave absorption properties of the samples were characterized by a microwave vector network analyzer in the frequency range of 0.5–18 GHz. In terms of complex magnetic permeability, dielectric permittivity, maximum reflection loss, resonance peak and bandwidth, there were remarkable differences between two samples. We suggested that these different characteristics originate from the variation in particles size, surface state and oxygen vacancies, which determined the interfacial polarization and related microwave absorption performance of the samples.

Role of pH value during chemical reaction, and site occupancy of Ni2+ and Fe3+ ions in spinel structure for tuning room temperature magnetic properties in Ni1.5Fe1.5O4 ferrite

The magnetic properties of Ni1.5Fe1.5O4 ferrite have been investigated using the techniques of dc magnetometry and Mӧssbauer spectroscopy. The material has been prepared by chemical reaction of metal nitrates at different pH values and subsequently, annealed at different temperatures to improve the microstructure. The samples with single-phased cubic spinel structure have been used for magnetic study. The material showed a variety of magnetic features, including superparamagnetic and soft ferromagnetic properties. At room temperature, changes of the ferromagnetic parameters of the material have been found in the range 0–47emu/g for spontaneous magnetization, 0–0.37 for squareness, and 0–195Oe for coercivity. Variation of the pH value during chemical reaction and changes of the grain size by thermal treatment played an important role in tuning the coexisting superparamagnetic and ferromagnetic components in the material. Samples prepared at high pH value showed small grain size and superparamagnetic features, whereas the samples prepared at low pH value produced large grain size and better ferromagnetic features. The ferromagnetic properties of the material have been enhanced by lowering the pH value and increasing the annealing temperature. Mössbauer spectra provided insight of the local magnetic order, site occupancy of Ni and Fe ions and oxidation state of Fe ions in the spinel structure of Ni1.5Fe1.5O4 ferrite.

Magnetic hysteresis loss crossover in Ni0.4Zn0.6Fe1.95Ti0.05O4 ferrite

Ni0.4Zn0.6Fe2O4 and Ni0.4Zn0.6Fe1.95Ti0.05O4 ferrites were prepared by solid state reaction method and their magnetic properties were investigated. It was found that there is a magnetic hysteresis loss crossover around Bm = 4 mT, the hysteresis loss coefficient from 5.5 × 10−2 T−1 in Bm < 4 mT jump down to 4.0 × 10−2 T−1 in Bm > 4 mT in Ni0.4Zn0.6Fe1.95Ti0.05O4 sample by measuring field dependence of relative loss factor. This crossover was verified by measuring field dependence of real part permeability and magnetic loops. The possible mechanism of this crossover was discussed, and it was regarded that the crossover was due to magnetic domain wall pinning by Ti cation doped in ferrite.

Static conduction mechanisms in Co2+ and Ti4+ substituted M-type SrCox Tix Fe(12-2x) O19 ferrite

The static current density (J)-electric field (E) characteristics of SrCo x Ti x Fe(12−2x)O19 ferrite compositions (x = 0.0, 0.2, 0.3, 0.5, 0.6, 0.7, 1.0) have been investigated from 0.07 kV/m to 5.29 kV/m at room temperature. All compositions obey Ohms Law at low applied field and non-linearity conduction is observed at high field in compositions x = 0.0, 0.2, 0.3, 0.5, 0.6 and 1.0. The non-linear conduction mechanisms, Schottky, Poole-Frenkel, Ionic Hopping and Space Charge Limited Current mechanism, have been discussed. The current density is increased at higher substitution.

Investigation of DC current models in Co2+ and Ti4+ substituted M-type BaCox Tix Fe(12-2x) O19 ferrite

The static current density (J)-electric field (E) characteristics of BaCoxTixFe(12−2x)O19 ferrite compositions (x = 0.1, 0.3, 0.5, 0.7, 0.9) have been investigated at an applied field from 0.003 kV/m to 4.98 kV/m at room temperature. Compositions x = 0.3, 0.5 and 0.7 exhibit ohmic behavior at low applied field and non-linear conduction is observed in compositions x = 0.1, 0.3, 0.7 and 0.9 at higher applied field. The various non-linear conduction models, associated with Schottky, Poole-Frenkel, Ionic Hopping and Space Charge Limited Current mechanisms, have been discussed. The large current density has been found at higher substitution.

Matching permeability and permittivity of Ni0.5Zn0.3Co0.2In0.1Fe1.9O4 ferrite for substrate of large bandwidth miniaturized antenna

Nickel zinc cobalt indium ferrite of nominal composition Ni0.5Zn0.3Co0.2In0.1Fe1.9O4 was synthesized by a co-precipitation technique. The effect of sintering temperature on structural and electromagnetic properties was studied over the frequency range of 10 MHz to 6 GHz. The crystallite size increases from 45 to 60 nm, with an increase in sintering temperature from 800 to 1000 °C. The relative permeability (μr) and relative permittivity (er), both varies between 5 and 8 with sintering temperature and remains consistent up to 700 MHz, but ferrimagnetic resonance frequency reduces from 900 to 700 MHz. For sintering temperature of 900 °C, almost matching value of permeability and permittivity equals to 5.5 and 5.3 respectively were obtained up to 700 MHz. The loss tangent are found to be of the order of 10−2 in the same frequency band. Matching values of er (~5.3) and μr (~5.5) are very effective in proper impedance matching of substrate material with free space. Analysis in High frequency structural simulator verifies that the synthesized magneto-dielectric material based antenna can miniaturize size (~65 %), lowers reflection losses (RL) by 15 %, higher −10 dB RL bandwidth (8–12 %) and higher voltage standing wave ratio bandwidth (9–13 %) at resonant frequency of 450 MHz. The observed matching values also result in higher gain and radiation efficiency. Hence, the excellent electromagnetic properties obtained in our investigation for the suitably sintered Ni0.5Zn0.3Co0.2In0.1Fe1.9O4 ferrite shows a lot of potential to be used as a substrate material in miniaturizing microstrip antenna for futuristic electronic devices.