Ferrite System Research Articles

Effect of indium substitution on the electrical and magnetic properties of Ni–Zn ferrite

Indium-substituted polycrystalline nickel zinc ferrites of different compositions Ni0.65Zn0.35Fe2−x In x O4 (x = 0.00, 0.04, 0.08, 0.12, 0.16, 0.2) have been prepared by solid-state reaction route. Calcination and sintering of all samples were done in air atmosphere at 950 °C and 1250 °C, respectively, followed by natural cooling to room temperature. Characterization of the basic composition was done by X-ray diffractometry, saturation magnetization and Curie temperature. The effect of incorporation of larger indium ions in place of iron was studied with the help of saturation magnetization, Curie temperature, permeability, magnetic loss factor, DC electrical resistivity and dielectric properties. The highest magnetization and permeability values of the present system under study are 74.1 emu/g and 438 for the basic composition (concentration x = 0). The DC electrical resistivity was found to decrease up to x = 0.3 and increase thereafter. The variation in the electric and magnetic properties of this ferrite system is dominated by the decrease in iron concentration. Characteristic high dielectric constant values were recorded for these bulk ceramic materials.

Magnetic Investigation of Various NiFe2−x Bi x O4 Ferrite Nanostructures Synthesized by Ball Milling Technique

NiFe2−x Bi x O4 (x = 0, 0.1, 0.2, 0.3) nanoparticles with various grain sizes were synthesized via annealing treatment followed by ball milling of its bulk component materials. Commercially available bismuth, nickel and iron oxide powders were first mixed and then annealed at 1200 °C in an oxygen environment furnace for 4 h. The samples were then milled for 2 h by high-energy ball milling. X-ray diffraction (XRD) pattern indicated that in this stage the samples are single phase. The microstructure investigation was carried out by a scanning electron microscope with maximum magnification of 30,000. The average grain size for different samples was estimated by XRD technique and transmission electron microscopy. Magnetic behavior of the samples at room temperature was studied using an alternating gradient force magnetometry. The Neel temperature of the powders was measured by a Faraday balance. Based on magnetic studies, increase in bismuth content leads to a decrease in the saturation magnetization, coercive field and Neel temperature. This can be attributed to the substitution of Bi3+ ion in the ferrite system as a nonmagnetic cation.

Effects of Ni Concentration on the Structural and Magnetic Properties of NiZnFe<sub>2</sub>O<sub>4</sub> Ferrites Synthesized via a Polymer Precursor

In this paper, we report the experimental observations of the effects of Ni concentration on the structural and magnetic properties of NixZn1-xFe2O4 (x=0.2-0.8) ferrite nanoparticles synthesized by a chemical method via a polymer precursor. The synthesis process involves a reaction of aqueous solutions of metal salts (Fe3+, Zn2+ and Ni2+) with an aqueous poly-vinyl alcohol (PVA)-sucrose solution at 65-70oC. Controlled growth of the ferrite nanoparticles was achieved by encapsulation of the nucleating sites in the PVA-sucrose polymer micelles. Structural properties of the derived samples were analyzed with X-ray diffraction (XRD) and X-ray absorption near edge spectroscopy (XANES) studies. The magnetic properties of the NixZn1-xFe2O4 (x=0.2-0.8) nanoparticles were evaluated at room temperature with a vibrating sample magnetometer (VSM). XRD analysis confirmed the formation of single phase cubic spinel ferrite structure. The local structural analysis of the Ni-Zn ferrite crystal system performed with XANES studies at Fe K-edge revealed the migration of Fe3+ ions from the octahedral sites to tetrahedral sites with the increase in Ni2+concentration in the ferrite structure.It was observed that the magnetization increases with the increase in Ni concentration till the maximum saturation magnetization was observed in the composition Ni0.5Zn0.5Fe2O4. Further increase in Ni concentration reduces the magnetization. The obtained results were analyzed in correlation with the cationic distributions at the lattice sites in these ferrite nanoparticles.

Low-temperature combustion synthesis of cobalt magnesium ferrite magnetic nanoparticles: effects of fuel-to-oxidizer ratio and sintering temperature

The effects of glycine-to-nitrate molar ratio (G/N) and sintering temperature of 600 °C on the solution combustion synthesis of nanocrystalline Co0.8Mg0.2Fe2O4 (CMFO) are reported. The structural, morphological and magnetic properties of CMFO could be controlled by using different combinations of glycine fuel and metal nitrates and also sintering temperature. Thermodynamic considerations of the combustion processes show that the exothermicity, adiabatic flame temperature and the amount of gases released increase with increase in G/N. The auto-combusted and sintered powders obtained were characterized by X-ray diffraction, Raman spectroscopy, scanning electron microscopy (SEM), thermo-gravimetric analysis–differential scanning calorimetry and vibrating scanning magnetometer measurements. SEM images of CMFO showed that the G/N ratio and sintering temperature had pronounced effect on the microstructure regarding density and porosity. The magnetization, crystallite sizes and crystallinity of the CMFO spinel phase increased with increase in G/N ratio and sintering temperature. Raman spectroscopic analysis showed that only the fuel-rich sample gave the five Raman active modes characteristic of a spinel structure. The obtained results were also discussed in comparison with ferrite system formed by different synthesis processes. XRD of CMFO auto-combustion powders prepared with different G/N ratios: (a) G/N = 2.22, (b) G/N = 1.48 and (c) G/N = 0.74.

Structural phase change in Co2.25Fe0.75O4 spinel oxide by vacuum annealing and role of coexisting CoO phase on magnetic properties

The spinel oxide Co2.25Fe0.75O4 has been prepared by co-precipitation route. The as prepared material has been annealed at 800 °C under vacuum. Properties of the samples annealed under vacuum have been compared with the sample annealed in air. Synchrotron X-ray diffraction, Raman spectroscopy and X-ray absorption near edge structure spectroscopy have been used for structural phase characterization. The cubic spinel structure in air annealed sample has been splitted into Co and Fe rich phases. The Co rich spinel phase has transformed into Cobalt monoxide (CoO) after vacuum annealing. This has resulted an increase of Fe:Co ratio in the Fe rich spinel phase. Raman spectra indicated a transformation of the distribution of Co and Fe ions from normal spinel like structure for the sample annealed in air to mixed spinel structure for the samples annealed under vacuum. The existence tetravalent Fe4+ ion has been confirmed in all the samples and it is new information for Co doped spinel ferrite system. All the samples exhibited ferrimagnetic behavior and exchange bias effect. The focus point is that vacuum annealing has been used as an effective route of material processing to control the structural phase and also, enhancement of magnetic properties in Co rich ferrite.

Studies on structural and electrical properties of Li0.5−0.5xCoxFe2.5−0.5xO4 (0≤x≤0.6) spinel ferrite

In the present work, nanocrystalline Li0.5−0.5xCoxFe2.5−0.5xO4 (for x=0.0, 0.1, 0.2, 0.3, 0.4, 0.5 and 0.6) ferrite systems were synthesized by solution combustion method. The Rietveld analysis of X-ray result confirms the formation of a single phase spinel cubic crystal structure of the ferrite sample. The lattice constant of the material increases from 8.33Å to 8.36Å with increasing cobalt content in lithium ferrite. The cation distribution study reveals that the Co–Li ferrite is in the mixed spinel structure of the composition. The DC electrical resistivity result confirms the semiconducting nature and the Curie temperature decreases with increase in Co2+ content. The dielectric constant, loss tangent and dielectric loss decrease with frequency and remain constant at higher frequencies are observed, showing the usual dielectric dispersion due to space charge polarization. The impedance spectroscopy analysis of samples reveals the grain interior contribution in the conduction process. The AC conductivity as a function of frequency verifies that the small polarons are responsible for conduction process.

Effects of sintering temperature on structural and electromagnetic properties of MgCuZn ferrite prepared by microwave sintering

Nanocrystalline magnesium–copper–zinc (Mg0.30Cu0.20Zn0.50Fe2O4) ferrites were prepared by microwave sintering technique. The effects of the sintering temperature on particle size and magnetic properties were investigated. In this article, optimum sintering temperature required for MgCuZn ferrite system for obtaining good electromagnetic properties, suitable for applications in low temperature co-fired ceramics (LTCC) chip components was studied. The grain size, initial permeability, dielectric constant and saturation magnetisations were found to increase, and dielectric loss was found to decrease with the increasing sintering temperature. Mg–Cu–Zn ferrites with a permeability of μ = 1110 (at 1 MHz) were fully densified at the standard LTCC sintering temperature of 950°C.

Cation distribution correlated with magnetic properties of nanocrystalline gadolinium substituted nickel ferrite

Nano crystalline NiFe2−xGdxO4 (0.0≤x≤0.4) ferrite was prepared by citrate method. The samples were characterized with X-ray diffraction, FT-IR spectroscopy, TEM and magnetic measurements. The effect of Gd3+ cations substitution on structural, microstructural and magnetic properties of prepared nanoparticles was investigated. From Rietveld analysis, the system was found to be inverse spinel structure with Gd3+ residing on octahedral B-site 16c and the grain boundary, while Ni2+ occupying the B-site at both 16c and 16d. The lattice parameter (a) changes nonmonotonically, first increases then decreases with Gd doping content. The M–H and M–T relations had demonstrated a change in the magnetic moment and a ferrimagnetic–superparamagnetic transition in the ferrite system. For low temperature measurements, an increase in gadolinium content resulted in increasing the coercive field while the saturation of magnetization (Ms), first deceases then increases with Gd doping content. At room temperature Ms decreases with increasing Gd substitution.

Structural Observations, Density and Porosity Studies of Cu Substituted Ni-Zn Ferrite through Standard Ceramic Technique

Polycrystalline NiCuZn ferrites prepared by solid state reaction method with various concentrations of copper generalized as Ni0.7-xCuxZn0.3Fe2O4 with the x varying from 0 to 0.50 in steps of 0.05 variations. In this paper we present the structural, density and porosity. The powders of the samples were used to characterize the x-ray diffraction. The XRD patterns of the samples provide the evidence of the single cubic crystal symmetry phase. The microstructure of the NiCuZn ferrite average grain size is recorded by SEM. The NiCuZn ferrite system having low cost and low firing metals for preparing the multi layer ferrite chip inductors and higher densification than the Mn-Zn ferrite.

Influence of the divalent and trivalent ions substitution on the structural and magnetic properties of Mg0.5−xCdxCo0.5Cr0.04TbyFe1.96−yO4 ferrites prepared by sol–gel method

A series of the divalent and trivalent co-substituted Mg0.5−xCdxCo0.5Cr0.04TbyFe1.96−yO4 spinel ferrite systems (where x=0–0.5 in steps of 0.1 and y=0.00–0.10 in steps 0.02) are synthesized by sol–gel auto combustion method. The product materials were characterized by the thermo gravimetric analysis and differential scanning calorimetry (TGA/DSC), Fourier transform infrared spectra (FTIR), nitrogen adsorption (BET), X-ray diffraction (XRD), scanning electron microscope (SEM), atomic force microscopy (AFM) and vibrating sample magnetometer (VSM). The X-ray diffraction patterns and Fourier transform infrared spectroscopy confirm spinel nanocrystalline phase. The crystallite size is determined by Scherer's formula from 36.6 to 69.4nm. The X-ray density is found in the range of 5.09–6.43(g/cm3). The morphological features are studied using scanning electron microscope and AFM. Saturation magnetization (Ms) and remanence (Mr) magnetization extracted from M–H loops exhibit the decreasing trends 21.4–16emu/g and 9.1–6.3emu/g, respectively. A significant decrease in the intrinsic parameters is observed in the prepared samples due to the weakening of the A–B interaction as iron enters into the tetrahedral A-site. The coercivity lies in the range of 300–869Oe as a function of co-substitution contents. The coercivity of the sample with x=0.1, y=0.02 was found maximum i.e. 869Oe. The obtained results suggest that the investigated materials may be potential candidates for high density recording media applications.

Structural and magnetic properties of Ni0.8Co0.2−2xCuxMnxFe2O4 spinel ferrites prepared via solution combustion route

Ni0.8Co0.2−2xCuxMnxFe2O4 ferrites (with x=0.01, 0.03, 0.05, 0.07 and 0.09) were prepared using solution combustion route. X-ray diffraction analysis indicates the presence of the characteristic most intense (311) peak along with other reflections confirming the formation of spinel ferrite in each composition. SEM images show formation of porous structured agglomerates with submicron sized grains. The microstrain measurement of ferrite series is non-linear with variation in dopant concentration for a given magnetic field. The magnetic hysteresis at room temperature indicates the ferrimagnetic behavior of synthesized ferrite system. The magnetic and mechanical properties were seen to be comparatively higher for x=0.07 composition. The presence of sexset in Mössbauer spectra confirms the ferrimagnetic nature of all the ferrites.

Electrical and Dielectric Relaxation Characterization of Ni1−x Zn x Ga0.5Fe1.5O4

The ferrite system, Ni1−x Zn x Ga0.5Fe1.5O4 (x ranges from 0.0 to 0.5 in steps of 0.1), has been synthesized by a solid-state reaction technique. Single-phase cubic spinel structure was confirmed with X-ray diffraction (XRD) and Fourier transform infrared (FT-IR) results. The effect of introducing zinc in the unit cell on the electrical properties was investigated in the ranges 102–105 Hz and 300–600 K of frequency and temperature, respectively. Semiconducting behavior over all studied ranges of frequency and temperature was observed. This behavior is attributed to the cation–anion–cation interaction, which is most predominant at B-sites in these samples. Variation of the universal exponents with temperature indicates the presence of a correlated barrier hopping (CBH) mechanism. The determined transition temperature T C was found to decrease with increasing the compositional parameter x.

Precursor combustion synthesis of nanocrystalline cobalt substituted nickel zinc ferrites from hydrazinated mixed metal fumarates

In present investigation, a systematic approach towards synthesis of nanocrystalline ferrites, CoxNi0.6−xZn0.4Fe2O4 (x=0.1 and 0.4) has been reported by room temperature decomposition of precursors, CoxNi0.6−xZn0.4Fe2 (C4H2O4)3·6N2H4 (x=0.1 and 0.4). The precursor complexes were characterized by Fourier transform infrared spectroscopy (FTIR), chemical analysis and thermal studies like isothermal mass loss, total mass loss, thermogravimetry (TG), derivative of thermogravimetry (DTG) and differential thermal analysis (DTA). The TG–DTG–DTA patterns of both precursors reveal multistep decomposition with complete ferritization at 410°C. The thermally decomposed products were characterized by X-ray diffractometry (XRD) for phase purity. The FT-IR spectroscopy studies of the same shows complete removal of all organic moieties from decomposed precursors. The nanophasic nature of synthesized ferrites was confirmed by transmission electron microscopy (TEM) analysis as well as from broadening of XRD peaks. The AC magnetization studies show the existence of single domain and superparamagnetic particles, which supports nanosize particles distribution in the ferrite system under study.

Structural, magnetic and dielectric studies of copper substituted nano-crystalline spinel magnesium zinc ferrite

Nano-crystalline Mg0.5Zn0.5−xCuxFe2O4 (x=0.0, 0.1, 0.2, 0.3, 0.4 and 0.5) ferrite powders were synthesized using co-precipitation method. The influence of Cu2+ ions substitution on the structural and magnetic properties was investigated. X-ray diffraction measurements revealed the formation of nano-crystalline ferrite with single cubic spinel phase. The lattice constant was found to decrease with increasing Cu2+ ions content. Infrared spectral analysis confirmed formation of the spinel structure for the respective ferrite system. Magnetic data showed that the saturation magnetization (Ms) increases with Cu2+ concentration up to x=0.2 and then decreases with further increase of Cu2+ ions in this ferrite system. The proposed cation distribution deduced from X-ray diffraction, infrared spectra and magnetization data indicated mixed ferrite type. Dielectric constants ε′, dielectric loss ε′′, dielectric loss tangent tanδ and ac conductivity, σac, were investigated as a function of frequency and temperature. Influence of Cu2+ substation on the ac conductivity exhibited significant behavior at low frequencies and low temperatures, T⩽100°C. Both dielectric constants (ε′, ε″) found to increase with the increase of the temperature. At low temperatures, dielectric loss tanδ indicated a decrease with frequency with slight change at high temperatures.

Enhanced magneto-capacitance response in BaTiO3–ferrite composite systems

Combined effect of BaTiO3 morphology and magnetoresistance or magnetostriction led to enhance the magneto-capacitance response of BaTiO3 : ferrite composite systems.

Microwave combustion synthesis of Co1−xZnxFe2O4 (0 ⩽ x ⩽ 0.5): Structural, magnetic, optical and vibrational spectroscopic studies

Nanostructured pure and zinc doped cobalt ferrites (Co1−xZnxFe2O4 where x fraction ranging from 0 to 0.5) were prepared by microwave combustion method employing urea as a fuel. The nanostructured samples were characterized by using various instrumental techniques such as X-ray powder diffractometry, high resolution scanning electron microscopy, energy dispersive X-ray analysis, UV–visible diffuse reflectance spectroscopy, photoluminescence spectroscopy and Fourier transformed infrared (FT-IR) spectroscopy. Vibrating sample magnetometry at room temperature was recorded to study the magnetic behavior of the samples. X-ray analysis and the FT-IR spectroscopy revealed the formation of cobalt ferrite cubic spinel-type structure. The average crystallite sizes for the samples were in the range of 3.07–11.30nm. The direct band gap (Eg) was estimated using Kubelka–Munk method and is obtained from the UV–vis spectra. The band gap value decreased with an increase in zinc fraction (2.56–2.17eV). The violet and green emission observed in the photoluminescence spectra revealed that cobalt ferrites are governed by defect controlled processes. The elemental analysis of zinc doped cobalt ferrites were obtained from energy dispersive X-ray (EDX) analysis. From the magnetic measurements, it is observed that cobalt ferrite and zinc doped cobalt ferrite systems fall under the soft ferrite category. The saturation magnetization (Ms) value of undoped cobalt ferrite is 14.26emu/g, and it has reached a maximum of 29.61emu/g for Co0.7Zn0.3Fe2O4.

Structural and magnetic properties of magnesium ferrite nanoparticles prepared via EDTA-based sol–gel reaction

Abstract Magnesium ferrite (MgFe 2 O 4 ) nanoparticles have been prepared, for the first time, by ethylene diamine tetraacetic acid (EDTA)-based sol–gel combustion method. The prepared ferrite system is calcined at 400, 500 and 600 °C. Thermo-gravimetric and differential thermal analysis (TGA–DTA), X-ray diffraction (XRD), Fourier transform infrared (FTIR) spectroscopy, high resolution transmission electron microscopy (HRTEM) and vibrating sample magnetometry (VSM) were applied for elucidating the structural and magnetic properties of the prepared system. XRD patterns revealed that the prepared system have two spinel MgFe 2 O 4 structures, namely cubic and tetragonal phases that are dependent on calcination temperature ( T c ). The crystallite sizes varied from 8.933 to 41.583 nm, and from 1.379 to 292.565 nm for the cubic and tetragonal phases respectively depending on T c . The deduced lattice parameters for the cubic and (tetragonal) systems are a =8.368, 8.365 and 8.377 and ( a =7.011, 5.922, 5.908 and c =6.622, 8.456, 8.364) A at T c =400, 500 and 600 °C respectively. While the cation distribution of the cubic phase is found to be mixed spinel and T c -dependent, it is an inverse spinel in the tetragonal phase where the Fe 3+ ions occupy both the tetrahedral A- and octahedral B-sites in almost equal amount; the Mg 2+ ions are found to occupy only the B-sites. The HRTEM and selected-area electron diffraction (SAED) revealed the detailed morphology of the nanoparticles, and confirmed their crystalline spinel structure. VSM indicated the existence of an appreciable fraction of superparamagnetic particles at room temperature, with pure superparamagnetic behavior observed for samples calcined at 400 °C. Besides, the magnetic properties are found to change by thermal treatment as a result of the varied phase concentration, cation distribution and lattice parameters. Thus, the new synthesis route used in this study by applying EDTA as an organic precursor for preparing MgFe 2 O 4 nanoparticles at rather low temperatures proved to be efficient in obtaining nanoparticles with favorable structural and magnetic properties. Such properties would qualify them for several potential applications including e.g. in hyperthermia treatment, as contrast agents in magnetic resonance imaging (MRI), and in ferroelastomers technology.

Study on Mössbauer Signature, Hyperfine Interaction Parameters and Removal of Delafossite Phase of Al3+-Modified Copper Ferrite

The effect of Al3+ substitution on Mossbauer signature and hyperfine interaction parameters of copper ferrite (CuFe2O4) is studied at 300 K. The X-ray powder diffraction pattern analysis shows that all the four compositions of the ferrite system, CuAlxFe2−xO4 (x = 0.0, 0.2, 0.4, and 0.6), have single-phase fcc spinel structure. On the other hand, Mossbauer spectral analysis reveals that x = 0.0 and 0.2 compositions possess paramagnetic singlet of delafossite (CuFeO2) phase along with two magnetic sextets of spinel ferrite phase. On Al3+ substitution for Fe3+ in the system (x ≥ 0.4), formation of this secondary unwanted phase of CuFeO2 is found to be prevented. The hyperfine interaction parameters are determined and found to be influenced by Al3+ substitution. The noncollinear spin arrangement in the system is verified and the actual cationic distributions are suggested.

Effect of gamma irradiation on the structural and magnetic properties of Co–Zn spinel ferrite nanoparticles

In this work, the structural and magnetic properties of Co1−xZnxFe2O4 (0.0≤x≤1.0) ferrite nanoparticles were studied before and after gamma irradiation. The as-synthesized samples of Co–Zn ferrite nanoparticles prepared by sol–gel auto-combustion technique were analysed by XRD which suggested the single phase; cubic spinel structure of the material. Crystal defects produced in the spinel lattice were studied before and after Co60 γ-irradiation in a gamma cell with a dose rate of 0.1Mrad/h in order to report the changes in structural and magnetic properties of the Co–Zn ferrite nanoparticles. The average crystallite size (t), lattice parameter (ɑ) and other structural parameters of gamma-irradiated and un-irradiated Co1−xZnxFe2O4 spinel ferrite system was calculated from XRD data. The morphological characterizations were performed using scanning electron microscopy (SEM). The magnetic properties were measured using pulse field hysteresis loop tracer by applying magnetic field of 1000Oe, and the analysis of data obtained revealed that the magnetic property such as saturation magnetization (Ms), coecivity (Hc), magneton number (nB) etc. magnetic parameters were increased after irradiation.

Study of samarium modified lead zirconate titanate and nickel zinc ferrite composite system

In the present work, composites of samarium substituted lead zirconate titanate and nickel zinc ferrite with compositional formula 0.95Pb 1−3 x /2 Sm x Zr 0.65 Ti 0.35 O 3 –0.05Ni 0.8 Zn 0.2 Fe 2 O 4 ( x =0, 0.01, 0.02 and 0.03) were prepared by the conventional solid state route. X-ray diffraction analysis was carried out to confirm the coexistence of individual phases. Microstructural study was done by using scanning electron microscope . Dielectric constant and loss were studied as a function of temperature and frequency. To study ferroelectric and magnetic properties of the composite samples, corresponding P – E and M – H hysteresis loops were recorded. Change in magnetic properties of electrically poled composite sample ( x =0.02) was studied to confirm the magnetoelectric (ME) coupling. ME coefficient (d E /d H ) of the samples ( x =0 and 0.02) was measured as a function of DC magnetic field. • We are reporting the effect of Sm substitution on PZT–NiZn ferrite composites. • Observation of both P – E and M – H loops confirms ferroelectric and magnetic ordering. • With Sm substitution, significant improvement in properties was observed. • Increase in magnetization for electrically poled sample is evidence of ME coupling. • Electric polarization is generated by applying magnetic field.