Cobalt Zinc Ferrite Research Articles

Preparation of cobalt–zinc ferrite (Co0.8Zn0.2Fe2O4) nanopowder via combustion method and investigation of its magnetic properties

Research highlights: {yields} Cobalt-zinc ferrite was prepared by combustion method. {yields} Properties of the sample were characterized by several techniques. {yields} Curie temperature was determined to be 350 {sup o}C. -- Abstract: Cobalt-zinc ferrite (Co{sub 0.8}Zn{sub 0.2}Fe{sub 2}O{sub 4}) was prepared by combustion method, using cobalt, zinc and iron nitrates. The crystallinity of the as-burnt powder was developed by annealing at 700 {sup o}C. Crystalline phase was investigated by XRD. Using Williamson-Hall method, the average crystallite sizes for nanoparticles were determined to be about 27 nm before and 37 nm after annealing, and residual stresses for annealed particles were omitted. The morphology of the annealed sample was investigated by TEM and the mean particle size was determined to be about 30 nm. The final stoichiometry of the sample after annealing showed good agreement with the initial stoichiometry using atomic absorption spectrometry. Magnetic properties of the annealed sample such as saturation magnetization, remanence magnetization, and coercivity measured at room temperature were 70 emu/g, 14 emu/g, and 270 Oe, respectively. The Curie temperature of the sample was determined to be 350 {sup o}C using AC-susceptibility technique.

The effect of solution temperature on crystallite size and magnetic properties of Zn substituted Co ferrite nanoparticles

In this work zinc substituted cobalt ferrite nanoparticles (Co 0.5Zn 0.5Fe 2O 4) have been synthesized by the coprecipitation method, using stable ferric, zinc and cobalt salts with sodium hydroxide, at different solution temperatures, from room temperature to 363 K. The cobalt–zinc ferrite crystalline phase, the particle size and the morphology of the resulting nanoparticles were studied by X-ray diffraction and transmission electron microscopy. The average crystallite size of each sample was calculated from the broadening of the most intense peak (3 1 1), using Scherrer's formula and the results show crystallite sizes increased from 6 to 8 nm by increasing the solution temperature from room temperature to 363 K respectively. Room temperature VSM measurements show that the prepared nanoparticles have superparamagnetic behavior and did not saturate at maximum field of 800 kA/m. The variation of AC-susceptibility of the samples with respect to temperature was measured and it was found that the blocking temperature increased from 198 to 270 K by increasing the solution temperature from room temperature to 363 K respectively. FTIR spectra of the samples have been analyzed in the frequency range 400–4000 cm −1, which also confirms the results of XRD.

Nanophase cobalt, nickel and zinc ferrites: synchrotronXAS study on the crystallite size dependence of metal distribution

Nanophase cobalt, nickel and zinc ferrites, in which the crystallites are in the size range 4-25 nm, were synthesised by coprecipitation and subsequent annealing. X-Ray absorption spectroscopy using synchrotron radiation (supported by X-ray powder diffraction) was used to study the effects of particle size on the distributions of the metal atoms over the tetrahedral and octahedral sites of the spinel structure. Deviations from the bulk structure were found which are attributed to the significant influence of the surface on very small particles. Like the bulk material, nickel ferrite is an inverse spinel in the nanoregime, although the population of metals on the octahedral sites increases with decreasing particle size. Cobalt ferrite and zinc ferrite take the inverse and normal forms of the spinel structure respectively, but within the nanoregime both systems show similar trends in being partially inverted. Further, in zinc ferrite, unlike the normal bulk structure, the nanophase system involves mixed coordinations of zinc(ii) and iron(iii) consistent with increasing partial inversion with size.

Investigation of sintered cobalt-zinc ferrite synthesized by coprecipitation at different temperatures: a relation between microstructure and hysteresis curves

The magnetic properties of sintered samples of cobalt-zinc ferrites produced from the corresponding coprecipitate were calculated based on hysteresis curves (Hc). The Hc values confirmed that soft ferrites were obtained by the procedure. A possible relation between the magnetic hysteresis curves and the microstructure of the sintered samples was investigated. X ray diffraction, thermal analysis and scanning electron microscopy were used to characterize the microstructure and the phases present in the sintered ceramic pieces, as well as those of their coprecipitated tri-metallic hydroxide precursor powders. It was found that sintering of Co0.5Zn0.5Fe2O4 at 1400 °C led to "honeycombing" of the ferrite grains and that there was no single phase in the microstructure of a sample sintered at 1400 °C. Thus, a more complete study was made of the behavior of the microstructure at lower sintering temperatures, i.e., in the 1100-1350 °C range.

Synthesis of chromium substituted nano particles of cobalt zinc ferrites by coprecipitation

Nano particles of chromium substituted cobalt zinc ferrite have been synthesized by a chemical co-precipitation method. X-ray diffraction studies of the nano particles of CrxCo0.5−xZn0.5Fe2O4 (x=0.1 to 0.5) heat-treated at 300 °C show that the particle sizes are in the range of 2 to 7 nm. Room temperature Fe-57 Mössbauer spectra of all the samples show only two doublets, confirming the presence of superparamagnetic relaxation in the nano particles. An exponential decrease in the superparamagnetic blocking temperature, with increasing chromium concentration, is observed for these samples.

Large-Scale Synthesis of Uniform and Crystalline Magnetite Nanoparticles Using Reverse Micelles as Nanoreactors under Reflux Conditions

We have synthesized uniform and highly crystalline magnetite nanoparticles from the reaction of iron salts in microemulsion nanoreactors. The particle size can be controlled from 2 nm to 10 nm by varying the relative concentrations of the iron salts, surfactant, and solvent. Transmission electron microscope images of the nanoparticles reveal that they are very uniform in size distribution. Structural characterization using X-ray diffraction and X-ray magnetic circular dichroism shows that the nanoparticles are magnetite. The magnetic characterization of the nanoparticles showed that they are superparamagnetic at room temperature. Using a similar synthetic procedure, we have been able to synthesize nanoparticles of several mixed metal ferrites including cobalt ferrite, manganese ferrite, nickel ferrite, and zinc ferrite.

Dynamic magnetoelectric effects in bulk and layered composites of cobalt zinc ferrite and lead zirconate titanate

Low-frequency magnetoelectric (ME) coupling is investigated in bulk samples and multilayers of cobalt zinc ferrite, Co1-xZnxFe2O4 (x=0–0.6), and lead zirconate titanate. In bulk samples, the transverse and longitudinal couplings are weak and of equal magnitude. A substantial strengthening of ME interactions is evident in layered structures, with the ME voltage coefficient a factor of 10–30 higher than in bulk samples. Important findings of our studies of layered composites are as follows. (i) The transverse coupling is stronger than the longitudinal coupling. (ii) The strength of ME interactions is dependent on Zn substitution, with a maximum for x=0.4. (iii) A weak coupling exists at the ferromagnetic-piezoelectric interface, as revealed by an analysis of the volume and static magnetic field dependence of ME voltage coefficients. (iv) The interface coupling k increases with Zn substitution and the k versus x profile shows a maximum centered at x=0.4. (v) The Zn-assisted enhancement can be attributed to efficient magneto-mechanical coupling in the ferrite.

Study of magnetic interactions in Co–Zn–Fe–O system

Cobalt–zinc ferrites with compositions Co 0.5Zn 0.34Fe 2O 4, Co 0.37Zn 0.51Fe 2O 4, Co 0.3Zn 0.6Fe 2O 4, Co 0.2Zn 0.74Fe 2O 4, were prepared by ceramic techniques. The effects of compositional variation on porosity, coercivity, remanence, saturation magnetisation, magnetic moments, and Y–K angles are reported. The coercivity exhibits almost similar behaviour to that of porosity, whereas, the remanence decreases with increasing Zn-content. The saturation magnetisation and magnetic moments exhibit decreasing behaviour with increasing Zn-content, which may be due to the increase of the B–B interaction followed by the decrease in A–B interaction. The Y–K angles increase with increasing Zn-concentration, which is attributed to the presence of triangular-type spin arrangement on B sites.

Temperature dependent electrical resistivity of Co–Zn–Fe–O system

Cobalt zinc ferrites with composition Co 0.2Zn 0.73Fe 2O 4, Co 0.30Zn 0.60Fe 2O 4, Co 0.37Zn 0.51Fe 2O 4 and Co 0.5Zn 0.34Fe 2O 4, were prepared by solid state reaction technique in a single phase form. The electrical resistivity, X-ray density, bulk density and porosity of each sample have been measured. A change of slope has been observed in the Arrhenius plots indicating the presence of two regions of activation energy.

The substitution of cobalt for nickel in stoichiometric nickel-zinc ferrite

In the past, cobalt (II) ions have been added to nickel-zinc ferrites to capitalize on the anisotropic character of Co+2 in stabilizing domain walls and reducing magnetic losses. This paper emphasizes increasing losses. The effect of Co+2 on the real permeability (μ′) and magnetic loss (μ″) when cobalt was sequentially substituted for nickel in stoichiometric nickel-zinc ferrite was measured at 50–1500 MHz. The compositions examined were included in the formulation CoxNi0.5−xZn0.5Fe2O4. in which the cobalt atom fraction x took values from x=0.032 to 0.50. Air density of the measured toroids decreased from 4.52 g/cm3 at x=0.032 to 4.28 g/cm3 at x=0.50. A maximum for μ″ was found in the region x=0.03–0.04, depending upon the frequency. This increase was marked at the lower frequencies, but it essentially disappeared by 800 MHz. The magnetic loss spectrum for cobalt-zinc ferrite was described by a single relaxation dispersion with a relaxation time of 6.22×10−10 s. As nickel replaced cobalt, the relaxation time increased to 14.9×10−10 s at x=0.032. An earlier analysis of nickel-zinc ferrite (x=0) yielded a relaxation time of 11.9×10−10 s, confirming the approximate coincidence of maxima in both μ″ and relaxation time. The fact that μ″ decreases at x≳0.04 (as cobalt replaces nickel) does not mean that the reflected attenuation must decrease. Sample thickness also influences the result. For shorted samples 0.250 in. thick, the replacement of nickel by cobalt increased attenuation despite decreasing values of μ″, and shifted the frequency of maximum attenuation to higher values.

ΔE‐effect in CoZn ferrites

AbstractA study of the dependence of the elastic behaviour of polycrystalline mixed cobalt‐zinc ferrites on magnetic field (ΔE‐effect) and temparature has been made using an ultrasonic method. The observed ΔE‐effect in the case of cobalt zinc ferrites has been interpreted in terms of two domain processes.

Thermal variation of initial susceptibility in cobalt-zinc ferrites

Thermal variation of initial susceptibility in cobalt-zinc ferrites

ΔE effect in CoZn ferrites

A study of the dependence of the elastic behaviour of polycrystalline mixed cobalt-zinc ferrites on magnetic field (ΔE-effect) and temparature has been made using an ultrasonic method. The observed ΔE-effect in the case of cobalt zinc ferrites has been interpreted in terms of two domain processes.

The far-infrared spectra of some mixed cobalt zinc and magnesium zinc ferrites

The far-infrared spectra of five mixed ferrites in the range 200 to 640 cm−1 are reported. Four bands are observed. The high frequency band (v1) and low frequency band (v2) are assigned to the tetrahedral and octahedral complexes, respectively. A small band (v3) around v2 is observed and its intensity increases with divalent octahedral metal ion concentration. This band is assigned to the octahedral divalent metal-oxygen ion complexes. The lowest band observed for the highest concentration of cobalt is attributed to the lattice vibrations of the system. Die Ferninfrarot-Spektren von fünf Mischferriten im Bereich 200 bis 640 cm−1 werden mitgeteilt. Vier Banden werden beobachtet. Die hochfrequente Bande (v1) und die niederfrequente Bande (v2) werden den'tetraedrischen bzw. oktaedrischen Komplexen zugeordnet. Eine schwache Bande (v2) bei v2 wird beobachtet, deren Intensität mit der Konzentration divalenter oktaedrischer Metallionen zunimmt. Diese Bande wird den oktaedrischen divalenten Metall-Sauerstoff-Komplexen zugeordnet. Die niedrigste Bande, die für die höchste Kobaltkonzentration beobachtet wird, wird den Gitterschwingungen des Systems zugeschrieben.

DC conductivity and dielectric behaviour of cobalt-zinc ferrites

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Effect of magnetic field and temperature on the elastic behaviour of cobalt-zinc ferrites

A study of the dependence of the elastic behaviour of polycrystalline mixed cobalt-zinc ferrites on temperature and magnetic field has been made using a composite oscillator method. As the temperature is increased the Young's modulus attains a minimum at a temperature below the Curie point. Thereafter it exhibits a positive temperature coefficient up to the Curie point and decreases with further increase of temperature. This anomalous behaviour has been explained in terms of magnetic anisotropy energy. In the case of cobalt ferrite and Co 0.6Zn 0.4Fe 2O 4 the Young's modulus is found first to decrease and later to increase with increasing magnetic field, finally becoming constant at the saturation field. In contrast, in the case of Co 0.4Zn 0.6Fe 2O 4 and Co 0.2Zn 0.8Fe 2O 4 the Young's modulus does not show an initial decrease but increases with increasing magnetic field. The observed ΔE effect in the case of cobalt ferrite has been interpreted in terms of two domain processes, i.e. domain rotation against uniaxial strain anisotropy and the movement of 90° boundary walls. A study of the effect of the simultaneous application of temperature and magnetic field on the elastic behaviour of mixed cobalt-zinc ferrites has also been carried out.

X-ray spectroscopic study of cobalt-zinc ferrites

Abstract K-absorption edges and the associated fine structures of cobalt and iron in cobalt-zinc ferrites of composition, ZnxCo1-xFe2O4 (x = 0, 0.25, 0.50 and 0.75) have been recorded employing a 40cm curved crystal spectrograph of transmission type. It is found that the cobalt and iron ions in these samples exist in valence states two and three respectively. Bond lengths have been determined using the X-ray fine structure methods. It is noted that estimated bond lengths are close to those obtained from crystallographic data. It is pointed out that the X-ray fine structure methods can be used to complement diffraction methods for the determination of bond lengths in samples containing atoms of nearly equal scattering power.

Elastic behaviour of mixed cobalt-zinc ferrites

The composition and temperature dependence of the elastic properties of cobalt-zinc ferrites have been studied using the composite oscillator method originally due to Balamuth and Rose. The values of Young's modulus ( Y) and the rigidity modulus ( n) are found to increase with an increase of zinc content. A linear dependence of the longitudinal and shear velocities on the density is also observed, as in the case of the nickel-zinc ferrites. The dependence of elastic behaviour of these mixed ferrites on temperature is similar to that in the case of the simple and mixed ferrites studied earlier. The variation of Young's modulus with temperature follows Wachtman's equation while a linear equation describes the variation of the rigidity modulus ( n) with temperature.

Magnetic Properties of Mixed Ferrites: I. Behaviour near the Curie Point

Detailed measurements on the variation of magnetization with applied field and temperature in the region of the Curie point are reported for nickel ferrite, cobalt ferrite, several cobalt-zinc and nickel-zinc ferrites, for manganese ferrite and for a magnesium-zinc ferrite. New observations on the magnetocaloric effect in magnesium zinc ferrite have also been made. Anomalies observed in the form of the curves of constant magnetization of ferrites with mixed structure but not with the fully inverse structure are tentatively ascribed to the presence in the specimens of two kinds of region with different Curie points. X-ray examination of some of the ferrites showed that it is unlikely that major variations of composition are responsible for the anomalies.