Magnetic Properties Of Cobalt Ferrite Research Articles

Synthesis of CoFe2O4 Nanomaterials via Sol–Gel Auto‐Combustion Method using Different Chelating Agent, and Its Effects on Magnetic and Dielectric Properties

Herein, the structural and magnetic properties of cobalt ferrite (CoFe2O4 [CFO]) nanomaterials obtained from sol–gel auto‐combustion method using different chelating agent (tartaric acid, citric acid, and oxalic acid) are reported. The obtained precursors from the different chelating agents are calcined at 500 °C for 5 h. The X‐ray diffraction (XRD) analysis suggests that all the synthesized samples show the single‐phase spinel ferrite structure without existing any secondary impurity phases. The lattice parameter, cell volume, density, crystallite size, and dislocation density are computed for all the synthesized samples utilizing the XRD data. The irregular‐shaped grains morphology with a homogeneous distribution is observed through scanning electron microscopy study. The sample synthesized by using the tartaric acid as a chelating agent shows a high magnetization value, highest coercivity, and highest anisotropy constant (K) when compared to those of other chelating agents. High grain‐boundary activation energy is also observed for the CFO nanomaterials obtained from the tartaric acid as a chelating agent.

Synthesis, Structural and Magnetic Properties of Cobalt Ferrite (CoFe2O4) Nanoparticles by Simple Co-precipitation Technique

Synthesis, Structural and Magnetic Properties of Cobalt Ferrite (CoFe2O4) Nanoparticles by Simple Co-precipitation Technique

Effect of Mn and Zn binary Co-substitution on structure and magnetic properties of cobalt ferrites

Mn-Zn binary co-substituted cobalt ferrite (Co1-x(MnZn)xFe2O4 (0 ≤ x ≤ 0.4)) was synthesized by conventionally compacting and magnetic field assisted injection molding. XRD and SEM analysis characterized the single-phase spinel structure, preferred 〈001〉 orientation, and uniform grain size. XPS analysis reveals the cation redistribution in the mixed spinel structure of co-substituted samples, which has a direct consequence on magnetic properties. The addition of Mn-Zn increases the saturation magnetization (Ms), while decreases magnetocrystalline anisotropy constant (K1), leading to a decrease of magnetostrictive saturation field (HS). For pressure samples, the maximum (dλ/dH)max is −0.15 ppm/Oe under 300 Oe applied field at x = 0.2. The samples with 〈001〉 fiber texture were prepared by magnetic field alignment of the semi-solid slurry to achieve higher magnetostrictive properties. The highest magnetostriction λS reaches −432 ppm, which is 200 % higher than pressed samples, and the corresponding maximum strain derivative (dλ/dH)max reaches −0.88 ppm/Oe at a lower magnetic field.

Origin of the uniaxial magnetic anisotropy in cobalt ferrite induced by spark plasma sintering

Cobalt ferrite (CFO) is a promising candidate for magnetostrictive applications like actuators or sensors. We have recently shown that uniaxial magnetic anisotropy can be induced in CFO by reactive sintering using spark plasma sintering (SPS), which leads to an improvement of its magnetostrictive properties. However, the origin of the anisotropy and the formation mechanism remain unexplained so far. In this study, different SPS processes have been conducted to determine which parameter is responsible for the induced uniaxial anisotropy. We demonstrate that the magnetic anisotropy arises during the cooling step when done under SPS’s uniaxial compression. In addition, we also investigate the fundamental origin of the magnetic anisotropy induced during the SPS process. We show that the polycrystalline anisotropic cobalt ferrite obtained after SPS exhibits no texture. However, the SPS samples turn isotropic after being annealed in air at 400 °C/2 h, as shown by magnetic and magnetostrictive measurements. A change in ionic distribution after the annealing is also observed by Mössbauer spectroscopy. Our findings suggest that the induced magnetic anisotropy results from the ionic distribution of the Co2+ in the CFO’s spinel lattice, a mechanism previously observed in magnetic annealed CFO. This study advances the in-depth understanding of the relationship between SPS processing and magnetic properties of cobalt ferrite.

Influence of Ce-Mn co-doping on the structure and magnetic properties of cobalt ferrites

In this study, we selected Ce3+ and Mn2+ as co-doped ions in order to improve the magnetic properties of cobalt ferrite. The nominal composition Co1−xMnxFe2−xCexO4 (x = 0, 0.05, 0.10, and 0.20) nanoparticles were prepared by facile co-precipitation technique, and the effect of co-doping content on the structural and magnetic properties of cobalt ferrite was investigated. The structural result confirmed the formation of cubic spinel structure for all co-doped samples, although secondary phase of CeO2 was detected in the high co-doping content ones. Fourier transform infrared spectroscopy confirmed the presence of metal-oxygen bonding. All samples exhibited two frequency bands corresponding to the phonon vibrational stretching in the octahedral and tetrahedral lattice positions, respectively. The surface morphology analysis revealed the spherical shape of the ferrite nanoparticles. After co-doped with Ce3+ and Mn2+ ions, the magnetic parameters of cobalt ferrite were significantly improved. The maximum magnetization saturation is 66.5 emu/g when x = 0.05, and the maximum coercivity is 2288 Oe when x = 0.10. The two values are approximately 29% and 47% higher than that of the un-doped one. At the same time, the maximum energy product reaches 0.72 MG·Oe, which is about 118% higher than that for pure cobalt ferrite, i.e. 0.33 MG·Oe. The reasons may be related to the substitution of Fe3+ and Co2+ with Ce3+ and Mn2+, and also the resulting changes in crystallite sizes of the samples. These results demonstrate the effectivity of Ce-Mn co-doping in improving the magnetism of cobalt ferrite.

Exploring the impact of nickel doping on the structure and low-temperature magnetic features of cobalt nano-spinel ferrite

Tailoring the magnetic features of cobalt ferrite nanoparticles (NPs) has been achieved via varying the doping percent of nickel. The nickel-substituted cobalt ferrite NPs NixCo1-xFe2O4 (0 ≤ x ≤ 1.0) are constructed by the eco-friendly coprecipitation method. The formation of a nearly cubic single-phase spinel frame is assured by the analysis of XRD data. Moreover, the Rietveld analysis based on structure refinement is implemented in this study to precisely determine the microstructural parameters and estimate the cation distribution. A linear drop-in lattice constant with boosting the Ni2+ ion percent is acclaimed, in regard to Vegard's law. The creation of nanoparticles that are nearly spherical along with polyhedron shape and have a diameter of (about 39–45 nm) has been affirmed by utilizing high-resolution transmission electron microscopy (HRTEM). Also, the crystalline essence of the formed nanoparticles has been declared by selective area electron diffraction (SAED). The magnetic properties have been collected from the hysteresis loops and FC–ZFC curves. These curves have been tweaked as a function of low-temperature from 5 K up to 300 K and in the existence of an external magnetic field (± 70KOe). The magnetization curves revealed that CoFe2O4 (NPs) correspond to the hard ferrimagnetic material, whereas NiFe2O4 (NPs) matched well with identical soft ferrimagnetic material. Also, the divergence betwixt the theoretical and experimental values of the magnetic moment is well explained by the model of "Random Canting of Spins, (RCS)". In addition, a remarkable reduction is found in the recorded values of magnetic parameters by increasing Ni2+ content and decreasing the temperature towards 5 K. These findings imply the potential of Ni2+ ions doping in enhancing the magnetic properties of cobalt ferrite for vast magnetic applications.

Effects of aluminum substitution on the microstructure and magnetic properties of cobalt ferrites prepared by the co-precipitation precursor

Effects of aluminum substitution on the microstructure and magnetic properties of cobalt ferrites prepared by the co-precipitation precursor

Structural and temperature-dependent magnetic characteristics of Ho doped CoFe2O4 nanostructures

The magnetism in low-dimensional materials is the consequence of several factors, including the type of crystal structure and spatial distribution of nanoparticles. Understanding and exploring these challenges are vital to introduce nanomaterials for industrial applications. The present study reveals the substitutional effect of Holmium on the magnetic properties of cobalt ferrite. The nanostructures are prepared by co-precipitation procedure for the stoichiometric growth of CoHoxFe2-xO4 (0 ≤ x ≤ 0.1); Δx = 0.025 ferrite compositions. The crystal structure and phase determination of all the samples identify a typical cubic structure (Fd-3m); however, a secondary phase, appearing at x = 0.1, originates due to the formation of HoFeO3. An increasing trend in lattice constant, X-ray density and hopping lengths with Ho doping in Co ferrite is observed in the synthesized nanoparticles. The structural analysis by high-resolution transmission electron microscopy confirms the crystal structure of spinel ferrite. The magnetic characteristics measured at room temperature depict that the coercivity, saturation magnetization, and magneton number increase due to the impact of Ho3+ substitution. The saturation magnetization of CoHo0.05Fe1.95O4 nanoparticles as a function of temperature satisfies Bloch's law, and the coercivity of the sample remained in good agreement with Kneller's law.

A deep insight into the magnetic properties of cobalt ferrite by non-equilibrium thermodynamics with internal variables

The paper presents for the first time an in-depth theoretical magnetic characterization of cobalt ferrite nanoparticles (CoFe2O4) by using the thermodynamic approach of non-equilibrium with internal variables. Considering that a complete knowledge of the structure and properties is crucial to design a material for a specific application, a complete thermodynamic characterization of magnetic properties turns out to be useful for a plethora of technological and biomedical purposes. The non-equilibrium thermodynamics is exploited to calculate the internal variables as a function of the perturbation frequencies. Our results allow to fully characterizing the investigated material in terms of magnetization by orientation and by deformation (M(1) and M(0)), magnetic field B(1), magnetization displacement current (E), entropy production (σ), phenomenological coefficients (L(0,0) and L(1,1)) and state coefficients (a(0,0), a(1,1)). CoFe2O4 has been selected as a proof of concept; our theoretical investigation and parameters are applicable to all the para- and ferromagnetic materials, including biomolecules and biological tissues allowing to compare healthy and pathological behavior, subjected to a variable magnetic field for which it is possible to conceive a linear approximation.

Co<SUP>2+</SUP> Distribution and the Related Magnetic Evolution in Ca-substituted Spinel CoFe₂O₄

Magnetic properties of cobalt ferrites with a portion of CoSUP2+/SUP ions being replaced by CaSUP2+/SUP were investigated by vibrating-sample magnetometry (VSM). The CaSUBx/SUBCoSUB1-x/SUBFe₂O₄ (x ≤ 0.2) specimens were prepared as thin films by a sol-gel deposition method. According to the VSM results, the saturation magnetization (MSUBS/SUB) of the Ca-substituted ferrite decreased from that of CoFe₂O₄ proportional to the Ca composition x. Raman spectral analyses revealed that the Ca-substituted ferrites had a lower tetrahedral CoSUP2+/SUP population in the spinel lattice compared to CoFe₂O₄. The decreasing trend of MSUBS/SUB is consistent with the result of theoretical evaluation in which the relative population of CoSUP2+/SUP ions among the tetrahedral and octahedral sites is proportional to the relative Raman scattering intensities of 615 and 470 cmSUP-1/SUP peaks, respectively.

Role of Tb-Cr Substitution on the Structural and Magnetic Properties of Cobalt Ferrites

The impact of Tb-Cr substitution in cobalt-based ferrites having composition Co1-xTbxFe2-yCryO4 (x=0.0-0.1, y=0.0-0.5) prepared by solid state reaction method on structural, magnetic and dielectric parameters was explored. Structural analysis was carried out by X-ray diffraction technique. A variation in lattice parameter (a) was observed as a function of doping. The lattice constant ‘a’ increases from 8.37 Å to 8.39 Å, whereas crystallite size (D) decreases from 44 nm to 28 nm with Tb-Cr substitution. Unit cell volume was found in the range 586.8 Å3 - 590.6 Å3. X-ray density, bulk density as well as porosity were also affected with the inclusion of Tb-Cr ions. Saturation magnetization and remanence were observed to decrease from 62 emu/g to 51 emu/g and 13.38 emu/g to 8.29 emu/g, respectively with the addition of Tb-Cr contents. The incorporation of Tb-Cr cations caused the decrease in dielectric parameters like dielectric constant as well as dielectric loss.

Sintering temperature dependence on evolving microstructure and magnetic characteristics of cobalt ferrites

This paper focuses on the effect of sintering temperature on the structural, microstructural and magnetic properties of cobalt ferrite (CF). CF with sintering temperatures of 600 ℃ to 1400 ℃, was synthesized using the oxide mixture route technique. The structural and microstructural development of the samples were investigated using X-Ray Diffractometer, Transmission Electron Microscope and Scanning Electron Microscope, while the magnetic dynamic properties of the samples were analyzed using Impedance/ Material Analyzer over 1 MHz to 1 GHz. The results show that the complex permeability which include the real permeability and loss factor of the samples at 10 MHz have shown an increase in their values through increasing the sintering temperature. As sintering temperature acted as a temporary agent for structural and microstructural development, the improvement of crystallization and microstructure by heat treatment, contributed to a single CF phase formation and grain growth, resulting in the removal of porosity and microstrain in the samples. This in turn enhanced the superexchange interactions between magnetic moments via elimination of domain wall pinning point, thus contributes to the improvement of magnetic characteristics of the samples.

Effect of Mn substitution on structural and magnetic properties of cobalt ferrite

Manganese substituted Cobalt Ferrite Co1-xMnxFe2O4() nanoparticles were prepared using low temperature chemical co-precipitation method. All the samples were annealed at 900°C for 3 hours. The crystal lattice symmetry and phase purity were performed by X-ray diffraction (XRD). The varying dopent concentration affects the crystalline size, surface morphology and magnetic properties of the cobalt ferrite. The particle sizes are found to be in the range of 29-37 nm. SEM with EDAX examines the morphological and compositional analysis of the nanoparticles. EDAX confirms the presence of Co, Mn, Fe and O. Fourier transform infrared spectroscopy (FTIR) study confirms the formation of spinel ferrite. The saturation magnetization, magnetic remanence and coercive field of CoMn nanoparticles are obtained at room temperature. Saturation magnetization initially increases and then decreases for higher value of dopent, which shows applicability of these materials for recording media and magnetic data storage. Copyright © 2017 VBRI Press.

Eco-Friendly Synthesis, TEM and Magnetic Properties of Co-Er Nano-Ferrites

Synthesis of Cobalt-Erbium nano-ferrites with formulation CoErxFe2-xO4 (x = 0, 0.005, 0.010, 0.015, 0.020, 0.025, and 0.030) using technique of citrate-gel auto-combustion was done. Characterization of prepared powders was done using XRD, EDAX, FESEM, TEM, AFM, and FTIR spectroscopy, VSM: magnetic properties, respectively. XRD Rietveld Analysis, SEM, TEM, and EDAX analysis studied spectral, structural, and magnetic properties. XRD pattern of CEF nanoparticles confirms single-phase cubic spinal structure. The structural variables are given by lattice constant (a), lattice volume (v), the average crystallite size (D) and X-ray density (dx), bulk density (d), porosity (p), percentage of pore space (P%), surface area (s), strain(ε), dislocation density (δ), along with ionic radii, bond length and hoping length were calculated. SEM and TEM results reveal the homogeneous nature of particles accompanied by clusters having no impurity pickup. TEM analysis gives information about the particle size of nanocrystalline ferrite, while EDAX analysis confirms elemental composition. The emergence of two arch-shaped frequency bands (ν_1 and〖 ν〗_2) that represent vibrations at the tetrahedral site (A) and octahedral site(B) was indicated by spectra of FTIR. The XRD Rietveld analysis confirms crystallite size lying between 20.84 nm-14.40 nm, while SEM analysis indicates the formation of agglomerates and TEM analysis indicates particle size ranging between 24nm-16 nm. The XRD Rietveld analysis confirms crystallite size lying between 20.84nm-14.40nm, while SEM analysis indicates the formation of agglomerates and TEM analysis indicates particle size ranging between 24 nm - 16 nm. The magnetization measurements indicated that increasing Er3+ content in cobalt ferrites decreases magnetization from 60emu/g to 42emu/g while coercivity decreases (18990) as compared to CoFe2O4 (18998) in cobalt ferrites with doping. The present study investigates the effect of different compositions of Er3+ replaced for Fe on structural and magnetic properties of cobalt ferrites.

The effect of temperature on the structural, dielectric and magnetic properties of cobalt ferrites synthesized via hydrothermal method

Abstract A series of cobalt ferrite nanoparticles were prepared using hydrothermal process by varying the reaction temperature. The structural, magnetic and dielectric properties have been studied with the help of X-ray diffractometer (XRD), vibrating sample magnetometer (VSM) and impedance analyzer respectively. XRD spectra of all samples confirmed the formation of cobalt ferrite (CoFe2O4) nanoparticles (NPs). The lattice constant ‘a’ for temperature series samples is averaged around 8.4023 Å. Crystallite size of temperature series is calculated by Debye–Scherer formula that lies in the range of 15.04–20.49 nm. Its values increase because the chance of coalescence increases by increasing temperature. The maximum packing factor is obtained for the sample with highest reaction temperature. From VSM data, we get the M–H hysteresis curves for complete temperature series which confirms the magnetic nature. The maximum saturation magnetization 150.67 emu/g is obtained for the sample prepared at highest temperature. Different magnetic parameter such as saturation magnetization, coercivity, retentivity, squareness ratio, anisotropy constant and magneton number has been calculated from VSM data. AC response of all prepared ferrites was studied with impedance analyzer of frequency range 20 Hz to 20 MHz. Ferrites are the insulating materials, so, eddy current does not induce in transformer cores made of ferrite materials. In the medical field cobalt ferrite is used for drug delivery, as a biosensor and in MRI.

Magnetization and thickness dependent microwave attenuation behaviour of Ferrite-PANI composites and embedded composite-fabrics prepared by in situ polymerization

Ultrahigh efficient and effective electromagnetic-interference (EMI) shielding composites have been fabricated with the combination of Polyaniline and zinc-cobalt ferrites (Co1-xZnxFe2O4, 0.1 ≤ x ≤ 0.4). Ferrite nanoparticles synthesized via the sol-gel method were functionalized to polyaniline via in situ polymerization. Average crystallite sizes of the nanoparticles were estimated using Debye–Scherrer and Rietveld method and found to be in between 20-30 nm. FTIR spectra revealed the formation of interactions between the PANI molecules and the ferrite nanoparticles. Substitution of the nonmagnetic Zn ions considerably changes the magnetic properties of cobalt ferrites as observed from the M-H loops recorded by VSM at room temperature. The EMI-shielding performance of the fabricated composites was examined at various thicknesses with the polymer filler ratio of 1:1 in X-band frequency region using a vector network analyser. The EMI shielding performance of composites was found to be increasing with the thickness of composites where a thickness of 3.0 mm achieved an SE of ∼ 100 dB for the Co0.7Zn0.3Fe2O4-PANI composite. Composite absorbers were deposited on cotton fabrics for protective clothing by in situ incorporation during the synthesis of composites which displayed relatively high EMI shielding effectiveness (SE) (40-45 dB) at a thickness of only 0.30 mm for the fabrics. The PANI-Ferrite nanocomposites can be established as promising high capacity electromagnetic shielding materials because of the dipole polarization and the magnetic losses with low cost, lightweight, high durability and good flexibility.

Structural and magnetic properties of Mn doped cobalt ferrite nanoparticles synthesized by Sol-Gel auto combustion method

Co1-xMnxFe2O4 (with x = 0.0, 0.2, 0.4, 0.6) ferrites nanoparticles were synthesized by the sol–gel auto combustion method. The crystal structure, morphology, elemental analysis and magnetic properties of the samples were systematically investigated using X-ray diffraction (XRD), Fourier-transform infrared spectroscopy (FTIR), Raman Spectroscopy, High resolution scanning electron microscopy (HRSEM), Energy dispersive X-ray spectroscopy (EDX), and Vibrating sample magnetometer (VSM) analysis. The XRD results confirmed the cubic spinel structure up to x = 0.2. Scherrer and Williamson-Hall (W-H) method were applied to determine crystallite size and strain present in the sample. The FT-IR spectra showed the absorption peaks confirmed the presence of metal–oxygen stretching bands in Mn doped cobalt ferrites. Raman spectra showed four strong and sharp modes, identifies the cobalt ferrite phase. HRSEM images clearly showed that Co1-xMnxFe2O4 (with x = 0.0, 0.2, 0.4, 0.6) ferrite grains appear in spherical shape with less agglomeration. The elemental analysis (EDX) was performed for the above samples and their spectrum confirmed the presence of Co, Fe, Mn and O elements in the prepared Mn doped Cobalt ferrite materials. The magnetic measurements of the calcined samples were carried out at room temperature using vibrating sample magnetometer. By the substitution of cobalt magnetic ions with Mn2+, it is possible to tune the magnetic properties of cobalt ferrite as a promising material for various technological applications.[copyright information to be updated in production process]

Effects of Scandium Doping on Structural and Magnetic Properties of Cobalt Ferrite Thin Films

Structural and magnetic properties of Sc-substituted cobalt ferrites were studied by X-ray diffraction, Raman spectroscopy, X-ray photoelectron spectroscopy, and vibrating-sample magnetometry. The ScSUBx/SUBCoFeSUB2-x/SUBO₄ (x ≤ 0.3) specimens prepared as thin films by a sol-gel deposition method were polycrystalline having cubic spinel structure with a small increase in the lattice constant compared to CoFe₂O₄. The Raman spectral analyses suggested that the Sc-doped specimens have higher tetrahedral CoSUP2+/SUP population than that of pristine CoFe₂O₄. The magnetic hysteresis curves of the ScSUBx/SUBCoFeSUB2-x/SUBO₄ specimens indicated that the saturation and remanent magnetization decrease proportionally with the increase of Sc composition (x). The decrease in the ferrimagnetic parameters is understandable in terms of the octahedral substitution of non-magnetic ScSUP3+/SUP ions. However, the octahedral ScSUP3+/SUP ions caused an increase of the coercivity.

Eco-Friendly Synthesis, Crystal Chemistry, and Magnetic Properties of Manganese-Substituted CoFe2O4 Nanoparticles.

The authors report on the effect of manganese (Mn) substitution on the crystal chemistry, morphology, particle size distribution characteristics, chemical bonding, structure, and magnetic properties of cobalt ferrite (CoFe2O4) nanoparticles (NPs) synthesized by a simple, cost-effective, and eco-friendly one-pot aqueous hydrothermal method. Crystal structure analyses indicate that the Mn(II)-substituted cobalt ferrites, Co1–xMnxFe2O4 (CMFO, x = 0.0–0.5), were crystalline with a cubic inverse spinel structure (space group Fd3m). The average crystallite size increases from 8 to 14 nm with increasing Mn(II) content; the crystal growth follows an exponential growth function while the lattice parameters follow Vegard’s law. Chemical bonding analyses made using Raman spectroscopic studies further confirm the cubic inverse spinel phase. The relative changes in specific vibrational modes related to octahedral sites as a function of Mn content suggest a gradual change of measure of inversion of the ferrite lattice at nanoscale dimensions. Small-angle X-ray scattering and electron microscopy revealed a narrow particle size distribution with the spherical shape morphology of the CMFO NPs. The zero-field-cooled and field-cooled magnetic measurements revealed the superparamagnetic behavior of CMFO NPs at room temperature. The sample with x = 0.3 indicates a lower value of blocking temperature (9.16 K) with the improved (maximum) value of saturation magnetization. The results and the structure-composition–property correlation suggest that the economic, eco-friendly hydrothermal approach can be adopted to process superparamagnetic nanostructured magnetic materials at a relatively lower temperature for practical electronic and electromagnetic device applications.

The possibility of vanadium substitution on Co lattice sites in CoFe2O4 synthesized by sol–gel autocombustion method

In this study, the effect of vanadium addition on the structural and magnetic properties of cobalt ferrite (Co1−xVxFe2O4; where x = 0, 0.05, 0.10, 0.15, 0.20, and 0.25) prepared by a novel sol–gel autocombustion method was investigated. The formation of cubic spinel structure (space group Fd3m) was confirmed by X-ray diffraction in combination of Rietveld structure refinement analysis and transform infrared spectroscopic spectrum (FT-IR) analyses. Also, phase and elemental analyses confirmed that an inevitable secondary phase of hematite along with the spinel phase appears by addition of vanadium; therefore, a nanocomposite was formed in the sample containing vanadium. However, the SEM observations in combination of the results obtained by Rietveld structure refinement analysis showed that the presence of vanadium can affect the size of synthesized cobalt ferrite. VSM measurements showed that saturation magnetization and coercivity values are strongly dependent on the vanadium content and particle size, so that the maximum value of coercivity was obtained equal to ~916 Oe for Co0.85V0.15Fe2O4.