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Magnetic and microwave absorbing properties of cerium-substituted zinc ferrite synthesized using the milling technique have been studied. Cerium substituted on zinc ferrite was synthesized from ZnO, Ce2O3, and Fe2O3 powders in a mole ratio to the form of ZnCexFe(2−x)O4 (x = 0.01 up to 0.05) by solid-state reaction. The mixture of these compounds was milled using the high energy milling (HEM) technique and sintered at 1200 °C for 5 h. The identification result of the XRD shows that all samples are a single phase that follows the structure of ZnFe2O4. The TEM (Transmission Electron Microscope) image of ZnCexFe(2−x)O4 powders show that all samples have homogenous morphology but not uniform powder with particle sizes of about 100–500 nm. The magnetic properties of the samples were analyzed using a vibrating sample magnetometer (VSM). The result shows ferromagnetic behavior, with the Ms value around 19.37 up to 8.03 emu/g and the Hc value around 134–324 Oe. Microwave absorption ability was measured using VNA (Vector Network Analyzer), and their results indicated that the RL curve was deeper with increasing Ce3+ ions concentration. The best RL shows the ZnCexFe(2−x)O4 sample with a value of x = 0.05, i.e., 17.62 dB at a frequency of 10.76 GHz. It means that ZnCe0.5Fe1.95O4 powder can absorb microwaves at 98.26% at a frequency of 10.76 GHz. [ABSTRACT FROM AUTHOR]

This article studied the effect of oxygen vacancies and cationic inversion on the magnetic properties of zinc ferrite (ZnFe2O4, ZFO) thin films. The ZFO thin films were deposited using pulsed laser deposition (PLD) at three different oxygen partial pressures ( P o 2 ), viz., 0.16, 0.24, and 0.32 mbar at 800 ℃ substrate temperature on Si(100) substrate. X-ray diffraction analysis revealed the pure phase formation of the synthesized zinc ferrite thin films. The saturation magnetization (Ms), as estimated using magnetization (M) versus applied magnetic field (H) hysteresis loop of ZFO thin films, was decreased with increasing oxygen partial pressures. The X-ray photoelectron spectroscopy (XPS) analysis for O 1 s and Zn 2p element in ZnFe2O4 thin films, with high lattice oxygen ratio, i.e., OII/OI of 1.88 and lowest inversion degree (i.e., σ = 0.41), suggested the presence of maximum oxygen vacancies for the films grown at 0.16 mbar leading to the high value of magnetization (134 emu/cc). [ABSTRACT FROM AUTHOR]

The physical characterization and magnetic interactions of cadmium-doped zinc ferrite nanoparticles Zn 1 - x Cd x Fe 2 O 4 , x ≤ 10 % have been studied. The samples were synthesized using the co-precipitation technique and analyzed for the structural phases, morphological, mechanical, optical, and magnetic properties using XRD, SEM, FTIR, DRS, PL, and VSM techniques. The spinel structure's lattice parameters increased, and the size of the nanoparticles increased with the additional quantity of the dopant. SEM images revealed the existence of spherical particles with an average particle size of 36.32–39.57 nm. FTIR spectral analysis indicated the existence of absorption bands of metal oxide at higher and lower frequency regimes due to the stretching vibrations of both octahedral and tetrahedral sites. Diffuse reflectance spectral analysis (DRS) was used to measure the bandgap energies with the estimated values of 1.897, 2.012, 2.027, and 2.036 eV, which increased as the dopant concentration increased. The photoluminescence (PL) spectra for the emission wavelengths range from 485 to 478 nm with emission energies of 2.56–2.60 eV for the PL peaks. The magnetic properties were determined by employing a vibrating sample magnetometer (VSM) with an applied magnetic field up to 50 kOe at low and room temperatures (4 and 300 K). The magnetic hysteresis loops show a decrease in magnetic saturation from 36.458 to 6.682 emu/g, large coercivity and magneto-crystalline anisotropies at 4 K, and a decrease in magnetic moments and permeabilities with the doping of Cd 2 + ions. Interionic and magnetic interactions were explained by the Yafet–Kittel (YK) model. [ABSTRACT FROM AUTHOR]

In order to investigate the size dependence of magnetic properties in the single-domain and superparamagnetic regimes, zinc ferrite ZnFe 2 O 4 nanoparticles were synthesized with sizes around 15 nm by the hydrothermal method. The zinc ferrite nanoparticles were characterized by XRD, TEM, FT-IR, and VSM. According to the Rietveld refinement results, the nanoparticles exhibited a cubic single-phase spinel-type structure. The TEM observations indicated that the nanoparticles were spherical in shape. The FT-IR analysis revealed two dominant absorption bands, confirming the formation of a single-phase spinel structure with two sub-lattices: tetrahedral and octahedral. Magnetic measurements conducted over a wide range of temperatures and magnetic fields revealed that the ferrite nanoparticles were ferrimagnetic dressed with spin-glass behavior below the blocking temperature ( T B ) and superparamagnetic above T B . The saturation magnetization and the first anisotropy constant of the nanoparticles were found to increase with decreasing temperature. The superparamagnetic critical size, D SP , of the nanoparticles was found to be about 13 nm, suggesting that the prepared ferrite nanoparticles were within the superparamagnetic regime, and thus by implication within the single domain regime. [ABSTRACT FROM AUTHOR]

Ferrite spinel's MFe2O4 (M = Co, Fe, Zn, Mn, and Cu) nanoparticles were produced by a co-precipitation method. The X-ray diffraction (XRD) analysis was used to verify phase purity, crystal structure, and average crystallite size of MFe2O4 nanoparticles. All samples have not any phase impurity, which has a spinel structure with crystallite sizes between 7 and 29 nm. The results of far Fourier transform infrared (FTIR) of all samples were revealed in two strong bands about 570 cm−1 and 380 cm−1, which characterize the intrinsic lattice vibrations of octahedral and tetrahedral sites of the spinel structure, respectively. To measure the magnetic properties, a vibrating sample magnetometer (VSM) was used, and the results showed that the manganese nano-ferrite presents the highest saturation magnetization of 55.2 emu/g, while zinc ferrite reveals a low saturation magnetization value of 2.114 emu/g, among different synthesized nano-ferrites. Also, our findings indicated that although both particle size and cation distribution, the magnetic properties are affective on the magnetic properties; however, the role of particle size is more significant. [ABSTRACT FROM AUTHOR]

This paper reports a potential and easy method to prepare nickel ferrite nanoparticles with improved dielectric and magnetic properties by doping with zinc. The structural studies and Rietveld refinement of the XRD pattern confirm the cubic spinel structure of the ferrite phase belonging to the Fd3m space group. Morphological and elemental composition analyses of the prepared samples are carried out using scanning electron microscopy and energy dispersive spectroscopy (EDAX). The frequency variation of the dielectric constant and ac conductivity have been studied. The dependence of dielectric constant and ac conductivity on the frequency of the alternating applied electric field is explained by the Maxwell–Wagner model. The zinc doping in nickel ferrite nanoparticles is helpful in modifying the dielectric properties and thereby designing materials matching the application requirements. Magnetic measurements were carried out at 300 K and 5 K points toward an enhanced magnetic property in zinc-doped samples. The saturation magnetization value for zinc ferrite nanoparticles is around 23 emu/g at 300 K and 56 emu/g at 5 K which clearly indicates the superparamagnetic behavior of the samples. The maximum value for Ms is obtained for the Ni0.5Zn0.5Fe2O4 sample which is 74 emu/g and 101 emu/g at 300 and 5 K, respectively. The enhanced dielectric and magnetic properties inherited by Zn doping in nickel ferrite (NFO) nanoparticles suggest the improved potential of these superparamagnetic NZFO nanoparticles for various applications. [ABSTRACT FROM AUTHOR]

Nanoparticles of cobalt, nickel, and zinc spinel ferrites were successfully synthesized by a low-cost method named as proteic sol-gel method, and a comparative study was performed. Commercial metal nitrates and gelatin from bovine skin were used as precursors. Thermogravimetric analysis and differential scanning calorimetry were performed to investigate the thermal behavior of the precursor powders as well as to select the appropriate calcination temperature for oxide formation. Structural, morphological, optical, and magnetic properties were studied by X-ray diffraction, Mössbauer spectroscopy, transmission electron microscopy, vibrating sample magnetometry, Raman spectroscopy, and UV/VIS diffuse reflectance spectroscopy. Spherical nanoparticles with a single cubic spinel structure were obtained. The results indicate that the average particle sizes are less than 10 nm. CoFe 2 O 4 and NiFe 2 O 4 exhibited ferrimagnetic and superparamagnetic behavior simultaneously, whereas ZnFe 2 O 4 was found to be paramagnetic. The optical band gaps obtained were 1.40, 1.75, and 2.12 eV for CoFe 2 O 4 , NiFe 2 O 4 , and ZnFe 2 O 4 samples, respectively. [ABSTRACT FROM AUTHOR]

The present study aims to develop low magnetic anisotropy Ni-Zn nanoferrites with cobalt substitution. The results enable the development of nanoferrite samples with superior magnetic properties suitable for high-frequency core applications through an understanding of the influence of cobalt in the manipulation of the magnetic anisotropy of the nanoferrite. Ni0.65-xZn0.35CoxFe2O4 (x varies from 0.00 to 0.24 in steps of 0.04) particles were synthesized by sol–gel method using polyvinyl alcohol as a chelating agent. X-ray diffraction patterns of all the samples showed sharp peaks corresponding to spinel structure with no extra phases. Transmission electron micrographs depict uniform size distribution of particles in the range 185 to 247 nm. Magnetic properties were measured at 300 K and 5 K. Excellent control to reduce the magnetic anisotropy to a negligible amount can be achieved by incorporating minute amounts of cobalt in nickel-zinc ferrite. [ABSTRACT FROM AUTHOR]

In this study, erbium-substituted Zn nanoferrites were synthesized by a simple coprecipitation method. The effect of pH on various physical parameters of erbium-substituted Zn nanoferrites was studied. The synthesized ferrite nanoparticles were characterized by XRD, FTIR, and SEM techniques and dielectric measurements. The gravimetric analysis showed the annealing temperature of these ferrites up to 700 °C. The result of XRD revealed the crystal structures of zinc nanoferrites. The FTIR spectra showed the weaker absorption peak due to Er–O stretching vibrations in zinc nanoferrites at pH 11. The SEM analysis showed that synthesized erbium-substituted Zn nanoferrites have a spherical shape with a size range from 42 to 46 nm. Dielectric properties exposed the typical semiconductor behavior of the erbium-substituted Zn nanoferrites. The electric constant at low pH was due to Fe+2 dielectric losses that dominated the sum of intrinsic and extrinsic loss. Increased in dielectric loss is associated with random crystallite orientation and impurities. The ZnFe2O4 nanoparticles with a decrease in dielectric loss revealed the crystallite orientation at pH 8 and 11. Tangent loss revealed the conductivity at higher pH 11 with a decrease in tangent loss. [ABSTRACT FROM AUTHOR]

Synthesis of non-magnetic metallic zinc (Zn) nanoparticles (NPs) and (Zn)x/Cu0.5Tl0.5Ba2Ca2Cu3O10−δ (CuTl-1223) nanoparticle-superconductor composites was carried out by chemical sol-gel and solid-state reaction methods, respectively. Different concentrations of Zn NPs from 1.0 to 4.0 wt.% were inserted in CuTl-1223 superconducting matrix to obtain desired (Zn)x/CuTl-1223 nanoparticle-superconductor composites. The structural properties of these NPs and composites were studied by X-ray diffraction (XRD) technique. The unaffected crystal symmetry of the host CuTl-1223 superconducting phase after the inclusion of Zn NPs from XRD patterns suggested that these NPs were settled across the grain boundaries. Transport electrical properties of (Zn)x/CuTl-1223 composites were investigated by resistivity versus temperature (RT) measurements, and zero resistivity critical temperature (Tc) was found to be increased with Zn NPs contents up to x = 3 wt.%. The enhancement in Tc could be due to the non-magnetic metallic Zn 3d10 (S = 0) NPs that facilitated the conduction of charge carriers across the grain boundaries, while Tc was suppressed beyond x = 3 wt.% contents of Zn NPs due to reduced superconducting volume fraction of CuTl-1223 matrix. Using the LCR meter, dielectric parameters, namely real part (ɛ/r), imaginary part (ɛ//r), tangent loss (tanδ), and ac-conductivity (σac), were measured at varying frequencies and temperatures. The values of ɛ/r, ɛ//r and tanδ were found to be maximum at lower frequencies and became constant at high frequencies, while the value of σac was found to be minimum at lower frequencies and was increased with increasing frequency. [ABSTRACT FROM AUTHOR]

Microwave combustion technique (MCT) was used to synthesize of spinel Ni1-xSrxFe2O4 (x = 0.0, 0.1, 0.3 and 0.5) nanoparticles (NPs) by employing the fuel L-arginine. The physical characteristics of the as-prepared NPs were obtained by following methods, viz., powder X-ray diffraction (XRD), high-resolution scanning electron microscope (HR-SEM), energy-dispersive X-ray (EDX), UV-visible diffuse reflectance spectra (UV-Vis DRS), Fourier-transform infrared spectra (FT-IR), and vibrating sample magnetometer (VSM) techniques. The diffraction studies revealed that the average crystallite size exists in the band of 14.25 to 27.52 nm. The HR-SEM pictures revealed the agglomerated and spherical morphology of spinel Ni1-xSrxFe2O4 (x = 0 to 0.5) nanoparticles. Elemental analysis ensured the existence of Ni, Sr, O, and Fe ions. The energy band gap of the NPs was observed to exist in the range of 2.95 to 3.39 eV upon varying the concentration of Sr2+ dopant. The broad peaks at 437 cm−1 and 582 cm−1 correspond to octahedral (B-) metal stretching (Ni-O) and tetrahedral (A-) metal stretching (Fe-O) of nickel ferrite respectively. Magnetic results revealed that the prepared NPs are ferromagnetic in nature. The antibacterial activity (ABA) of gram-positive Staphylococcus aureus and Bacillus subtilis and gram-negative Escherichia coli and Klebsiella pneumonia has been investigated using pure and Sr2+-substituted NiFe2O4 NPs. It was found that the improved activity is intensified with smooth Sr2+ doping as it causes a decrease in the grain size. [ABSTRACT FROM AUTHOR]

In this paper, we investigate the magnetic, dielectric, and impedance properties of Ba2 − ySryZn2Fe12O22 (y = 0.0–1.5) hexaferrite prepared by solid-state reaction process. The magnetic hysteresis loop suggested that the prepared hexaferrite exhibits room temperature hard ferromagnetic activity. The saturation magnetization (Ms), remanence (Mr), and magneton number (nB) values are decreased with Sr2+ substitutional dopant at the Ba2+ site. On the other hand, Sr2+ doping enhances the β, Ha, and Ke values. The squareness ratio (Mr/Ms) is calculated to be 0.50, indicating the uniaxial anisotropy of BSZFO (y = 0.0–1.5) hexaferrite. Dielectric constant and dielectric loss values increased from 147 to 290 and 0.058 to 0.94, increasing Sr2+substitution from 0.0 to 1.5 at 1 MHz. This study has supported the rise in AC conductivity and decreases DC conductivity with the Sr2+ substitution. [ABSTRACT FROM AUTHOR]

Zinc ferrite (ZnFe2O4) nanoparticles were prepared by chemical co-precipitation method. Structural characterization was performed using X-ray diffraction (XRD) and transmission electron microscopy (TEM). Formation of spinel phase was confirmed from XRD studies. Crystallite size and lattice constant of the prepared sample were calculated. TEM images reveal spherical-shaped particles with nanosized distribution. Room temperature magnetic hysteresis loop was recorded using vibrating sample magnetometer (VSM). The magnetization loops exhibit a very narrow loop and behave like superparamagnetic nature. Using the Langevin function, the magnetic behaviour of the prepared nanoparticles was investigated. From the curve fitting, saturation magnetization and reduced magnetization were determined. As-prepared sample was further annealed at three different temperatures namely 800 °C, 1000 °C, and 1200 °C for 2-h duration. The effects of annealing on the structural and magnetic properties were further investigated using XRD and VSM. The observed results on the magnetic characteristics of ZnFe2O4 and applicability of the Langevin function are being discussed. [ABSTRACT FROM AUTHOR]

Composites of ZnFe2O4/La0.67Sr0.33MnO3 with different weight percentages were synthesized using sol-gel method and their magnetic behavior was investigated. Powder X-ray diffraction studies show spinel structure for zinc ferrite and rhombohedral for La0.67Sr0.33MnO3. An additional minor phase of α −Fe2O3 and ZnO was also noticed in zinc ferrite suggesting non-stoichiometric nature. Fourier transform infrared spectroscopy studies display cohabitation of two phases belonging to ferrite and perovskite phase with varying peak intensities. Field-dependent magnetization measurement at room temperature shows partial variation in saturation magnetization and remanent magnetization values with increase in La0.67Sr0.33MnO3 weight percent in zinc ferrite. Except for zinc ferrite, d M d H shows single peak with smooth variation, pointing to easy rotation of magnetic dipoles under applied fields. [ABSTRACT FROM AUTHOR]

ZnxCu1-xFe2O4 (0.05 ≤ x ≤ 0.85) nanoparticles were synthesized by sol-gel method and were annealed at 500 and 900 °C in air for 3 h. Characterization techniques like XRD, Raman spectroscopy, and vibrating sample magnetometer were used to investigate phase, cation distribution, and magnetic properties. XRD studies showed that all the as-prepared samples are of cubic spinel phase. Tetragonal phase was observed in the samples with x < 0.15 after annealing, whereas all other samples retained cubic phase. Raman spectroscopy showed increase of Zn2+ ions in the tetrahedral site with the increase in Zn2+ concentration in the nanoparticle samples. Cation distribution and magnetic ordering enhanced the magnetization value with increasing x value, and a maximum was observed in the as-prepared and annealed samples. The coercivity decreased with the increase in Zn2+ concentration. The highest magnetization value of 110 emu/g with coercivity of 25 Oe was observed in the present study at 60 K for the sample annealed at 900 °C with x = 0.5. Law of approach to saturation method was adopted to study the magnetic ordering in the nanoparticle samples. The blocking temperature decreased with increase in Zn2+ concentration and annealing temperature. Cation distribution associated magnetic ordering and anisotropy variation with the increasing Zn2+ concentration explains the observed magnetic behavior in these nanoparticle samples. [ABSTRACT FROM AUTHOR]

Despite increasing solicitude in magnesium-zinc ferrites as advanced ceramics, there is still much uncertainty regarding their mechanical and magnetic properties. Precursors Co2+ ions substituted magnesium zinc spinel ferrites with chemical formula Mg0.8Zn0.2-xCoxFe2O4; (0 ≤ x ≤ 0.2) (MZCFO) were scrutinized. XRD patterns confirmed the formation of the spinel structure for all MZCFO nanoferrites with no traces of any secondary phases. An excellent correlation is between the structural, mechanical, and magnetic theoretical and experimental results; supporting the validity of cation distribution. The experimental lattice parameter of MZCFO is found in the range 8.3893–8.3803 Å, and the theoretical one is found in the range 8.3882–8.3833 Å. The average crystallite size is calculated using the two methods (Debye–Scherrer and Williamson–Hall), which was found in the range ~15–50 nm, to confirm the nanocrystalline nature of all MZCFO ferrites. The FE-SEM micrographs illustrate the nanoferrite morphology exhibiting rocky-shaped particles with variable pore size. The HR-TEM micrographs of the as-prepared nanoferrites reveal agglomerated round-shaped nanoferrite particles. EDX spectra reveal the presence of all chemical elements, and SAED micrographs confirm the polycrystalline nanosized nature of MZCFO samples. Also, FTIR analysis affirmed the spinel structure by exhibiting the distinctive vibrational band of the ferrite bonds. Experimental and theoretical elastic moduli (bulk (B), rigidity (G), Young (E)) besides Poisson ratio (σ) and Debye temperature (ϴD) of MZCFO nanoferrites were investigated. The bond length is the main reason for the insignificant variation in the elastic moduli of MZCFO with further cobalt substitution. Cation distribution is the main reason for the nanoferrite Mg0.8Zn0.12Co0.08Fe2O4 (x = 0.08) to have the highest MS value (40 emu/g) and the exceptional level of flexibility obtained for the mechanical properties. The coercivity exhibits an increasing demeanor with Co2+ substitution (HC = 569.35 at x = 0.2), which is correlated to the strong magnetic anisotropy property of Co2+ species in B sites. These advantages can initiate a considerable attention in implementing this ferrite in applications such as high-density magnetic recording, loudspeakers, and sensors. [ABSTRACT FROM AUTHOR]

The present work reports on the synthesis characterization of Ca(Co1.5-Ni0.5)Y-type ferrite/GO nanocomposites with 10, 20 and 30 wt% of GO named as C1, C2 and C3, respectively, via ultrasonication technique. The Co-Ni doped Ca-ferrite (Ca2Co1.5Ni0.5Fe12O22) was prepared via sol-gel technique sintered at 900 °C for 5 h, and graphene oxide (GO) was prepared by modified Hummer's method. The structural features and physical properties of the composites were studied by X-ray diffraction, dielectric and electrical measurements. XRD results confirmed the phase formation of Y-type hexaferrite and formation of GO, while the XRD pattern of composites is similar to the pattern of pure Y-type ferrite indicating that restacking of graphene sheets is prevented and ferrite particles are homogenously dispersed on the surface of the graphene oxide sheets. The pure GO exhibits the largest value of dielectric constant (1 × 106) at lower frequency range. The dielectric measurement showed that concentration of GO in composites directly related to dielectric constant. The composite with 30 wt% loading of GO has maximum dielectric constant (25 × 103) in all composites. It is observed that DC resistivity of composites at room temperature decreased from 12.4 × 108 to 0.96 × 108 ohm-cm with increasing GO concentration. It was observed that resistivity of Y-type ferrite/GO composites decreased with increasing temperature, which indicate the semiconducting nature of composites. The value of activation energy decreased from 0.283 to 0.031 eV with increasing GO concentration in composites, which is consistent with resistivity results. [ABSTRACT FROM AUTHOR]

The paper explains the different concentrations of rare earth element (REE) cerium-doped nickel ferrite nanoparticles prepared by the sol-gel method. The structural, morphological, and magnetic properties are characterized by XRD, SEM/TEM, and VSM techniques respectively. The XRD pattern shows the single phase with the spinel nature. The calculated particle size is confirmed with SEM/TEM analysis. The VSM technique is carried out to study the magnetic characterization of the prepared sample. Also, the decrease in the saturation magnetization and coercivity of the ferrite samples when varying the concentration of cerium ions is found. The antibacterial activity of nickel ferrite nanoparticles is also analyzed on gram-positive and gram-negative bacteria. [ABSTRACT FROM AUTHOR]

Magnesium-substituted Ni-ferrite (MgxNi1 − xFe2O4; 0 ≤ x ≤ 1) nanoparticles were prepared by sol-gel method and were annealed at 550 °C and 900 °C in air. All the as-prepared samples and the samples annealed at 550 °C were single phase whereas some additional peaks of α-Fe2O3 was observed for the samples annealed at 900 °C. Lattice constant increased with the increase in Mg2+ concentration. Crystallite size did not show any systematic variation with the increase in Mg2+ concentration and was increased after annealing in these nanoparticle samples. The highest MS values of 42 and 46 emu/g were observed at 300 and 60 K respectively for the as-prepared sample with x = 0.05 and the lowest values of 21 and 26 emu/g were observed at 300 and 60 K respectively for the 550 °C-annealed sample with x = 1. The magnetization and coercivity decreased with the increase in Mg2+ concentration. The non-saturation behavior was found to be increased with the increase in Mg2+ concentration in these samples. The observed magnetic behavior can be understood on the basis of increase in nonmagnetic Mg2+ concentration, cation distribution in the lattice sites, growth of crystallite size, and the decrease in anisotropy with the increase in Mg2+ concentration in these nanoparticle samples. [ABSTRACT FROM AUTHOR]

First-principles calculations of density functional theory (DFT) are used to investigate the structural, electronic, and magnetic properties of the spinel system CdxCo1−xFe2O4 (x = 0, 0.5, and 1). High-temperature series expansions (HTSE) combined with the Padé approximants (PA) method and mean field theory (MFT) have been used to calculate the critical temperature (TC). The lattice parameter and the local magnetic moments of Co and Fe increased when Cd content x increases. The obtained theoretical results show that the Curie temperature decrease with x. Density of states (DOS) calculations show a half-metallic behavior for x = 0.5 and semiconducting behavior for x = 0 and 1. This work, provide useful information for the substitution effect of a nonmagnetic ion on the properties of spinel ferrites, based on first-principles calculations and HTSE. [ABSTRACT FROM AUTHOR]

In this work, Magnesium-doped zinc aluminate nanoparticles are synthesized using microwave combustion technique by employing L-alanine as fuel. The incorporation of Mg2+ ions plays a pivotal role in influencing the optical, structural, and magnetic properties of zinc aluminate nanoparticles. The synthesized nanoparticle are characterized by X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FT-IR), high-resolution scanning electron microscopy (HR-SEM), energy dispersive X-ray analysis (EDX), diffuse reflectance spectroscopy (DRS), and vibrating sample magnetometer (VSM).The XRD patterns confirmed the formation of single-phase cubic spinel structure of ZnAl2O4 (gahnite). The average crystallite sizes estimated from Debye-Scherrer is found to be in the range of 6 to 12 nm. HR-SEM images revealed the spherical morphology with uniform distributions. The optical bandgap of the synthesized nanoparticles is found to be in the range of 5.45 eV–5.76 eV. Magnetic measurement reveals that pure and doped zinc aluminate nanoparticles have superparamagnetic nature. These obtained results of Zn1-xMgxAl2O4 (0 ≤ x ≤ 0.5) are found to be well suited for optoelectronics, magnetic, and catalytic applications. [ABSTRACT FROM AUTHOR]

In this study, zinc (Zn)-doped YBaCuO (YBCO)-123-based high-temperature superconducting samples were produced using the sol-gel method, which is commonly used for preparing nanosize materials. Zn ions were substituted by Cu ions (YBa2Cu3-xZnxO), and Zn doping effects on structural, electrical, and mechanical properties of the YBCO-123 superconductors were examined in detail. Undoped sample was prepared under same conditions. X-ray diffraction analysis (XRD) was used to determine phase analysis and lattice parameters of the superconducting samples. To analyze the microstructure properties, scanning electron microscope (SEM) measurements were performed. Resistivity and microhardness measurements were also carried out for superconducting and mechanic properties, respectively. Vickers microhardness, young modulus, fracture toughness, and yield strength values of the samples were calculated. Microhardness measurements were analyzed using the Kick's law, proportional sample resistance (PSR) model, EPD model, the Hays-Kendall (HK) approach, and indentation-induced cracking (IIC) model. [ABSTRACT FROM AUTHOR]

In this research, the structural, morphological, and magnetic properties of Bi-doped cobalt ferrite (CoFe2-xBixO4) nanoparticles with x = 0.0, 0.05, 1, 0.15, and 0.2, prepared by the sol-gel method, were studied. In order to characterize the samples, several equipment and analyses including thermo-gravimetric and differential thermal analysis (TGA/DTA), X-ray diffraction (XRD), field emission scanning electron microscope (FESEM), Fourier transform infrared spectrometer (FT-IR), and vibrating sample magnetometer (VSM) were used. The average crystallite sizes of the prepared CoFe2-xBixO4 were calculated using the Scherer, UDM, SSP, and Halder-Wagner methods. The average crystallite sizes for the samples were found in the range of 26 to 44 nm, which can be attributed to the grain growth of the particles. FT-IR spectrum showed bands in the range of 430 to 590 cm−1 due to the stretching vibration of an oxygen atom and metal ions (Fe-O), confirming the formation of spinel ferrite. Surface morphology of the samples was studied using FESEM. The VSM results showed that the saturation and remanence magnetizations increased by raising the doping values up to x = 0.1. The Curie temperature of the cobalt nanoferrites was determined using Faraday's technique. The highest Curie temperature was found to be 580 °C for the undoped sample. [ABSTRACT FROM AUTHOR]

Zinc-doped lithium ferrite nanoparticles with general formula Li0.46Zn0.04Fe2.5O4 were prepared by Co-precipitation method and their thin films were grown by spin coating method. X-ray diffraction (XRD) confirmed the spinel structure of the synthesized samples. Fine morphology of the films was obtained by controlling the parameters. AC electrical properties including dielectric constant (έ), dielectric loss tangent (tanδ), AC electrical conductivity (σac), and impedance (Z) were studied as a function of frequency at different temperatures and at 1 MHz frequency in a temperature range of 40–500 °C. Dielectric constant, dielectric loss tangent, and ac electrical conductivity showed the decreasing trend with increase in temperature while opposite trend was observed for impedance. Zinc-doped Li-ferrite has better absorption properties in the studied frequency and temperature range as compared to that of Li-ferrites. [ABSTRACT FROM AUTHOR]

In this work, we investigated the effect of doping zinc ions onto nickel ferrite upon the structure, morphology, and magnetic properties of Ni1 − xZnxFe2O4 ferrite nanoparticles (x = 0, 0.25, and 0.75) prepared via co-precipitation method. X-ray diffraction analysis showed the presence of the most intense peak corresponding to the (311) crystallographic orientation of NiFe2O4 cubic spinel phase, and the crystallite size obtained from Scherrer formula increased from 6.8 to 11.2 nm when the Zn concentration increases from x = 0 to x = 0.75. Fourier transform infrared spectroscopy analysis confirmed the presence of a prominent band associated to the vibrations of metal ions, as a feature of spinel ferrite phase formation, observing that their band positions were very sensitive to Zn doping concentration. Transmission electron microscopy studies allowed to determinate that for all Zn concentrations, the particle sizes are around 15 nm. The magnetic properties were studied by using the vibrating sample magnetometer at room temperature. The results reveal superparamagnetic behavior determined by the shape of the hysteresis loop, presenting decreased coercive magnetic field and increased saturation magnetization, with increased zinc concentration. Additionally, from field cooling and zero field cooling curves, we can observe the typical behavior of the blocking process assembly of superparamagnetic nanoparticles. Alternate current susceptibility measurements show that the blocking temperature is frequency dependent and shifts toward higher temperatures by increasing the frequency, a characteristic of superparamagnetic, and glassy systems. Furthermore, τ0, related to the jump attempt frequency of the magnetic moment of the nanoparticle between the opposite directions of the magnetization easy axis, is in the range of 2 × 10−10 and 7 × 10−13 s for the three different Zn concentrations, which agrees with characteristic of non-interacting superparamagnetic systems. [ABSTRACT FROM AUTHOR]

The aim of this study was to investigate the effect of annealing temperature and cobalt cation (Co2+) doping on the magnetic properties of zinc ferrite (ZFO) nanoparticles. The nanoparticles were prepared through sol-gel combustion process with citric acid as the fuel. The obtained nanoparticles were annealed at several temperatures from 300 to 1000 °C for 2 h. Spinel formation was proved by X-ray diffraction (XRD) patterns, and the average crystallite size in all samples was estimated between 22 and 32 nm. It is worthwhile to mention that Fe2O3 and ZnO are detected as the medium phases. Meanwhile, Fe2O3 phase transformation to the other allotropes has happened around 400 °C and was characterized via the simultaneous thermal analysis (STA) and XRD. For higher annealing temperatures, diffusion has gradually been completed and, finally, the single phase of spinel structure was prepared at 1000 °C. In addition, field-emission scanning electron microscopy (FESEM) images revealed that the nanoparticle size after annealing was between 30 and 200 nm for the whole samples. The formation of the spinel phase was considered the most important factor on the magnetic properties of ZFO. Cobalt doping, annealing temperature, and also Fe2O3 phase were the main factors on changing magnetic properties. Paramagnetic nanoparticles with higher coercivity for doped samples rather than un-doped samples have been obtained. [ABSTRACT FROM AUTHOR]

The nanocrystalline zinc ferrite (ZnFe O ) thin films were grown on the fused quartz substrate using pulsed laser deposition. The effects of atmospheric conditions on structural, magnetic, and morphological properties have been systematically studied using X-ray diffraction, vibrating sample magnetometry, and atomic force microscopy. The films showed textured growth of zinc ferrite for the substrate temperatures at ≥ 600 °C irrespective of the ambient environment. Interestingly, thin films of zinc ferrite showed a magnetic hysteresis loop in contrast to the paramagnetic nature of their bulk counterpart. The value of saturation magnetization (4 π M ) increased from 130 to 360 G when the substrate temperature was increased from room temperature (RT) to 800 °C in the oxygen atmosphere. In the absence of oxygen pressure, the value of 4 π M is observed to be 330 G for the film deposited at RT and found to increase to a value of 670 G when the film is deposited at 400 °C and the maximum value of 2580 G is observed for the film deposited at 700 °C. However, the value of 4 π M of 800 °C dropped down to 2000 G. [ABSTRACT FROM AUTHOR]

Cobalt and manganese-substituted zinc ferrite XZnFeO (X = Co, Mn) nanoparticles have been synthesized by co-precipitation method and characterized for structural, morphology, and magnetic properties by X-ray diffraction (XRD), scanning electron microscopy (SEM), and vibrating sample magnetometry (VSM). The Rietveld refinement method is employed to refine the XRD powder data, and the structural parameters are calculated from the refinement. Substitution of cobalt and manganese causes the lattice parameter to decrease. Particle size, measured from XRD, lies in the nanometer regime. A low saturation magnetization value is obtained in both samples, and the presence of non-collinear spin arrangement is found at octahedral sites. The maximum entropy method (MEM) is employed to study the strength of the bond between the atoms at tetrahedral and octahedral sites in the unit cell of ferrites. Optical band gap energy of the samples is determined by using UV-VIS techniques. [ABSTRACT FROM AUTHOR]

The polycrystalline LiZnFeO ferrites with different iron-deficient contents ( x = 0.000 ∼0.235) have been synthesized via a solid-state method. Based on the deconvoluted X-ray photoelectron spectroscopy (XPS) spectra of Fe 2 p for LiZn ferrites, the Fe and Fe ion percent contents have been estimated via the area proportion of each peak, respectively. With the increase of iron-deficient content ( x), the ion percent ratio of Fe/Fe shows a monotone decrease. Furthermore, according to the equivalent circuit of ferrite of a 'brick wall' model, resistivity and permittivity frequency spectra (100 Hz ∼1 MHz) of LiZn ferrites have been investigated, and LiZn ferrites show grain boundary and grain characteristics at low and high frequencies, respectively. In addition, the ferromagnetic resonance (FMR) linewidth has been separated to anisotropy and porosity line broadening contributions by an approximate calculation based on a spin-wave approach. [ABSTRACT FROM AUTHOR]

Copper ferrite-doped magnesium zinc ferrite, i.e., MgZnCuFe O (0.0 ≤ x ≤ 0.5) has been synthesized by conventional solid-state reaction technique. The role of copper ion substitution on the crystal and lattice structure and also on the dielectric properties of MgZnFe O ferrite is studied. XRD investigation exposes that the synthesized samples are polycrystalline single-phase cubic spinel in structure without the occurrence of any secondary phase corresponding to any structure. Small deviation in the lattice parameter from 8.412 to 8.374 Å of copper-doped MgZnFe O has been observed due to difference in ionic radii of cations with increase in copper doping. Small shift in Raman modes towards higher wavenumber has been observed with Cu doping. Room-temperature dielectric properties show that for each sample, the dielectric constant decreases with an increase of frequency and becomes constant at higher frequencies. Dielectric loss decreases with increase in Cu concentration. The dielectric constant increases to a great extent in prepared samples. [ABSTRACT FROM AUTHOR]

Barium hexaferrite with nominal chemical composition BaMnZnFeO has been synthesized by sol-gel method, using polymethyl methacrylate (PMMA) as a template. Fourier transform infrared spectroscopy (FT-IR) and X-ray powder diffraction (XRD) were used for approving the formation of barium hexaferrites. In addition, transmission electron microscopy (TEM) and scanning electron microscopy (SEM) were performed to investigate the structural and morphological properties of BaM. The dielectric properties were studied by impedance measurements as a function of frequency (in the range 0.1 Hz-1 MHz). The XRD patterns confirmed the formation of single-phase magnetoplumbite with crystallite size around 73 nm. The results of dielectric parameters and conductivity measurements showed three regions with different behaviors in electrical conduction mechanism. [ABSTRACT FROM AUTHOR]

Superconducting samples of the type (ZnFeO)GdBaCuO were synthesized by the conventional solid-state reaction technique. The nanosized (ZnFeO) content x varied from 0 to 0.1 wt% of the samples' total mass. The prepared samples were characterized using X-ray powder diffraction (XRD) and scanning and transmission electron microscopes (SEM and TEM). The effect of ZnFeO addition, which acts as flux pinning centers, was investigated using ac magnetization at different applied dc magnetic fields. It was found that addition of the nanosized (ZnFeO) up to 0.06 wt% enhances the critical current density J and the superconducting transition temperature T. On the other hand, the superconducting properties of these samples are deteriorated for x > 0.06 wt%. The irreversibility line was thermally activated. The logarithmic plot of H versus (1 − T/ T(0)) shows a crossover at about 500 Oe, reflecting the transition from two- to three-dimensional vortex fluctuations. The B- T curves are well fitted according to Matsushita's model, which is based on the de-pinning mechanism caused by thermally activated flux creep. [ABSTRACT FROM AUTHOR]

In this work, single phase zinc ferrite (ZnFe O) nanoparticles with a mean crystallite size of 12 nm were successfully prepared just by high energy wet milling of metallic Zn and Fe powders and water as the raw materials, without any subsequent heat treatments. Variation of the magnetization with respect to temperature was studied by Faraday balance. Room temperature M-H curve of the as-milled powder has an s-shape, which shows it has ferrimagnetic order. To investigate the effect of annealing on magnetic properties of the as-milled powder, it was annealed at different temperatures from 150 to 800 °C and characterized by XRD and magnetometry. The results show that cation distribution of the as-milled nanoparticles is different from that of the bulk zinc ferrite (normal spinel) and by annealing it changes drastically, and finally, it changes to that of the bulk one. [ABSTRACT FROM AUTHOR]

In this paper, cobalt zinc ferrite (CoZnFeO) nanoparticles (NPs) have been prepared using chemical co-precipitation method. In order to investigate the annealing induced effects on their various physical properties, the prepared samples have been annealed at 500 °C, 650 °C and 1000 °C and then compared with as-prepared sample. X-ray diffraction (XRD) patterns of as-prepared and annealed samples at various temperatures exhibit single phase spinel structure. Enhancement in crystallinity and crystallite size is observed with the increase in annealing temperature. The annealing has also greatly influence the morphology and grain size of prepared NPs. The CoZnFeO NPs have shown remarkable enhancement in magnetic moment with increase in annealing temperature. The bandgap energies of CoZnFeO NPs have been measured via UV Spectrometer and observed to decrease with annealing temperature. FTIR spectra of the samples reveal the presence of both high frequency and low-frequency bands due to tetrahedral and octahedral sites, which corroborate well with the XRD results. The observed characteristics of cobalt zinc ferrite NPs as a function of annealing temperature are the rising contender for many data storage and nanodevice applications. Finally, the genotoxicity of prepared nanoferrites has been checked via comet assay. [ABSTRACT FROM AUTHOR]

The influence of the precipitant and ferric concentration on the magnetic properties of coprecipitated zinc ferrite nanoparticles has been investigated. The nanoparticles were characterized using X-ray diffraction, scanning and transmission electron microscope, and vibrating sample magnetometer techniques. The results showed that the single-phase zinc ferrite with partially inverse spinel structures can be formed at high concentrations. The inversion coefficient calculated by the Rietveld method decreases with increasing of the concentrations, may be due to the crystal growth. The magnetic measurements exhibited that the coprecipitated zinc ferrite nanoparticles were superparamagnet and magnetization decreases with increasing of the concentrations through decreasing of inversion coefficient. [ABSTRACT FROM AUTHOR]

Three different ferrites with nominal compositions, NiFeO, NiZnFeO, and NiZnCo FeO, were synthesized by wet chemical citrate sol-gel process, mainly to understand how doping with different cations affects the magnetic properties. X-ray diffraction (XRD) confirmed the existence of a single phase without detectable impurities. XRD analysis using the Rietveld refinement technique showed that the samples crystallize in a cubic spinel structure with the Fd-3m space group and the lattice constants were evaluated. Scanning electron microscopy of the calcined samples revealed particles that were approximately 100 nm size. The elemental analysis by energy dispersive spectroscopy showed that the element concentrations were at the stoichiometric ratio in all samples. The magnetic properties measured at room temperature using a vibrating sample magnetometer revealed enhancement in the magnetic properties of nickel ferrite when doped with zinc and cobalt. The high field regimes of the hysteresis loops were modeled using the Law of Approach to Saturation to determine the cubic anisotropy coefficient ( K). The anisotropy coefficient increased with doping Zn and Co, which could be explained in terms of the site occupancy of the dopants in the cubic spinel lattice. [ABSTRACT FROM AUTHOR]