Increase In Saturation Magnetization Research Articles

Synthesis and characterizations of Mg-Cu-Co-Dy ferrites and their composites with graphene nanoplatelets (GNP)

Nanocrystalline spinel ferrite Mg0.5Cu0.25Co0.25Fe1.97Dy0.03O4 (MCCD-ferrites) and their composites with graphene nanoplatelets (GNP =0.0%, 1.25% 2.5%, 3.75%, 5%) were prepared by sol-gel technique and sintered at 850 oC for 5 hours. Measurements in the areas of X-ray diffraction, electrical, optical, dielectric and magnetic properties were used to analyze the effects of the inclusion of graphene with ferrite nanoparticles. The crystallite size was determined in the range of 27.62 – 41.46 (nm). The optical bandgap was found in the range of 3.50 eV to 2.88 eV. The dielectric loss was measured between 8 Hz and 8 MHz at room temperature (RT). Magnetic characteristics of the materials are measured and calculated. The magnetic performances of MCCDF-GNP Composites nanoparticles are improved with an increase in saturation (Ms) magnetization. This material can be utilized for humidity sensors, antennae, and micro memory chips.

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.

Effect of microwave processing on Mn doped ZnO diluted magnetic semiconductor characteristics

5 and 7.5 at% Mn doped ZnO samples were prepared by microwave treatment following thermal curing. The XRD phase analysis reveals the Mn may be present in the unreacted Mn3O4 form or bonded with wurtzite ZnO forming substitutional solid solution (Zn0.99Mn0.01O and Zn0.95Mn0.05O) or spinel (ZnMn2O4). The Fourier transform infra-red (FTIR) band shift to higher wavenumber for the microwave treated samples appearing at 538 and 619 cm−1 indicates formation of ZnMn2O4 spinel structure. Identification of tiny particles in the wall of ZnO lamellae and decrease in Zn2p binding energy signifies vigorous chemical changes taken place on microwave treatment. The structural evolution was depicted by 3d modelling. Quantitative estimation of Mn in the samples was performed by microwave plasma atomic emission spectroscopy (MPAES) and the result matches with the calculated value. Raman spectroscopy shows clear peaks of ZnO, Mn3O4 and MnO2 compounds for all the samples prepared. Whereas, shoulder peak of ZnMn2O4 is observed for 7.5 at% Mn doped microwave pre-treated sample. The optical absorption spectra show major peak near to 360 nm signifying bandgap of ZnO in the visible range. The cation substitution in the host lattice by dopant creates oxygen vacancy (VO) in excess, responsible for increasing bound magnetic polaron, which is clearly evidenced by the presence of broad PL peak near to 535 nm and 548 nm for microwave treated samples. The microwave treatment assists the incorporation of Mn into ZnO lattice as evidenced by reduction of photoluminescence (PL) peak intensity. The magnetic hysteresis loop (B-H curve) of the samples clearly shows increase in saturation magnetisation by ~16.1 and ~24.7 % on microwave treatment of 5 and 7.5 at% Mn doped ZnO respectively.

Biocompatible Tb doped Fe3O4 nanoparticles with enhanced heating efficiency for magnetic hyperthermia application

Magnetic hyperthermia has a specific limitation in treating localized and relatively accessible malignant tumors regardless of its promising therapeutic regime. In this present work, Tb doped Fe3O4 magnetic nanoparticles (MNPs) prepared via coprecipitation root and confirmed the structural conformation and phase purity by XRD, FTIR, TEM, and SEM analysis. TGA analysis was carried out for thermal stabilization and to verify the formation of a stable phase. The occupancy of Tb ions at the octahedral sites and cationic distribution can be calculated from Rietveld refinement analysis. The relaxation mechanism, dipolar- dipolar interactions among the particles, and randomly directed magnetic anisotropy axes were investigated by ESR spectroscopy. The magnetic results enumerate that increasing Tb doping concentration leads to increased saturation magnetization and decreased coercivity and retentivity. The self-heating properties of the doped nanoparticles were characterized by measuring specific absorption rate (SAR). The improved saturation magnetization and enriched SAR value enable the doped MNPs for magnetic hyperthermia application with excellent efficacy.

Synthesis, characterization, dielectric and magnetic properties of substituted Y-type hexaferrites

Fabrication of a series of zinc–strontium hexaferrites, Sr2Zn2−xMnxFe12−yHoyO22 (x = 0.0–1.0, y = 0.0–0.1) was carries out by chemical co-precipitation route with the aim to enhance the saturation magnetization and coercivity and decrease the resistivity to make the materials applicable for recording media of high-density applications. The synthesized hexaferrites were interpreted by Scanning Electron Microscopy (SEM) and X-ray diffraction (XRD). The results of XRD investigation certify the single magnetoplumbite phase formed in hexaferrites with regular crystallite particle size in the 31–38 nm range. Magnetic and dielectric properties of the hexaferrites were also observed. The dielectric parameters (dielectric loss also its tan loss and dielectric constant) were measured at ambient temperature and in 1.0 MHz to 3.0 GHz frequency range. These parameters of Mn–Ho-substituted Zn–Sr hexaferrites showed constant trend with frequency up to a certain value after that resonance sort of behavior was observed. In all the hexaferrites dielectric parameters initially decrease with frequency then become almost constant followed by resonance type behavior. The dielectric parameters of the synthesized samples decrease with dopant content initially but then increase up to maximum dopant level. The saturation magnetization (Ms) and remanence (Mr) increase as the dopant content increases due to magnetic substituents. The squareness ratios of all the nanomaterials synthesized in the present studies is less than 0.5. The coercivity (Hc) decreases by the substitution of Mn and Ho.

Fractional substitution of Mn ions in cobalt-copper ferrite: Effect on its magnetic, dielectric and microstructural properties

A sol–gel auto-combustion route has been employed for the preparation of Mn-substituted Co-Cu ferrite with chemical composition Co0.9Cu0.1Fe2-xMnxO4 (where x = 0.00, 0.03, 0.06, 0.09, 0.12, and 0.15). Intricate techniques like X-ray diffraction (XRD), Inductively coupled plasma atomic emission spectroscopy (ICP-AES), X-ray photoelectron spectroscopy (XPS), SEM-EDX, and TEM-SAED have been employed to achieve details of the prepared compositions. The crystalline nature and monophasic formation of the formulated compositions have been authenticated from XRD and SAED analyses, while ICP-AES results confirmed the formation of the samples as intended. The SEM and TEM studies gave an elaborate insight into sample surface morphology and particle size. XPS studies revealed the chemical states of the species present in the sample. Mössbauer analysis corroborated the oxidation state of Fe as 3+ and the ferrimagnetic nature of the prepared material. Magnetic studies presented an initial increase in saturation magnetization (Ms) with Mn-substitution followed by a decrease upon further substitution. The Curie temperature showed a steadily declining trend with Mn ion substitution. The Mn-substituted Co-Cu ferrite predominantly showed an increase in dielectric constant analogous to the pristine material.

Tuning of reduced remanent and (BH)max by exchange spring phenomenon in ferrimagnetic composite

The (x)% BaFe12O19 (BHF) + (100-x)% CoFe2O4 (CFO) (x = 0 to 100) magnetic composites are prepared to explore its magnetic properties. The XRD patterns reveal the presence of both BaFe12O19 and CoFe2O4 crystal symmetries in the composite. The FESEM and TEM micrographs reveal the uniform distribution of nanoparticles. The theoretical saturation magnetization is calculated by Vegard’s law, which is nearly equal to the experimental observation. The maximum reduced remanent (Mr/Ms) and magnetic energy product (BH)max are found to be 0.43 and 0.456 MGOe, respectively, for x = 50 i.e. (50)% BHF + (50)% CFO. It is explained by assuming magnetic interaction at the interfaces of soft and hard magnetic phases. The coercive field, remannet magnetization, reduced remanent, saturation magnetization, and (BH)max increase with a decrease in measuring temperatures. The enhancement of magnetic parameters at a low temperature is observed due to the decrement of the thermal energy of magnetic moments at the surface. The saturation magnetization increases with an increase in annealing temperature, which could be due to the minimization of spin disorders at the surface of nanoparticles. The enhanced reduced remanent (Mr/Ms) and (BH)max are found for the (50)%BHF + (50)%CFO composite annealed at a higher temperature. The evidence of magnetic interaction between two magnetic phases in the composite has been realized by employing the Henkel plots and dMdH versus H curve techniques.

Magnetic hyperthermia properties of CoFe2O4 nanoparticles: Effect of polymer coating and interparticle interactions

In this work, CoFe2O4 magnetic nanoparticles (MNPs) were synthesized by an eco-friendly co-precipitation method. The effect of Triethylene glycol (TEG) coating on the structural, magnetic and magnetothermal properties of MNPs was investigated. The formation of crystalline MNPs with a cubic spinel structure and the single phase state was confirmed by the X-ray diffraction (XRD) and infrared spectra (FT-IR) techniques. The spherical morphology and aggregation of the MNPs, as a sign of the presence of interparticle interactions, were revealed by the field emission scanning electron microscopy imaging. A remarkable result has been found by the SQUID and Mössbauer spectroscopy measurements revealing that the polymer coating increases the saturation magnetization through the control of the metal-oxygen-metal bonds and reduction of the spin disorder at the nanoparticle surface. Furthermore, the Henkel plots indicated a dominant role of the dipole-dipole over exchange magnetic interactions in the samples which affected the heating efficiency of the ferrofluids measured under different AC magnetic fields (2.2, 2.7, and 3.3 mT) with a frequency of 92 kHz showing a linear dependence of the thermal efficiency with the AC field amplitude. It was shown that TEG coating increases the heating efficiency of the CoFe2O4 MNPs, which was attributed to an increase in saturation magnetization and a decrease in the strength of the magnetic interactions between the coated nanoparticles.

The influence of reaction and annealing temperature on physical and magnetic properties of CuFe2O4 nanoparticles : Hydrothermal method

Pure copper ferrite nanoparticles (CuFe2O4 NPs) were synthesized by using a simple hydrothermal method and annealed at different levels of temperatures. The single–phase cubic spinel structure was confirmed by X-ray diffraction pattern and average crystallite size was found to increase from 34 to 42 nm as the annealing temperature increases. FT-IR spectra confirmed metal oxides Fe-O and Cu-O, the formation of pure spinel magnetic copper ferrite nanoparticles. The five Raman active modes of vibrations confirmed the cubic structure of prepared yield (A1g + Eg + 3T2g). The average particle size identified by TEM analysis exists within the nano range with cubic structures. The magnitudes of the zeta potential indicated the potential stability and surface charge of the nanoparticles. The pore size was estimated by BJH technique and the obtained distribution as 18.5 nm in diameter. The optical study revealed the decreasing nature of the bandgap with increasing annealing temperature. The dielectric parameters were analysed with varying frequency range and it was observed that decreasing nature of dielectric loss is suitable for microwave application. The influence of annealing temperature revealed the increase of saturation magnetization, remanence and coercivity owing to the increased crystallite size. The electrochemical analyses of as-prepared and the annealed (750 °C) CuFe2O4 NPs exhibited high specific capacitance at a low scan rate which indicates the good result for supercapacitor application.

Enhanced Magnetic Hyperthermia of Magnetoferritin through Synthesis at Elevated Temperature.

Iron oxide nanoparticles have attracted a great deal of research interest in recent years for magnetic hyperthermia therapy owing to their biocompatibility and superior thermal conversion efficiency. Magnetoferritin is a type of biomimetic superparamagnetic iron oxide nanoparticle in a ferritin cage with good monodispersity, biocompatibility, and natural hydrophilicity. However, the magnetic hyperthermic efficiency of this kind of nanoparticle is limited by the small size of the mineral core as well as its low synthesis temperature. Here, we synthesized a novel magnetoferritin particle by using a recombinant ferritin from the hyperthermophilic archaeon Pyrococcus furiosus as a template with high iron atom loading of 9517 under a designated temperature of 90 °C. Compared with the magnetoferritins synthesized at 45 and 65 °C, the one synthesized at 90 °C displays a larger average magnetite and/or maghemite core size of 10.3 nm. This yields an increased saturation magnetization of up to 49.6 emu g−1 and an enhanced specific absorption rate (SAR) of 805.3 W g−1 in an alternating magnetic field of 485.7 kHz and 49 kA m−1. The maximum intrinsic loss power (ILP) value is 1.36 nHm2 kg−1. These results provide new insights into the biomimetic synthesis of magnetoferritins with enhanced hyperthermic efficiency and demonstrate the potential application of magnetoferritin in the magnetic hyperthermia of tumors.

Synthesis, Characterizations, and Magnetic Properties of Mixed Spinel Mg1-xZnxFe2O4 Ferrites

Mixed spinel Mg1-xZnxFe2O4 ferrites (where x = 0, 0.2, 0.4, and 0.6) nanoparticles were synthesized by using microwave-assisted combustion route. As-synthesized powdered samples were checked by XRD analysis, field emission-scanning electron microscopy, and vibration sample magnetometer to investigate the structural, morphology, and magnetic properties, respectively. XRD results exhibited that the crystallite size increases with the decrease of Zn+2 ion concentration for series of mixed spinel Mg1-xZnxFe2O4 ferrite expect x=0.2. All the mixed spinel Mg1-xZnxFe2O4 ferrite has different grain sizes with uniform distribution also presence voids in the samples. Pure magnesium ferrite has a lower net magnetization value but when magnesium ions (Mg+2) are replaced by zinc ions (Zn+2) then the value of saturation magnetization increases.

Impact of the Zn–Co content on structural and magnetic characteristics of the Ni spinel ferrites

The manuscript describes the impact of the chemical composition (Co2+/Zn2+ ions content), crystal and magnetic characteristics of substituted Ni0.3Zn0.7-xCoxFe2O4 (0≤x ≤ 0.7) Ni-based spinels (or NZCF). The initial NZCF powders were prepared using the classic ceramics method. All investigated samples were characterized by a single-phase state with a spinel-like structure – SG: Fd-3m. The average chemical composition of the final NZCF powders correlated well with the initial stoichiometry. After XRD data refinement, we observed a linear decrease of the lattice parameters and volume of the unit cell from a = 8.4085 Å till a = 8.3689 Å and from V = 594.51 Å3 till V = 586.14 Å3 with x increasing from 0 to 0.7, respectively. It was explained by the smaller ionic radius of Co2+ compared to Zn2+. A strong impact of the Co2+/Zn2+ ratio in Ni0.3Zn0.7-xCoxFe2O4 (0≤x ≤ 0.7) Ni-based spinels on their magnetic characteristics was demonstrated. An increase in Co2+ content from x = 0.0 to x = 0.7 leads to an increase in the remnant magnetization Mr and coercivity Hc with non-linear changes in magnetization saturation Ms. It can be explained by the competition of two factors: i. Larger magnetic moment of the Co2+ ion in comparison with the Zn2+; and ii. The features of the substituent distribution in the spinel matrix. It was observed that anisotropic parameters curves are not rectilinear. This behavior has been explained by the disproportionate contribution of two competing effects, namely, an increase in the f stiffness of the Ni3+(Zn2+, Co2+/3+, Fe3+/4+) –O2- - Fe3+/4+(Ni3+, Zn2+, Co2+/3+) indirect superexchange interactions and an increase in the Ms saturation magnetization with an increase in the x concentration of the Co2+/3+ cations.

Structural, elastic and magnetic properties of Ca doped copper ferrite nanoparticles

Calcium doped Copper ferrite (CaxCu1-xFe2O4, x = 0.0, 0.1, 0.2, 0.3) nanoparticles were prepared by co-precipitation method. The effect of calcium doping in structural, elastic and magnetic properties of copper ferrite were explored by X-ray diffraction (XRD), Scanning electron microscope (SEM), Fourier transform infrared (FTIR), and Vibrating Sample magnetometer (VSM). X-ray diffraction verified the single phase cubic spinel structure and hematite phase also present in x = 0.02 with the space group Fd3m. The average crystallite size ranged in 44–58 nm and increased with increasing Ca concentration. Scanning electron microscope images showed that the ferrite particles seem in spherical shape with agglomeration. The Fourier transform infrared spectrum showed the two main absorption bands of spinel structure in the wavenumber scale of 476–576 cm−1 assigned to the stretching vibration of A and B sites. The three types of moduli of elasticity, Poisson's ratio, velocities of elastic waves and Debye temperature estimated using FTIR. Vibrating Sample magnetometer exhibited the room temperature ferromagnetic behavior and coercivity decreases with Ca concentration while saturation magnetization increases.

Enhanced microwave absorption features of Ba3Co2Fe24O41 hexaferrite by high lanthanium doping concentration

AbstractControlling material structure and its electromagnetic properties, including complex permittivity and permeability, could enhance the microwave absorption performance of the material in terms of reflection loss and effective absorption bandwidth. In this study, La‐substituted barium hexaferrite, Ba3−xLaxCo2Fe24O41 (x = 0, 0.1, 0.3, and 0.5) compounds were successfully prepared using the solid‐state reaction method, and their corresponding microstructures, static magnetic properties, and electromagnetic features in 2–18 GHz were investigated. The doping of La content increased saturation magnetization, coercivity, and remnant magnetization. The Ba2.7La0.3Co2Fe24O41 epoxied sample with 3.5 mm thickness possessed an excellent microwave absorption of −47.3 dB at 3.52 GHz, and its corresponding effective absorption bandwidths were 3.75 GHz (2.25–6 GHz) and 0.57 GHz (17.43–18 GHz). It is shown that doping with various La concentrations on Ba3Co2Fe24O41 can be used as an effective technique to tune the performance of microwave absorbers based on barium hexaferrite.

Impact of Cu2+ cations substitution on structural, morphological, optical and magnetic properties of Co1-xCuxFe2O4 nanoparticles synthesized by a facile hydrothermal approach

Spinel ferrites have received extended discussions among different ceramic magnetic nanoparticles due to dependence of its physiochemical properties on the fabrication processes and composition. In this context, copper doped cobalt ferrites (Co1-xCuxFe2O4) with different Cu2+ doping content (i.e., 0.0 ≤ x ≤ 0.4) were successfully fabricated via hydrothermal method. The impact of exchanging divalent cobalt (Co2+) cations by divalent copper (Cu2+) cations on structure-magneto-optic characteristics of Co1-xCuxFe2O4 ceramic magnetic nanoparticles was studied. The spinel single cubic phase of prepared samples with the signature of CuO phase for x ≥ 0.2 was proved by powder X-ray diffraction (XRD) and infrared spectroscopy (IRS) studies. The particle size distribution depending on the Cu2+ doping content was studied by means of XRD and Transmission electron microscopy (TEM) analysis. The particle size is in the range between 11 and 16 nm. The metal-oxygen vibrational modes and the Force constant of spinel structure bonds were investigated using IRS analysis. The optical analysis in the ultraviolet–visible spectrum region by UV–Vis spectroscopy indicates that the optical energy gap of Co1-xCuxFe2O4 nanoparticles range from 1.77 to 2.2 eV. The specific surface area and optical energy gap values of Co1-xCuxFe2O4, demonstrates the possibility of using this compound effectively in water purification processes. The scanning electron microscopy (SEM) and (TEM) analysis confirmed the nano-sized spherical-shaped particle morphology of our investigated nanoparticles. A significant increase in saturation magnetization from 79 to 106 (emu/g) was observed with increase in Cu2+ content from 0.0 to 0.4. Substitution of Co2+ ions in cobalt ferrite lattice structure with Cu2+ ions allow variations in their nanocrystals size, optical energy gap and magnetic characteristics, which has great benefit in using these compounds in many potential applications.

X-ray Photoelectric and magnetic properties of chemically synthesized Cd–Ni Ferrite nanomagnetic particles

Cadmium nickel (Cd–Ni) ferrite samples have been successfully synthesized via chemical co-precipitation technique. The structural analysis revealed the formation of FCC framework and Fe-phase in a trivalent state. The crystallite size is decreased with increasing Cd2+ ion composition whereas the lattice constant is increased. SEM was used to obtain the surface morphology and average grain size of the microstructure. The FTIR shows the formation of metal oxide, hydroxyl and carboxylic groups. EDX revealed the formation of Ni2+, Cd2+, Fe3+, and O2− ions in proper stoichiometric composition. Large optical losses were revealed by Cd2+ poor-NiFe2O4 samples whereas Cd2+ rich-CdxNi1−xFe2O4 samples revealed low optical losses and showed enhanced photoconductivity and photoelectric effect. Result from optical analysis showed that Cd2+ rich-CdxNi1−xFe2O4 nanoparticles can be used as infrared (IR) detector, ultraviolet (UV) filter and in optoelectronics device applications. VSM measurement showed an increase in saturation magnetization and decrease in coercivity as Cd2+ ion content is increased. The remanance magnetization and magnetic anisotropy were also examined. Photoluminescence (PL) spectroscopy examined the nature of the light emission of the samples at the excitation wavelength 380 nm and emission of series of colours such as red, green, yellow, orange and violet light at different wavelengths were found.

Development of quantitative parameter–property relationship and technology parameter choosing software of Fe(Si)–SiO2 soft ferromagnetic composites

Intelligent technology parameter choosing software is the future development trend of realizing precisely control and efficient production. However, the technology parameter choosing software has not been reported probably due to the lack of in-depth understanding of quantitative relationship between technology parameter and magnetic properties for soft ferromagnetic composites. This paper describes a novel strategy to construct quantitative relationship model and develop technology parameter choosing software. Using gas precursor concentration parameter during fluidized bed chemical vapor deposition as an example, the microstructure and performances of Fe(Si)–SiO2 soft ferromagnetic composites obtained were systematically studied. The quantitative relationships between gas precursor concentration and magnetic performances were built based on the gas precursor concentration dependence of SiO2 insulating layer thickness and other classical theoretical models. The findings suggest that the saturation magnetization increase with the gas precursor concentration; however, the impacts of the gas precursor concentration on electrical resistivity and eddy current loss are relatively complex. Informed by these quantitative relationship models, the supporting software has been designed, which can configure the technology parameter automaticity according to the target performance of soft ferromagnetic composites. The results may deepen the understanding on the quantitative relationship and provide ideas for developing efficient production control software.

Studies on structural and magnetic properties of cobalt substituted nickel nano ferrites prepared by microwave assisted self-propagating high temperature route

The Ni1-xCoxFe2O4(x = 0.2, 0.4 and 0.6) ferrite nanoparticles synthesized by novel Microwave assisted self-propagating route. The ferrite sample were studied using as ‘X-ray diffraction (XRD)’, ‘Fourier Transform Infrared Spectroscopy (FTIR)’, ‘Scanning Electron Microscope (SEM)’ and its magnetic properties. The XRD pattern reveals the single phase spinel structure confirmation Nickel ferrites with cobalt composition with crystallite size 30 nm. A decreasing pattern was observed in variation of porosity with Co content from 20.6 to 15.31%. The FTIR study describes, the sintering temperature affects the shift in tetrahedral site to lower frequency and preferences for site occupancy for Co and Fe ions. The SEM image shows average size of nano nanoparticles synthesized at 50 and 90O C about 50 and 60 nm. The increase in saturation magnetization from 29 to 37 emu/gm with increase in Co content due to its quick magnetic interaction. The said composition a may pplication of electronic memory devices, magnetic recording media.

Effect of Substituting Hf for Zr on Fe-Co-M-Nb-B (M = Zr, Hf) Amorphous Alloys with High Saturation Magnetization

The soft magnetic amorphous ribbons of (FexCo1−x)85M9Nb1B5 (M = Zr or Hf, x = 0.4, 0.5, 0.6, 0.7, 0.8, and 0.9) were investigated in this study. Replacing Zr by Hf turned out to increase saturation magnetization and, at the same time, reduce the coercivity, both of which serve together in enhancing the soft magnetic performance of the alloys. Moreover, the optimum ratio of Fe/Co was determined after the survey on different alloys with varying Fe/Co ratio resulting in the maximum saturation magnetization while keeping the coercivity low. After optimization, the highest saturation magnetization of 1.62 T was achieved with coercivity of 11 A/m. While substitution of Hf for Zr slightly reduced the crystallization onset temperature of the amorphous structure, the thermal stability of the soft magnetic amorphous alloys was not significantly affected by the Zr/Hf replacement.

Synthesis, structural and microwave absorption properties of Cr-doped zinc lanthanum nanoferrites Zn1-Cr La0.1Fe1.9O4 (x=0.09, 0.18, 0.27 and 0.36)

Cr-doped zinc-lanthanum nanoferrites Zn 1- x Cr x La 0.1 Fe 1.9 O 4 ( x = 0.09, 0.18, 0.27, and 0.36) were successfully synthesized using sonochemical reactors. Effect of powder production parameters were extensively studied and powder characterization was performed. Existence of cubic spinel structures in the prepared nanoferrites with the average crystallite size ranging from 35 to 51 nm was confirmed by X-ray diffraction studies. An electrochemical impedance analyzer was used to measure the dielectric constant ( ε ′), loss tangent (tan δ), and complex dielectric constant ( ε ") with respect to frequency and composition ratio. Maxwell–Wagner polarization and hopping mechanism were calculated to distinguish the variations in ε ′, tan δ, and ε ". The Nyquist impedance plots for nanoferrites revealed the pseudocapacitance as well as resistive behavior. Vibrating sample magnetometer studies reveled the ferromagnetic behavior of nanoferrites. Substantially increased saturation magnetization and decreased coercivity were noted with respect to increased Cr 2+ ions in the prepared nanoferrites. It was found that the addition of chromium in Zn 1- x Cr x La 0.1 Fe 1.9 O 4 nanoferrites enhances the optical, electrical, and magnetic properties of the nanoferrites.