Fe2O4 Nanoferrite Research Articles

Comparison of optical absorption and diffuse reflectance spectra techniques for determining the optical energy band gap of dried and calcined Ni0.5Mn0.5Fe2O4 nanoferrite

Ultrafine particles of Ni0.5Mn0.5Fe2O4 were synthesized by coprecipitation technique to study the effect of both physical forms (ferrofluid and powder) and thermal treatment (drying at 100 °C and calcination at 600 °C for two hours) on the structural properties of Ni0.5Mn0.5Fe2O4 nanoferrite. In addition, the work presents a comparison between using optical absorption and optical diffuse reflectance spectra in studying the optical direct energy band gap. x-ray diffraction (XRD) and transmission electron microscopy (TEM) were used to study the phase, size, and morphology of dried and calcined Ni0.5Mn0.5Fe2O4 nanoparticles, respectively. Fourier transform infrared (FTIR) spectra revealed the characteristic peaks of the synthesized ferrite and provided further information on the functional groups. The optical absorption spectra were used to evaluate the optical direct energy band gap of dried and calcined Ni0.5Mn0.5Fe2O4 nanoferrite as a ferrofluid, whereas, the optical diffuse reflectance spectra were used to evaluate the optical direct energy band gap of dried and calcined Ni0.5Mn0.5Fe2O4 nanoferrite in powder form.

Synthesis and characterization of PANI-CZF nanocomposites for enhanced electromagnetic interference shielding

The Zn0.5Cu0.5Fe2O4 nano ferrites were prepared by the solution combustion method using aloe vera gel. The polyaniline-Zn0.5Cu0.5Fe2O4 nano ferrite composites were prepared by Ex-situ polymerization method with different weight percentage ratio. The prepared samples were examined by X-Ray diffraction, SEM, EDAX, BET, TEM, VSM and Impedance analyser to investigate their structural, morphological, elemental analysis, average pore size and the porosity, magnetic, and dielectric properties, respectively. The cubic spinel structure was confirmed by X-ray diffraction patterns. Addition of PANI to zinc-copper nano ferrite exhibits shift in crystalline peaks towards larger angle. The existence of spherical and clumped particles was revealed by SEM examination. The retentivity and coercivity are determined and the magnetic moment values were decreases with increase in PANI to the ferrite nanocomposites. The ac conductivity constant at lower frequency and there is a sudden increase and decrease in its value as a function of frequency shows resonance behaviour. The CZF-1 (CZF 30%) composite shows highest ac conductivity and dielectric constant. The electromagnetic shielding interference studies were conducted for S-band frequency. The CZF-1 (CZF 30%) nano composite shows highest shielding effectiveness as compared to other composite in the frequency range 2 to 3 GHz. The experimental result showed that these materials are used for applications in electromagnetic interference shielding.

PH influenced synthesis and characterization of Ni0.3Cu0.3Zn0.4 Fe2O4 nano ferrite for energy storage and high frequency applications

A spinel nanocrystalline Ni0.3Cu0.3Zn0.4 Fe2O4 was prepared using co-precipitation method maintaining pH -7,10 and 12. The pH influenced structural, spectroscopic and magnetic parameters were recorded by X-ray diffraction (XRD), FTIR and VSM. The crystallite size (31.12 nm to 45.32nm), lattice dimension (8.4175 Å to 8.4368 Å), strain (2.525x10-3 to 3.669x10-3), dislocation density (1.024 x10151/m2 to 4.867 x10151/m2) shows considerable structural enhancement due to pH variation. The Fe-O group analysis by FTIR within 400-600 cm-1 corresponds to tetrahedral (587 cm-1 to 591cm-1) and octahedral (442 cm-1 to 444 cm-1) vibration confirms the formation of spinel nanoferrites. The smooth hysteresis M-H loop with coercivity (12.5826 Oe to 11.2212 Oe), magnetic saturation (62.8431 emu/g to 66.2495 emu/g) and retentivity (0.6375 emu/g to 0.6988 emu/g) describes multi domain nature of prepared material. The obtained structural and magnetic parameter clearly indicates energy storage and high frequency application.

A new hybrid non-aqueous approach for the development of Co doped Ni-Zn ferrite nanoparticles for practical applications: Cation distribution, magnetic and antibacterial studies

Ni-Zn spinel nanoferrite with a composition Ni0.6-xZn0.4CoxFe2O4 (x = 0.00, 0.033, 0.066, 0.132, 0.264 and 0.528) was produced at a low reaction temperature using a novel hybrid direct non-aqueous approach that eliminates the need for a complexing agent and a precursor that adjusts pH. The developed Ni0.567Zn0.4Co0.033Fe2O4 (x = 0.033), Ni0.534Zn0.4Co0.066Fe2O4 (x = 0.066) and Ni0.072Zn0.4Co0.528Fe2O4 (x = 0.528) nanoferrites attains the single-phase spinel cubic nano symmetry with a crystallite size of 54.91, 47.55, and 48.98 nm, respectively. Spherical shaped nanoparticles with aggregated behaviour were confirmed for the produced nanoferrites. XPS spectra of Ni0.072Zn0.4Co0.528Fe2O4 nanoferrite confirms the detection of major photoemission peaks of Zn2p, Ni2p, Co2p, Fe2p, O1s, and C1s. According to the BET research investigation, Ni0.072Zn0.4Co0.528Fe2O4 nanoferrite having specific surface area of 2.309 m2/g. The highest saturation magnetization and coercivity of 37.09 emu/g and 108.85 Oe was attained at higher doping content of cobalt (x = 0.528). With this nano crystalline nature and excellent magnetic factors, the developed nanoferrites are highly beneficial for the recording media applications to get the suitable signal to noise ratio and also, for multi-layer chip inductors (MLCIs). From the antibacterial investigation, it was observed that the produced Co doped Ni-Zn ferrites (x = 0.033, 0.264) shows high zone of inhibition (ZOI) for E. coli and Bacillus subtilis but the rest of the samples (x = 0.0, 0.066, 0.132, 0.528) shows no ZOI for both the bacterial strains. Therefore, the prepared Co doped Ni-Zn nanoferrites also works as superior antibacterial agent for biological application.

Effect of sintering temperature on the structural, morphological, and the magnetic properties of Ni0.25Cu0.55 Zn0.20 Fe2O4 nano ferrite

Ni0.25Cu0.55Zn0.20Fe2O4 nano ferrite was synthesized using sonochemical method. The as-synthesized nano ferrite was sintered at different (200 °C, 400 °C, 600 °C, and 800 °C) sintering temperature and characterized using various characterization techniques. Identification of the phase was studied using X-ray diffraction. Rietveld refinement confirmed a single-phase cubic spinel structure with Fd3m space group. Average crystallite size and micro strain were estimated using Williamson-Hall plot. FTIR reveals that with the increase in the sintering temperature there is shift in the tetrahedral and octahedral band position. FESEM and TEM images revealed the nanocrystals exhibit irregular shapes which transformed into cubic and hexagonal morphology with the increase in the sintering temperature. The EDAX was employed to confirm the elemental composition of the synthesized Ni0.25Cu0.55 Zn0.20Fe2O4 nano ferrite. The optical behaviour of Ni0.25Cu0.55 Zn0.20Fe2O4 nano ferrite sintered at different temperature was characterized by UV-Diffuse reflectance studies (UV-DRS). Formation of spinel ferrite and distribution of cations at different sintering temperature in Ni0.25Cu0.55 Zn0.20Fe2O4 nano ferrite were determined using Raman spectroscopy. Saturation magnetization (Ms), remanence (Mr), coercivity (Hc), squareness ratio (Mr/Ms), magnetic moment (nB), and anisotropy constant (K) increases with the increase in temperature (200 °C, 400 °C and 600 °C) except 800 °C. Zero field cooling (ZFC), field cooling (FC), and blocking temperature (Tb) were also measured. The blocking temperature (Tb) indicate that the Ni0.25Cu0.55 Zn0.20Fe2O4 nano ferrite exhibit superparamagnetic behaviour, making them suitable for biomedical applications.

Efficient lead removal from aquatic solution by (Co0.7Zn0.3)0.9Ni0.1Fe2O4 ferrite with tunable optical and magnetic properties.

A new material based on (Co0.7Zn0.3)0.9Ni0.1Fe2O4 ferrite was prepared by using a flash auto-combustion method. The characterization of XRD, SEM, EDX, FTIR, and VSM analysis presented that the (Co0.7Zn0.3)0.9Ni0.1Fe2O4 nanoferrite was prepared in single phase with crystallite size 32 nm and had dislocation density about 9.8 × 10−4 nm−2. EDS spectrum confirms the presence of constituting metal ions in (Co0.7Zn0.3)0.9Ni0.1Fe2O4 ferrite which is well-comparable with the standard stoichiometric ratios. VSM exhibits narrow loop with saturation magnetization about 67.076 emu/g, this is related to ferromagnetic and soft magnetic materials. Values of the energy band gap are 3.8 and 4.8 eV for the indirect and direct transition. The removal efficiency of the (Co0.7Zn0.3)0.9Ni0.1Fe2O4 nanoferrite was evaluated using adsorbing Pb(II) as typical heavy metals. Batch adsorption experiment was used to study the effects of pH of the aqueous solution, as well as contact time. Moreover, we examined the adsorption mechanism, isotherms, and kinetics. The removal efficiency of the (Co0.7Zn0.3)0.9Ni0.1Fe2O4 nanoferrite for Pb(II) adsorption was 99 % at pH 7 after 40 min, besides the isothermal data followed Langmuir isotherm model. While, kinetic data obeyed pseudo-second-order model. The (Co0.7Zn0.3)0.9Ni0.1Fe2O4 nanoferrite and heavy metal ions interacted by the following mechanisms: surface complexation, precipitation, and isomorphic substitution.

Coexistence of superparamagnetism and superspin glass in non-stoichiometric Zn0.5Ca0.5Fe2O4 nanoferrite

In this manuscript, we report the coexistence of superparamagnetic-super spin glass phase in aggregated non-stoichiometric Zn0.5Ca0.5Fe2O4 ferrite nanoparticles (ZCF NPs). A polycrystalline sample of ZCF NPs was synthesized by the self-ignition sol–gel route and characterized using a variety of techniques. Extensive temperature, field and wait-time dependent dc-magnetization & ac-susceptibility measurements were performed for elucidating the magnetism of ZCF NPs. M−H & Mössbauer data at 300 K and M−T curves in ZFC & FC protocols revealed that ZCF NPs exhibit dominant superparamagnetic (SPM) character at 300 K with Ms = 16 emu/g & TB ∼ 120 K. Magnetically disordered surface over a single domain core of ZCF NPs has been established by the shift in coercivity at 5 K in ZFC and FC protocols. ZFC magnetization for a single stop and wait protocol exhibited an ageing dip at the stop temperature (72 K) with waiting time. It is shown that the in-phase peak of ac-susceptibility vs. temperature curves shifts towards higher temperature with driving frequencies and obeys dynamic scaling & Vogel-Fulcher law. These findings affirmed presence of glassy states in ZCF NPs due to interacting magnetic nanoparticles. On cooling the random ensemble of ZCF NPs, interparticle dipolar interactions lead to genesis of glassy behaviour, which is identified as superspin glass (SSG). Observation of memory and rejuvenation in a quasi-equilibrium magnetic state due to the collective nature of low-temperature spin dynamics differ ZCF NPs from canonical spin-glass. Extensive magnetic studies on ZCF NPs revealed a crossover of SPM to SSG phase just below TB at 115 K due to the random distribution of magnetic momenta, anisotropy and interparticle interactions.

Formation Mechanism and Lattice Parameter Investigation for Copper-Substituted Cobalt Ferrites from Zingiber officinale and Elettaria cardamom Seed Extracts Using Biogenic Route.

Biogenic routes for the synthesis of nanoparticles are environmentally friendly, nontoxic, biocompatible, and cost-effective compared to traditional synthesis methods. In this study, cobalt ferrite was synthesized using Zingiber officinale and Elettaria cardamom Seed extracts. Effect of copper contents (x = 0.0, 0.3, 0.6 and 0.9) on the plant extracted was investigated by XRD, SEM, EDX, UV-Vis., PL, FE-SEM, FTIR and photocatalytic activity. XRD results revealed that nanoparticles exhibit a cubical spinel structure with an average diameter of 7–45 nm, calculated by the Debye Scherer formula. The value of the lattice parameter decreased from 8.36 Å to 8.08 Å with substitution of copper, which can be attributed to mismatch of ionic radii of Cu2+ (0.73 Å) and Co2+ (0.74 Å) ions. SEM analysis showed that nanoparticles exhibit a spherical shape (~13 nm diameter) for undoped samples and low Cu concentration, while they changed to a hexagonal structure at higher Cu concentration (x = 0.9) with a diameter ~46 nm and a decreased degree of agglomeration. FE-SEM further confirmed the nanoparticles’ size and shape. EDX analysis confirmed the presence of cobalt, iron, and oxygen without contamination. The optical absorption spectra of UV-vis and PL showed red-shift, which can be accredited to larger crystalline sizes of nanoparticles. FTIR spectra showed two main bands at 410 and 605 cm−1, indicating the presence of intrinsic vibrations of the octahedral and tetrahedral complexes, respectively. The photocatalytic activity of Co0.4Cu0.6 Fe2O4 nanoparticles was investigated using methylene blue (MB) and methyl orange (MO) dyes under visible light irradiation. The degradation rate (93.39% and 83.15%), regression correlation coefficient (0.9868 and 0.9737) and rate constant (0.04286 and 0.03203 rate·min−1) were calculated for MB and MO, respectively. Mechanisms for the formation and photocatalytic activity of Cu-substituted plant-extracted cobalt ferrite were discussed. The Co0.4Cu0.6 Fe2O4 nanoferrite was found to be an efficient photocatalyst, and can be exploited for wastewater treatment applications for MB/MO elimination.

Exploring the structural, elastic, optical, dielectric and magnetic characteristics of Ca2+ incorporated superparamagnetic Zn0.5−xCa0.1Co0.4+xFe2O4 (x = 0.0, 0.05 & 0.1) nanoferrites

This work is aimed to understand influence of 10% Ca doping on the structural, optical, dielectric and magnetic behavior of half doped Zinc-Cobalt nanoferrites. Zn0.5−xCa0.1Co0.4+xFe2O4 (x = 0.0, 0.05 & 0.1) nanoferrites with crystallite size in 10–13 nm range were synthesized through a sol-gel auto-incinerated route. Rietveld profile refinement of PXRD patterns, observation of spinel ferrite type fcc Laue rings in SAED patterns, Raman modes (A1g,T2g & Eg) and metal-oxide (υ1 & υ2) bonds in 400–600 cm−1 IR range illustrated formation of single phase mixed valent spinel type fcc nanoferrites. In these nanoferrites Zn2+ ion resides at tetrahedral (TA) site, while Co2+ & Ca2+ ions preferentially fill the octahedral OB site and Fe3+ ion occupy both TA & OB sites. Moderate optical absorbance in blue color region and strong absorbance in the lower UV region is observed in these nanoferrites, which is owing to presence of mixed valent ions at the OB and TA sites respectively. 10% Ca doping in these half doped Zn-Co nanoferrites led to considerable decrement in the band gap energy (Eg) and turning them to semiconducting state (Eg in 2.5–2.3 eV range). In these nanoferrites hopping of electrons between divalent Fe2+, Ca2+, Zn2+, Co2+ & trivalent Fe3+ & Co3+ cations led to systematic decrease in the dielectric parameters with frequency. These nanoferrites exhibited superparamagnetism with a high magnetic moment (~ 2.9–3.0μB/f.u.) at room temperature. Systematic enhancements in saturation magnetization (Ms), coercivity (Hc), remanence (Mr) and squareness ratio at low temperatures revealed changing of superparamagnetic character to soft ferrimagnetic state of these nanoferrites. At 20K, highest value of Ms = 119 emu/g was observed for Zn0.5Ca0.1Co0.4Fe2O4 nanoferrite, while highest Hc = 2911 Oe & Mr = 61.0 emu/g were recorded for Zn0.4Ca0.1Co0.5Fe2O4 nanoferrite. Thus, a moderate 10% Ca2+ ion incorporation in Zn0.5−xCa0.1Co0.4+xFe2O4 (x = 0.0, 0.05 & 0.1) nanoferrites is emerged as an effective route for obtaining superparamagnetic nanoferrites with high magnetic moment and reduced band gap energy. Unique magneto-optical characteristics of Zn0.5−xCa0.1Co0.4+xFe2O4 (x = 0.0, 0.05 & 0.1) nanoferrites would project them as a good material for opto-magnetic, drug carrier, biomedical contrast agent and magnetic storage applications.

Irreversible magnetic behavior with temperature variation of Ni0.5Co0.5Fe2O4 nanoparticles

In this paper, the irreversible magnetic behavior of Ni0.5Co0.5Fe2O4 nano-ferrite has been discussed with varying the temperature. The nano-ferrite discussed in present work synthesized using sol gel technique. The formation of the phase of Ni0.5Co0.5Fe2O4 was confirmed using X-ray diffraction (XRD), and their Rietveld refinement shows it crystallized into cubic structure with lattice constant 8.3541 Å under space groupFd3-m. The homogeneity and the morphology of the sample was analysed using FESEM along with EDAX measurement. The irreversibility of Ni0.5Co0.5Fe2O4 was studied in three modes ZFCW, FCC and FCW using field dependent magnetic measurements in temperature range of 2 K–300 K under the presence of 50 Oe. However, the magnetic hysteresis of sample was studied at different temperature T = 5 K, 50 K, 100 K, 120 K, 200 K, 300 K from varying the field upto ±5 Tesla. Further, the asymmetry observed in the magnetization and demagnetization curve gives the value of Hm, which increased with lowering the temperature due to magnetic crystalline phase as well as the micro-strain of the sample. Finally, retentivity, coercivity and saturation magnetization of the present sample makes it a potential candidate for magnetic memory devices, magnetic resonance imaging, medical diagnosis applications.

Structural, cation distribution, optical and magnetic properties of quaternary Co0.4+xZn0.6-xFe2O4 (x = 0.0, 0.1 and 0.2) and Li doped quinary Co0.4+xZn0.5-xLi0.1Fe2O4 (x = 0.0, 0.05 and 0.1) nanoferrites

This study explore the influence of 10% Li doping on the crystallography, cation distribution, morphology, optical and magnetic properties of middle range Cobalt–Zinc nanoferrites. Single-phase intrinsic quaternary Co0.4+xZn0.6-xFe2O4 (x = 0.0, 0.1 and 0.2) and 10% Li doped quinary Co0.4+xZn0.5-xLi0.1Fe2O4 (x = 0.0, 0.05 and 0.1) nanoferrites with average crystallite size in the 13–34 nm range were synthesized through sol-gel auto-combustion method. Rietveld profile refinement of the PXRD patterns, presence of fcc rings in the SAED patterns and observation of active Raman modes illustrated single phase formation of mixed spinel nanoferrites in the fcc structure without impurity. In these nanoferrites Zn2+ ions preferentially occupy the tetrahedral site and Co2+ & Li1+ ions occupy the octahedral site with total preference. Both intrinsic quaternary and Li doped quinary nanoferrites significantly absorbs optical light in the UV band. The band gap energy decreases with decreasing Zn concentration and Li doping in these nanoferrite leads to blue shift of more than 1eV in the band gap energy. Co0.4+xZn0.6-xFe2O4 (x = 0.1 and 0.2) and Co0.4+xZn0.5-xLi0.1Fe2O4 (x = 0.0, 0.05 and 0.1) nanoferrites exhibited S-shape ferrimagnetic hysteresis loops at 300 K, 200 K, 100 K & 20 K. The Co0.4Zn0.6Fe2O4 nanoferrite display superparamagnetism at 300 K with a blocking temperature at 183 K. Systematic enhancement in the saturation magnetization (Ms), coercivity (Hc), remanence (Mr) and squareness ratio with lowering the temperature in these nanoferrites revealed conversion of soft-ferrimagnetic to hard-ferrimagnetic character. 10% Li doping in these nanoferrites resulted in significant enhancements of the Hc, Mr and TB. Monotonic increase in the Ms, Hc, Mr and TB has also been observed with the decreasing Zn concentration in these nanoferrites. Rich magneto-optical properties of quinary Co0.4+xZn0.5-xLi0.1Fe2O4 (x = 0.0, 0.05 and 0.1) nanoferrites can find applications in the design and fabrication of magneto-optic and permanent magnet based devices.

Amelioration of ceramic properties via different preparation techniques

In the present study, Co0.7Ca0.3Fe2O4 nanoferrite was prepared by citrate auto-combustion and conventional ceramic methods. When synthesized via different methods, material properties would change even with the same starting compositions. X-ray diffraction, scanning electron microscope (SEM), and magnetic and mechanical properties of the investigated samples have been compared. A critical comparison between the preparation methods is demanded to choose the most suitable preparation conditions, material properties, raw materials and fabricating processes. The obtained data indicate that the citrate method gives the lowest value for the particle size (16 nm), while appropriate mechanical properties were obtained with the ceramic method. The magnetic hysteresis measurements at different temperatures (100 and 300 K) were achieved using a vibrating sample magnetometer. Magnetic constants such as squareness ratio, saturation magnetization and coercivity were calculated and reported. The mechanical measurements confirm that the samples prepared by the standard ceramic method have good bending strength, bending modulus and hardness. Therefore, these samples are suitable candidates for most commercial applications.

Biodiesel from Fatty Acids Found in Brazilian Native Cultures as Soybean and Cotton Using the Nanocatalyst Ni<sub>0.5</sub>Zn<sub>0.5</sub>Fe<sub>2</sub>O<sub>4</sub>

Biodiesel is a biodegradable fuel derived from renewable biomass, such as soybean and cottonseed oil, which may be obtained by different processes and requires a material to catalyze the obtaining reactions. The irons spinel comes overlapping as excellent materials to catalyze the biodiesel production reactions. Thus, the purpose of this work was the use of Ni0.5Zn0.5Fe2O4 nanoferrite as a catalyst in esterification reactions. The nanoferrite was synthesized by combustion in large scale, 200g/batch, where time and the temperature of the reactions were measured, and characterized by XRD and measuring its surface area. The biodiesel was obtained from methyl and ethyl esterification of acidified soybean oil and cottonseed, at a temperature of 160°C for 1 hour, molar ratio 1:15, 3% of catalyst and analyzed by chromatography. The nanoferrite has shown peaks of greater intensity corresponding to a majority crystal phase of the spinel and a surface area of ​​64.17m2/g. The conversion results for the soybean oil were 99.08% in methyl route and 98.38% in ethyl route. For cottonseed oil were 88.79% in methyl route and 78.65% in ethyl route.

On the role of cationic distribution in determining magnetic properties of Zn0.7-xNixMg0.2Cu0.1Fe2O4 nano ferrite

We report Ni addition induced changes in cationic distribution and its role in determining magnetic properties of Zn0.7-xNixMg0.2Cu0.1Fe2O4 (x=0.0–0.7) nano ferrite synthesized by sol-gel auto-combustion method. X-ray diffraction demonstrates presence of cubic spinel phase, with crystallite size between 32.1–43.0nm. Scanning electron microscope (SEM) images reveal modification of pore sizes. Saturation magnetization (Ms): 43.2–69.9Am2/kg and Néel magnetic moment (nBN):1.74–2.86μB increases up to x=0.42, but at higher values of Ni content (0.42<x≤0.70) Ms and nBN decreases, accredited to migration of Fe3+ ions from A to B site or vice versa. With increasing Ni content, coercivity increases and range between 16.3–131.1Oe. Zero values of Yafet-Kittel angle (αY-K) suggest presence of Néel-type magnetic ordering in Zn0.7-xNixMg0.2Cu0.1Fe2O4. Similar variation of bond angles (θB−B3, θB−B4), Ms, nBN with Ni establishes the role of cationic distribution in determining magnetic properties.

On the study of Structural properties and Cation distribution of Zn0.75-xNixMg0.15Cu0.1Fe2O4 nano ferrite: Effect of Ni addition

Effect of Ni addition on structural properties and, cation distribution of Zn0.75-xNixMg0.15Cu0.1Fe2O4 (x = 0.0, 0.15, 0.30, 0.60, 0.75) ferrites, prepared using sol-gel autocombustion method was studied using X-ray diffraction (XRD) technique. XRD analysis reveals the formation of spinel phase even in dry gel form. The lattice constant (aexp.) decreases with Ni2+ substitution and follows Vegard's law. Scherrer's grain diameter (D) lies within the range of 17.33 - 26.47 nm. Due to difference in the ionic radii of Zn2+ and Ni2+ significant changes are observed in the structural parameters - unit cell volume (V), hopping length at A (La) and B (Lb) site, and x-ray density (ρXRD). Linear increase in Neel magnetic moment (nBN) with oxygen positional parameter is observed in the studied samples, attributed to simultaneous weakening of A-B interaction and strengthening of the B-B interaction.

Study of Various Site Interactions Using Maximum Entropy Method on Mechanically Alloyed Ni0.5Zn0.5Fe2 O 4 Nanoferrite Particles Sintered from 1100 to 1400 ∘C

In this article, numerical values of the bond strength between tetrahedral-tetrahedral, octahedral-octahedral, and tetrahedral-octahedral site interactions in ferrites are evaluated by using maximum entropy method (MEM) and compared with that of existing theoretical predictions for the Ni0.5Zn0.5Fe2 O 4 nanoferrite particles prepared by mechanical alloying via high-energy ball milling and sintered at different temperatures from 1100 to 1400 ∘C. Interestingly, octahedral-octahedral site interactions are found to have the weakest interaction in all the samples. The structural parameters of the prepared sample have been studied by employing the Rietveld refinement method, using JANA 2006 software. The magnetic properties and the optical band gap energy of the samples are determined using vibrating sample magnetometer and UV-VIS technique respectively.

Structural phase transformation of as-prepared Mg–Mn nanoferrites by annealing temperature

As-prepared Mg0.2Mn0.8Fe2O4 nanoferrite samples by coprecipitation method were annealed at different temperatures T. XRD, TEM, IR, VSM and Mössbauer techniques were used to characterize the samples. This study proved the transformation of the sample structure from cubic spinel to Z-type hexagonal phase at 700°C. This transformation was assigned to Jahn–Teller effect of the Mn3+ and Fe2+ ions and/or atomic disorder in the crystal lattice. All the deduced structural parameters were affected by the transformation process. The infrared and structural parameters showed dependence on T, whereas tetrahedral band position did not. TEM images showed agglomeration of the nanoparticles, where the average particle size ranged 25–55nm and was a little higher than R. Study on the elastic properties proved the weakening of inter-atomic bonds inside the crystal lattice as T increases. The magnetic properties were affected by the transformation process and showed T dependence, whereas Ms and Hc proved dependence on porosity. Hyperfine interaction parameters, area ratio (B/A) and spontaneous magnetization were discussed as functions of T.

Statement of retraction — Magnetic behavior of functionally modified spinel Ni0.4Ca0.6Fe2O4 nanoferrite

Statement of retraction — Magnetic behavior of functionally modified spinel <font>Ni</font>_0.4<font>Ca</font>_0.6<font>Fe</font>₂<font>O</font>₄ nanoferrite

Electric and dielectric study of cobalt substituted MgMn nanoferrites synthesized by solution combustion technique

Abstract Cobalt substituted Mg–Mn nanoferrites with formulae Mg0.9Mn0.1CoxFe2−xO4, x=0.0, 0.1, 0.2 and 0.3, have been synthesized for the first time by the solution combustion technique. The effects of Co2+ ions on the dc resistivity, dielectric constant and dielectric loss tangent of Mg–Mn nanoferrites at room temperature are presented in this paper. X-ray diffraction confirmed the formation of a single phase spinel structure. Particle size was found to increase, 20.9–23.9 nm, with increasing Co2+ concentration. The dc resistivity was increased by two order of magnitude with substitution of Co2+ ions while the dielectric constant was found to be decreasing with the increasing concentration of cobalt ions. The value of dc resistivity obtained for Mg0.9Mn0.1Fe2O4 nanoferrite in our work is greater than the value obtained for the same composition prepared by the conventional ceramic technique. Further, the dielectric constant and dielectric loss tangent were observed to be decreasing with the increase in frequency.

Structural and Magnetic Studies of Co0.6Zn0.4Fe2O4 Nanoferrite Synthesized by Solution Combustion Method

Co0.6Zn0.4Fe2O4 nanomagnetic system is prepared by solution combustion method. The powder sample is characterized by X-ray diffraction (XRD), transmission electron microscope analysis (TEM), Fourier transform infrared spectroscopy (FTIR), Mössbauer spectroscopy, and superconducting quantum interference device (SQUID; at low and room temperatures). The average crystallite sizes of the prepared samples obtained from XRD is 22 nm, which is well confirmed by the size obtained from TEM. The magnetic study shows that sample is ferromagnetic at room temperature. This result is also supported by Mössbauer spectrum obtained at room temperature.