Sr Hexaferrites Research Articles

Flash combustion prepared Sm and Co doped Sr hexaferrite for environmental applications

Nanotechnology is offering solutions to water contamination issues, as new techniques are needed to improve the removal of harmful compounds from water bodies. Despite previous reviews on this topic, nanotechnology is paving the way for more effective water treatment methods. Understanding the substitute influence of divalent Co2+ and rare earth elements Sm3+ on the structure, magnetic, and removal efficiency of hexagonal ferrites requires an understanding of a sequence of SrFe12O19, SrFe11.5Co0.5O19, Sr0.95Sm0.05Fe12O19, and Sr0.95Sm0.05Fe11.5Co0.5O19 M-type hexagonal ferrites were prepared using the flash technique. The XRD examination revealed that the crystallized material formed a single M-type hexagonal phase. The characteristics of M-type hexagonal ferrites include absorption bands with low wavenumbers in the FTIR curves between 400 to 1000 cm−1. There was a variation in magnetic characteristics with the replacement of Sm3+ and Co2+ doping, possibly due to the spin canting impact created by rare earth Sm3+ and Co2+ ions. The goal of the research is to explore the potential of doping magnetic hexaferrites and its influence in wastewater treatment. Various parameters, such as pH and contact duration, that influence the adsorption of lead ions from aqueous solutions were also examined. At pH 7 and 25 °C after 70min, the maximal removal efficiency of the Sr0.95Sm0.05Fe11.5Co0.5O19 was found to be 99%. Magnetic separation was carried out by applying an external magnetic field using a permanent magnet. The strong magnetization of the ferrites (51–58 emu/g) enabled the rapid separation of the magnetic particles from the solution, with over 95% of the ferrite particles being recovered within 10 to 70 min. The Freundlich isotherm model fitted all the isotherm data. Adsorption kinetics were explained by the pseudo-first-order, pseudo-second order, and intraparticle diffusion models. The investigated samples’ adsorption capacity remained efficient till 5 cycles.

Photocatalytic degradation of the remazol red ultra RGB dye using SrFe12O19-Fe3O4 magnetic oxides dispersed in silica: Effect of reduction temperature

Dyes are the most frequently discarded industrial wastes in aquatic ecosystems, among which Remazol Red ultra RGB stands out. In this context, magnetic iron-based catalyst dispersed in silica were prepared by Pechini route as an alternative for the photodegradation of Remazol Red Ultra RGB. The XRD and Mössbauer spectroscopy results indicated the formation of a magnetic material that, after reduction treatment with H2, forms a magnetite phase combined with Sr hexaferrite dispersed in amorphous silica. The TPR-H2 profiles indicated the reduction of Fe3+ to Fe2+ within the considered temperature range, the amount of Fe2+ increased with rising temperature. The SEM images showed sponge-like morphology for the samples. The EDS spectra and mapping confirmed a high uniformity in the distribution of active iron species in the silica. The magnetic measurements showed a lower magnetic signal for the sample reduced at 600 °C, due to the lower magnetic moment of Fe2+ formed after the reduction. The diffuse reflectance spectra showed a main absorption region between 500 and 200 nm and the estimated band-gap values were of 1.4 and 1.9 eV for the reduced sample and the fresh oxide, respectively. The surface charge was obtained via zeta potential, demonstrating good stability under pH changes and reaching a negative potential in the pH range from 2 to 6. The photocatalytic tests showed that the samples with higher content of Fe2+ demonstrated a greater photocatalytic degradation of the Remazol Red Ultra RGB dye, reaching 100 % degradation in 1 h for the solid reduced at 600 °C. A plausible mechanism for the photodegradation of Remazol Red Ultra RGB was proposed, considering the different elementary steps involving the participation of iron sites and the formation of oxidant radicals.

Dopant site occupancies and iron valence states in SrZnxFe18−xO27 W-type hexaferrites using site-selective X-ray/electron spectroscopy

Zn-doped W-type Sr hexaferrite (SrZnxFe18−xO27; SrZnx-WHF) is an anticipated rare-earth-free hard magnetic material with strong magnetocrystalline anisotropy and saturation magnetization. To examine the origin of its high magnetic performance, the site distribution of Zn over seven crystallographically inequivalent Fe sites and the site-dependent valence states of Fe were investigated using site-selective elemental/chemical analysis techniques. The dominant occupation of Zn2+ at the 4etet(S) and 4ftet(S) tetrahedral sites was determined quantitatively using high-angular-resolution electron-channeling X-ray spectroscopy and statistical data analysis. The combined application of high-angular-resolution electron channeling electron spectroscopy and atomic-column resolution scanning transmission electron microscopy–electron energy-loss spectroscopy helped unambiguously clarify that most of the Fe2+ ions existed at the 6goct(S-S) octahedral site. Density functional theory calculations have shown that Zn doping leads to a redistribution of the charges toward Fe ions at this site. This redistribution preserves the local charge balance and amplifies the total number of parallel spins. Hence, the enhanced magnetocrystalline anisotropy and saturation magnetization in SrZnx-WHF can be inferred to originate from the charge redistribution at the 6goct(S-S) site, which is influenced by the presence of nonmagnetic Zn.

Samarium substituted M-type Sr hexaferrites: The structural, magnetic and electrochemical properties for supercapacitor applications

In the current project the samarium substituted strontium hexaferrites with general formula SrSmxFe12-xO19 (where x = 0, 0.1, 0.2, 0.3, 0.4, and 0.5) nanocrystalline powder have been successfully synthesized employing sol-gel auto-combustion route. The fabricated samples have been sintered at 1200 °C for 2 h. The structural, functional group, morphological, elemental, optical, magnetic, dielectric and electrochemical properties have been studied by X-Ray diffractometer, Fourier transformer infrared spectroscopy, scanning electron microscopy, Energy dispersive X-Ray, UV–visible, vibrating sample magnetometer, Inductor capacitor and resistor meter and cyclic voltammetry, galvanostatic charging discharging respectively. The structural analysis confirms the formation of the single-phase Magnetoplumbite structure of all the samples. The crystallite size decreases with increasing Sm+3 ions concentration. The characteristic bands of hexagonal structure present in the range of 400–660 cm−1 which correspond to metal–oxygen (M − O) stretching and vibrational bonds. The bandgap increases from 4.21 to 4.86 eV. The magnetic properties reveal the clear ferromagnetic M − H curve in which the value of coercivity increases and saturation magnetization decreases. The dielectric constant and tangential loss of the material both decrease with increasing frequency. Conversely, the ac conductivity of the material increases with increasing applied frequency. This is the natural behavior of ferrites. This behavior can be attributed to the polarization and orientation of the dipoles within the material in response to the applied electric field. The observed increase in σ at higher frequencies suggests that the material may be useful in applications where high-frequency electrical properties are desired such as in the development of high-speed electronic devices. The specific capacitance increases monotonically up to 1020 F g −1 with increasing Sm+3 concentration. The samarium substituted hexaferrites are recommended to fabricate the high energy density charge storage devices such as supercapacitors.

Tunable electrical and impedance characteristics of Co–Zn doped M-type Sr Hexaferrites: Role of grain, grain boundaries, electrical transport mechanisms and software/circuit modeling

M-type hexaferrites SrCoxZnxFe12-2xO19 (x = 0.0, 0.2, 0.4, 0.6, 0.8, and 1.0) have been synthesized using the sol-gel method. The structural, dielectric, and electrical properties of Zn2+ and Co2+ substituted strontium ferrite have been carried out. The dielectric and electric properties of prepared hexaferrites have been examined over the frequency range of 100 Hz to 2 MHz. The formation of the hexagonal phase has been confirmed by the X-ray diffraction (XRD) analysis. The substitution of Co2+ and Zn2+ causes a reduction in crystallite size from 39.50 to 26.42 nm being the smallest in the case of x = 1.0. Scanning electron microscopy (SEM) indicates the formation of honeycomb-like grain structures in composition x = 1.0. The dielectric spectrum shows that the dielectric constant and loss tangent vary non-monotonically with the doping of Co–Zn content. A non-Debye type relaxation is shown by the electric modulus of the prepared compositions. There is a reduction in relaxation time with the increase in doping of Co–Zn. The impedance spectra indicate the effects of both grain and grain boundaries on the electrical properties. The impedance analysis has been presented with the modeling of electrical processes in the samples using an equivalent circuit model comprising of parallel RC circuit for grains and grain boundaries. The obtained simulated results are in agreement with the measured results.

The influences of additives in M−type (Ba and Sr) hexaferrites’ microstructure, sintering and magnetic properties: A review

Interest in the utilization of M−type hexaferrites in magnetic applications as a substitution for rare earth minerals is rapidly growing due to the low cost and compatible magnetic properties of such materials. However, low magnetic properties and high sintering temperatures are the primary drawbacks that limit the use of SrM and BaM in various applications. Therefore, it is essential to carry out processes aimed at reducing the sintering temperature and enhancing magnetic properties beyond the threshold of 0.125 kOe coercivity, 0.5 mr/ms, and achieving higher remanence values to make them suitable for hard magnetic applications. These improvements can be achieved through synthesis techniques involving substitution and/or additives. Notably, numerous studies have been conducted on different synthesis methods and substitution techniques, and they have reached their limits. Therefore, there is a current need for comprehensive reviews and studies on the effects of additives and sintering aids. In this paper, we review investigations and studies that focus on the impact of additives, namely silica, CaO, CaCO3, Bi2O3, B2O3, CuO, and Al2O3, on the microstructure, sintering temperature, and magnetic properties of SrM and BaM hexaferrites.

Effect of La3+/Cu2+ and La3/Ni2+ substitution on the synthesis, magnetic and dielectric properties of M−type Sr1-xLaxFe12-xMxO19 (M = Cu and Ni) hexaferrite

Here, we report a comprehensive study to explore the synthesis and comparative analysis of co-substituted M−type La3+/Cu2+ and La3+/Ni2+ hexaferrite (Sr1-xLaxFe12-xMxO19 where M = Cu and Ni; (x = 0.0, 0.05, 0.1, 0.15, and 0.2)) prepared through the sol–gel auto-combustion approach. X-ray diffraction (XRD) analysis shows both systems' single-phase structure of Sr hexaferrite. The structural parameters decreased as the number of substituted ions increasedas the crystal lattice contracts due to the smaller ionic radii being doped. Theaverage crystallite sizes were found using the Scherrer equation using the highest intensity peaks, and the results show nano-sized particles. The morphological structure of Sr-hexaferrite was studied using Field Effect Scanning Microscopy (FESEM). As a result, irregularly shaped particles with slight agglomeration are observed on the topography in both systems. Two absorption bands were observed in all synthesised samples' Fourier-transformed infrared spectroscopy (FTIR) spectra, supporting the ferrite's formation. These materials are a good option for high-density recording media. Both samples show high magnetic natures, which can be observed from the hysteresis loop. Overall, the room temperature magnetic parameters measured slightly increase as the dopant materials increase. The squareness ratio of the synthesizedsamples shows the uniaxial anisotropy with single magnetic domain particles. The Maxwell-Wagner and Koop model clarifies the reason the dielectric characteristics exhibit the typical behavior of ferrites.

Nano structural engineering of Ba-substituted Sr-hexaferrites for viable microwave absorbance and magnetic data storage

This work focuses on optimization of magnetic attributes of Sr hexaferrites using Ba as a substituent at Sr-site, for viable utilization in magnetic data storage devices and as microwave attenuation media. In this context, a series of Sr1-xBaxFe12O19 samples was prepared using a facile hydrothermal route. X-ray diffraction confirmed the hexagonal structure with space group P63/mmc. The morphological analysis revealed that the samples had hexagonal nanorod-like morphology which was quite suitable for microwave-absorbing devices and data storage. The analysis demonstrated that the particle sizes were decreased while the width of particles increased with increasing Ba contents. The dielectric parameters were suitably tuned as a function of frequency and Ba contents. The saturation magnetization, coercivity, remanent magnetization, and squareness ratio of all the sample compositions showed an increasing behavior with Ba contents, revealing that the prepared samples were favorable for use as microwave absorbers, data storage devices, and magnetic recording media.

Encapsulation of Ba–Sr hexaferrite nanoparticlesand MWCNTs in conductive polymer matrix for improved dielectric spectroscopy, electromagnetic shielding and microwave absorption applications

Ba–Sr hexaferrite nanoparticles were produced using Sol-Gel auto combustion, whereas carrier fluid ultrasonication dispersion and in-situ polymerization were used to synthesize their composites with MWCNTs and conductive polymers. Structural investigations were accomplished using X-rays diffraction, secondary electron microscopy, Infrared and Raman Spectroscopy. The low frequency dielectric measurements revealed increased dielectric losses (304 at 100 Hz for pure nanoparticles, which increases up to 2721 and 7861 for ternary composites within polyaniline and Polythiophene matrix), indicating good energy dissipation behavior. The diminishing magnetism resulted from the weakening of exchange coupling or domain wall pinning at the interface of Ferrite-MWCNTs and Ferrite-Polymer, causing the shifting of magnetic resonance peak towards lower frequency in the shielding effectiveness (Absorption) plots. Increasing DC conductivity adds to the nominal increase of Shielding effectiveness (Reflection) values owing to the rise in charge carrier conduction. The maximum total shielding effectiveness, perceived for the composition of Ba0.5Sr0.5Fe12O19/MWCNTs/Polythiophene, was −34 dB and −33 dB at 8.1 GHz and 16.2 GHz, respectively. The microwave absorption of our samples was evaluated as a function of frequency and thickness, revealing its dependence on the quarter wavelength phenomenon with maximum reflection loss of −39 dB observed for ternary composite with Polythiophene matrix at 7.4 GHz resonance frequency. The resonance bands coincide with the operating frequency of military radars for shipborne and airborne surveillance and navigation in the X band.

Application of Calcium Hexaferrite as Microwave Absorbing Material: Review

Many studies have been conducted on Spinel, Garnet, and Hexa-ferrites in single and multi-doped concentrations. This article is an attempt to review the researcher's work on Ca, Ba, and Sr hexaferrite by substituting a variety of various ions such as Al, La, Sn, Zr, Co, Cr, and Ir. This review paper investigates M-type (Ca, Sr, Ba) Hexa-ferrites with a space group of P63/mmc that were synthesized using various techniques and characterized by XRD for crystallographic information, SEM and TEM for surface morphology, VSM for magnetic behaviour, and Vector Network Analyzer (VNA) for microwave absorption properties. Changes in a material's chemical composition affect features such as coercivity, saturation magnetization, and Curie temperature, as well as managing these properties and utilizing these compounds in the field of microwave absorption properties and magnetic field industry.

Influence of cerium ions on structure-dependent magnetic properties of Ba–Sr M-type hexaferrite nanocrystals

The present study is a systematic effort to investigate the structure-sensitive magnetic parameters of Ce3+ substituted Ba–Sr hexaferrite nanocrystals chemically formulated as Bao .5Sr0.5CexFe12−xO19 where x = 0.0–0.2 with Δx = 0.05. The hexaferrite powders were prepared using the sol–gel self-ignition route and structurally characterized by means of powder X-ray diffraction and Fourier transform infrared spectroscopy. The creation of the M-type hexaferrite phase within the synthesized samples was revealed from the Rietveld refinement of the X-ray diffractograms. The occurrence of a secondary phase of CeO2 was revealed within the hexaferrites for the substitution, x > 0. The refined X-ray diffraction data were utilized to compute the lattice parameters, X-ray density, and lattice parameter ratio. The crystal structure plotted from the refined XRD data reveals the occupancy of the ions at different lattice sites. The XPS data of the hexaferrite were analyzed to confirm the oxidation states of the constituent elements. The nanocrystalline nature of the hexaferrites was revealed from the crystallite sizes calculated using Scherer's formula. The analysis of FTIR spectra confirms that only a fraction of Ce3+ accommodated in the lattice and the remaining Ce content reside in the form of the CeO2 phase. The morphology of the hexaferrites was analyzed from the FESEM profiles of the ferrite samples. The magnetic behavior study was performed by analyzing the Curie temperature, hysteresis loops, and hyperfine interactions by means of susceptibility, V.S.M, and Mössbauer spectroscopy, respectively. The hexaferrites with increasing coercivity, decreasing saturation magnetization, and decreasing Curie temperature are reported in the study. The substituted Ce3+ ions inhibit the grain growth and create lattice imperfections giving rise to hexaferrites with tuned magnetic parameters suitable for different applications.

Impact of the indium content on structural, magnetic, and electrodynamic properties of nanocomposites based on In-substituted Sr hexaferrite and Ni–Zn spinel ferrite with excellent absorption characteristics

SrInxFe12-xO4/Ni0.5Zn0.5Fe2O4 (0.00 ≤ x ≤ 0.04) nanocomposites (SIFO/NZFO NCs) were synthesized using a one-pot sol-gel auto-combustion technique. The EDX method was used to verify the chemical composition. An X-ray diffractometer (XRD) was used for the structural analysis. Scanning electron microscopy (SEM) was used to study the morphological characteristics. The impact of indium doping on the magnetic properties of the nanocomposites was investigated using magnetization measurements at T = 300. A kink was observed in the M − H curves for lower indium content (x ≤ 0.02), which was suppressed with further increasing indium content until it vanished at a higher content. A single peak at a higher indium content replaced two peaks at a lower indium content (x 0.02), according to the switching field distribution (i.e., dM/dH vs. H). When the indium concentration increased, the saturation, remanence magnetization, and coercive field increased until x = 0.01, and then decreased, according to the analysis of the M − H loops. The obtained results reveal that an exchange interaction at the surface of the SIFO and NZFO nanoparticles (NPs) exists. The degree of intergranular dipolar interactions diminishes with increasing indium content within the hard-soft ferrite SIFO/NZFO NCs and becomes insignificant at higher indium contents. Moreover, the core of the SIFO and NZFO NPs also contains magnetic super-exchange interactions between Fe and O ions. At high frequencies (2–20 GHz), a correlation was found between the hard phase composition (indium content) and electrodynamic characteristics. Analyses were performed on the evolution of essential parameters (real and imaginary permittivity and permeability) in relation to the frequency. In this frequency range, the effect of electromagnetic radiation absorption was observed. A significant level of electromagnetic absorption (>-12 dB) in the frequency range was observed for investigated nanocomposites (NCs). The NCs with lower indium content (0.00 ≤ x ≤ 0.01) have higher reflection looses coefficients (−18 … -36 dB). This opens broad perspectives for the practical application of magnetic media for intensive electromagnetic absorption.

Effect of La3+ Substitution on the Structure and Magnetic Properties of M-type Sr Hexaferrites

Effect of La3+ Substitution on the Structure and Magnetic Properties of M-type Sr Hexaferrites

Sn-Co co-substituted SrSnxCoxFe12-2xO19 strontium hexaferrites: Correlation between chemical composition, magnetic and electrical properties

M-type strontium hexaferrites attract great attention due to the scientific importance and practical significance. It was observed the correlation between chemical composition, structural parameters, magnetic and electrical properties in heterovalent double substituted Sr hexaferrites. As substituents were used Co2+ and Sn4+ ions. X-ray diffraction data is used to compute a variety of parameters, including lattice parameters, and size of crystallite, in addition to validating purity of the materials. All investigated samples were single phase and characterized by the P63/mmc space group. Increase of the substituent concentration leads to the increase of the lattice parameters that correlated well with average ionic radii of the Fe3+, Co2+ and Sn4+. The average size of a crystallite was between 31 and 45 nm. Magnetic parameters were obtained from field dependences of the specific magnetization It was observed non-linear dependence in magnetic properties as function of the chemical composition. Increase of the sn-Co concentration leads to increase of the DC electrical resistivity. The dielectric constant is reduced while DC electrical resistivity increased from 5.94 to 11.7 × 109 Ohm cm, suggesting that materials can be employed in microwave devices because of their high resistivity and minimal dielectric constant.

Dielectric properties and magnetic behavior OF Gd3+ substituted M-type SrFe12O19 nanoferrites by auto combustion method using urea and citric acid mixtures as a dual fuel

Nanosized M-type hexaferrites Sr(1-x)GdxFe12O19 (x ​= ​0.00; 0.01<x ​< ​0.09; insteps of 0.02) have been synthesized by auto combustion method using urea and citric acid mixtures. Influences of Gd3+ ions substitution on structural, electrical and magnetic properties of Sr1-xGdxFe12O19 nanoferrites were investigated by XRD, FTIR, FESEM, LCR meter and VSM techniques. The PXRD studies confirmed the formation of single phase lattice whereas as the sample with x ​= ​0.09 exhibits about 5% of secondary phase. It was found that the lattice parameter increased with increasing in Gd3+ ion content. FTIR spectra have shown two absorption bands. The dielectric parameters were described based on the Maxwell–Wagner's two layer model. It is observed that the dielectric constant (ε′), the loss tangent (tanδ), decrease whereas the AC conductivity (σac) increases with increasing applied field frequency. Moreover, the vibrating sample magnetometer (VSM) analysis confirmed that M-SrHF's are hard magnetic in behavior. It was observed that the values of saturation magnetization (MS), remanence magnetization (Mr), coercivity (HC) and magnetic parameters of strontium ferrites decrease with the increase of the dopant Gd3+ in strontium ferrites. In addition, Gd3+ substituted SrFe12O19 are most useful for magnetic recording media and electro-magnetic devices.

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.

Structure, Spectra, Morphology, and Magnetic Properties of Nb5+ Ion-Substituted Sr Hexaferrites

SrFe12−xNbxO19 (x = 0.00–0.15) was here synthesized by a conventional solid-state reaction method. Thermogravimetry and differential scanning calorimetry curves revealed the sample reactions at four temperature ranges, and the optimal reaction stability was obtained at 1240 °C. A single-phase polycrystalline form of SrFe12O19 was obtained until the substitution reached 0.09, and the average crystallite size was found to be in the range of 44.21–60.02 nm. According to Fourier-transform infrared spectra, the formation of Fe–O bonds occurred at 69 and 450 cm−1 in the M-type ferrite, while Raman spectra revealed that all the peaks in the sample corresponded to Raman vibration modes and M-type structures. Through the shift of the peaks, it is speculated that Nb5+ enters into the lattice. The hysteresis loops of the samples were measured by vibrating-sample magnetometry, and the calculated results demonstrated that the coercivity increased with increases in the doping amount (686.3 Oe). At the same time, the saturation magnetization remained at a large value (&gt;72.49 emu/g), which has rarely been reported.

Structural, magnetic, and photocatalytic investigation of Hexaferrites/PANI nanocomposites

A1-xSmxFe12-xCoxO19 (A = Ba, Sr, and x = 0.03, 0.05, 0.07) nanoparticles were prepared via sol-gel auto combustion meanwhile A1-xSmxFe12-xCoxO19/PANI (A = Ba, Sr, and x = 0.03, 0.05, 0.07) nanocomposites were synthesized by in situ polymerization. In order to achieve the required hexagonal and PANI structure, fourier transform infrared spectroscopy (FTIR) were manipulated. The bands at 400 and 500 cm−1 wavenumbers confirmed the formation of hexaferrites in all samples while two bands at 1463 and 1554 cm−1 wavenumber represented the existence of quinoid and benzenoid rings in A1-xSmxFe12-xCoxO19/PANI (A = Ba, Sr, and x = 0.03, 0.05, 0.07) nanocomposites. The X-ray diffraction spectroscopy (XRD) is in exact accordance with JCPDS No. 01-072-073 for Ba1-xSmxFe12-xCoxO19 (x = 0.03, 0.05, 0.07) and No. 00-024-1207 for Sr1-xSmxFe12-xCoxO19 (x = 0.03, 0.05, 0.07). The arising two novel peaks at 20 and 25° was the evidence for the PANI structure beside Ba and Sr hexaferrites peaks in A1-xSmxFe12-xCoxO19/PANI (A = Ba, Sr, and x = 0.03, 0.05, 0.07) nanocomposites. Field emission scanning electron microscopy (FESEM) of A1-xSmxFe12-xCoxO19 (A = Ba, Sr, and x = 0.03, 0.05, 0.07) nanoparticles indicated the complete hexagonal structure of hexaferrites. In A1-xSmxFe12-xCoxO19/PANI (A = Ba, Sr, and x = 0.03, 0.05, 0.07) nanocomposites the sphere particles of PANI covered the unabridged hexagonal shape of hexaferrites. The magnetic properties of products were measured by vibrating sample magnetometer (VSM). The saturation magnetization of A1-xSmxFe12-xCoxO19 (A = Ba, Sr, and x = 0.03, 0.05, 0.07) nanoparticles modified erratically. By adding non-magnetic PANI, the saturation magnetization decreased. The photocatalytic properties of A1-xSmxFe12-xCoxO19 (A = Ba, Sr, and x = 0.03, 0.05, 0.07) nanoparticles revealed that insertion of rare earth increased the photodegradation of methylene blue, while polymerization promoted the degradation process in A1-xSmxFe12-xCoxO19/PANI (A = Ba, Sr, and x = 0.03, 0.05, 0.07).

Effect of mechanical milling on magnetic, dielectric and magneto-electric properties of Z- type (Ba, Sr) hexaferrites

The Z-type hexaferrites Sr3Co2Fe24O41 (SCFO) and Ba3Co2Fe24O41 (BCFO) were prepared via sol-gel method and were ball milled for different duration to study the effects of reduction in particle on the physical properties of these compounds. The phase formation was confirmed by using X-ray diffraction (XRD) whereas Scanning Electron Microscopy (SEM) was employed to analyze the surface morphologies of these samples. Magnetization measurements i.e. (M-H) at room temperature were performed by using Vibrating Sample Magnetometer (VSM) and it is observed that the magnetic coercive field (Hc) has increased with reduction in particle of the samples i.e., with ball milling. Magneto electric effects of (Ba, Sr) Z-type hexaferrites at room temperature were measured indirectly by examining the change in polarization (P-E loop) with and without magnetic field. It is evident from P-E loops of SCFO that magnetic field affects the electric polarization for all ball-milled samples and it is an indication of ME coupling in these samples at room temperature.

Impact of Gd substitution on the structure, hyperfine interactions, and magnetic properties of Sr hexaferrites

Gd3+-substituted nano-sized Sr-hexaferrite, SrGdxFe12-xO19 (0.00 ≤ x ≤ 0.05) NHFs (SrGd NHFs), were fabricated by a one-pot sol-gel combustion approach assisted by citric acid. The crystal structures, surface morphologies, magnetic properties, and hyperfine interactions of the calcined samples were characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM), X-ray photoelectron spectroscopy (XPS), energy-dispersive X-ray spectroscopy (EDX), high-resolution TEM (HR-TEM), vibrating sample magnetometry (VSM), and Mössbauer spectrometry. The oxidation states and chemical compositions of the NHFs were evaluated using XPS. The single-phase crystalline structures of all products were confirmed by XRD analysis. The average crystallite sizes determined from the peaks of the highest intensity using the Scherrer equation were between 38 and 50 nm. Using 57Fe Mössbauer spectroscopy data, the quadrupole splitting, hyperfine magnetic field, isomer shift, and line width variation of the products were determined. The Mössbauer spectra showed that octahedral (Oh) 12k and 2a sites were preferentially occupied by Gd3+ions. The Gd3+content was found to have no influence on the electron density around the Fe3+ions at any crystallographic site. The magnetization (M) versus magnetic field (H) data were collected at room (300 K) and ultra-low (10 K) temperatures. Neither the zero-field cooling (ZFC) nor field cooling (FC) mode plots of magnetization vs. temperature revealed any blocking temperature peaks. Both the M-H curves and FC-ZFC magnetization revealed ferrimagnetic behavior of the products. Furthermore, the FC-ZFC magnetization exhibited super-spin glass behavior at low temperatures. Reductions in the coercive field (Hc), saturation magnetization (Ms), and remanence (Mr) magnetization were achieved with Gd substitution of up to 0.03 into the hexaferrite system; however, with further increase in Gd content, these values started to increase. The calculated squareness ratio (Mr/Ms) revealed that all of the NHF samples were composed of single magnetic domain particles with uniaxial anisotropy.