Ba1−xZnxFe12O19 (0.0≤x≤0.3) hexaferrites were produced via sol-gel auto combustion technique. XRD patterns show that all the samples are single-phase M-type barium hexaferrite (BaM). Scanning ...electron microscopy (SEM) revealed that grains have a size range of 0.5–2µm. The magnetic hysteresis (σ-H) loops revealed the ferromagnetic nature of NPs. The average crystallite sizes were calculated by applying Scherrer equation on the base of XRD powder patterns of all samples and found to be in the range of 16.78–48.34nm. In particular, Ba1−xZnxFe12O19 (0.0≤x≤0.3) hexaferrites have suitable magnetic characteristics (saturation magnetization in a range of 63.00–67.70emu/g and coercive field in a range of 822–1275Oe) for magnetic recording and permanent magnets. Effective crystalline anisotropy constants (Keff) are between 4.20×105 and 4.84×105Erg/g. Magnetic moment increased by the substitution of non-magnetic Zn2+ ions. The anisotropy field (Ha) or intrinsic coercivity values above 13255Oe reveals that all samples are magnetically hard materials. Tauc plots were drawn to specify the direct optical energy band gap (Eg) of NPs. The Eg values are in a narrow range between 1.69eV and 1.76eV.
•Diamagnetic Zn2+ ionsubstitution on magnetic and optical properties of barium hexaferrite has been investigated.•All products are ferromagnetic.•The grain sizes are much larger than the critical dimension of 431nm to exhibit single-domain nature.
In the present study, SrBixFe12−xO19 (0.0≤x≤1.0) nanomaterials were successfully synthesized by using chemical co-precipitation method. Products were characterized by X-ray diffraction (XRD), ...Scanning Electron Microscopy (SEM), Vibrating sample magnetometer (VSM), Mössbauer spectroscopy, AC conductivity and dielectric measurements. The crystal structural information studied by X-ray diffraction (XRD) indicated the formation of single phase pure hexagonal structure, while electron-dispersive X-ray spectroscopy (EDX) revealed the stoichiometric ratio among Bi, Sr, Fe elements. The crystallite sizes of the products were in the range of 65–82nm. VSM analysis showed a tendency in saturation magnetization as Bi2O3 concentration raises, which can be ascribed to preferential site occupied by Bi3+ ions. The frequency-dependent ac conductivity plots exhibited similar trends for all samples. A significant temperature-dependent behavior was only observed at low and medium frequencies. The replacement of non-magnetic Bi3+ ions by Fe3+ ones having magnetic moment of 5µB decrease the magnetic moment of 4f1 site. The AC conductivity increases with frequency as hopping of the charge carriers increases between Fe2+and Fe3+. The DC conductivity exhibited an improvement with increasing temperature and Bi content, and the highest conductivity was measured as 2.84×10−9Scm−1 for x=0.8 at 120°C. The variation of dielectric constant, dielectric loss and tangent loss was observed with the frequency and temperature due to change of electrical conductivity as x changes.
•SrBixFe12−xO19 (0.0≤x≤1.0) nanomaterials were synthesized via chemical co-precipitation.•VSM analysis showed a tendency in saturation magnetization as Bi2O3 concentration raises.•The DC conductivity exhibited an improvement with increasing temperature and Bi content.•The interface polarization determines the conductivity at lower frequencies.
BaBixLaxYxFe12−3xO19 (0.0≤x≤0.33) hexaferrites were synthesized by sol–gel autocombustion method and the effects of Bi, La, Y substitutions on structural, magneto-optical properties of barium ...hexaferrite were investigated. X-ray diffraction (XRD), Scanning electron microscopy (SEM), Vibrating sample magnetometer (VSM), and Percent diffuse reflectance spectroscopy (DR %), were used to study the physical properties. XRD peaks showed pure single phase of hexagonal ferrites and the average crystallite size varies in a range of 42.35–49.90nm. Room temperature (RT) specific magnetization (σ–H) data revealed the strong ferromagnetic nature of hexaferrite with remanant specific magnetization (σr) in the range of 29.9–34.6Am2/kg and extrapolated specific saturation magnetization (σs) in the range 53.69–67.42Am2/kg. The maximum coercive field (Hc) of 3.812×105A/m (belongs to BaFe12O19) decreases to minimum 2.177×105A/m with increasing ion substitution. Magnetic anisotropy was confirmed as uniaxial and effective anisotropy constant (Keff) takes values between 2.532×105J/m3 and 3.105×105J/m3. The anisotropy field (Ha) around 1.6T revealed that all samples are magnetically hard materials. The Tauc graphs were plotted to estimate the direct optical energy band gap (Eg) of hexaferrite. The Eg values decreased from 1.88eV to 1.69eV with increasing Bi, La, Y compositions.
•BaBixLaxYxFe12−3xO19 (0.0≤x≤0.33) hexaferrites were synthesized via sol–gel autocombustion route first time.•Room temperature (RT) specific magnetization (σ–H) data revealed the strong ferromagnetic nature of hexaferrite with remanant specific magnetization (σr) in the range of 29.9–34.6emu/g and extrapolated specific saturation magnetization (σs) in the range 53.69–67.42emu/g.•The anisotropy field (Ha) around 16,000Oe revealed that all samples are magnetically hard materials.
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•SrBixLaxYxFe12−3xO19 (0.0≤x≤0.33) hexaferrites have been prepared by sol-gel autocombustion.•XRD patterns show that SrBixLaxYxFe12−3xO19 (0.0≤x≤0.33) hexaferrites exhibit hexagonal ...structure.•The intrinsic coercivity (Hci) above 15000Oe reveals that all samples are magnetically hard materials.
SrBixLaxYxFe12−3xO19 (0.0≤x≤0.33) hexaferrites were produced via sol-gel auto combustion. XRD patterns show that all the samples are single-phase M-type strontium hexaferrite (SrM). The magnetic hysteresis (σ-H) loops revealed the ferromagnetic nature of nanoparticles (NPs). The coercive field decreases from 4740Oe to 2720Oe with increasing ion content. In particular, SrBixLaxYxFe12−3xO19 NPs with x=0.0, 0.1, 0.2 have suitable magnetic characteristics (σs=62.03–64.72emu/g and Hc=3105–4740Oe) for magnetic recording. The intrinsic coercivity (Hci) above 15000Oe reveals that all samples are magnetically hard materials. Tauc plots were used to specify the direct optical energy band gap (Eg) of NPs. The Eg values are between 1.76eV and 1.85eV. 57Fe Mössbauer spectroscopy data, the variation in line width, isomer shift, quadrupole splitting, relative area and hyperfine magnetic field values on Bi3+ La3+ and Y3+ substitutions have been determined.
ZnxCa0.5-x/2Mg0.5-x/2Fe2O4 (x = 0.0–0.6) nano-spinel ferrite (NSFs) were prepared by ultrasonic irradiation with Moringa oleifera leaf extract (group A) and without Moringa oleifera leaf extract ...(group B). The synthesis done with Moringa oleifera leaf extract is green synthesis. The structure and morphologies of both group A and B NSFs were investigated by XRD, SEM, TEM, and FT-IR in details. The crystallite sizes of group A and B products were calculated as within the range of 11–17 nm and 16–28 nm, respectively. The magnetic features of different nanoparticles of group A and B NSFs have been investigated at room (T = 300 K) and low (T = 10 K) temperatures by means of a vibrating sample magnetometer (VSM). All samples displayed superparamagnetic (SPM) behavior at room temperature, with no or negligible coercivity and retentivity. Nevertheless, the different samples revealed opened M−H hysteresis loops at a temperature of 10 K, which indicates their ferromagnetic (FM) behavior at very low temperatures. The various magnetic parameters including the saturation magnetization (Ms), remanent magnetization (Mr), squareness ratio (Mr/Ms), magneton number (nB), coercive field (Hc), etc. were extracted. The ZnxCa0.5-x/2Mg0.5-x/2Fe2O4 (x = 0.0 – 0.6) NSFs prepared using Moringa oleifera extract (Group A samples) displayed lower Ms values in comparison to NSFs prepared without using Moringa oleifera extract (Group B samples). Whereas, the coercivity is found to be larger in Group B samples than in Group A samples. These is mainly ascribed to the variations in particles size upon the use of Moringa oleifera extract. Compared to non-substituted Ca0.5Mg0.5Fe2O4 NSFs, it is noticed that the Ms value increases with Zn2+ ions substitution. The increase of Ms value is ascribed to the strengthening of exchange interactions and redistribution of cations (particularly Fe3+ ions) within the spinel lattice. At T = 10 K, the Hc value decreases with the rise of the Zn2+ content, which is attributed to the larger crystallites/particles that lead to the lower volume fraction of grains boundaries, which in turn conduce to less pinning of domain walls. The SQR values at 10 K for all NSFs of group A and B are between 0.2 and 0.3, which is below the theoretical limit of 0.5, reflecting the NPs consist of multi-magnetic domains. The obtained magnetic properties of group A NSFs are interesting, suggesting that this method could be considered as an alternative and effective green synthesis route with appropriate control of size, morphology, and physical features of magnetic nanoparticles.
A simple sol-gel auto combustion process was used to synthesize La3+ substituted M-type strontium hexaferrite, Sr1-xLaxFe12-xO19 (0.0≤x≤ 0.5). Structural, magnetic, and optical behavior as a function ...of La3+ substitutions were investigated by Fourier transformed infrared spectroscopy (FT-IR). X-ray powder diffraction (XRD). Scanning electron microscopy (SEM), Mössbauer spectroscopy, vibrating sample magnetometer (VSM), and Diffuse reflectance spectroscopy (DRS). XRD data showed single phase magnetoplumbite structure and Rietveld analysis confirmed P63/mmc space group for all the series. The average crystallite size was found to be in the range of 43.2–48.4nm. The variation in line width, isomer shift, quadrupole splitting, relative area and hyperfine magnetic field values have been determined from 57Fe Mössbauer spectroscopy data. The fittings accounted for the Fe2+/Fe3+ charge compensation mechanism at the 2a site due to replacement of Sr2+ by La3+. The saturation magnetization (σs) decreases from 57,21 to 63,23emu/g and remnant magnetization (σr) decreases from 35.6emu/g to 28.7emu/g with increasing La substitution. The decrement is sharper at coercive field (Hc) from maximum value of 5325 to minimum 1825Oe. Demagnetizing factor (N) is 3 times more for the x=0.3, 0.4, and 0.5. However all samples exhibit ferromagnetic behavior at room temperature. Magnetic anisotropy of Hexaferrites was detected as uniaxial and effective anisotropy constants (Keff) were between 5.93×105 and 4.76×105 Ergs/g. The high magnitudes of anisotropy fields (Ha) in the range of 13863–15574Oe reveal that all hexaferrites are magnetic hard materials. Tauc plots were applied to extrapolate the direct optical energy band gap (Eg) of hexaferrites. The Eg values decreased from 1.83 to 1.34eV with increasing La content.
•Pulsed laser ablation in liquid was employed to synthesize the hard/soft ferrites.•The magnetization is convolution of individual hysteresis loops of hard and soft.•The dipolar interaction between ...hard-hard and soft–soft grains are dominant.
Green pulsed laser ablation in liquid (PLAL) method was employed to synthesize the nanocomposites of SrGd0.03Fe11.97O19 (hard), and CoTm0.01Tb0.01Fe1.98O4 (soft) with different ratios by the application of a pulsed laser beam. The structural and morphological were carried out using XRD, SEM, TEM, and the observed magnetic behavior is elucidated in the light of these results. The magnetic hysteresis loop of the composite was found to be the convolution of the individual hysteresis loops of hard and soft magnetic materials at 300 and 10 K. This result along with the switching field distribution (SFD) plots at both temperatures revealed that the dipolar interaction between the hard-hard and soft–soft grains are more dominant than the exchange coupling interaction between the hard and soft grains. The saturation magnetization and remanent magnetization at both temperatures decreased with the increase of spinel ferrite content, whereas the coercive field increased with the increase of spinel ferrite content at low temperature.
Single-phase M-type hexagonal ferrites, SrBixFe12−xO19 (0.0≤x≤1.0), were prepared by a co-precipitation assisted ceramic route. The influence of the Bi3+ substitution on the crystallization of ...ferrite phase has been examined using powder X-ray diffraction (XRD), scanning electron microscopy (SEM), Fourier transform infrared spectroscopy (FT-IR) and Mössbauer spectroscopy. The XRD data show that the nanoparticles crystallize in the single hexagonal magnetoplumbite phase with the crystallite size varying between 65 and 82nm. A systematic change in the lattice constants, a=b and c, was observed because of the ionic radius of Bi3+ (1.17Å) being larger than that of Fe3+ ion (0.64Å). SEM analysis indicated the hexagonal shape morphology of products. From 57Fe Mössbauer spectroscopy data, the variation in line width, isomer shift, quadrupole splitting and hyperfine magnetic field values on Bi substitutions have been determined.
Barium hexaferrite, BaFe12O19, substituted by Bi3+ and La3+ (BaBixLaxFe12−2xO19 where 0.0≤x≤0.5) were prepared by solid state synthesis route. The effect of substituted Bi3+ and La3+ ions on the ...structure, morphology, magnetic and cation distributions of barium hexaferrite were investigated by X-ray powder diffractometry (XRD), scanning electron microscopy (SEM), energy dispersive X-ray spectroscopy (EDX), Fourier transform infrared spectroscopy (FT-IR) and Mössbauer spectroscopy. XRD powder patterns were refined by the Rietveld analysis method which confirmed the formation of single phase magneto-plumbite structure and the substitution of La3+ and Bi3+ ions into the lattice of barium ferrite. These results show that both La3+ and Bi3+ ions completely enter into barium hexaferrite lattice without disturbing the hexagonal ferrite structure. The EDX spectra confirmed the presence of all the constituents in expected elemental percentage. From 57Fe Mössbauer spectroscopy data, the variation in line width, isomer shift, quadrupole splitting and hyperfine magnetic field values on Bi and La substitutions have been determined. Cation distribution in the presently investigated hexaferrite system was estimated using the relative area of Mössbauer spectroscopy.
This study investigated the electrical and dielectric features for NiCo (Ni0.5Co0.5Fe2O4) NSFs, Pr-NiCo (Ni0.5Co0.5Pr0.1Fe1.9O4) NSFs, PrY-NiCo (Ni0.5Co0.5Pr0.1Y0.1Fe1.8O4) NSFs and PrYDy-NiCo ...(Ni0.5Co0.5Pr0.1Y0.1Dy0.1Fe1.7O4) NSFs have been synthesized hydrothermally. The microstructure of all compositions was characterized thru XRD, SEM, EDX, TEM and HR-TEM. XRD analyses proved the formation of cubic structure and the absence of any impurity. The cubic morphologies of all products have been confirmed by HR-TEM and SEM measurements. The chemical composition presented by EDX was matched with the predicted chemical composition. Temperature (T) and frequency (f) dependent electrical and dielectric measurements were made to evaluate ac/dc conductivities, dielectric constant/losses, and dissipation factor as well as Cole-Cole plots of impedance functions for all NiCo NSFs substituted with Pr3+, Pr3+Y3+ and Pr3+Y3+Dy3+-ions. The ac conductivity measurements confirmed that it obeyed power law rules, largely dependent on the ion substitutions in the host NiCo NSFs. The dielectric constant of NiCo NSFs leads to the usual dielectric distribution, which is strongly influenced by substituted Pr3+, Pr3+-Y3+ and Pr3+-Y3+-Dy3+ ions. Impedance analysis indicated that the conduction mechanisms in all samples were mainly due to grain-to-grain boundaries. The variation in dispersion factors with frequency, like Koop's phenomenological model, is generally attributable to the conduction mechanism in ferrites.
•NiCo NSFs, Pr-NiCo NSFs, PrY-NiCo NSFs and PrYDy-NiCo NSFs have been synthesized hydrothermally.•The ac conductivity measurements largely dependent on the ion substitutions in the host NiCo NSFs.•The dielectric constant strongly influenced by substituted Pr3+, Pr3+-Y3+ and Pr3+-Y3+-Dy3+ ions.•Impedance analysis indicated that the conduction mechanisms in all samples were mainly due to grain-to-grain boundaries.
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