Nanospinel Li2xCu1-xAlyFe2-yO4 ferrites with composition x = y = 0.0, 0.2, 0.3 and 0.4, were successfully synthesized via hydrothermal method. The effect of co-substitution (Li and Al) on structural, ...morphological and magnetic properties of CuFe2O4 nanoparticles were investigated using Powder X-ray Diffraction (XRD), Fourier-Transform Infrared spectroscopy (FT-IR), Scanning Electron Microscopy (SEM), Vibrating Sample Magnetometer (VSM) and Mossbauer spectroscopic techniques. The cation distribution of all composition was calculated. Both XRD and FT-IR analyses confirmed the synthesis of single-phase spinel cubic product for all the substitutions. Mossbauer investigation showed that the Li1+ and Al3+ ions occupied B-sites. Nonetheless, some amounts of Li1+ occupy A-site. The magnetization hysteresis loops M (H), revealed that the final products with x, y = 0.0, 0.3 and 0.4 exhibit superparamagnetic (SPM) behavior at room temperature, however the composition x, y = 0.2 displays a ferromagnetic-like (FM) behavior. The saturation magnetization (Ms) reduces with rising the Li and Al contents. Compared to pristine CuFe2O4 spinel, the remanent magnetization (Mr), coercive field (Hc) and the magneto-crystalline anisotropy fields (Ha) improved for products synthesized with x, y = 0.2 and then decrease for x, y = 0.3 and 0.4. The squareness ratio Mr/Ms are less than 0.500, which suggest the single domain nanoparticles with uniaxial anisotropy for Li2xCu1–xAlyFe2-yO4 (0.0 ≤ x, y ≤ 0.4) nanoparticles. The magneto-crystalline anisotropy constant (Keff) value is improved for Li0.8Cu0.6Al0.2Fe1.8O4 (i.e. x, y = 0.2) magnetic nanoparticles and then decreased for higher Li and Al contents, due to the replacement of Cu and Fe ions with respectively Li and Al ions.
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.
Caffeic acid coated superparamagnetic iron oxide nanoparticles (SPION-CFA) was synthesized by reflux method. The structural, spectroscopic and magnetic properties were studied by X-ray diffraction ...(XRD), Transmission electron microscopy (TEM), Scanning electron microscopy (SEM), and Vibrating sample magnetometer (VSM) techniques. Thermal gravimetric analysis (TG) and Fourier transform infrared spectroscopy (FT-IR) confirmed the presence of CA on the surface of SPION. The theoretical analyzes performed on recorded room temperature VSM spectrum confirmed the formation of superparamagnetic nature of SPION-CFA. The particle size dependent Langevin function was applied to determine the average magnetic particle dimension (Dmag) around 11.93nm. In accordance, the average crystallite and particle sizes were obtained as 11.40nm and ~12.00nm from XRD and TEM measurements. The extrapolated specific saturation magnetization (σs) is 44.11emu/g and measured magnetic moment is 1.83µB. These parameters assign small order of magnetization for NPs with respect to bulk Fe3O4. Magnetic anisotropy was offered as uniaxial and calculated effective anisotropy constant (Keff) is 34.82×104Erg/g. The size-dependent saturation magnetization suggests the existence of a magnetically inactive layer as 1.035nm for SPION-CFA.
•The effects of CFA on the microstructure and magnetic properties of SPION have been investigated.•Product was structurally and magnetically characterized.•Product presented superparamagnetic behavior at room temperature.
Several divalent cations together with tetravalent Ti4+ ion were replaced by two trivalent Fe3+ ions of barium hexaferrite in the form of BaFe10M2+Ti4+O19. Samples were prepared by using solid state ...reaction route and 1wt% B2O3 was added to inhibit the crystal growth at lower temperatures. Magnetic, dielectric and microwave properties of samples were investigated by X-ray crystallography, scanning electron microscopy, magnetization and near field microwave measurements. Magnetization measurements revealed that saturation magnetization of the cation substituted samples is less than that of the pure barium hexaferrite. Except Co2+ substituted barium hexaferrite, coercivities of the samples are nearly 1kOe. While measurement of dielectric constants of Zn2+, Mn2+, Co2+ and Cu2+ substituted samples yields a significant enhancement (≈10–102 times) with respect to Ni2+ substituted barium hexaferrite in permittivity through local polarization of Fe3+ electronic charges activated with nearby divalent ions. It is suggested that Zn2+ and Mn2+ substitution acts to reduce the electron hopping probability between Fe2+ and Fe3+. All samples have approximately the same microwave absorption properties in such a way that minimum reflection loss (RL) of −10dB occurs at 15GHz. Meanwhile, Zn2+ and Mn2+ substituted samples have quite wide absorption bandwidths of 4GHz at −10dB.
Narrow size distribution nickel ferrite nanoparticles with average particle size of around 6nm has been synthesized via rapid thermo-decomposition method in the presence of oleylamine in solution ...which acted as neutralizing, stabilizing and reducing agent OAm coated NiFe2O4 NPs. X-ray powder diffraction (XRD), Fourier Transform Infrared Spectra (FT-IR), Thermal Gravimetric Analysis (TGA), Scanning Electron Microscopy (SEM), Transmission electron microscopy (TEM), Vibrating Simple Magnetometer (VSM) and also Mössbauer Spectroscopy were used for structural, morphological, spectroscopic and magnetic characterization of the product. The XRD analysis revealed the formation of single phase nickel ferrite with Fd-3m space group. Both FT-IR and TGA analyses confirmed the formation of desired nanocomposite. FT-IR analysis also showed characteristic IR absorption bands of the spinel nickel ferrite phase and oleylamine. TEM and SEM analysis showed that product have almost spherical structural morphology. TEM images showed that NiFe2O4 nanoparticles have narrow size distribution and Energy Dispersive X-ray (EDX) analysis confirmed the presence of metal ions in the required stoichiometric ratio. Superparamagnetic property of the product was confirmed by VSM. From 57Fe Mössbauer spectroscopy data, the variation in line width, isomer shift, quadrupole splitting and hyperfine magnetic field values have been determined. The Mössbauer spectra for OAm coated NiFe2O4 NPs. is consisting of one paramagnetic central doublets and one magnetic Zeeman sextet. Finally, the synthetic procedure can be extended to the preparation of high quality metal or alloy nanoparticles.
(FeCo)84CuB15 soft magnetic alloys with Fe/Co ratios (5:1, 3:1, and 1:1) were prepared using the planar flow casting method. The structural and magnetic properties together with magnetic ...field-sensing performance of the ribbons were investigated in detail. X-ray diffraction (XRD) and scanning electron microscopy (SEM) were used for the structural characterization. The magnetic parameters were determined by vibrating sample magnetometer and B-H loop tracer. The 2-D magnetic field variations on the surface of the ribbons were determined via a magnetic force microscope. The fluxgate sensors were prepared using the casted ribbons to test magnetic field sensing ability by measuring the second harmonic voltage induced in the pick-up coils by the lock-in amplifier. The working range and the noise of the sensors were also determined. The amorphous structure of the ribbons was confirmed by X-ray diffraction (XRD) patterns. The magnetic hysteresis measurements revealed the soft magnetic behaviour of the alloys having magnetization values as high as 1.3 T and coercivities around 1 Oe. As Fe/Co ratio increases, permeability values increase substantially. Meanwhile, the coercivities remained almost the same as close to 1 Oe. The alloys' magnetic field sensing feature decreased drastically as the Fe/Co ratio rose. Besides, noise parameters degraded. The linear response of the sensors to the external magnetic field (i.e., working range) enlarged with increasing Fe-content in the alloys.
•The (FeCo)84CuB15 alloys were produced by planar flow casting method.•The ribbons having different Fe/Co ratios were obtained for investigation.•The sensor elements of a fluxgate magnetometer were prepared by the casted ribbons.•The structural, magnetic and sensor properties of the alloys investigated in details.•The optimal Fe/Co ratio yielding the best sensor features was determined.
In this study, effect of lanthanum substitution on the phase composition, lattice parameters and magnetic properties of barium hexaferrite has been studied in samples synthesized in ammonium nitrate ...melt. Samples, prepared with different lanthanum amount and having various initial Fe/(Ba+La) ratios in between 12 and 2 {(Ba1−xLax)·n Fe2O3, where 0≤x≤1 and 1≤n≤6)}, are sintered at temperatures from 800 to 1200°C. The lattice parameters, both a and c, decreases with increasing La amount which results in a decrease of the unit cell volume. The scanning electron microscope micrographs show that the pure and La-substituted sample with x=0.3, both calcinated at 1000°C, have grain sizes smaller than 1μm. The coercivities of the La-substituted samples increase with increasing La amount and reaches to a maximum value of 5.73kOe, when x=0.3. Sintering at higher temperatures (above 1000°C) decreases the coercivity, resembling a transition from single to multi-domain behavior of the particles, while saturation magnetization of the samples continues to increase due to the increasing grain size. Magnetization measurements of the samples prepared with different Fe/(Ba+La) molar ratios, n's, revealed that the specific saturation magnetization slightly increases with decreasing n, while coercivities fluctuates around 5.5kOe. However, a sharp increase in the saturation magnetization has been observed in the sample having n=1 and washed in HCl. It was measured as 59.2emu/g at 15kOe, which is higher than that of the pure sample (57.5emu/g). Thus, the magnetic parameters are optimized in the sample Ba0.7La0.3Fe12O19 so as to maximize both coercivity and specific saturation magnetization in the HCl-washed sample synthesized by starting with an unusually low Fe/(Ba+La) molar ratio of 2 (or n=1).
► Effect of lanthanum substitution on the phase composition, lattice parameters and magnetic properties of barium hexaferrite has been studied. ► Samples are prepared with different lanthanum amounts and various initial Fe/(Ba+La) ratios {(Ba1−xLax)·n Fe2O3, where 0≤x≤1 and 1≤n≤6)}. ► Optimum La concentration that maximizes the coercivity at 5.73kOe was determined as x=0.3 in Ba1−xLaxFe12O19 samples ► Saturation magnetization has also been increased by choosing the initial Fe/(Ba+La) molar ratio as 2 (i.e., n=1) with HCl treatment. ► Chemical formula of the sample which has both the highest coercivity and saturation magnetization is determined as (Ba0.64La0.36)Fe10.5O19.89.
•Fe3O4 NPs were synthesized in the MWCNTs starting from a single iron precursor.•Magnetic properties of the Fe3O4–MWCNT hybrid at low temperatures were evaluated.•Fe3O4–MWCNT hybrid is ...superparamagnetic at room temperature with an Ms=33.8emu/g.•Blocking temperature seems to be larger than 400K determined by ZFC measurements.
Carbon nanotubes embedded with nanosized magnetic materials are novel and interesting materials which could provide a wide range of possible applications with an emphasis in biomedicine. A facile and efficient method was developed to fill multi-walled carbon nanotubes (MWCNTs) with Fe3O4 nanoparticles. X-ray diffraction, Fourier transform infrared spectrometry, thermal gravimetry, transmission electron microscopy, and vibrating sample magnetometry were used to characterize the physical and magnetic properties of the hybrid obtained. The results confirmed that MWCNTs and Fe3O4 NPs coexisted in the hybrid. The magnetic measurement shows that Fe3O4-filled pretreated MWCNTs exhibit superparamagnetism. Results showed that the Fe3O4-filled pretreated MWCNTs exhibited superparamagnetism at room temperature and possessed a higher saturation magnetization (Ms) (around 33.8emu/g) than that of the unfilled MWCNTs (around 0.35emu/g). The product displays potential applications in biomedicine and engineering.
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.
