In this study, we investigated Cu–Co ferrite nanofibers (NFs) that were synthesized for the first time employing the electrospinning technique.

(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 magnetom-eter 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.

Mn(0.5)Zn(0.5)ErxDy(x)Fe(2-2x)O(4) (x <= 0.1) spinel nanoferrites (SNFs) were fabricated successfully via Ultrasonic irradiation. Structural and morphological analysis were investigated via X-ray diffraction diffractometer (XRD), scanning (SEM) and transmission electron microscopes (TEM), Fourier-transform infrared spectroscopy (FTIR), and Surface Area Analyzers (BET). XRD showed the formation of highly pure Mn-Zn spinel ferrite phase with an average crystallite size within 19-26 nm range. The formation of spherical nanoparticles with small particles size was also approved by SEM and TEM techniques. Magnetization response to the magnetic field applied (M vs H) and temperature and (M vs T under ZFC and FC modes), were investigated to understand the impact of Er and Dy co-doping mechanism on the magnetic features of MnZn SNFs. The findings through the magnetization measurements demonstrate superparamagnetic (SPM) behavior with single magnetic domain particles for different prepared products and with no coercivity (H-c) and remanence (M-r) at RT and at temperatures above the T-B (blocking temperature). At lower temperatures below T-B, it has been illustrated that the prepared SNFs have ferrimagnetic (FM) behavior with the existence of coercivity (H-c) and remanence (M-r). The calculated squareness (SQR = Mr/Ms) at T = 10 K are ranging between 0.14 and 0.29, which are below the predicted value of 0.5, reflecting the MMD nature in different prepared SFNPs at T = 10 K. In comparison to pristine product, the saturation magnetization (M-s) initially increased for lower co-doping contents of Er and Dy up to x = 0.04 and then decreased by the further Er and Dy co-doping concentrations (x > 0.04). (c) 2022 Elsevier B.V. All rights reserved.

The SrFe12-xTbxO19 (x <= 0.10) nanohexaferrites (HFs) have been synthesized via citrate solgel approach. The phase formation, chemical purity, morphology and composition of the products were analyzed by X-ray powder diffractometer (XRD), Scanning and Transmission electron microscopes (SEM and TEM). Electromagnetic properties as such as frequency dependences of the loss tangents and reflection losses were investigated in the range of frequency from 2 to 18 GHz. The set of experimental data allowed to establish the nature of the electromagnetic power losses in SrFe12-xTbxO19 nanohexaferrites (HFs). It was demonstrated two main mechanisms of the electromagnetic radiation absorption in high frequency range (2-18 GHz): 1. Absorption due to natural ferromagnetic resonance (NFMR) and 2. Absorption due to dipole polarization. The results show the promise of using these materials for microwave applications (ensuring electromagnetic compatibility).

Barley plants were grown in water solutions containing nutrient elements and superparamagnetic iron oxide nanoparticles (SPIONs), particularly the magnetite nanoparticles (Fe3O4; 15–20-nm particle size). No visible detection of toxicity on plants’ growth had been observed. The different samples from two different organs of the plants, i.e., roots and leaves, were investigated using X-ray diffraction (XRD), bright-field microscope, and transmission electron microscope (TEM). To track the SPIONs, magnetic measurements using vibrating sample magnetometry (VSM) and Mössbauer spectroscopy at room temperature were also performed in the two different dried root and leaf organs of the plants. The magnetic signals measured in root and leaf organs clearly indicated an uptake of Fe3O4 magnetic nanoparticles (MNPs) by the barley plant from aqueous medium containing Fe3O4 MNPs and their subsequent accumulation in the plant organs. The different parameters such as hyperfine magnetic field, quadrupole splitting, isomer shift, and line width were deduced from Mössbauer spectroscopy data. The Mössbauer spectra are constituted of two magnetic sextets (A site, B site) and paramagnetic central doublet.

Department of Biophysics, Institute for Re Imam Abdulrahman Bin Faisal University, Arabia. E-mail: malmessiere@iau.edu.sa; ya Department of Physics, College of Science, I P. O. Box 1982, Dammam, 31441, Saudi Ar Department of Chemistry, Istanbul Medeni Turkey Department of Nanomedicine, Institute for R Imam Abdulrahman Bin Faisal University, Arabia Department of Physics, Hitit University, 19 TUBITAK-UME, National Metrology Institu Turkey School of Materials Science and Engine Kensington, Sydney, NSW 2052, Australia Institute of Inorganic Chemistry, RWTH Germany Department of Chemistry, Bharath Instit (BIHER), Bharath University, Chennai, 6000 Cite this: RSC Adv., 2019, 9, 30671

Sr(Zn,Nd)xFe12−xO19 (0.0 ≤ x ≤ 1.0) nanohexaferrites (NHFs) were obtained using citrate sol–gel approach. XRD and FE-SEM analysis were performed to confirm the formation of Sr M-type hexaferrite. Main electrodynamics characteristics (frequency dependences of real and imaginary parts of the permittivity and permeability) were measured in the range 5–18 GHz (region of the natural ferromagnetic resonance). Permittivity and permeability data correlates well. All samples were characterized by peak on the frequency dependences due to electrical and magnetic losses respectively. However, for compounds with x = 0.1 and 0.9 we observed second peak (at 14–15 GHz). This was explained by double oxidation state for iron ions (Fe3+/Fe4+). Presence of the Fe4+ ions was due to heterovalent Zn2+ substitution. Absence of the second peak for compounds x = 0.3; 0.5 and 0.7 was explained by charge disproportionation (according to the following scheme: 2Fe4+ = Fe3+ + Fe5+) under the influence of the crystal field energy. It was demonstrated that modification of crystal and magnetic structures by heterovalent substitution leads to transformation the microwave characteristics (reflection losses).

This study reports the preparation and characterization of nanocrystalline spinel powder of cubic copper ferrite nanoparticles (NPs) which have been fabricated via a cost-effective citrate sol–gel approach. The structural and morphological properties of the nanoparticles are analyzed by X-ray diffraction (XRD), Fourier transform spectroscopy (FT-IR), and scanning electron microscopy (SEM) whereas magnetic properties and Mössbauer analysis were performed using vibrating sample magnetometer (VSM) and Mössbauer spectra, respectively, and were characterized in detail. The empirical aim of this study is to perceive the transition phase of CuFe 2 O 4 as cubic symmetry which was confirmed by SEM images, and a couple of studies reported on the cubic structure of copper ferrite and discussed the magnetic properties. However, the present study gives the detailed information of the formation of cubic structure and magnetic behavior of the CuFe 2 O 4 cubic structure. X-ray diffraction measurements of resulting NPs show that the grain size of the particles is about 42.08 nm while SEM analysis showed that the particles have cubic nanostructured shapes with non-homogeneous sizes in around 80–100 nm. From 57 Fe, Mössbauer parameters consist of one superparamagnetic doublet and superposition of four sextets. VSM result shows the enhanced superparamagnetic nature of the CuFe 2 O 4 NPs.

In this work, the optical, film formation, morphological and the magnetic properties of a novel type of nanocomposite system, composed of polystyrene (PS) latex and core‐shell superparamagnetic nanoparticles (SP‐MNPs), is presented. The film formation and optical properties were examined by UV‐vis technique, morphological changes by scanning electron microscopy and magnetic properties studied using vibrating sample magnetometer (VSM) as a function of SP‐MNPs content. A series of mixtures were prepared by mixing of PS latex dispersion with different amount of SP‐MNPs in the range of (0–100 wt%). PS/SP‐MNPs films were then prepared from these mixtures on glass substrates using drop casting method. After drying, film was separately annealed at elevated temperatures between 100°C and 250°C. In order to monitor film formation process, transmittance of these composites was measured after each annealing step as a function of SP‐MNPs content. It was found that below a critical SP‐MNPs content, PS percolates into the SP‐MNPs hard phase and forms an interconnected network upon annealing. However, above this critical value, PS latexes were no longer film forming at all temperatures. Besides, composite films showed superparamagnetic behaviors. The saturation magnetization ( M s ) first increased and reached to 0.014 emu/cm 3 at 50 wt% SP‐MNPs, then decreased to 0.010 emu/cm 3 with increasing SP‐MNPs content. The maximum value of M s was approximately 0.020 emu/cm 3 and was obtained for the 85 wt% SP‐MNPs content film. These results indicated that the optical, film formation and magnetic properties of PS/SP‐MNPs composite films can be readily tuned by varying SP‐MNPs content. POLYM. COMPOS., 40:1018–1033, 2019. © 2018 Society of Plastics Engineers

Cr3+-ion-substituted Ba nanohexaferrites (NHFs) were prepared via a sol-gel auto-combustion approach. The structural, magnetic, and microwave properties of the products were investigated by X-ray diffractometry, transmission electron microscopy, vibrating sample magnetometry, and reflection/ transmission measurements in a vector network analyzer. A single barium hexaferrite phase was verified from the X-ray diffraction patterns. An average particle size of 2 mu m and hexagonal crystal shapes were observed by scanning electron microscopy. Hard ferromagnetic ordering was also observed in room-temperature M-H hysteresis curves. Magnetic measurements revealed that both the saturation magnetization and coercivity of the nanoparticles decreased as the Cr3+ content increased. The substitution of Cr3+ ions in the Ba NHFs shifted the matching frequency at which microwave absorption occurs from 14 to 12 GHz. In addition, the Cr3+-ion-substituted barium NHFs showed better microwave absorption capability (-41 dB) than a pure Ba hexaferrite sample (-33 dB). (C) 2018 Elsevier B.V. All rights reserved.

In the current study, Ni0.4Cu0.2Zn0.4La x Y x Fe2-x O4 (x = 0.00 - 0.10) nanospinel ferrites (NSFs) were fabricated via an ultrasonic irradiation route. The creation of single phase of spinel nanoferrites (NSFs) was investigated by X-ray powder diffractometry (XRD) and selected area diffraction pattern (SAED). The cubic morphology of all samples was confirmed by scanning and transmission electron microscopies (SEM and TEM) respectively. The UV-Vis investigations provided the direct optical energy band gap values in a narrow photon energy interval of 1.87-1.92 eV. The 57Fe Mössbauer spectroscopy analysis explained that the hyperfine magnetic fields of Octahedral (Oh) and Tetrahedral (Td) sites decreased with substitution. The paramagnetic properties of NPs decrease with increase of content of doped ions. Investigations of magnetic properties reveal a superparamagnetic nature at 300 K and soft ferromagnetic trait at 10 K. The M s (saturation magnetization) and M r (remanence) decrease and the H c (coercivity) increases slightly with La3+ and Y3+ substitution. The observed magnetic traits are deeply discussed in relation with the morphology, structure, magnetic moments and cation distributions. The microwave characterization of the prepared NSFs showed that, dissipation (i.e., absorption) of incoming microwave energy occurs at a single frequency, for each sample, lying between 7 and 10.5 GHz. The reflection losses (RL) at these frequencies range from -30 to -40 dB and the mechanism of which is explained in the framework of dipolar relaxation and spin rotation. The best microwave properties were obtained with a LaY concentration of x = 0.08 having an RL of -40 dB @ 10.5 GHz and an absorption bandwidth of 8.4 GHz @ -10 dB. With these high values of RL and absorbing bandwidth, LaY doped NiCuZn NSF products would be promising candidates for radar absorbing materials in the X-band.

In this study, Zn2+ substituted (into Ba position) barium hexaferrites with the chemical composition Ba1−xZnxFe12O19 (0.0 ≤ x ≤ 0.3) were produced by sol-gel approach. The Rietveld refinement of XRD powder patterns revealed both purity and the hexagonal structure of all products which have crystallite size within the range of 17–48nm. The effect of Zn2+ ion substitution on the temperature-dependent and magnetic properties of Ba1−xZnxFe12O19 hexaferrites have been investigated in the temperature range 10–300K and a magnetic field of ± 50kOe. Magnetization measurements revealed that all samples have hard ferromagnetic type magnetization and uniaxial anisotropy. As a result of Zn2+ substitution, the saturation magnetization gradually increases both at room temperature and at 10K whereas coercivity decreases initially and then increases sharply reaching to a saturation at the highest zinc amount. On the other hand, as the temperature decreases both the saturation magnetization and the coercivity increase. The increase in the saturation magnetization was explained by weakened fluctuations of magnetic moments due to the low thermal energy and the increase in coercivity was due to the changing magnetic anisotropy with Zn substitution.

In this study, nanocrystalline BaCryFe12-yO19 (0.0 <= y <= 1.0) hexaferrite powders were prepared by sol-gel auto combustion method and the effect of Cr3+ ion substitution on morphology, structure, optic and magnetic properties of Barium hexaferrite were investigated. X-ray powder diffraction (XRD) analyses confirmed the purity of all samples. The XRD data shows that the average crystallite size lies between 60.95 nm and 50.10 nm and same was confirmed by Transmission electron microscopy. Transmission electron and scanning electron microscopy analyses presented the hexagonal morphology of all products. The characteristic hysteresis (sigma-H) curves proved the ferromagnetic feature of as grown nanoparticle samples. Specific saturation magnetization (sigma(s)) drops from 46.59 to 34.89 emu/g with increasing Cr content while the coercive field values lie between 770 and 1652 Oe. The large magnitude of the magnetocrystalline (intrinsic) anisotropy field, (H-a) between 11.0 and 12.6 kOe proves that all products are magnetically hard. The energy band gap values decrease from 2.0 eV to 1.84 eV with increasing Cr content. From Fe-57 Mossbauer spectroscopy, the variation in line width, isomer shift, quadrupole splitting and hyperfine magnetic field values were determined and discussed. (C) 2017 Elsevier B.V. All rights reserved.

Co1−2xNixMnxFe2−yNdyO4 (0.0 ≤ x = y ≤ 0.3) nanoparticles (NPs) were synthesized by the citrate sol–gel route. All the products were characterized using X-ray diffraction (XRD), field-emission scanning electron microscopy, high-resolution transmission electron microscopy, and a vibrating-sample magnetometer (VSM). The cubic structure of all the samples was confirmed by phase identification of XRD patterns, using Rietveld refinement. VSM analysis confirmed the soft ferromagnetic behavior of the synthesized products. The saturation (Ms) and remanent (Mr) magnetizations decreased with an increase in the amount of substitution elements. Compared with that of pure CoFe2O4 NPs, the coercive field (Hc) increased up to 890 Oe at x = y = 0.03. The squareness ratio was found to be in the 0.55–0.46 interval, indicating that the various synthesized NPs exhibit a single domain and uniaxial anisotropy. The effective magnetocrystalline anisotropy constant (Keff), magneton number \(({n_B})\), and anisotropy field (Ha) were also determined, and are discussed.

In this study, spinel ZnFe 2 O 4 nanoparticles (NPs) were synthesized by citrate sol-gel route using nickel nitrates, ferric nitrates and citric acid by annealing at 900, 1000, and 1100 ∘ C. We reported the structural and magnetic properties (including Mössbauer analysis) for anisotropy ZnFe 2 O 4 NPs annealed at different temperatures. Fourier transform infrared (FT-IR) and X-ray powder diffraction (XRD) were utilized to analyze the structural properties of magnetic nanoparticles (MNPs). Morphological features of resultant MNPs were examined by scanning electron microscopy (SEM). The observed XRD results displayed that the crystallite size increased from 38.60 to 49.28 nm with increasing the annealing temperature in a distinct linear trend. The enhancement of saturation magnetization of the uniaxial ZnFe 2 O 4 NPs was studied and varied from 1.28 to 1.66 emu/g as the annealing temperature increases. The Mössbauer spectra results show that ZnFe 2 O 4 ferrites were paramagnetic in nature at room temperature (RT).

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 (M-s) reduces with rising the Li and Al contents. Compared to pristine CuFe2O4 spinel, the remanent magnetization (M-r), coercive field (H-c) and the magneto-crystalline anisotropy fields (H-a) improved for products synthesized with x, y = 0.2 and then decrease for x, y = 0.3 and 0.4. The squareness ratio M-r/M-s 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 (K-eff ) 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.

SrBixLaxFe12-2xO19 (0.0≤x≤0.5) hexaferrites were synthesized by sol-gel auto combustion technique. The influence of Bi and La substitutions on structural, magnetic and optical properties were investigated by X-ray diffraction (XRD), Furrier transformed infrared (FT-IR), Vibrating sample magnetometer (VSM) and Percent diffuse reflectance spectroscopy (DR %). XRD analysis confirmed the single phase formation for all the samples, the purity of the products was also confirmed by FT-IR. The specific magnetization (σ-H) curves revealed the ferromagnetic nature of the samples. The extrapolated specific saturation magnetization (σs) decreases from 63.45emu/g to 49.84emu/g with increasing Bi, La substitutions. Similar decrement is observed from 32.6emu/g to 25.8emu/g at remnant magnetization (σr). The average crystallite size varies in a range of (43.28–51.40)nm. The coercive fields are between 4682 and 5315Oe. Magnetic anisotropy was assigned as uniaxial and calculated effective anisotropy constants (Keff) are between 5.57×105 Ergs/g and 4.03×105 Ergs/g. The observed high magnitudes of intrinsic coercivity (Hci) above 16,000Oe confirm hard magnetic nature of the samples. The Tauc plots were used to extrapolate the direct optical energy band gap (Eg) of hexaferrites. The Eg values decreased from 1.81 to 1.68eV with increasing Bi, La contents.

In this study, oleylamine (OAm) capped FeMnyCoyFe2−2yO4 (0.0 ≤ y ≤ 0.4) nanocomposites (NCs) were prepared via the polyol route and the impact of bimetallic Co3+ and Mn3+ ions on the structural and magnetic properties of Fe3O4 was investigated. The complete characterization of FeMnyCoyFe2−2yO4@OAm NCs were done by different techniques such as XRD, SEM, TGA, FT-IR, TEM, and VSM. XRD analyses proved the successful formation of mono-phase MnFe2O4 spinel cubic products free from any impurity. The average crystallite sizes were calculated in the range of 9.4–26.4 nm using Sherrer’s formula. Both SEM and TEM results confirmed that products are nanoparticles like structures having spherical morphology with small agglomeration. Ms continued to decrease up to Co3+ and Mn3+ content of y = 0.4. Although Mössbauer analysis reveals that the nanocomposites consist three magnetic sextets and superparamagnetic particles are also formed for Fe3O4, Co0.2Mn0.2Fe2.6O4 and Co0.4Mn0.4Fe2.2O4. Cation distributions calculation was reported that Co3+ ions prefer to replace Fe2+ ions on tetrahedral side up to all the concentration while Mn3+ ions prefer to replace Fe3+ ions on the octahedral.

In this study, bimetallic (Cu-Mn) substituted M-type Ba1-2xMnxCuxFe12O19 (0.0 ≤ x ≤ 0.1) hexaferrites were fabricated via sol-gel auto-combustion route. The effect of bimetallic substitution on structure, morphology and magnetism of BaFe12O19 was studied. Scanning Electron Microscopy confirm images reveal the nanosize of the prepared products with flake morphology. X-ray powder diffraction analysis confirmed their complete conversion to BaFe12O19 hexagonal crystal phase. The results from the magnetic investigations conducted by Vibrating Sample Magnetometer (VSM) and 57Fe Mössbauer suggested that the saturation magnetization (Ms) and the coercive field of Ba1-2xMnxCuxFe12O19 hexaferrites decrease as the concentration of Cu and Mn increases. The cation distribution calculation showed that the occupancy of Fe3+ ions is increased at 12k and 2b sites with the increase in Cu and Mn substitution.