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Herein for synthesis of Fe-doped NiCo2O4 nanospinel oxides ((NiFexCo2−xO4 (x ≤ 0.10), Fe→NiCo NSOs)) under ambient condition, method of a facile gas liquid diffusion was employed. Mossbauer spectroscopy, SEM together with EDX, XRD, TEM and VSM techniques have been used to determine the hyperfine interactions, morphology, structure, composition and magnetic characteristics of the products respectively. XRD and EDX analyses approved the absence of any secondary phase. Their crystallite is within 11–19 nm range. The products' flower like morphology was proved by SEM analysis. Magnetic features of Fe→NiCo (x ≤ 0.10) NSOs are elucidated by the examination of magnetization vs. field curves conducted at both low (10 K) and high (300 K, RT) temperatures. This analysis reveals that these nanostructures manifest paramagnetic performance at RT and transition to a ferromagnetic essence at 10 K. Magnetization shows fluctuations with growing doping content. The obtained SQR (squareness ratio) values tend toward vanishing at RT and approach zero at 10 K, indicating that even at lower temperatures, Fe→NiCo (x ≤ 0.10) NSOs do not exhibit complete alignment like single domain ferromagnets. These findings emphasize the feasibility of tailoring the specific magnetic properties of Co-Ni NSOs through the precise modulation of Fe concentration. The Mössbauer spectra composed of two doublets. [ABSTRACT FROM AUTHOR]

The Ho3+ ion-substituted SrBa nanohexaferrites, Sr0.5Ba0.5Fe12−xHoxO19 (x ≤ 0.1) (Ho → SrBa NHFs), were fabricated via ultrasonic-assisted sol–gel route. The hexagonal structure and plate-like morphology were confirmed by X-ray powder pattern (XRD), transmittance electron microscope (TEM), scanning electron microscope (SEM), and high-resolution transmittance electron microscope (HR-TEM). It has been found out that the crystallite size (DXRD) was within 45–74 nm range. Both elemental mapping and energy-dispersive X-ray spectroscopy (EDX) analyses provided the purity and expected chemical composition of the products. Using the M–H hysteresis loops (at 300 and 10 K), magnetic properties of Ho → SrBa NHFs are analyzed. Upon a sudden fall at x = 0.02, as soon as Ho ions are added, the magnetization is improved with the Ho substitution and prominently enhanced with decreasing temperature. However, the coercivity Hc is decreased with the Ho substitution. The Ho-doped samples represent a magnetically soft material at both high and low temperatures, which is also confirmed through M–T measurements. Their squareness ratio is found to be less than 0.5, suggesting the generation of multi-magnetic domains. The unsubstituted HFs and the samples with x = 0.02 and 0.06 show usual M–T variations with typical field-cooling (FC) and zero-field-cooling (ZFC) branches. However, the other samples (with x = 0.04, 0.08, and 0.10) exhibit unusual behavior with anomalies in their M–T plots. From 57Fe Mössbauer spectroscopy data, the variation in line width, isomer shift, quadrupole splitting, and hyperfine magnetic field values on Ho3+ substitution have been determined. Mössbauer spectra show that Ho3+ ions located at generally octahedral 12 k site. The s-electron density of around Fe3+ ions has not influenced doped content. [ABSTRACT FROM AUTHOR]

Ni0.8Cu0.1Zn0.1MoxFe2–2xO4 (x ≤ 0.1) nanospinel ferrites (Mo → NiCuZn NSFs) were produced by sol–gel approach. A spinel structure formation with no impurities was confirmed by X-ray diffraction (XRD) patterns. The nanoparticles' morphology and chemical composition of the products have been confirmed via SEM, TEM, HR-TEM, and EDX. By fitting Mössbauer spectra at RT, Hyperfine parameters were determined. A superparamagnetic state was observed in all samples. The Mo4+ were found to reside in the B site mainly. Isomer shift values showed that Mössbauer spectra composed magnetic Fe3+ sextets. Magnetic characteristics of Mo → NiCuZn NSFs are probed employing hysteresis loops at 300 K and 10 K. The significant role of Mo ions in the magnetic characteristics of the host material is revealed by employing saturation magnetization (Ms), magnetic moment ( n B ), coercivity (Hc), SQR (squareness ratio), and magneto-crystalline anisotropy constant. While the samples show a superparamagnetic behavior at 300 K, they represent a magnetically soft material at 10 K. The magnetic parameters, with a minimum magnetization at x = 0.06, fluctuate with respect to Mo concentration at each temperature. The Ms and nB become the maximum for the Mo → NiCuZn NSFs (x = 0.02) which yields the minimum Hc. The SQR is negligible at 300 K and low (much less than 0.5) at 10 K, reflecting the generation of multi-magnetic domains and a relatively low anisotropy field. [ABSTRACT FROM AUTHOR]

Sr0.8Ni0.2Fe12−2xMoxO19 (x ≤ 0.35) nanohexaferrites (NHFs) were obtained by a sol–gel combustion route. The phase identification was performed through X-ray powder diffraction (XRD), transmission electron microscopy (TEM), and high-resolution transmission electron microscopy (HR-TEM). The morphological and chemical composition analyses were verified by scanning electron microscope (SEM) and energy dispersive X-rays (EDX), respectively. The crystallite size (DXRD) of all produced samples has been estimated between 31 and 56 nm. Magnetization versus applied magnetic field (M–H) measurements of different products were conducted at 300 K (room temperature, RT) and 10 K, and the results revealed their ferrimagnetic character. Undoped Sr0.8Ni0.2Fe12O19 NHFs have the maximum magnetic parameters at both temperatures. 10 K magnetization data such as MS (saturation magnetization), Mr (remnant magnetization), nB (magneton number), and HC (coercivity) belonging to Sr0.8Ni0.2Fe12O19 NHFs are MS,max = 99.6 emu/g, Mr,max = 48.2 emu/g, nB,max = 18.83 μB, and HC,max = 3406 Oe, respectively. Moreover, the squareness ratio (SQR = Mr/MS) is 0.489 at RT and 0.484 at 10 K. Those magnitudes assign the single-domain structure with uniaxial crystal anisotropy for this hexagonal product at both temperatures. Some magnetic parameters like coercivities (in a range of (286–475) Oe) and Mr (in a range of (7.8–14.1) emu/g) drop sharply due to the Mo6+ doping process. Calculated SQR values are between 0.111 and 0.206, which indicate the multi-domain wall structure for NHFs at both temperatures. Undoped Sr0.8Ni0.2Fe12O19 NHFs can be classified as magnetically hard materials, while Mo-doped samples can be classified as soft magnetic materials. [ABSTRACT FROM AUTHOR]

This study focused on the impact of Ga–Gd co-substitution on the structural, magnetic features and hyperfine interactions of nanosized NiCuZn spinel ferrites [Ni0.4Cu0.4Zn0.2GaxGdxFe2-2xO4 (x ≤ 0.04) NSFs] synthesized via sonochemical approach using ultrasonic irradiation. X-ray powder pattern (XRD) analyses confirmed cubic spinel structures of products. Crystallites and particle sizes of all samples are found to be between 9–14 nm and 18–22 nm, respectively. The NSF morphology and chemical composition were investigated by transmission and scanning electron microscope (TEM and SEM) along with energy-dispersive X-ray (EDX). The cation distribution of all ions was evaluated by Mossbauer spectroscopy. The high spin Fe3+ ions determined the isomer shift (I.S.) values. For lower rare-earth dopant ratios, we found that Gd3+ ions occupy B sites, while Ga3+ ions reside in A sites, and thereafter, some Ga3+ ions start to enter B sites. Magnetometry measurements were used to evaluate the effect of magnetic field (H) and temperature (T) on the magnetization of products. For each sample, both coercivity (Hc) and saturation magnetization (Ms) increase when the T decreases below ambient temperature. All substituted samples display Ms values higher than those of non-substituted ones; however, Hc values diminish for x content up to 0.02 and thereafter enlarge. Different magnetization measurements revealed superparamagnetic-to-ferromagnetic transition below the blocking temperature ( T B ). [ABSTRACT FROM AUTHOR]

Nowadays, CoFe2O4 (cobalt ferrite) nanoparticles have fascinated numerous researcher's consideration because of their latent implementation in water treatment. CoFe2O4 nanoparticles are cost-efficient magnetic materials and are stable under diverse environments. Therefore, they are effortlessly removed from purified water by means of an external magnetic field and reclaimed for quite a lot of cycles. In this analysis, the focus was given on learning the influences of some aspects including calcination temperature, crystalline size, pH, synthesis method, and dopant type on the magnetic properties of CoFe2O4 nanocomposites and nanoparticles. The implementation of CoFe2O4 nanoparticles in water purification and its capability to be united with various nanoparticles for adsorption and photocatalysis were entirely conferred. The chance of retrieval and reprocess of CoFe2O4 nanoparticles and its nanocomposites were discussed. Finally, the holes which are still not built up for study in the modification of physical properties and further magnetic properties of CoFe2O4 nanoparticles for its complete usage in water treatment were delineated. Henceforth, using CoFe2O4 nanoparticles and its nanocomposites at trade scale for water treatment will definitely reduce the expenses of water as it uses visible light as the energy source and because of its capability to be recycled numerous times. [ABSTRACT FROM AUTHOR]

The magnetic and exchange-coupling properties of SrTb0.01Tm0.01Fe11.98O19/(CoFe2O4)x (x = 1.0, 1.5, 2.0, 2.5, and 3.0) hard/soft nanocomposites produced via a one-pot sol–gel combustion route were investigated in detail. Their structures and morphologies were explored by X-ray powder diffraction (XRD), scanning electron microscopy (SEM), transmission electron microscopy (TEM), and high-resolution transmission electron microscopy (HR-TEM). The XRD results showed integration between hexaferrite and spinel ferrite phases. The SEM images exhibited hexagonal plate-shaped particles decorated with cubic particles relevant to SrTb0.01Tm0.01Fe11.98O19 and CoFe2O4, respectively. The magnetic properties of the prepared nanocomposite ferrites were also investigated. Smooth M–H hysteresis loops with no "bee waist" established that the hard/soft SrTb0.01Tm0.01Fe11.98O19/CoFe2O4 phases were efficiently exchange-coupled. A drastic increase in saturation magnetization (Ms), remanence (Mr) and coercivity (Hc) was noticed on increasing the content of the soft phase (x). (BH)max (maximum energy product) showed maximum values of 19.9 and 87.2 kJ m−3 for the nanocomposite with x = 3.0 at 300 and 10 K, respectively. The exchange coupling among the soft and hard ferrite grains was proven by the switching field distribution (SDF) plots. Excellent exchange-coupling behavior was noticed for the nanocomposite with x = 3.0. The prepared hard/soft ferrite nanocomposites have been found to be promising candidate nanomaterials for permanent nanomagnets. [ABSTRACT FROM AUTHOR]

This paper emphasizes the structure, morphology, optical, and magnetic properties of sonochemically prepared terbium-substituted cobalt ferrite nanoparticles, CoTb x Fe 2-x O 4 (0.00 ≤ x ≤ 0.10). The formation of cubic spinel nanosized ferrite structure was confirmed by X-ray diffraction (XRD), Field-emission scanning electron microscopy (FE-SEM), and Fourier-transform infrared (FT-IR) spectroscopy. The crystallites sizes were found in the range of 11–14 nm. Ultraviolet–visible percentage diffuse reflectance investigations were performed on pristine and Tb3+-doped cobalt spinel ferrite CoFe 2 O 4 nanoparticles. The direct energy band gap (E g) values were determined by applying the Kubelka–Munk theory and Tauc plots were found to be in a narrow band range of 1.37–1.44 eV. Analyses of magnetization versus the magnetic field (M(H)) were performed. The magnetic parameters, including the saturation magnetization (M s), squareness ratio (SQR = M r /M s), magnetic moment ( n B ), remanence (M r), and coercivity (H c) were evaluated. The M(H) curves exhibited a soft ferrimagnetic nature. It was demonstrated that the Tb3+ substitutions strongly influenced the magnetization data. Indeed, the M s , M r , H c , and n B values decreased with increasing Tb3+ substitution. [ABSTRACT FROM AUTHOR]

This investigation deals with CoFe2-xNdxO4 (x ≤ 0.2) nanoparticles (NPs) fabricated by sonochemically. The purity of all products was verified via X-ray powder diffraction. The crystallite size of the samples was calculated as less 12 nm. The spectral analyses also confirmed the presence of spinel ferrites. Both morphology and chemical purity of the spinel ferrite systems were confirmed by SEM, EDX, and elemental mapping analyses. The analyses of magnetization versus applied magnetic field, M(H), were performed. The following magnetic parameters like saturation magnetization Ms, squareness ratio (SQR = Mr / Ms), magnetic moment nB, coercivity Hc, and remanence Mr have been evaluated. The M(H) curves revealed the soft ferromagnetic nature for all CoFe2-xNdxO4 NPs. It is showed that the Nd3+ substitutions significantly affect the magnetization data. A decreasing trend in the Hc, Ms, nB, and Mr values was detected with Nd3+ substitution. [ABSTRACT FROM AUTHOR]

We report a comprehensive evaluation of the microstructures, magnetic, and hyperfine traits of Ca2+/Mg2+ co-substituted strontium nanohexaferrites (SHFs) of chemical compositions Sr1–2xCaxMgxFe12O19 (x ≤ 0.1). These SHFs were prepared using sol–gel unified auto-combustion strategy and characterized by diverse analytical measurements to determine the effects of Ca2+/Mg2+ co-substitution on the aforesaid properties. XRD and high resolution transmission electron microscpe (HRTEM) analyses confirmed the nucleation of HF nanocrystallites. UV-visible diffuse reflectance (DR–UV–Vis) spectra were used to evaluate the optical band gap of the proposed SHFs, which was reduced with the increase in co-substitution contents. The 57Fe Mössbauer spectra was exploited to assess the quadrupole splitting, spectral line-width variation, isomer shift, distribution of cations (Ca2+ and Mg2+), and hyperfine magnetic fields. Measured magnetic parameters such as saturation magnetization, remanence, squareness ratio (SQR), coercivity, and magnetic moment were significantly improved due to the Ca2+/Mg2+ co-substitution. All the prepared SHFs revealed ferrimagnetic nature both at 10 and 300 K. Achieved SQR values ≈0.5 of the studied SHFs clearly disclosed their single domain character possessing uniaxial anisotropy. Highlights: Sr1–2xCaxMgxFe12O19 (x ≤ 0.1) SHFs via sol–gel auto-combustion method. Sr1–2xCaxMgxFe12O19 (x ≤ 0.1) SHFs exhibit hexagonal platelet-like structure. Mössbauer results of these SHFs showed a continuous decay in the hyperfine magnetic field up to x = 0.08 before being escalated beyond this concentration. Sr1–2xCaxMgxFe12O19 (x ≤ 0.1) SHFs exhibit ferrimagnetic nature both at 10 and 300 K. [ABSTRACT FROM AUTHOR]

The crystal structure and magnetic properties of SrNbxFe12–xO19 (0.00 ≤ x ≤ 0.08) nanohexaferrites (NHFs) fabricated using a sol–gel technique is presented in this study. The X-ray powder diffractometry (XRD) and Infrared spectroscopy (FT-IR) confirmed the formation of M-type hexaferrite phase. The analyses of magnetization versus applied magnetic field, M(H), were performed at room (300 K; RT) and low (10 K) temperatures. The Bohr magneton number (nB), saturation (Ms) and remanent (Mr) magnetization values increase slightly with increasing Nb3+ content. The room-temperature values of the magnetic parameters Mr = 31.41–33.28 emu/g, Ms = 57.10–60.14 emu/g and coercivity (Hc) between 4274 and 4540 Oe, at 10 K, magnetization data were detected that are much higher with respect to RT values: Mr = 45.96–51.06 emu/g, Ms = 94.42–95.99 emu/g. The magnetic results indicate that the samples are magnetically hard materials at both considered temperatures. The squareness ratio (SQR) is found to be around 0.50, implying single-domain NPs with uniaxial anisotropy for pristine and substituted samples. With exception, the x = 0.0 sample indicated the formation of multi-domain structure with uniaxial anisotropy at 10 K. Field cooling (FC) susceptibility measurements were applied in temperature range of 5–350 K for pristine sample and samples that contained some Nb3+ ions. The analyses of dc susceptibility data also proved that Nb3+ ion substitution increases the magnetization and, additionally, allows for an easier alignment of the magnetic domains. The obtained magnetic results were investigated deeply with relation to structural and microstructural properties. The observed remanent magnetization (Mr) and coercivity (Hc) render the products are useful for permanent magnets and high-density recording media. [ABSTRACT FROM AUTHOR]

Nanohexaferrites of BaVxFe12−xO19 (0.0 ≤ x ≤ 0.1) were prepared using sol–gel auto-combustion. The structure and morphology of BaVxFe12−xO19 (0.0 ≤ x ≤ 0.1) nano-sized hexaferrites were explored by X-ray diffraction (XRD), scanning electron microscopy (SEM) coupled with EDXS. XRD analysis indicated particle size in the 55–60-nm interval. SEM and EDXS investigations confirmed the formation of the desired composition of V-substituted Ba-hexaferrites. The magnetic properties of products were studied. The magnetic M(H) hysteresis loops revealed that all produced nanohexaferrites display ferromagnetic-like comportment. The deduced saturation magnetization (Ms), retentivity (Mr), magneto-crystalline anisotropy fields (Ha), and coercive field (Hc) were enhanced for low V3+ contents and were maximum for BaV0.04Fe11.96O19 (x = 0.04) nanohexaferrites, showing the strengthening of magnetic properties. [ABSTRACT FROM AUTHOR]

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. [ABSTRACT FROM AUTHOR]

In this study, spinel ZnFe2O4 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 ZnFe2O4 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 ZnFe2O4 NPs was studied and varied from 1.28 to 1.66 emu/g as the annealing temperature increases. The Mössbauer spectra results show that ZnFe2O4 ferrites were paramagnetic in nature at room temperature (RT). [ABSTRACT FROM AUTHOR]

A mixed spinel ferrite nanoparticle, Mg1−xZnxFe2−xAlxO4 NPs (0.0 ≤ x ≤ 0.8), were synthesized effectively by co-precipitation method and sintered at 600 °C for 10 h. The structural and magnetic properties of the products were studied through X-ray powder diffraction (XRD), scanning electron microscopy, transmission electron microscopy (TEM), high resolution transmission electron microscopy (HRTEM) and vibrating sample magnetometer. The cubic spinel phase was confirmed by XRDs with particle size between 24.5 and 40.2 nm. The lattice parameters for the products are increased with increasing the Zn2+ and Al3+ ratio due to the successfully integrated into the cubic system without changing the original structure. Although it was observed from the cation distributions, that the cubic phase is was an inverse spinel, wherein which the Fe3+ and Mg2+ ions occupied both the tetrahedral A and octahedral B- sites, the Zn2+ ions preferred to occupy the A- sites and Al3+ occupy preferred the B -sites. The morphology of the nanoparticles NPs detailed was using TEM, HR-TEM, and SAED in selected area confirmed the particle size and crystalline spinel structure. Magnetization results at room temperature presents a narrow hysteresis loop for all ratios, which is specific of the soft magnetic materials. Also, we noticed that the increase in the magnetization with increasing the ratio of Zn2+ and Al3+ consistent with the enhancement of crystallinity. Moreover, we found that the saturation magnetization, coercively and remanent for Mg1−xZnxFe2−xAlxO4 where x = 0.6 sample is the highest, indicating the potential of Zn and Al substitution in enhancing the magnetic properties of magnesium ferrite. According to AC magnetic susceptibility measurements, the nanoparticles exhibit superparamagnetic/spin glassy behaviour with a very strong inter-nanoparticles interaction. Additionally, AC susceptibility measurements indicated a relative sensitivity of samples to the variation of applied frequency, which is an important result for the applications in hyperthermia based therapy. This is the first study in which both Zn2+ and Al3+ ions with varying concentration were tried to substitute into MgFe2O4 simultaneously and their effects on magnetic properties of MgFe2O4 was investigated. [ABSTRACT FROM AUTHOR]