Influence of Controlled Dipolar Interaction for Polymer-Coated Gd-Doped Magnetite Nanoparticles toward Magnetic Hyperthermia Application

To maximize heat release from immobilized nanoparticles (NPs), a detailed understanding of the controlled dipolar interaction is essential for challenging magnetic hyperthermia (MH) therapies. To design optimal MH experiments, it is necessary to precisely determine magnetic states impacted by the inevitable concurrence of magnetic interactions under a common experimental form. In this work, we describe how the presence of dipolar interaction significantly alters the heating mechanism of host materials when NPs are embedded in them for MH applications. The concentration of the NPs and the intensity of their interaction can profoundly impact the amplitude and shape of the heating curves of the host material. The heating capability of interacting NPs might be enhanced or diminished, depending on their concentration within the host material. We propose chitosan- and dextran-coated Gd-doped Fe3O4 NPs directing dipole interactions effective for the linear regime to enlighten the pragmatic trends. The outcomes of our study may have substantial implications for cancer therapy and could inspire novel approaches for maximizing the effectiveness of MH.

Unraveling the Complex Interplay of Phase Transitions in Spinel Ferrites: A Comprehensive Quantum Mechanical Vibrational Study of ZnFe2O4

The rich phase transition landscape of spinel ferrites and its profound impact on their physical properties have garnered significant interest in recent years. The complex interplay of divalent and trivalent cations distributed across A- and B-sites gives rise to a captivating variety of interactions. In this study, we delve into the structural, electronic, magnetic, and vibrational properties of ZnFe2O4 as a function of the degree of inversion, employing first-principles density functional theory with global and range-separated hybrid functionals and a local basis set. The ground state of ZnFe2O4 is an open-shell system, characterized by Zn atoms occupying tetrahedral sites, Fe atoms residing in octahedral sites, and Fe atom spins exhibiting ligand parallel alignment. In the normal structure, the antiparallel arrangement is less stable than the ferro arrangement by 0.058 eV (673 K) for fully relaxed structures, decreasing to 0.034 eV (395 K) upon incorporating a zero-point vibrations contribution. For normal ferromagnetic ZnFe2O4, we calculated scattering for A1g, Eg, and 3T2g symmetry at 676.6, 367.1, and (189.7, 457.7, 602.3) cm-1, respectively. Additionally, four T1u vibrational frequencies predicted by group theory were obtained at 524.59, 358.48, 312.49, and 192.9 cm-1, demonstrating excellent agreement with the experimental studies. We also explored the influence of spin rearrangement and inversion (X = 0.5 and 1) on Raman and infrared spectra. By analyzing the infrared spectra of isotopic substitutions, we reevaluated the assignments of the four T1u modes in light of available experimental data. Notably, the sensitivity of peak positions and intensities for some Raman modes, particularly A1g and T2g(2), to spin arrangement could provide a convenient experimental tool for detecting phase transitions induced by changes in temperature or external electric fields. This investigation shines a light on the complex interplay of phase transitions in spinel ferrites, paving the way for a deeper understanding of their properties and potential applications.

Gadolinium doped zinc ferrite nanoarchitecture reinforced with a carbonaceous matrix: a novel hybrid material for next-generation flexible capacitors

Herein, nanostructured Gd-doped ZnFe2O4 (GZFO) has been synthesized via the sol-gel route and its CNT-reinforced nanohybrid was formed via an advanced ultrasonication method. The as-synthesized, hybrid electroactive materials have been supported on aluminum foil (AF) to design a flexible electrode for hybrid capacitor (HC) applications. Nanostructured material synthesis, Gd-doping, and CNT reinforcement approaches have been adopted to develop a rationally designed electrode with a high surface area, boosted electrical conductivity, and enhanced specific capacitance. Electrochemical impedance spectroscopy, galvanostatic charge/discharge, and cyclic voltammetry processes have been used to measure the electrochemical performance of the prepared ferrite material-based working electrodes in a 3M KOH solution. A nanohybrid-based working electrode (GZFO/C@AF) shows superior rate capacitive and electrochemical aptitude (specific capacitance, rate performance, and cyclic activity) than its counterpart working electrodes (ZFO@AF and GZFO@AF). The hybrid working electrode (GZFO/C@AF electrode) shows a high specific capacitance of 887 F g-1 and good retention of 94.5% for 7000 cycles (at 15 Ag-1). The maximum energy density and power density values for the GZFO/C@AF electrode are 40.025 Wh Kg-1 and 279.78 W Kg-1, respectively. Based on the findings of the electrochemical experiments, GZFO/C@AF shows promise as an electrode material for hybrid capacitors that provide energy to wearable electronic devices.

Sustainable application of nanoparticles in wastewater treatment: Fate, current trend & paradigm shift

Existing water and wastewater treatment techniques are becoming increasingly difficult to employ due to the discovery of new toxins, the rapid development of population and industrial activities, and the limited quantity of water resources. Treatment of wastewater is a critical need in modern civilization due to a scarcity of water resources and rising industrial activity. Some of the techniques utilized include adsorption, flocculation, filtration, and others, although they are only used for primary wastewater treatment. However, the development and deployment of modern wastewater management with high efficiency and low capitalization are critical in terms of mitigating the environmental consequences of waste. The employment of different nanomaterials in the treatment of wastewater has opened up a world of possibilities for heavy metal and pesticide removal, as well as the treatment of microbes and organic contaminants in wastewater. Nanotechnology is a rapidly evolving technology because of certain nanoparticle's outstanding physiochemical and biological capabilities as contrasted to bulk counterparts. Secondly, it has been established that this is a cost-effective treatment strategy with significant potential in wastewater management, transcending the limitations imposed by currently existing technology. Advances in nanotechnology to reduce water contamination have been presented in this review, including the use of various nanomaterials such as nanocatalysts, nanoadsorbents, and nanomembranes in the treatment of wastewater containing organic contaminants, hazardous metals, and virulent pathogens.

Influence of Y3+ and La3+ ions on the structural, magnetic, electrical, and optical properties of cobalt ferrite nanoparticles

In the current study, nanocrystalline CoY_0.5xLa_0.5xFe_2-xO₄ (where x = 0.00, 0.02, 0.04, 0.06, 0.08, and 0.10) ferrites have been synthesized via a sol-gel auto combustion process. The synthesized powders were pressed into pellet forms and sintered at 900 °C for 4 h in the air. X-ray diffractometry (XRD) confirmed the single-phase cubic spinel structure of the synthesized samples having the mean crystallite domain sizes ranging from 122 and 54 nm. FTIR spectroscopic analyses revealed two strong bands within the range of 600 to 350 cm^-1, further confirming the cubic inverse spinel structure of the prepared materials. The surface morphologies and composition were investigated by Field Emission Scanning Electron Microscopy (FE-SEM) and Energy Dispersive X-ray (EDX) Spectroscopy. The magnetic hysteresis curves recorded at room temperature exhibit ferrimagnetic behavior. The highest coercivity (Hc∼1276 Oe) was found at a high doping (x = 0.10) concentration of Y³⁺ and La³⁺ in cobalt ferrite. Dielectric constant increase with increased doping concentration whereas real-impedance and dielectric loss decrease with increased in doping concentration and applied frequency. The band gap energy increased from 1.48 to 1.53 eV with increasing Y³⁺ and La³⁺concentrations in the UV-Vis region. The elevated levels of magnetic and dielectric substances in the ferrite nanoparticles suggest that the material could be used for magnetic recording media and high-frequency devices.

Effects of Rhenium Substitution of Co and Fe in Spinel CoFe2O4 Ferrite Nanomaterials

In this work, nanoparticles of Co_1-xRe_xFe₂O₄ and CoFe_2-xRe_xO₄ (0 ≤ x ≤ 0.05) were synthesized by the sol-gel method. The Rietveld refinement analysis of XRD and Raman data revealed that all of the prepared samples were single phase with a cubic spinel-type structure. With the substitution of Re, the lattice parameters were slightly increased, and Raman spectra peak positions corresponding to the movement of the tetrahedral sublattice shifted to a higher energy position. Furthermore, Raman spectra showed the splitting of T_2g mode into branches, indicating the presence of different cations at crystallographic A- and B-sites. The SEM micrograph confirms that surface Re exchange changes the coordination environment of metals and induces Fe-site structure distortion, thereby revealing more active sites for reactions and indicating the bulk sample's porous and agglomerated morphology. The vibrating sample magnetometer (VSM) results demonstrated that the synthesized nanoparticles of all samples were ferromagnetic across the entire temperature range of 300-4 K. The estimated magnetic parameters, such as the saturation magnetization, remanent magnetization, coercivity, blocking temperature (T_B), and magnetic anisotropy, were found to reduce for the Co-site doping with the increasing doping ratio of Re, while in the Fe site, they enhanced with the increasing doping ratio. The ZFC-FC magnetization curve revealed the presence of spin-glass-like behavior due to the strong dipole-dipole interactions in these ferrite nanoparticles over the whole temperature range. Finally, the dielectric constant (ε_r') and dielectric loss (tanδ) were sharply enhanced at low frequencies, while the AC conductivity increased at high frequencies. The sharp increases at high temperatures are explained by enhancing the barrier for charge mobility at grain boundaries, suggesting that samples were highly resistive. Interestingly, these parameters (ε_r', tanδ) were found to be higher for the Fe-site doping with the increasing Re doping ratio compared with the Co site.

Effect of praseodymium in cation distribution, and temperature-dependent magnetic response of cobalt spinel ferrite nanoparticles

This work reports cation distribution, magnetic, structural, and morphological studies of rare-earth Pr doped cobalt ferrite nanoparticles CoFe_2-xPr_xO₄(x= 0, 0.02, 0.04, 0.06 at%) fabricated by sol-gel auto-combustion method. X-ray diffraction analysis, field emission scanning electron microscopy (FESEM), high resolution transmission electron microscopy (HRTEM), selected area electron diffraction (SAED), and Fourier-transform infrared (FTIR) microscopy were utilized to study the structural and morphological characteristics of the prepared samples. Rietveld refinement by the Material Analyses Using Diffraction (MAUD) software showed the formation of mono-phase cubic spinel structure with Fd-3m space group; however, there was a trace of impure PrFeO₃phase for the sample CoFe_1.96Pr_0.04O₄(x= 0.06). Cation distribution was inferred from the XRD patterns using MAUD program. FESEM analysis revealed the spherical-shaped particles with dimensions close to the data extracted from XRD analysis and HRTEM images confirmed it. FTIR measurements revealed the presence of two prominent stretching vibrational modes confirming the successful formation of ferrite spinel structure. Magnetic properties of the nanoparticles were measured at two different temperatures 300 K and 10 K. For the low temperature of 10 K a high sensitive measurement method as Superconducting Quantum Interference Device (SQUID) magnetometry was used and Vibrating Sample Magnetometer (VSM) recorded the magnetic data at 300 K. Comparison of the magnetic results exhibited a significant enhancement with temperature drop due to the reduction in thermal fluctuations. Paramagnetic nature of rare-earth ions may be the main reason forM_Sdecrement from 76 emu g^-1(x= 0.0) to 60 emu g^-1(x= 0.02) at 300 K. At 10 K, the estimated cation distribution played a vital role in justification of obtained magnetic results. All the obtained data showed that the synthesized magnetic nanoparticles can be implemented in permanent magnet industry and information storage fields, especially when it comes to lower temperatures.

Soft Chemistry Synthesis and Characterization of CoFe1.8RE0.2O4 (RE3+ = Tb3+, Er3+) Ferrite

Nanosized CoFe1.8RE0.2O4 (RE3+ = Tb3+, Er3+) ferrites were obtained through wet ferritization method. These ferrites were characterized by X-ray diffraction (XRD), scanning electron microscopy (FE-SEM), transmission electron microscopy (TEM/HR-TEM), Fourier transform infrared spectroscopy (FTIR), Mössbauer spectroscopy and magnetic measurements. The XRD results revealed that the average crystallite size is 5.77 nm for CoFe1.8Tb0.2O4 and 6.42 nm for CoFe1.8Er0.2O4. Distribution of metal cations in the spinel structure estimated from X-ray diffraction data showed that the Tb3+ and Er3+ ions occupy the octahedral sites. TEM images indicated the presence of polyhedral particles with average size 5.91 nm for CoFe1.8Tb0.2O4 and 6.80 nm for CoFe1.8Er0.2O4. Room temperature Mössbauer spectra exhibit typical nanoscaled cobalt ferrite spectra in good agreement with XRD and TEM data. The saturation magnetization value (Ms) is 60 emu/g for CoFe1.8Tb0.2O4 and 80 emu/g for CoFe1.8Er0.2O4. CoFe1.8RE0.2O4 nanoparticles showed similar antimicrobial efficacy against the five tested microbial strains, both in planktonic and biofilm state. The results highlight the promising potential of these types of nanoparticles for the development of novel anti-biofilm agents and materials.

Structural and magnetic properties of CoFe2O4ferrite nanoparticles doped by gadolinium

This work's main purpose is to investigate the effect of Gd³⁺substitution on the structural, cation distribution, morphological, and magnetic characteristics of cobalt ferrite nanostructures. The nanostructures were synthesized through the sol-gel auto combustion technique. X-ray diffraction (XRD) analysis with the Rietveld refinement through the Material Analysis Using Diffraction (MAUD) program confirmed a single-phase spinel structure for lower contents of Gd³⁺. However, for higher concentrations, a trace of second phase GdFeO₃was evident. The crystallite size reduction from 17 to 11 nm with Gd³⁺doping confirmed the formation of nanocrystalline Co-Gd ferrite. Cation distribution was another parameter inferred from the experimental data of XRD analyzed by the MAUD program. Fourier-transform infrared spectra confirmed the formation of spinel structure through two prominent vibrational modes observed at the desired wavelength range. FESEM analysis confirmed the data obtained from the XRD about the structure and morphology of the nano samples. Saturation magnetization (M_S) of the nano samples evaluated at 10 K showed a decreasing behavior from 94 to 86 emu g^-1by Gd³⁺doping, while a fluctuating trend ofM_Swas observed at room temperature. Coercive field (H_C) evaluated at 10 K reached a maximum value of about 1145 kA m^-1for the sample CoFe_1.96Gd_0.04O₄, and then it decreased. At the same time,H_Cexperienced no considerable change at 300 K. The possible concepts attributed to such a trend ofH_Cwere also investigated. Overall, the significant impact of Gd³⁺doping on the cobalt ferrite nanoparticles causes Gd-Co ferrite to have a desirable capacity of permanent magnet materials and storage of information with high density. As a result, this ferrite may be a proper candidate to be utilized, especially at lower temperatures.

Influence of Ce3+ Substitution on Antimicrobial and Antibiofilm Properties of ZnCexFe2-xO4 Nanoparticles (X = 0.0, 0.02, 0.04, 0.06, and 0.08) Conjugated with Ebselen and Its Role Subsidised with γ-Radiation in Mitigating Human TNBC and Colorectal Adenocarcinoma Proliferation In Vitro

Cancers are a major challenge to health worldwide. Spinel ferrites have attracted attention due to their broad theranostic applications. This study aimed at investigating the antimicrobial, antibiofilm, and anticancer activities of ebselen (Eb) and cerium-nanoparticles (Ce-NPs) in the form of ZnCexFe2-XO4 on human breast and colon cancer cell lines. Bioassays of the cytotoxic concentrations of Eb and ZnCexFe2-XO4, oxidative stress and inflammatory milieu, autophagy, apoptosis, related signalling effectors, the distribution of cells through the cell-cycle phases, and the percentage of cells with apoptosis were evaluated in cancer cell lines. Additionally, the antimicrobial and antibiofilm potential have been investigated against different pathogenic microbes. The ZOI, and MIC results indicated that ZnCexFe2-XO4; X = 0.06 specimen reduced the activity of a wide range of bacteria and unicellular fungi at low concentration including P. aeruginosa (9.5 mm; 6.250 µg/mL), S. aureus (13.2 mm; 0.390 µg/mL), and Candida albicans (13.5 mm; 0.195 µg/mL). Reaction mechanism determination indicated that after ZnCexFe2-xO4; X = 0.06 treatment, morphological differences in S.aureus were apparent with complete lysis of bacterial cells, a concomitant decrease in the viable number, and the growth of biofilm was inhibited. The combination of Eb with ZFO or ZnCexFe2-XO4 with γ-radiation exposure showed marked anti-proliferative efficacy in both cell lines, through modulating the oxidant/antioxidant machinery imbalance, restoring the fine-tuning of redox status, and promoting an anti-inflammatory milieu to prevent cancer progression, which may be a valuable therapeutic approach to cancer therapy and as a promising antimicrobial agent to reduce the pathogenic potential of the invading microbes.

Antibacterial and antibiofilm activities of silver-decorated zinc ferrite nanoparticles synthesized by a gamma irradiation-coupled sol-gel method against some pathogenic bacteria from medical operating room surfaces

This work aimed at the gamma irradiation-assisted synthesis of silver (Ag)-decorated ZnFe2O4 (ZFO) ferrite nanoparticles (NPs), which were tested for their antibacterial and antibiofilm activities against some pathogenic bacteria from medical operating room surfaces. The prepared Ag-decorated ZFO NPs were characterized via XRD, SEM, EDX, elemental mapping, and FTIR analysis. The antibacterial potential was tested as ZOI and MIC, while antibiofilm activity was estimated by the tube method. The growth curve assay, the effect of UV on the antimicrobial activity, and cell membrane leakage were evaluated, and the antibacterial reaction mechanism was investigated by SEM/EDX analysis. The XRD and FTIR results confirmed the successful preparation of Ag-decorated ZFO NPs. Antibacterial results revealed that the most potent decorated sample was Ag0.75@ZFO NPs, recording the most significant inhibition zone against Staphylococcus vitulinus (24.67 ± 0.577 mm) and low MIC (0.097 μg mL-1) against S. vitulinus. The antibiofilm activity of Ag0.75@ZFO NPs was the highest, recorded as 97.3% for S. aureus and 95.25% for Enterococcus columbae. In the case of UV exposure, bacterial growth reached the lowest grade. Finally, it was seen that the amount of cellular protein released from bacterial cells is directly proportional to the concentration of Ag0.75@ZFO NPs, which clearly explains the formation of pits in the cell membrane. The synthesized nanocomposites may find an application after mixing with operating room paints to reduce the harmful effect of pathogenic microbes and, therefore, eliminate bacterial contamination.

Influence of neodymium substitution on structural, magnetic and spectroscopic properties of Ni-Zn-Al nano-ferrites

Ni0.6Zn0.4Al0.5Fe1.5-x Nd x O4 ferrite samples, with x = 0.00, 0.05, 0.075 and 0.1, were synthesized using the sol-gel method. The effects of Nd3+ doping on the structural, magnetic and spectroscopic properties were investigated. XRD Rietveld refinement carried out using the FULLPROF program shows that the Ni-Zn ferrite retains its pure single phase cubic structure with Fd3̄m space group. An increase in lattice constant and porosity happens with increasing Nd3+ concentration. FTIR spectra present the two prominent absorption bands in the range of 400 to 600 cm-1 which are the fingerprint region of all ferrites. The change in Raman modes in the synthesized ferrite system were observed with Nd3+ substitution. The magnetization curves show a typical transition, at the Curie temperature T C, from a low temperature ferrimagnetic state to a high temperature paramagnetic state. The saturation magnetization, coercivity and remanence magnetization are found to be decreasing with increasing the Nd3+ concentration.

Adsorption and photocatalytic activity of biosynthesised ZnO nanoparticles using Aloe Vera leaf extract

In this article, we demonstrates the growth of phase pure ZnO nanostructures from Aloe-Vera leaf extract and degradation of an organic dye-Malachite Green (MG)- from aqueous medium using the same as catalyst. Adsorption mechanisms were evaluated using Lagergren’s pseudo-first-order, pseudo-second-order and intraparticle diffusion kinetic models. X-Ray diffraction data showed that the synthesised ZnO is crystalline with hexagonal wurtzite phase. Average crystallite size and lattice strain was estimated from Scherrer equation and Williamson-Hall analysis with the help of Rietveld refinement data. Crystallite size obtained from Scherrer method is 12.62 nm while that from Williamson-Hall analysis is 19.27 nm. Uniform growth of ZnO nano-sheets were confirmed by FE-SEM analysis. Optical characterisation was carried by UV-Visible spectroscopy and the band gap ZnO nanoparticles was found to be 3.19 eV. Zn-O stretching vibrations were recorded at 550 cm−1 using FTIR spectrophotometer. Results showed that biosynthesised ZnO nanosheets are particularly effective for the degradation of MG dye.

Ni0.4Cu0.2Zn0.4TbxFe2-xO4 nanospinel ferrites: Ultrasonic synthesis and physical properties

The Fe³⁺ ions were replace with Tb³⁺ ions as highly paramagnetic rare earth element within the structure of Ni_0.4Cu_0.2Zn_0.4Fe₂O₄ nano-spinel ferrites (NSFs). The structural, magnetic, spectroscopic and optic properties have been studied in details. All products have been synthesized via ultrasonic approach via Qsonica ultrasonic homogenizer, frequency: 20 kHz and power: 70 W for 60 min. No annealing or calcination process was applied for any product. The microstructural analysis of products has been done via X-ray powder diffractometry (XRD) which presented the cubic spinel structure with nanosized distribution of all. The cubic morphology of all products were confirmed by both HR-TEM and FE-SEM. Optical band gap (E_g) values were assessed by applying %DR (percent diffuse reflectance) analysis and Kubelka-Munk theory. The Tauc schemes showed that E_g values are in a narrow range (1.87-1.98 eV). The quadrupole splitting, line width, hyperfine magnetic field, isomer shift values and cation distribution have been determined from ⁵⁷Fe Mossbauer analysis. The magnetic properties of various nanoparticles have been obtained from VSM (vibration sample magnetometer) measurements at 10 and 300 K (RT). The magnetic results revealed superparamagnetic and soft ferromagnetic traits at 10 and 300 K, respectively. M_s (saturation magnetization) and M_r (remanence) initially increase with increasing Tb³⁺ substituting level up to x = 0.06 then diminish for further x values. H_c (coercivity) shows an opposite variation tendency of M_s and M_r. The observed magnetic traits are deeply discussed in relation with the structure, morphology, magnetic moments and cation distributions.

Structural, optical and magnetic properties of Tm3+ substituted cobalt spinel ferrites synthesized via sonochemical approach

Co-Tm nano-spinel ferrite with chemical formula CoTm_xFe_2-xO₄ (0.0 ≤ x ≤ 0.08) NPs were prepared via sonochemical approach. X-ray powder diffraction patterns, microscopic images (SEM and TEM) and infrared spectra proved the formation of Co spinel ferrite. The effect of Tm³⁺ substituted on spinal structure was evaluated by lattice parameters, tetrahedral and octahedral bond length and cationic distribution. The band gap energy (Eg) of samples were estimated by performing UV-Vis percent diffuse reflectance (% DR) and applying the Kubelka-Munk theory. Eg values are in an interval between 1.33 eV and 1.64 eV. The analyses of magnetization were performed at room (300 K; RT) and low (10 K) temperatures. Different magnetic parameters including coercivity H_c, saturation magnetization M_s, remanence M_r, squareness ratio (SQR = M_r/M_s) and magnetic moment n_B were deduced and discussed. The results showed superparamagnetic (SPM) nature at RT for x = 0.00 and 0.02 samples. However, the other products exhibit ferromagnetic (FM) nature. At 10 K, all synthesized NPs display FM behavior. An amazing increase in the magnitudes of M_s, M_r and H_c was observed at 10 K in comparison to RT, which is principally due to the reduced thermal fluctuations of magnetic moments at lower temperatures. The Tm³⁺ substitution affects considerably the magnetizations data. An enhancement in the M_s, M_r, and n_B was detected on increasing the Tm³⁺ concentration. The SQR values at RT are found to be smaller than 0.5 postulating a single domain nature with uniaxial anisotropy for all produced ferrites. However, SQRs are in the range 0.66-0.76 at 10 K, suggesting the multi magnetic domain at low temperature, except the x = 0.02 product where the SQR = 0.47 indicating the single magnetic domain. The obtained magnetic results were investigated deeply with relation to structural and microstructural properties.

Impact of La3+ and Y3+ ion substitutions on structural, magnetic and microwave properties of Ni0.3Cu0.3Zn0.4Fe2O4 nanospinel ferrites synthesized via sonochemical route

In the current study, Ni_0.4Cu_0.2Zn_0.4La_xY_xFe_2−xO₄ (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.

The best microwave properties for the NSFs were obtained with an LaY concentration of x = 0.08, RL of −40 dB @ 10.5 GHz and absorption bandwidth of 8.4 GHz @ −10 dB. The NSF products show promise as radar absorbing materials in the X-band.

Crystal chemistry and single-phase synthesis of Gd3+substituted Co–Zn ferrite nanoparticles for enhanced magnetic properties

Rare earth (RE) ions are known to improve the magnetic interactions in spinel ferrites if they are accommodated in the lattice, whereas the formation of a secondary phase leads to the degradation of the magnetic properties of materials.

Sonochemical synthesis of Gd3+ doped CoFe2O4 spinel ferrite nanoparticles and its physical properties

In this work, a facile and green method for gadolinium doped cobalt ferrite (CoFe_2-xGd_xO₄; x=0.00, 0.05, 0.10, 0.15, 0.20) nanoparticles by using ultrasonic irradiation was reported. The impact of Gd³⁺ substitution on the structural, magnetic, dielectric and electrical properties of cobalt ferrite nanoparticles was evaluated. The sonochemically synthesized spinel ferrite nanoparticles were characterized by X-ray Diffraction (XRD), scanning electron microscopy (SEM), Raman spectroscopy, Fourier transform infrared (FTIR) spectroscopy, X-ray photoelectron spectroscopy (XPS), vibrating sample magnetometer (VSM). X-ray diffraction (XRD) study confirmed the formation of single phase spinel ferrite of CoFe_2-xGd_xO₄ nanoparticles. XRD results also revealed that ultrasonic irradiation seems to be favourable to achieve highly crystalline single crystal phase gadolinium doped cobalt ferrite nanoparticles without any post annealing process. Fourier Transform Infrared and Raman Spectra confirmed the formation of spinel ferrite crystal structure. X-ray photoelectron spectroscopy revealed the impact of Gd³⁺ substitution in CoFe₂O₄ nanoparticles on cation distribution at the tetrahedral and octahedral site in spinel ferrite crystal system. The electrical properties showed that the Gd³⁺ doped cobalt ferrite (CoFe_2-xGd_xO₄; x=0.20) exhibit enhanced dielectric constant (277 at 100Hz) and ac conductivity (20.2×10^-9S/cm at 100Hz). The modulus spectroscopy demonstrated the impact of Gd³⁺ substitution in cobalt ferrite nanoparticles on grain boundary relaxation time, capacitance and resistance. Magnetic property measurement revealed that the coercivity decreases with Gd³⁺ substitution from 234.32Oe (x=0.00) to 12.60Oe (x=0.05) and further increases from 12.60Oe (x=0.05) to 68.62Oe (x=0.20). Moreover, saturation magnetization decreases with Gd³⁺ substitution from 40.19emu/g (x=0.00) to 21.58emu/g (x=0.20). This work demonstrates that the grain size and cation distribution in Gd³⁺ doped cobalt ferrite nanoparticles synthesized by sonochemical method, is effective in controlling the structural, magnetic, and electrical properties, and can be find very promising applications.

The structural and magnetic properties of dual phase cobalt ferrite

The bismuth (Bi³⁺)-doped cobalt ferrite nanostructures with dual phase, i.e. cubic spinel with space group Fd3m and perovskite with space group R3c, have been successfully engineered via self-ignited sol-gel combustion route. To obtain information about the phase analysis and structural parameters, like lattice constant, Rietveld refinement process is applied. The replacement of divalent Co²⁺ by trivalent Bi³⁺ cations have been confirmed from energy dispersive analysis of the ferrite samples. The micro-structural evolution of cobalt ferrite powders at room temperature under various Bi³⁺ doping levels have been identified from the digital photoimages recorded using scanning electron microscopy. The hyperfine interactions, like isomer shift, quadrupole splitting and magnetic hyperfine fields, and cation distribution are confirmed from the Mossbauer spectra. Saturation magnetization is increased with Bi³⁺-addition up to x = 0.15 and then is decreased when x = 0.2. The coercivity is increased from 1457 to 2277 G with increasing Bi³⁺-doping level. The saturation magnetization, coercivity and remanent ratio for x = 0.15 sample is found to be the highest, indicating the potential of Bi³⁺-doping in enhancing the magnetic properties of cobalt ferrite.

A. The effect of Y3+ substitution on the structural, optical band-gap, and magnetic properties of cobalt ferrite nanoparticles

In this study we investigated the structural, optical band-gap, and magnetic properties of CoY_xFe_2−xO₄ (0 ≤ x ≤ 0.04) nanoparticles (NPs) synthesized using a combustion reaction method without the need for subsequent heat treatment or the calcing process.

Crystal strain, chemical bonding, magnetic and magnetostrictive properties of erbium (Er3+) ion substituted cobalt-rich ferrite (Co1.1Fe1.9−xErxO4)

Induced strain and magnetostrictive coefficient (λ₁₁) with the applied magnetic field (H) for different compositions of Co_1.1Fe_1.9−xEr_xO₄.

Augmenting the catalytic activity of CoFe2O4 by substituting rare earth cations into the spinel structure

The current research work evaluates significant enhancement in photo-Fenton activity of pristine cobalt ferrite (CoFe₂O₄) by inserting very small quantity of rare earth cations such as cerium (Ce³⁺) and lanthanum (La³⁺) into its spinel structure.

Investigation on the structural, dielectric and impedance analysis of manganese substituted cobalt ferrite i.e., Co1−xMnxFe2O4 (0.0 ≤ x ≤ 0.4)

The microstructure and cation distribution of Co_1−xMnxFe₂O₄ were investigated and correlated with their electrical properties. Here, Mn substitution enhances the resistive properties which make them favorable for high-frequency applications.

Sol–gel synthesis and characterization of single-phase CoLaxFe2−xO4 ferrite nanoparticles dispersed in a SiO2 matrix

Single-phase CoLa_xFe_2−xO₄ (x = 0, 0.05, 0.10, 0.15, 0.20) nanoparticles dispersed in a SiO₂ (30 wt%) matrix were synthesized by a sol–gel method.