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An economically viable and superficial technique was indorsed to yield ZnFe 2 O 4 nanocrystals in the system to investigate the impact of pH variation on the optical, structural, electrical, and magnetic properties of as-prepared nanocrystals. The as-synthesized ZnFe 2 O 4 nanocrystals were premeditated with the application protracted to degradation of Methylene blue organic dye. The results specify that the pH plays the utmost decisive facet in photo-Fenton recital. From XRD (X-Ray diffraction) analyses, it was confirmed that as-synthesized nanocrystals belong to a cubic Fd3m crystal phase. The crystallite size was also determined by the Scherrer formula and it was noticed that as the pH rises the crystallite size also increased. FT-IR (Fourier Transform Infrared) analysis depicts two absorption peaks ∼ 500 and ∼600 cm -1 that represents tetrahedral (Td) and octahedral (Oh) sites. Using TEM (Transmission Electron Microscopy), the morphology was observed to be spherical particles with some agglomeration. Photoluminescence and UV-visible spectral studies were performed to investigate the optical properties. The bandgap energy was seen to decrease as the pH increased. Using BET analysis, the surface area for the as-synthesized samples was found to decrease on increasing the pH. The reaction results showed that the ZnFe 2 O 4 has good photocatalytic activity, which can be attributed to high surface area and pore volume, and large pore size. The ZnFe 2 O 4 produced by the co-precipitation route exhibited promising photocatalytic activity for the removal of textile dye, reaching nearly 99.2% of decolorization at 100 min. Therefore, ZnFe 2 O 4 particles rapidly prepared by the co-precipitation route have the potential for use in treatment of textile wastewater by the heterogeneous photo-Fenton process. With the help of VSM analysis, the coercivity and other magnetic properties were determined for the as-synthesized nanocrystal with plays a significant role in photocatalytic recyclability, which intends to premediate that the prepared nanocrystals can be used in industrial persistence., Competing Interests: Declaration of competing interest The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper., (Copyright © 2020 Elsevier Ltd. All rights reserved.)

This study designates the synthesis and characterization of undoped and Ni-doped CoFe2O4 nanoparticles within the highly ordered nanoscale channels of mesoporous silica SBA-15 matrix by using two-step nanocasting process. The impact of Ni doping in the structural and magnetic properties of CoFe2O4/SBA-15 nanocomposite was investigated by XRD, FT-IR, FESEM/EDX, N2-adsorption/desorption, and VSM techniques. XRD studies have depicted that Ni doping results in pure ferrite phase with crystallite size decreasing from 11.8 to 10.2 nm and lattice constant's reduction due to smaller ionic radii of the nickel ions as against cobalt ions. The formation of metal–oxygen complexes located in the spinel lattice was proved by FT-IR spectroscopy which exhibits two main absorption bands belonging to the tetrahedral and octahedral sites. Compared with CoFe2O4/SBA-15, Ni0.5Co0.5Fe2O4/SBA-15 nanocomposite possesses higher BET surface area and pore volume due to creation of additional porosity in the mixed ferrite sample. The surface morphology of the CoFe2O4/SBA-15 and Ni0.5Co0.5Fe2O4/SBA-15 nanocomposites, as measured by FESEM, indicates the fiber-like aggregates consisting of relatively uniform short rod-shaped grains. Ni doping is observed to influence the ferromagnetic behavior significantly, while the saturation magnetization gets reduced from 18.12 to 12.74 emu/g which is associated with the lower orbital contribution to magnetic moment of Ni2+ ions in as against Co2+ ions, conversely, the coercivity gets increased from 158 to 249 Oe, which suggests the hardening of the magnetic material, which may be due to the increase in surface anisotropy resulted from the matrix effect. Therefore, the present study notifies the potential magneto-electronic applications of Ni0.5Co0.5Fe2O4/SBA-15 nanocomposite, with the realization of controllable size and magnetic properties along with SBA-15 matrix. [ABSTRACT FROM AUTHOR]

Temperature and magnetic field–dependent electrical and magnetic properties of La1−xCaxMnO3 (x = 0.4, 0.5) polycrystalline materials prepared by the sol-gel method are studied. An apically compressed/elongated-type distorted orthorhombic pnma-O′–phase crystallization occurs in the sample with the addition of Ca. The crystallized phases are ensured by the Rietveld refinement using the Fullprof package. Dangling bonds on the surfaces of the nanosized particles affect the vibrational features. Field emission scanning electron microscopy (FESEM) images depict the agglomeration of uniformly sized grains. With increase of Ca concentration, super-exchange (SE) interactions overcome the dominant double-exchange (DE) interactions and shift the Curie-temperature to a lower value (TC = 267 – 234K). Based on the Banerjee's criterion, the Arrott plot confirms a second-order magnetic phase transition in the samples. Temperature-dependent evolution of the Griffiths-like phase (GP) is observed in the samples and GP% increases with Ca content. The various transitions in the different temperature ranges and magnetic field–dependent electrical transport behaviours are explained using different theoretical models. The dopant concentration influences the Mn3+/Mn4+ ratio, leading to changes in the conductivity, which is mediated by ferromagnetically (FM) ordered conduction channels, altering the metal to insulator (M-I) as well as the ferromagnetic to paramagnetic (FM-PM) as well as the ferromagnetic to antiferromagnetic (FM-AFM) transition temperatures. The electrical transport in the high temperature region is explained using variable range and small polaron hopping (VRH and SPH) models. Using Holstein's relation, it is evident that non-adiabatic SPH (NASPH) model is the most adequate method to explain the high-temperature electrical conductivity. The half-doped samples show a higher value (~ 95%) of magnetoresistance (MR). The present study shows an increase in the Tc and TM − I towards room temperature and in the MR percentage, which may be good for different applications. [ABSTRACT FROM AUTHOR]

In this report we discussed about the properties of magnetic nanoparticles which are important for the synthesis of nanoparticles of particular use. Various oxide-based nanoparticles can be synthesized depending on the properties which are needed for their applications. Various methods have been presented that offer control over the size, growth of the nanoparticles. Among the methods reported, hydrothermal method probably offers the most promising method for control and scalability. [ABSTRACT FROM AUTHOR]

[Display omitted] • Carbon supported Ni Nanoparticles are successfully synthesized using thermal decomposition method. • Casein is protein which is used as carbon source. • The crucial role of casein on particle size, crystal structure and magnetic properties is systematically investigated. • The prepared carbon supported Ni magnetic nanoparticles exhibit low-toxicity and stable ferromagnetic nature. Carbon supported nonprecious metal nanoparticles have gained significant attention for their low cost and excellent properties. However, immobilizing them with good dispersion on carbon supports is still a great challenge. Herein, we report a simple and low cost thermal decomposition method to prepare a high quality carbon supported nickel nanoparticles in presence of casein as carbon source. By optimizing the concentration of carbon source, engineered the particle size from 50 nm to 17 nm and morphology from pyramid to spherical. Further, the impacts of morphology and particle size on the magnetic properties of these nanoparticles are studied. Moreover, thermally stable, biocompatible, low cost with unique magnetic properties makes these materials as potential candidate for various applications including chemisorbers, sensor, and electrochemical uses. [ABSTRACT FROM AUTHOR]

Cupric oxide (CuO) nanoparticles are synthesized by the oxidation of Cu/Cu 2 O, which is obtained by the chemical reduction of Cu2+ ions with ascorbic acid. XRD pattern confirmed the formation of CuO, and FE-SEM image shows the clusters consisting of 25–30 nm sized particles. The band gap energy (3.7 eV) from optical absorption spectra is blue shifted to that of bulk values. The Néel temperature, T N ≈ 230 K for paramagnetic to antiferromagnetic transition was clearly seen. The magnetic hysteresis loops at 5 K showed weak ferromagnetic behavior. Based on the dc electrical conductivity (300–500 K), the apparent activation energy was 0.36 eV. The NO 2 gas sensing property of CuO was reasonably good in the temperature range of 200–300 °C, and the sensitivity increased with an increase in gas concentration but the effect of temperature is marginal. Image 1 • Cost effective, environmentally benign and rapid chemical method is developed to prepare CuO nanoparticles. • Cu–Cu 2 O core-shell structure can be obtained easily by the oxidation of metallic Cu nanoparticles obtained here. • Band gap energy (3.7 eV) for CuO is blue shifted to that of bulk CuO, and the Néel temperature is 230 K. • NO 2 gas sensing by CuO between 200–300 °C is reasonably good but the effect of temperature is marginal. [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]

Herein, non‐stoichiometric zinc ferrite nanoparticles, Zn0.86Fe2.14O4+δ,with grain sizes of being smaller than 11 nm were successfully prepared by varying the hydrothermal reaction duration and temperature. The influence of reaction temperature and time on the grain size of zinc ferrite nanoparticles was investigated. Non‐stoichiometric zinc ferrite nanoparticles underwent distinct processes at different reaction temperatures: at 200 °C, the growth mechanism follows an Ostwald ripening model with activation energy 124.7 kJ/mol, while at 120 °C, the particle growth is governed by aggregation and coalescence, Ostwald ripening mechanism with the activation energy 27.5 kJ/mol and digestive ripening process.The abnormal growth behavior of zinc ferrite nanoparticles is completely different from previous reports on the oxides. Detailed analysis of XPS, XRD, FT‐IR and Mössbauer spectra revealed that the presence of rich iron oxides on the surface of nanoparticles is responsible to the non‐stoichiometry. Moreover, unit cell volume and magnetic property of non‐stoichiometric zinc ferrite exhibited two extremum as the increase of grain size, which was closely related to the grain size‐dependent structure changing. The unusual growth behavior and the size dependent structure and property changes of non‐stoichiometric zinc ferrite nanoparticles reported in this work may be beneficial to guide the future development of magnetic materials. [ABSTRACT FROM AUTHOR]

Cobaltic oxide (Co 3 O 4) nanoparticles were synthesized by co-precipitation method using different concentrations of NaOH and NH 4 OH. Elemental analysis confirmed the presence of Co and O in the studied samples. The X-ray powder diffraction patterns (XRPD) demonstrated that the synthesized cubic Co 3 O 4 nanoparticles were of good crystallinity and Fourier transform infrared (FT-TIR) data supported the results of XRPD data. Different magnifying field emission scanning electron microscopy (FESEM) images confirmed that the surface of the synthesized Co 3 O 4 nanoparticles were highly dependent on the synthesis condition and used precipitants. The magnetic properties of the synthesized Co 3 O 4 nanoparticles were investigated using vibrating sample magnetometer (VSM) where different precipitants and concentrations influenced the magnetic properties of Co 3 O 4 nanoparticles. [ABSTRACT FROM AUTHOR]

Although coating technology and in‐situ synthesis have been widely applied to produce Fe3O4 NPs‐containing composite materials, there still exist potential risks to the environment. Herein, an eco‐friendly preparation of Fe3O4 nanoparticles (FNPs)‐coated wool felt is proposed based on the self‐glue effect of wool keratins in the NaHSO3/urea solution. It avoids the use of coating agents, and also the commercially available FNPs are directly utilized as raw materials, both making the residual FNPs completely recyclable. The resulting FNPs‐coated wool felt shows high magnetization (23.54 emu g−1) and excellent microwave‐assisted heating properties (the temperature rise is about 40°C after 10 min). The results of EDS‐SEM (energy dispersive spectrometer‐scanning electron microscope), loud amount (%), crease recovery angle (CRA), Fourier transform infrared (FTIR) spectrometer and X‐ray diffraction (XRD) prove that the dramatical swelling and the recoagulation of superficial keratins of wool fibers are the mechanism of the self‐glue effect. [ABSTRACT FROM AUTHOR]

In this study, we reported a facile synthesis of bimetallic FeCo nanoparticles (Fe-Co NPs) by FeSO4 .7H2 O and Co(Ac)2 .4H2 O in the presence of sodium borohydride and 2-thiotic acid. The structure and morphology of the nanoparticles were characterized by X-Ray Diffraction (XRD), Energy-dispersive X-ray spectroscopy (EDS), and Transmission Electron Microscopy (TEM). These small, spherical shape and pure phase FeCo bimetallic nanoparticles have saturation magnetization up to 221 emu/g. The results suggest that the long term stable and high saturation magnetization (Ms) FeCo nanoparticles can be used for data storage, catalysis, environmental remediation, high-performance inductors, magnetic hyperthermia treatment and magnetic resonance imaging applications. [ABSTRACT FROM AUTHOR]

Spherical magnetic Fe3O4 nanoparticles with different Nd doping amounts were successfully prepared using a simple hydrothermal method. The products were characterized by powder X-ray diffraction (XRD), transmission electron microscopy (TEM), dynamic laser scattering particle size (DLS), and vibrating sample magnetometer (VSM) analysis. Results showed that the spherical nanoparticles of pure Fe3O4, pure Nd2O3, and Nd-Fe3O4 were confirmed by XRD and TEM. The size of the prepared nanoparticles decreased first and then increased with increasing Nd doping amount by dynamic laser scattering. In addition, magnetic parameters, including saturation magnetization, remanent magnetization, and coercivity of Fe3O4 nanoparticles with different doping ratios of Nd, were analyzed by VSM. [ABSTRACT FROM AUTHOR]

The present work reconnoiters the dielectric, electrical, and magnetic properties of transition metal–doped lead sulfide nanoparticles (PbS-NPs) synthesized by co-precipitation technique. The particle size was assessed from the histogram obtained by transmission electron microscopy (TEM). Frequency- and temperature-dependent measurements of dielectric permittivity and ac conductivity have been carried out for transition metal–doped lead sulfide nanoparticles (PbS-NPs). The transition metal–doped lead sulfide nanoparticles show ferromagnetic nature with enhanced magnetization with the doping of Ni, Co, and Fe respectively as compared with pure lead sulfide nanoparticles. These nanoparticles may find its application in electronic storage and DMS spintronic devices due to their enhanced and regulated nature of dielectric and magnetic behavior. [ABSTRACT FROM AUTHOR]

Amorphous chromium (III) oxide (Cr 2 O 3) nanoparticles were synthesized by a solution plasma discharge procedure in CrCl 3 aqueous solution. X–ray diffraction, Fourier transform infrared spectroscopy, and thermal analysis were conducted to analyze the nanoparticles. Nanoscale Cr 2 O 3 with good magnetic properties can be employed in information storage and spintronics. Therefore, the magnetic properties of the product were measured to assess their potential application. The results showed that the obtained Cr 2 O 3 product was amorphous with a sheet-like morphology, in which small nanoparticles were attached to each other and wrapped by the water layer. Transmission electron microscopy results indicated that the covered particles produced in the CrCl 3 solution were spherical with a mean diameter of 50 nm. The sheet-like morphology was converted into thinner slices when discharge electrolysis was conducted in the solution containing H 2 SO 4. The amorphous phase could be transferred to nanocrystalline Cr 2 O 3 with an average grain size of 100 nm after calcination at 600 °C. The Cr 2 O 3 particles obtained in the H 2 SO 4 solution became more uniform after heat treatment. The results of the magnetic property measurement showed that the Verwey transition and blocking temperatures of the produced Cr 2 O 3 nanoparticles were 16 K and 66 K, respectively, and the separation of the zero-field-cooled curve and field-cooled curve occurred at 300 K. The magnetic properties of the nanoparticles were shown to be irreversible due to hysteresis. The formation process of amorphous Cr 2 O 3 was proposed as 2Cr + 3H 2 O → Cr 2 O 3 + 3H 2 and 4Cr3+ + 6OH− + 6e– → 2Cr 2 O 3 + 3H 2. [ABSTRACT FROM AUTHOR]

To enhance the magnetic property as well as to get the magnetic ordering in Sm2O3 which is a good dielectric material, Co-ion is substituted by a chemical route. Rietveld analysis of x-ray diffraction (XRD) pattern of the sample (Sm1.90Co0.10O3) suggests that all the dopants are properly substituted in the monoclinic lattice of Sm2O3. XRD analysis and Raman spectroscopic observation ruled out the segregation of Co-cluster or formation of any impurity in Sm1.90Co0.10O3. Magnetic susceptibility (χ ) of the sample measured in the range of 300–14 K by Faraday balance indicates the paramagnetic behavior down to 50 K, below which non-linear magnetic nature with ferromagnetic ordering is found. The onset of ferromagnetism in a doped dielectric host is investigated in detail by observing magnetization versus magnetic field (M–H) data and magnetization versus temperature (M–T) curves recorded under zero field cooled and field cooled conditions. All the data extracted from the magnetic measurements are analyzed to yield useful information of the newly developed diluted magnetic dielectric. [ABSTRACT FROM AUTHOR]

We report the chemical synthesis of Cr-doped ZnS nanocrystallites without using any capping ligand/surfactant. An unusual increase in bandgap observed for Cr-doped samples was understood in terms of the Burstein–Moss effect. Additionally, 4A2(F) → 4T1(F) and 4A2(F) → 4T2(F) transitions in the absorption spectra confirmed the substitution of Cr3+ ions at the octahedrally coordinated interstitial sites. Photoluminescence study showed a large amount of Zn vacancies owing to the incorporation of Cr3+ ions which intensified the self-activated blue–green luminescence. Room-temperature magnetization showed FM ordering up to the 2% Cr doping, which gradually transformed into paramagnetic behavior at higher values and became more enhanced in the low-temperature range. Thus, in the present synthesis method, the FM order could only be observed up to the 2% Cr doping concentration. Also, the activation energy was observed to increase with the increase of Cr doping concentration. [ABSTRACT FROM AUTHOR]

The iron oxide nanoparticles (IONPs) fabricated by pulsed wire evaporation were characterized by analytical electron microscopy and magnetic properties measurement system (MPMS). The IONPs produced at various charging voltages (2.6, 5.0 and 6.3 kV) exhibited the average size of 48 nm and the differences in shape, i.e., spherical (83%) and hexagonal (17%) structures. The hexagonal nanoparticles showed single-crystalline magnetite (Fe3O4) with major facets made of {111} planes. The chemical shifts in core–shell nanoparticles were observed by electron energy loss spectroscopy, indicating a dependency of the edge position related to the oxidation state of Fe. From the MPMS, the saturation magnetization and the coercivity of IONPs were measured to be 64 emu/g and 37 Oe at 300 K, respectively. The results provide useful information for the relationship between the nanostructure and magnetic behavior. TEM images of iron oxide nanoparticles (IONPs) fabricated by pulsed wire evaporation. Two distinct shapes of IONPs can be seen, i.e., hexagonal and core/shell structures. The hexagonal nanoparticles showed single-crystalline Fe3O4 magnetite with major facets made of {111} planes, while the core/shell nanoparticle consisted of Fe core and Fe3O4 shell. By magnetic property measurement system (MPMS), the saturation magnetization and the coercivity were measured to be 64 emu/g and 37 Oe at 300 K, respectively. This study provides the possibility for developing novel and various IONPs with unprecedented structures and/or magnetic properties. [ABSTRACT FROM AUTHOR]

A high magnetic field up to 6 T was introduced into the wet-chemical process to synthesize FePt nanoparticles. The effects of high magnetic field on the composition, crystal structure, shape, size and magnetic property of FePt nanoparticles were studied. Under the high magnetic fields, the grain size of FePt nanoparticles refined, and the shape transformed from cube to truncated-cube and concave-cube to cube. However, the high magnetic fields show no significance effects on the composition and crystal structure of FePt nanoparticles. As a result, the magnetic properties of FePt nanoparticles were tuned by high magnetic fields. The coercivity at low-temperature (10 K) and the blocking temperature both decreased at 6 T. The results highlight the feasibility of applying an in-situ high magnetic fields to tune magnetic properties of the wet-chemical synthesized nanoparticles. Image 1 • High magnetic fields refined the grain size of FePt nanoparticles. • High magnetic fields tailored the shape of FePt nanoparticles. • High magnetic fields tuned the magnetic property of FePt nanoparticles. • Structure-performance correlation under high magnetic fields was investigated. [ABSTRACT FROM AUTHOR]

Diluted magnetic semiconductors (DMSs), having interesting magnetic/transport properties, are currently being explored in photocatalytic application as well. This report presents photocatalytic and low temperature magnetic/transport study of chemically synthesized 3-5 nm sized cubic Zn1-xCuxS (0 ≤ x ≤ 0.04) DMS nanoparticles. Both studies have their own importance, former relates to dye degradation, while later attempts to understand origin of magnetic behavior in DMSs (which is still debatable). As a photocatalyst, Cu doped ZnS NPs showed enhanced degradation-efficiency for methylene blue dye. Magnetization study showed enhanced magnetic moment in Cu doped samples, which in the low temperature regime got further enhanced and was understood due to defect induced ferromagnetism. Low temperature transport study showed the decrease in resistivity of the Cu doped samples and was understood in terms of defects states created due to doping of the Cu ions and governed by conduction mechanism, namely thermal activation and variable range hopping. [ABSTRACT FROM AUTHOR]

• Nanocomposite of MZCF embedded PVDF films were prepared by solution casting method. • β-Phase of MZCF-PVDF films were confirmed by XRD, FESEM and FTIR spectroscopy. • Magnetic properties of the films are useful for applications in polymer based devices. • Dielectric constants have been modulated due to the electrostatic interaction in MZCF-PVDF films. • The reflection loss observed in X and K u bands have been enhanced substantially. Magnetic nanoparticles embedded poly(vinylidene fluoride) (PVDF) nanocomposite films with different weight percentages of Mn-Zn-Cu-ferrite (MZCF) nano-fillers were prepared by solution casting method. The structural, morphological, magnetic, dielectric and microwave absorption properties of all the MZCF-PVDF nanocomposite films were studied. Experimental observations reveal the enhancement of the electroactive β-phase of PVDF by the modification of internal structure of the PVDF. Variation of magnetization with magnetic field reveals the presence of magnetic ordering and high magnetic moment in the MZCF-PVDF nanocomposite films. Variation of dielectric properties shows the significant modulation of dielectric response of the MZCF-PVDF nanocomposite films. High value of reflection losses of the nanocomposite films within the range of 8–18 GHz was observed and large reflection loss makes the sample most suitable one for the applications in microwave devices. The present work also suggests that these nanocomposite films would be very useful as Radar absorbing material for EMI shielding applications. [ABSTRACT FROM AUTHOR]

In this work, the Fe60Pt40 nanoparticles were synthesized through the chemical reduction method by using the Fe(CO)5 and the Pt(acac)2 as the metallic precursor. The particle size of the synthesized FePt nanoparticles was controlled by adjusting the reaction conditions involving of the Fe(CO)5-injecting temperature and the soak time of reaction. The structure, morphology, and magnetic properties of the synthesized FePt nanoparticles were characterized by XRD, TEM, and vibrating sample magnetometer (VSM), respectively. The synthesized nanoparticles exhibit uniform size and good dispersity. The magnetization behaviors indicate that the nanoparticles present the core-shell magnetic structure including the ferromagnetic core part and the spin-disorder shell part. There exists a spin pinning effect of the shell part on the core part. The increase of particle size weakens the spin pinning effect. [ABSTRACT FROM AUTHOR]

In this paper, the law of approach to saturation (LAS) was applied to a series of Mn–Zn ferrite nanoparticles with compositional formula Mn1−xZnxFe2O4 where x = 0, 0.1, 0.2, 0.3, 0.4 and 0.5 to study the dependence of magnetization, M, on the applied magnetic field, H. Using the statistical parameters, the field range was chosen. The dependence of magnetization on the applied field was studied based upon the output of the statistical parameters for the curve fitted using different forms of LAS, namely, M = M s 1 − a H − b H 2 + kH , M = M s 1 − a H − b H 2 , M = M s 1 − b H 2 and M = M s 1 − 1 15 H A 2 H 1 2 H 3 2 + H R 3 2 + kH . A critical examination on the output parameters resulted from fitting into different equations, indicates the dependency of magnetization on the applied field as a characteristic of the composition of Mn–Zn ferrites. The statistical parameters, along with physically meaningful fitted parameters, provide knowledge on dependency of magnetization of different compositions of Mn–Zn ferrites over different regions of applied field. [ABSTRACT FROM AUTHOR]

The disorder-order phase transition of FePt/SiO2 core/shell nanoparticles (NPs) induced by rapid thermal annealing was investigated. The FePt/SiO2 NPs were synthesized using FePt cores as seeds. For as-prepared FePt/SiO2 NPs, the average size of the FePt core and the thickness of the SiO2 shell are about 4.8 and 1.2 nm respectively, and the FePt NPs exhibit a disordered fcc structure. The FePt core NPs show obvious phase transformation from a disordered to an ordered structure after they were annealed at 600 °C for 2 min. Moreover, increasing annealing time can promote effectively the formation of the ordered fct-FePt phase. The relatively large coercivity H c is obtained for FePt NPs with a thicker SiO2 shell. The H c decreases firstly with decreasing temperature from 300 to 100 K and then increases from 100 to 10 K, which is ascribed to the coexistence of magnetically hard fct-FePt and magnetically soft fcc-FePt in the sample, and the incomplete exchange coupling between the hard and soft magnetic phases. [ABSTRACT FROM AUTHOR]

Mn3O4 nanoparticles with particle sizes of 7.8, 11.4, and 18.3 nm were synthesized in the pores of mesoporous silica, and their crystal structure and magnetic properties were investigated. The powder X-ray diffractions at room temperature indicated that the crystal structural symmetry was the same as that for bulk crystal, and the lattice constants deviated from those for bulk crystal, which depended on the particle size. In addition, compared with the bulk crystal, the Jahn–Teller distortion for the nanoparticles was suppressed and decreased with decreasing the particle size. The coercive field for 7.8 nm was rather smaller than those for 11.4 and 18.3 nm. The nanoparticles with 11.4 and 18.3 nm exhibited pronounced three kinds of magnetic transition temperatures, whereas the susceptibility for 7.8 nm indicated the existence of two transition temperatures. These experimental results suggested that the Mn3O4 nanoparticles have a strong correlation between crystallographic structure and magnetic property, and the characteristic magnetic size effects are attributed to the reduction of Jahn–Teller distortion. [ABSTRACT FROM AUTHOR]

Due to their special qualities, core-shell nanomaterials with two or more functionalities have drawn a lot of attention. Core-shell materials exhibit stronger combined electrical, optical, magnetic, and electronic characteristics than single-component nanomaterials thanks to the creation of the core-shell structure and the synergistic interaction between components. However, the formation of core-shell structures is often difficult due to the incompatibility between components, especially for lattice-mismatched core-shell structures. In this study, CoFe@CoFe 2 O 4 -N-C nanoparticles (∼150 nm) were successfully prepared via an ultrasonic atomization coupling pyrolysis process. This exhibits higher coercivity (108 Oe), saturation magnetization (52.3 emu/g) and Curie temperature (>400 K) than CoFe nanoparticles. At the same time, it exhibits high UV–Vis and infrared absorption characteristics and has good electronic properties as a direct band gap semiconductor material (bandgap of 2.87 eV). These characteristics suggest that CoFe@CoFe 2 O 4 -N-C NPs have a lot of potential in sectors like magneto-optics and absorbent materials. [Display omitted] • Successfully synthesized NPs by CoFe core and CoFe 2 O 4 embedded N-modified C shell. • Higher coercivity, saturation magnetization, and Curie temperature than CoFe NPs. • High UV-Vis-IR absorption characteristics and good electronic properties. [ABSTRACT FROM AUTHOR]

Magnetism in dilute magnetic semiconductors (DMSs) has been a controversial topic since its discovery. There are many models which predict the origin of room temperature ferromagnetism (RTFM) in TM doped wide band gap semiconductors. Here, we report RTFM in chemically synthesized cubic Zn 1-x Ni x S (0 ≤ x ≤ 0.08) DMS nanoparticles of ∼3–5 nm size. Ferromagnetic behavior (at 300 K and 5 K) was found to increase with the increase in Ni doping concentration and was understood due to defect induced ferromagnetism. The low temperature magnetization measurement (ZFC-FC) shows that the nanoparticles are strongly coupled by magnetic interactions. Optical studies showed decrease in the energy bandgap along with the presence of sulfur and zinc vacancies and surface defects. Low temperature resistivity measurement depicted the semiconducting nature of the synthesized samples. With increase in doping concentration, an increase in the resistive behavior was observed which was explained in the realm of defects states created due to doping of the Ni ions. [ABSTRACT FROM AUTHOR]

A new molybdovanadate, [HN(CH3)3]10[Co2(VMo9O33)2]·8H2O (1) was synthesized by a conventional self-assembly reaction in aqueous solution and structurally characterized by elemental analysis, IR spectra, UV electronic spectroscopy, and X-ray diffraction. Compound 1 exhibits a sandwich-type framework based on molybdovanadate anions [VMo9O33]7− linked by a dinuclear cobalt(II) cluster, which is a first observation in a sandwich-type molybdovanadate system. Electrocatalytic experiments show that 1 exhibits bifunctional electrocatalytic activities for the oxidation of dopamine (DA) and the reduction of IO3−. Magnetic measurements of 1 indicate the presence of antiferromagnetic interactions between cobalt ions. [ABSTRACT FROM AUTHOR]

Two novel nanosized polynuclear cage-like clusters, formulated as [Nd 20 Ni 21 (IDA) 21 (NH 2 CH 2 COO) 6 (OAc) 3 (CO 3 ) 6 (C 2 O 4 ) 3 (μ 3 -O) 9 (μ 3 -OH) 12 (μ 2 -OH) 3 ·12H 2 O]·32H 2 O (1), and [Na 3 Pr 20 Ni 21 (IDA) 21 (NH 2 CH 2 COO) 6 (OAc) 9 (CO 3 ) 6 (C 2 O 4 ) 3 (μ 3 -O) 6 (μ 3 -OH) 15 (μ 2 -OH) 3 ·12H 2 O]·15H 2 O (2) (IDA = iminodiacetic acid), were successfully synthesized under solvothermal conditions by using the flexible ligand IDA. Compounds 1 and 2 are analogous and contain [Ln 20 Ni 21 ] units connected by IDA, CO 3 2− , NH 2 CH 2 COO − and C 2 O 4 2− . In addition, magnetic properties of compounds 1 and 2 reveal the existence of antiferromagnetic exchange interaction between adjacent metal ions. [ABSTRACT FROM AUTHOR]

A series of multicomponent Al-Co-Cr-Cu-Fe-Ni nanoparticles with different aluminum contents were prepared by modified arc-discharge method. The effect of Al element on crystal structure, microstructure, corrosion resistance, and soft magnetic properties were investigated. The evolution of phase structure changes from the initial single Cu-rich face-centered cubic (FCC) phase to FCC + M 3 Al-type L1 2 phases, and eventually to FCC + body-centered cubic (BCC) phases with increasing Al contents. Moreover, the as-prepared nanoparticles are spherical with an average size of about 110–180 nm, and the chemical compositions of the nanoparticles greatly deviate from the nominal compositions of the targets. Furthermore, the corrosion resistance deteriorates and the soft magnetic behavior increases, when the structure changes from the simple FCC phase to a mixture of FCC and BCC phase. The emergence of M 3 Al-type L1 2 phase in the FCC matrix brings the best corrosion resistance and the lowest soft magnetic property. The multicomponent nanoparticles with controllable structure and composition can be easily prepared by this method for particular applications. [ABSTRACT FROM AUTHOR]

Tungsten substituted nickel-zinc ferrite nanoparticles with chemical composition of Ni 0.5 Zn 0.5 W x Fe 2-x O 4 (x = 0.0, 0.2, 0.4, 0.6, 0.8 & 1.0) were successfully synthesized by a chemical co-precipitation method. The prepared ferrites were pre sintered at 850 °C and then annealed at 1000 °C in a muffle furnace for 3 h each. This sintered powder was inspected by X-ray diffraction (XRD), transmission electron microscopy (TEM), Fourier transform infrared spectroscopy (FTIR), and vibrating sample magnetometer (VSM) to study the structural, optical, and magnetic properties. XRD measurement revealed the phase purity of all the nanoferrite samples with cubic spinel structure. The estimated crystallite size by X-ray line broadening is found in the range of 49–62 nm. FTIR spectra of all the samples have observed two prominent absorption bands in the range 400–700 cm −1 arising due to tetrahedral and octahedral stretching vibrations. Vibrating sample magnetometer experiments showed that the saturation magnetizations ( M S ) decreased with an increase in non-magnetic tungsten ion doping. The electrical resistivity of tungsten doped Ni Zn nano ferrites were examined extensively as a function of temperature. With an increase in tungsten composition, resistivity was found to decrease from 2.2 × 10 5 Ω cm to 1.9 × 10 5 Ω cm which indicates the semiconducting behavior of the ferrite samples. The activation energy also decreased from 0.0264 to 0.0221 eV at x = 0.0 to x = 1.0. These low coercive field tungsten doped Ni Zn ferrites are suitable for hyperthermia and sensor applications. These observations are explained in detail on the basis of various models and theories. [ABSTRACT FROM AUTHOR]

In this study we report on both the successful synthesis of Er x Zn 1- x O nanoparticles (x = 0.000, 0.005, 0.010, 0.030, 0.050, 0.075, and 0.100) and characterization (structural, optical, and magnetic) of the as-produced nanomaterials. The nanoparticles were produced by the polymeric precursor method (Pechini's method). X-ray diffraction and Raman spectroscopy showed formation of hexagonal wurtzite phase in all samples. Meanwhile, only samples with a high Er-content (x = 0.075 and x = 0.100) exhibited a minority (up to 7 % w/w) secondary crystalline phase (Er 2 O 3). The Rietveld refinement method was employed to assess details of the structural parameters. It was demonstrated that the increase of the Er-content leads to systematic mean crystalline size reduction (from ∼80 to ∼13 nm) and band gap shrinking (from ∼3.17 to ∼3.00 eV). The UV-Vis spectra showed the presence of characteristic Er3+-ion absorption bands. Likewise, emission peaks associated with Er3+-ion 4S 3/2 → 4I 15/2 electronic transition were verified by room temperature photoluminescence (PL). Strong differences in the PL spectra profiles of the Er x Zn 1- x O nanoparticles with respect to the PL spectrum of a reference Er 2 O 3 sample, suggested that the majority of Er3+-ions replace Zn2+-ions in the wurtzite hosting matrix. Magnetic measurements show a paramagnetic behavior in all doped samples. The χ × T and M × H curves were successfully fitted to Curie-Weiss law and Brillouin modified model, showing the existence of short-range antiferromagnetic correlation. [Display omitted] • Er x Zn 1- x O NPs were synthesized by polymer precursor method. • Unit cell volume, particle size, band gap and magnetic properties depend on Er3+. • PL-spectroscopy confirms that Er3+ is replacing Zn2+ in wurtzite structure. • The magnetic data were fitted by Curie-Weiss and Brillouin modified models. • Antiferromagnetic interactions between Er3+ were detected. [ABSTRACT FROM AUTHOR]

In this research nickel zinc ferrite nanoparticles with composition of Ni1-xZnxFe2O4 (where x=0, 0.3, 0.7, 1) were synthesized by a sol-gel method at 600 °C for 5 hours. The structure of nanoparticles was studied using X-ray diffraction pattern. The lattice parameter of ferrite nanoparticles was calculated and indicates lattice constant of nanoparticles depend on zinc concentration. The crystallite size of nickel zinc nanoparticles was calculated by Debye–Scherrer equation and the crystallite sizes of nanoparticles decreased by increasing in x contents. Morphology of nanoparticles was observed and investigated using the scanning electron microscopy. The grain size of nickel zinc ferrite nanoparticles were in suitable agreement with the crystalline size calculated by X-ray diffraction results. Magnetic properties of nanoparticles were examined with vibration sample magnetometer. Hysteresis loops of nanoparticles reveal the super-paramagnetic behavior.

In this work, a facile and green method for gadolinium doped cobalt ferrite (CoFe 2−x Gd x O 4 ; x = 0.00, 0.05, 0.10, 0.15, 0.20) nanoparticles by using ultrasonic irradiation was reported. The impact of Gd 3+ 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−x Gd x O 4 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 Gd 3+ substitution in CoFe 2 O 4 nanoparticles on cation distribution at the tetrahedral and octahedral site in spinel ferrite crystal system. The electrical properties showed that the Gd 3+ doped cobalt ferrite (CoFe 2−x Gd x O 4 ; x = 0.20) exhibit enhanced dielectric constant (277 at 100 Hz) and ac conductivity (20.2 × 10 −9 S/cm at 100 Hz). The modulus spectroscopy demonstrated the impact of Gd 3+ substitution in cobalt ferrite nanoparticles on grain boundary relaxation time, capacitance and resistance. Magnetic property measurement revealed that the coercivity decreases with Gd 3+ substitution from 234.32 Oe (x = 0.00) to 12.60 Oe (x = 0.05) and further increases from 12.60 Oe (x = 0.05) to 68.62 Oe (x = 0.20). Moreover, saturation magnetization decreases with Gd 3+ substitution from 40.19 emu/g (x = 0.00) to 21.58 emu/g (x = 0.20). This work demonstrates that the grain size and cation distribution in Gd 3+ 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. [ABSTRACT FROM AUTHOR]

Polymer nanocomposites of various concentrations were prepared using iron oxide (Fe2O3) nanoparticles as filler in an 80:20 ratio of the polyurethane diol and polycaprolactone hybrid. Fourier transformed infrared spectroscopy studies were performed to find out the interaction of the nanoparticles with the polymer blend. Fe2O3 in the polymer composites was in the nanoscale and uniform dispersion was achieved, as revealed by X-ray diffraction. The thermal stability of the blend was assessed through thermogravimetry analysis and dynamic mechanical analysis. High-resolution scanning electron microscopy and transmission electron microscopy images ensured the development of the polymer hybrid around Fe2O3 nanoparticles and the prepared composites were indeed in the nanoscale. The magnetic behavior of the prepared nanocomposites is superparamagnetic with high magnetization values, as assessed by vibrating sample magnetometry analysis. [ABSTRACT FROM AUTHOR]

In this paper, PEG6000 was used as a surfactant to prevent the MnZn ferrite nanoparticles from aggregation. Introduction of PEG6000 didn’t affect structure of the products, but modified their dispersion state and decreased their particle size. Furthermore, saturated magnetization of the MnZn ferrite nanoparticles increased with an increase in the PEG6000 content, and presented the maximum of 110.3 emu/g at the PEG6000 content of 0.006 mol/l. This value is about 40% higher than that without any PEG6000, and almost the highest one reported to date for the MnZn ferrite nanoparticles. Hence the obtained results proved that the PEG6000 was a powerful surfactant to improve magnetic properties of the MnZn ferrite nanoparticles. [ABSTRACT FROM AUTHOR]

Nd-Fe-B nanoparticles with a particle size below 50 nm and excellent magnetic properties were obtained via a novel route which makes use of both spray drying and reduction-diffusion processes. Uniform Nd-Fe-B particles were formed by the optimization of Ca amount as a reducing agent and additional washing by milling in ethanol media. Especially, we implemented a two-step washing process which contributed to the excellent magnetic properties with high remanence and coercivity. After the removal of CaO by novel washing process, the maximum energy product ( BH ) max of the particles showed 22.1 MGOe. This value is superior to those reported in reduction-diffusion process. We used Henkel plot to assume the mechanism of magnetic interactions of the Nd-Fe-B nanoparticles. [ABSTRACT FROM AUTHOR]

Iron oxide nanoparticles (IONPs) have gained technological importance in many fields that broadly includes health, environment, and energy applications. Consequently, the synthesis of IONPs with different phases and morphologies possesses significant interest. Therefore, here we report the facile synthesis of IONPs through the hydrothermal method followed by calcination process at different temperatures (300 °C, 500 °C, and 700 °C) and studied the influence of various phases of IONPs on their magnetic and dielectric properties. The structural studies using X-ray diffraction confirmed that the as-prepared material possesses the Fe3O4 phase, and the increasing calcination temperatures leads to the phase transformation from maghemite ( $\gamma $ -Fe2O3 to hematite ( \alpha $ -Fe2O3 phase. The morphological studies revealed that the as-prepared material possesses flaky morphology with a size around 20 nm, \gamma $ -Fe2O3 to have nanoparticles of sizes around 50 nm, and \alpha $ -Fe2O3 phase with mixed morphology of hexagonal and elongated shaped particles with size ranges from 60–140 nm. The optical properties of synthesized materials revealed that the band gap energy is found to be varied in between 2 and 2.7 eV depending upon the phase of IONPs. The hysteresis behavior of as-prepared and calcined IONPs at 300 °C and 500 °C indicated the soft-ferromagnetic properties of the phases. However, the IONPs prepared at 700° showed the weak-ferromagnetic property due to the existence of mixed \alpha ) that varied in between 47.88 and 0.35 emu/g. The occurrence of the reduced M_{s} ascribed to the phase transformation of the respective IONPs system. The dielectric studies of IONPs exhibited drastic variations with increasing frequency and with respect to their phase. [ABSTRACT FROM AUTHOR]

Inspired by the ongoing development of multifunctional and hybrid nanomaterials for spintronics application, the structural, electronic and magnetic properties of FeSn co-doped In2O3nanoparticles have been studied. Effects of Sn as a tetravalent impurity in In1.96−xFe0.04SnxO nanoparticles on the room temperature ferromagnetism (RTFM) are investigated. Small concentration of Sn leads to an initially abrupt decrease in the magnetic moment from 0.78 emu g−1(for x = 0) to 0.37 emu g−1for (x = 0.005) beyond which it decreases gradually in a tunable manner to 0.23 emu gm−1(for x = 0.025). The Sn-induced suppression of the ferromagnetic moment is attributed to the appearance of mixed valent states Fe2+/Fe3+and depletion of itinerant carriers from the system with the increase in Sn content. Additionally, Sn as an electron dopant plays a pivotal role to diminish the ferromagnetic stability in this system by destabilising the formation of local-bound magnetic polaron. [ABSTRACT FROM AUTHOR]

In this article, chromium-doped gadolinium manganate (GdCr0.3Mn0.7O3) nanoparticles has been prepared by wet-chemical route in order to investigate their structural, optical, electrical, and room temperature magnetic properties. Microstructural and compositional analyses have been carried out by X-ray diffraction and scanning electron microscopy (SEM). Synthesised material is found to be in orthorhombic crystal structure with Pbnm space group. The spherical morphology of the nanoparticles has been examined from the SEM images. Functional groups have been identified using Fourier transform infrared spectroscopy. Dielectric constant, dielectric loss, AC conductivity ( σac), and activation energy in the range of 1 kHz-1 MHz from room temperature to high temperature (400°C) have been investigated. The frequency dependence of AC conductivity obeys the universal power law. The value of activation energy depends on increase in frequency. Room temperature magnetic behaviour suggests the material to be paramagnetic in nature. [ABSTRACT FROM AUTHOR]

Cobalt(II,III) oxid (Co 3 O 4 ) nanostructures have been successfully synthesized using [Co(NH 3 ) 6 ]Cl 3 and [Co(en) 3 ]Cl 3 (en: ethylenediamine) as the single precursors via hydrothermal method, and CoCl 2 ·6H 2 O through a facile ammonia-assisted approach. Indeed, ammine and en ligands, as well as ammonia vapor, act as the sources of hydroxide ion in the preparation of Co 3 O 4 nanoparticles. The structure of products was confirmed by X-ray diffraction (XRD) technique and Fourier-transform infrared (FT-IR) spectroscopy and their morphologies were examined by scanning electron microscopy (SEM). The optical study of the as-prepared Co 3 O 4 nanostructures using UV–Vis diffused reflectance spectroscopy (DRS) exhibited their semiconducting property by revealing one optical band gap in 3.3 eV. Moreover, the vibrating sample magnetometry (VSM) measurements showed a weak ferromagnetic behavior that could be attributed to uncompensated surface spins and/or finite-size effects. Further, the effects of the nature of the precursor, its concentration, temperature and reaction time on the size and morphology of the samples were studied in detail. [ABSTRACT FROM AUTHOR]

Carbon-encapsulated cobalt (Co@C) nanoparticles, with a tunable structure, were synthesized by chemical vapor deposition using Co nanoparticles as the catalyst and supported on a water-soluble substrate (sodium chloride), which was easily removed by washing and centrifugation. The influences of growth temperature and time on the structure and magnetic properties of the Co@C nanoparticles were systematically investigated. For different growth temperatures, the magnetic Co nanoparticles were encapsulated by different types of carbon layers, including amorphous carbon layers, graphitic layers, and carbon nanofibers. This inferred a close relationship between the structure of the carbon-encapsulated metal nanoparticles and the growth temperature. At a fixed growth temperature of 400 °C, prolonged growth time caused an increase in thickness of the carbon layers. The magnetic characterization indicated that the magnetic properties of the obtained Co@C nanoparticles depend not only on the graphitization but also on the thickness of the encapsulated carbon layer, which were easily controlled by the growth temperatures and times. Optimization of the synthesis process allowed achieving relatively high coercivity of the synthesized Co@C nanoparticles and enhancement of its ferromagnetic properties, which make this system promising as a magnetic material, particularly for high-density magnetic recording applications. [ABSTRACT FROM AUTHOR]

La 1− x Ga x FeO 3 ( x = 0.0, 0.1, 0.2, 0.3 and 0.4) nanoparticles were synthesized by polymerization complex method. X-ray diffraction (XRD) results reveal a pure orthorhombic phase structure. Increasing of Ga content, resulting in the decrease of average crystallite sizes calculated by XRD from 58.4 ± 5.9 to 13.4 ± 4.3 nm and the average particle sizes estimated by transmission electron microscope (TEM) images from 70.2 ± 4.5 to 21.4 ± 8.5 nm. The optical band gaps determined by UV–vis spectra showed a redshift from 2.145 to 1.954 eV that originates from surface effect caused by Ga substitution. The magnetic properties were investigated using a vibrating sample magnetometer (VSM). The room temperature hysteresis loops of La 1– x Ga x FeO 3 nanopowders indicate the antiferromagnetic behavior of pure sample and all doped samples of ferromagnetic behavior with the enhancement of coercive field ( H c ), remanence ( M r ) and magnetization ( M ) due to the more disordering spins induced at the surface of particle. It is evident from field cool (FC) measurement of La 0.6 Ga 0.4 FeO 3 sample that the Curie temperature ( T c ) is above 350 K. [ABSTRACT FROM AUTHOR]

In the present work, cobalt ferrite nanoparticles were synthesized by the combustion method using two different fuels, urea and citric acid. The fuels were altered to vary the size and also to study the effect of the fuel and size on the dielectric and magnetic properties of cobalt ferrite. The phase formation was confirmed by powder X-ray diffraction (XRD) and Fourier transform infrared spectroscopy (FT-IR). The average crystallite size of the particles was calculated using Scherrer's formula, and it was observed that the particles were of nanosize ranging from 10 to 13 nm. The surface morphology and chemical composition of the compounds were analyzed using scanning electron microscopy and energy-dispersive X-ray spectroscopy. The influence of fuel on the dielectric study and conductivity was determined at different temperatures (35-120 °C) and also at different frequencies (10 Hz-5 kHz). An increase in the dielectric constant, saturation magnetization ( M), coercivity ( H), and remanent magnetization ( M) was observed with an increase in the particle size. [ABSTRACT FROM AUTHOR]

Mn- and Co-doped and pure BiFeO (BFO) nanoparticles were synthesized through sol-gel method. The result of the Rietveld refinement based on X-ray diffraction (XRD) data revealed that BFO and 10 % Co-doped BFO sample crystallize in rhombohedral symmetry (R3c) structure. The transition of crystal structure can be found when Fe atoms were replaced by Mn atoms partially (from R3c to P4/mbm). Besides, Raman spectra further confirm the structure transformation which is consistent with the results of Rietveld refinements. Analysis of vibrating sample magnetometer (SQUID-VSM) magnetic hysteresis data shows the enhancement of magnetism in Mn- and Co-doped samples which were explained by the changing of bond length and angle which were obtained from the Rietveld refinement. [ABSTRACT FROM AUTHOR]

We present influences of silica coating process on the nanostructure and magnetic properties of superparamagnetic iron-oxide (SPIO) nanoparticles (NPs). The silica coating on SPIO NPs is done to render the composite particles suitable for biomedical applications. SPIO NPs synthesized using iron oleate in the present study are composed of an antiferromagnetic FeO core and a ferromagnetic Fe 3 O 4 shell except NPs of 7 nm in diameter, which are a single crystal of Fe 3 O 4 . The conversion of FeO phase to Fe 3 O 4 phase at their interface resulting from silica coating is confirmed using X-ray diffraction and magnetic measurements. The magnetic properties of SPIO NPs change with the increase in volume fraction of Fe 3 O 4 due to the conversion from FeO by the silica coating. In addition, a temperature-dependent magnetization reveals that the magnetic interaction between the antiferromagnetic FeO and the ferromagnetic Fe 3 O 4 influences the magnetic properties. These results suggest the strategy to obtain optimum magnetic properties of iron oxide/silica composite particles for biomedical applications. [ABSTRACT FROM AUTHOR]

Functionalized Fe nanoparticles (NPs) have played an important role in biomedical applications. In this study, metallic Fe NPs were deposited on SiO2 spheres to form a Fe/SiO2 composite. To protect the Fe from oxidation, a thin SiO2 layer was coated on the Fe/SiO2 spheres thereafter. The size and morphology of the SiO2@Fe/SiO2 composite spheres were examined by transmission electron microscopy (TEM). The iron form and its content and magnetic properties were examined by X-ray diffraction (XRD), inductively-coupled plasma mass spectrometry (ICP-MS) and a superconducting quantum interference device (SQUID). The biocompatibility of the SiO2@Fe/SiO2 composite spheres was examined by Cell Counting Kit-8 (CCK-8) and lactate dehydrogenase (LDH) tests. The intracellular distribution of the SiO2@Fe/SiO2 composite spheres was observed using TEM. XRD analysis revealed the formation of metallic iron on the surface of the SiO2 spheres. According to the ICP-MS and SQUID results, using 0.375 M FeCl3. 6H2O for Fe NPs synthesis resulted in the highest iron content and magnetization of the SiO2@Fe/SiO2 spheres. Using a dye loading experiment, a slow release of a fluorescence dye from SiO2@Fe/SiO2 composite spheres was confirmed. The SiO2@Fe/SiO2 composite spheres co-cultured with L929 cells exhibit biocompatibility at concentrations <16.25 μg/mL. The TEM images show that the SiO2@Fe/SiO2 composite spheres were uptaken into the cytoplasm and retained in the endosome. The above results demonstrate that the SiO2@Fe/SiO2 composite spheres could be used as a multi-functional agent, such as a magnetic resonance imaging (MRI) contrast agent or drug carriers in biomedical applications. [ABSTRACT FROM AUTHOR]

NiFe 2 O 4 nanoparticles were synthesized via mechanical activation of NiO and Fe 2 O 3 powders in a high energy planetary ball mill. The results indicated that after 30 h of ball milling the NiO/Fe 2 O 3 reacted with a solid-state reaction mode producing nickel ferrite particles with 12 nm in size. Differential scanning calorimetry (DSC) on the 30-h activated sample showed nickel ferrite’s Curie temperature to be around 573 °C. The 30 h-activated compacted powders were sintered from 900 to 1300 °C with 100 °C increments. From the XRD patterns results, however, increasing sintering temperature to 1300 °C led to an increase of the Ni-ferrite’s crystallite sizes; the sizes remained in nano scale and no phase change was observed. A critical grain size of 211 nm was found from plotting the grain size against coercivity, suggesting a single-domain particles area was reduced and multi-domain particles area was increased by increasing sintering temperature. The grain growth activation energy was found to be 64.43 kJ/mol. The electrical resistivity obtained was ∼10 6 Ω cm at 900 °C and its value decreased to ∼10 5 Ω cm at 1300 °C sintering. VSM studies showed saturation-magnetization increase from 8.5 emu/g in the 30 h-activated sample to 52.6 emu/g in those sintered at 1300 °C. Two different shapes of hysteresis loops were observed in the B–H curves. [ABSTRACT FROM AUTHOR]