Oxygen Positional Parameter Research Articles

Effects of thermal, stress, and electric fields on microstructure and ion distribution of (Mg0.1Mn0.1Co0.1Ni0.2Ti0.1Cu0.1Zn0.2)Fe2.1O4 spinel ferrites

In this work, conventional sintering, hot-pressing sintering, and spark plasma sintering techniques were utilized to simulate the thermal field, thermal-stress field, and thermal-stress-electric field, respectively. The effects of these fields on the microstructure and cation distribution of the (Mg0.1Mn0.1Co0.1Ni0.2Ti0.1Cu0.1Zn0.2)Fe2.1O4 ferrite (HEF) material were comprehensively analyzed. The results indicate that in the temperature range of 1000–1100 °C, the thermal field provides the driving force for sintering, promotes grain growth (average particle size: 2→7 μm), and increases crystallinity degree. The stress field brings the particles into close contact with each other, facilitates diffusion, and delays grain growth (0.5→5 μm). The electric field reduces grain boundary energy, causes mass transfer, and makes the grains finer (0.5→0.7 μm) and more uniform. Mathematical model analysis reveals that the thermal field is beneficial to the random distribution of cations, which yields an inversion degree (γ) of about 2/3 and increases the configuration entropy of HEF. The stress field leads to lattice distortion, permits ions with larger radius to occupy tetrahedral positions, and changes the cell parameters and oxygen position parameter of HEF. Finally, the interaction between electric field and crystal charges increases the electrostatic field energy, which promotes the formation of positive spinel structure and maximizes the crystal field stability energy. X-ray photoelectron spectra, Raman spectra, and change in lattice constant confirm the rationality of the mathematical model, and can be used to establish the model of the crystal structure under field effects.

Chemical synthesis of Mn–Zn magnetic ferrite nanoparticles: Effect of secondary phase on extrinsic magnetic properties of Mn–Zn ferrite nanoparticles

This paper presents a comprehensive investigation of the magnetic properties of co-precipitated MnxZn1–xFe2O4 nanoferrites, where x takes the values of 0.5, 0.6, and 0.7. X-ray diffraction patterns indicated the presence of spinel phase. However, the ferrite composition x = 0.6 contains little trace of secondary phase α-Fe2O3. The occurrence of cation redistribution in the current ferrite samples can be concluded from the deviation of oxygen position parameter (U) to that of optimum value (0.375). The bond angles facilitate the reduction of the A–B interaction and the increase of the B–B interaction. With the substitution of Mn2+ ions, the saturation magnetization (Ms) exhibits both drops and increases whereas the coercivity (Hc) consistently declines. The ferrite composition x = 0.7 exhibits the maximum value of Ms and is equal to 27.9 emu/g. The blocking temperature (TB) rises in proportion to the degree of Mn2+ ion doping. The observation of quadruple doublets in the Mӧssbauer spectra indicates that the ferrite nanoparticles exist in single domain state exhibiting the quadruple interactions. The range of isomer shift (δ) 0.199–0.267 mm/s indicates the existence of exclusively high spin Fe3+ ions. Two paramagnetic doublets are anticipated to exist as a result of the core and shell of present ferrite nanoparticles. In the core-shell morphology of nanoparticles, the core is characterized by larger quadruple splitting (Δ) while the shell is characterized by smaller Δ. The results are integrated in terms of magnetocrystalline anisotropy and secondary phase presuming the core-shell structure of nanoparticles.

Mössbauer analysis, structural parameter studies and magnetic properties of LiCoxFe5-xO8 (x= 0, 0.025, 0.05, 0.075, 0.1) nanoparticles

We report on detailed structural parameter analysis, Mössbauer spectra and magnetic properties of LiCoxFe5-xO8 (x = 0, 0.025, 0.05, 0.075, 0.1) nanoparticles prepared by sol-gel method. Prepared LiCoxFe5-xO8 nanoparticles crystalizes in inverse spinel structure with the crystallite size ranging from 23.7 to 29.8 nm. Hopping length, radii of tetrahedral and octahedral sites (rA and rB), tetrahedral bond length (dAx), octahedral bond lengths (dBx), tetrahedral and octahedral shared edges (dAxE, dBxE), unshared octahedral edges (dBxEU) values and oxygen positional parameter (u) are seen to increase with increasing Co concentration. Chemical state of all the elements are confirmed by X-ray photoelectron spectroscopy technique. The hyperfine field, isomer shift, quadrupole shift and line width parameters calculated from the Mössbauer spectra confirms the Co2+ substitution in LiFe5O8. The saturation magnetization value decreases from 59.2 to 54.1 emu/g with increasing Co concentration, which is examined by three sublattice model derived by Yafet and Kittel (Y-K model). Y-K angles increases with Co concentration from 16.46 to 19.98°. Curie temperature of LiFe5O8 decreases from 865 K to 858 K with increasing Co concentration to x = 0.1.

Electron density mapping and bonding in Mn doped CoFe2O4 using XRD, and its correlation with room temperature optical and magnetic properties

Single-phase Mn-doped Cobalt spinel ferrite prepared via the self-combustion method shows mixed spinel structure. Cation occupancy in tetrahedral A and octahedral B sites was observed through XPS, XRD, and VSM analysis. Crystallite size, porosity, surface area, and energy band gap results pave a path to optical absorption related applications. The energy band gap of MnxCo1-xFe2O4 nanoparticles were estimated using the Tauc plot and the values ranging from 1.123 eV to 1.247 eV. XPS-based energy level splitting of Mn 2p3/2 and Mn 2p1/2 confirms the occupation of Mn2+ and Mn3+ in octahedral and tetrahedral sites, respectively. The magnetic hysteresis from VSM depicts the formation of semi-hard ferrite with a maximum saturation magnetization of 79.612 emu/g and a coercivity of 1056 Oe, and the magnetic parameters decrease with the increase in manganese doping concentration. The Maximum Entropy Method (MEM)-based electron density mapping shows the electronic structure and bonding nature. Using MEM, a novel and favourable maximal coercivity condition is correlated with the high and moderate numerical bond critical density of 1.123 e/Å3 for A-O and 0.413 e/Å3 for B-O interactions, respectively. Strong A-O covalent bonds and feeble B-O covalent bonds are characteristics of spinel ferrites with high magnetization. The oxygen positional parameter values for all the samples not exceed 0.377 which is very close to the ideal value of 0.375.

Investigating the modification in structural properties of cobalt ferrite nanoparticles with increasing annealing temperature

In this paper, we have investigated the variation in structural parameters with annealing temperature for cobalt ferrite nanoparticles prepared by a simple coprecipitation technique. The samples are characterized using XRD measurement. XRD data confirms that the cobalt ferrite nanoparticles possess a spinel structure for both annealing temperatures 430°C and 600°C. It also shows an impurity phase if the samples are annealed at 600°C. Different structural parameters such as lattice parameters, bond lengths, oxygen positional parameters, etc. are calculated in more detail from XRD data, which will elucidate the connection between annealing temperature and structural properties.

Morphological, structural, surface, thermal, chemical, and magnetic properties of Al-doped nanostructured copper ferrites

Aluminum-doped copper ferrite nanoparticles synthesized via thermal decomposition were analyzed for Al3+ substitution effects. Nanocrystalline doped copper ferrite with a crystallite size <9 nm was characterized using several advanced techniques, including X-ray diffractometry (XRD), thermogravimetric analysis (TGA), differential scanning calorimetry (DSC), scanning electron microscopy (SEM), energy-dispersive X-ray spectroscopy (EDX), and X-ray photoelectron spectroscopy (XPS). The degree of thermal decomposition used for doping copper ferrite at the nanoparticle level correlates well with the quantitative, dimensional, and structural characterizations. The Scherrer equation and Williamson–Hall method were employed to determine the general lattice strain and constants. Structural properties, such as the oxygen positional parameters, radii of the octahedral and tetrahedral sites, hopping lengths, bond lengths and angles, site bonds, and edge lengths, were determined using XRD patterns. The improved A–B super-exchange interaction was demonstrated by the discrepancy in the theoretically anticipated bond angles. The analysis of magnetic hysteresis (M − H) using a vibrating sample magnetometer (VSM) and XPS confirmed the improvement in the super-exchange interaction. XPS results suggest that Fe and Cu in the crystal lattice are in the form of FeIII and CuII, respectively. The investigation of the degree of inversion, state, and composition using XPS aids to understand the properties of the nanostructured copper ferrites. The saturation and remnant magnetization were determined from hysteresis loops at 1.8 T obtained using the VSM at room temperature. The noncollinear spin and efficient sublattice interactions are responsible for the decrease in Ms and Mr.

Tailoring the structural, optical, photoluminescence, dielectric and electrical properties of Zn0·6Ni0·2Mg0·2Fe2-xLaxO4 (x = 0.00, 0.0125, 0.0250, 0.0375)

The green synthesis approach was used to manufacture the lanthanum modified spinel ferrites, which had the formula Zn0·6Ni0·2Mg0·2Fe2-xLaxO4 and were heated at 100 °C for 2 h. Through the use of XRD, FTIR, UV–visible, RLC study, four probe I–V, and PL spectroscopy the structural, optical, dielectric, electrical, and photoluminescence features were examined. XRD results confirmed that spinel ferrite have a cubic network. The substitution of La ions causes an overall increase in sample's lattice constants, which was credited to the disparity in ionic radii between Fe3+ (0.63 Aͦ) and La3+ (1.061 Aͦ) ions. From the XRD data, it was possible to compute the cationic distributions, oxygen positional parameters, tolerance factor, interatomic distances, bond lengths, bond length angles, and positional parameters. The computed Eg from the UV–Visible spectroscopy was decreased from 2.5 to 1.8eV. FTIR results revealed octahedral absorption band having 557.32–550.57 cm−1 range. The value of force constant from FTIR was revealed in the range of 2.27–2.21 dyne cm−1. The dielectric losses and constant are decreasing, whereas ac conductivity exhibited expanding behavior with high frequency. PL test result shows that La doping improves the material's light response, so the result showed that La-doped materials are suitable for magneto-optic devices. Electrical properties show that DC electrical resistivity decreases in the range of 1.65 × 10°5–5.01 × 10°3 Ω-cm. So, they are suitable for high-frequency circuits.

Study structural, surface morphological and magnetic properties of Mn(1-x) Znx Fe2O4 by solid state reaction method

The powder of Mn-Zn ferrite having the chemical formula Mn(1-x)ZnxFe2O4 where x varies from 0, 0.1, 0.2, 0.3, 0.4, and 0.5 were synthesized by solid state Reaction method. The X-Ray Diffraction studies confirm the formation of spinel cubic structure. The particle size was calculated by X-ray broadening studies. Also the structural parameters like Lattice Constant, X-ray density, bulk density (d), Porosity (P), ionic radius (Ra , Rb) and anion parameter or the oxygen positional parameter for all the samples. The micro structural features of the samples were obtained using a Scanning Electron Microscopy (SEM). The magnetic properties of Mn(1-x)ZnxFe2O4 ferrites were strongly affected by the Zn content. The saturation magnetization increased. It may be due to relatively high orbital contribution of Mn2+ ions to magnetic moment, which gives large induced anisotropy.

Magnetic studies of Mn2+substituted Zn-ferrite nanoparticles: Role of secondary phases, bond angles and magnetocrystalline anisotropy

Magnetic studies of MnxZn1–xFe2O4 (x = 0.5, 0.6, 0.7) nanoferrite particles prepared by sol-gel auto combustion method are presented. The deviation of the oxygen positional parameter (U) from the ideal value of 0.375 is an indicator for the cation redistribution in the present ferrite systems. The variation of bond angles estimated from the cation distribution seemed to be strengthening of A–B superexhange interaction. The nature of M − H loops revealed that the present ferrite nanoparticles are in the single domain state showing superparamagnetism. The saturation magnetization (Ms) increases while coercivity (Hc) decreases with the substitution of Mn2+ ion concentration. The highest value of Ms = 25 emu/g was reported for the composition x = 0.7. It was observed that the blocking temperature (TB) is decreasing and again increasing with the doping level of Mn2+. From FC-ZFC curves, the uneven variation of magnetization (M) at 10 K can be found. It attributes to the cation distribution in the ferrite samples at 10 K is different from those of at 300 K. The Mӧssbauer spectra revealed that the ferrite nanoparticles exhibited both quadruple and hyperfine interactions can be found in the composition x = 0.7 while the ferrite nanoparticles exhibited that only quadruple interaction can be in the compositions x = 0.5 and 0.6. The isomer shift (δ) values showed the presence of high spin Fe3+ ions only. The paramagnetic doublets having higher value of quadruple splitting (Δ) are assigned to the core structure while doublets lower value of quadruple splitting (Δ) is assigned to shell structure. The present results are incorporated in terms of cation distribution, magnetocrystalline anisotropy considering the core-shell morphology of ferrite nanoparticles.

Exploration of structural and magnetic aspects of biocompatible cobalt ferrite nanoparticles with canted spin configuration and assessment of their selective anti-leukemic efficacy

Single phase CoFe2O4 nanoparticles (CF NPs) were prepared by a simple co-precipitation method. The cation distribution over A and B sites was estimated from the Rietveld analysis. In addition, different structural parameters, viz, oxygen positional parameter, bond angle, bond length, and strength of different interactions were also determined. The M-H loop at room temperature with moderate coercivity (∼204 Oe) and remanent magnetization (∼0.85 emu/gm) implies that the sample is ferromagnetic in nature and suitable for drug delivery/biomedical applications. The magnetization does not change appreciably with temperature due to the Yafet-Kittel spin arrangement on the B sublattice. For the evolution of the anti-leukemic activity of CF NPs, cell viability assay was performed against the K562 cell line, as well as the cytotoxicity was determined against healthy human blood cells. Significant anti-leukemic efficacy was found in a time and concentration dependent manner (IC50: 27.77 µg/ml); whereas in the case of normal cells, a higher level of IC50 value (87.03 µg/ml) was observed. Oxidative stress was induced after treatment with CF NPs in cancer cells, which was reported by measuring cellular redox status, oxidative stress marker, and antioxidant enzyme activity. As evident by fluorescence imaging, the increased level of ROS produced DNA damage and ultimately leads to the death of the cancer cells.

Synthesis of Nickel-Zinc Ferrite Nanoparticles by the Sol-Gel Auto-Combustion Method: Study of Crystal Structural, Cation Distribution, and Magnetic Properties

Spinel ferrite nanocomposites of Ni1–xZnxFe2O4 (x = 0.25 and 0.75) were synthesized by sol-gel auto-combustion and annealed between 250°C and 1000°C. A single-phase spinel structure was found through X-ray diffraction (XRD). The crystallite size is in the range of 17.55–66.98 nm, and lattice parameters are in the range of 8.351–8.434 Å. X-ray analysis revealed a slight shift of the peaks towards shorter angles when the zinc concentration increased from 0.25 to 0.75. XRD measurements revealed the metal ion distribution in the spinel ferrite system. For each sample, XRD data were used to compute structural characteristics such as lattice spacing, lattice constant, crystallite size, oxygen position parameter, tetrahedral and octahedral ionic radii, and bond lengths. Energy dispersive spectroscopy (EDS) spectra and field emission-electron scanning microscope (FESEM) were used to evaluate the elemental content and morphology. EDS analysis confirmed the presence of expected elements in the samples and confirmed the high doping rate of more than 180% of Zn ions in Ni ferrite. The evaluated particle sizes were determined to be 79.2 and 118.4 nm for zinc content of 0.25 and 0.75, respectively. The nearly spherical shape of the nanoparticles was shown in the transmission electron microscope (TEM). The magnetic moment, remanent, coercivity, and saturation magnetization were calculated by using vibrating sample magnetometer (VSM) results. The saturation magnetization magnitudes showed the influence of cation distribution.

Si9+ Ion-Irradiation Induced Modification of Structural and Magnetic Properties of Zn-Nanoferrite

We report synthesis of ZnFe2O4 by sol gel auto-combustion technique, and study the effect of 120 MeV 28Si9+ ion irradiation (dose: 1 × 1012 −1 × 1014 ions cm−2) on structural, magnetic properties, correlation between them, probed by X-ray diffraction “XRD,” scanning electron microscopy-energy dispersive X-ray analysis “SEM–EDX,” magnetic measurements. Formation of single-phase spinel nanoferrite (grain diameter: 15.93–16.92 nm), is confirmed by XRD. EDX-SEM confirms formation of desired phase, non-homogeneous particle size dispersal. Results show that with increasing irradiation dose, lattice parameter decreases;reduction of Fe3+ ions on B-site, with concurrent increase on A-site, while Zn2+ ions remain more populated on A-site than on B-site. Irradiation shows decrease of oxygen positional parameter, and strain, increase of inversion-degree, modification of A–O–B, A–O–A, B–O–B super-exchange interaction, reduction of dead-layer thickness, resulting in reduction of coercivity, saturation magnetization. Linear dependence of coercivity on grain diameter suggests the studied samples lie in overlap-region between multiple-domains or single-domain.

Doped Nanostructured Manganese Ferrites: Synthesis, Characterization, and Magnetic Properties

Nanocrystalline aluminum-doped manganese ferrite was synthesized by facile thermal treatment method. Nanostructure-doped ferrite with crystalline size that ranged between 3.71 and 6.35 nm was characterized via X-ray diffraction (XRD), scanning electron microscopy (SEM), X-ray photoelectron spectroscopy (XPS), and vibrating-sample magnetometry (VSM). The Scherrer and Williamson-Hall hypothesis techniques were utilized to determine lattice constants and strain. Various types of structural properties including octahedral and tetrahedral site radius, bond lengths and angles, hopping parameter, oxygen positional parameters, site bonds, and edge lengths were determined from XRD spectrum analysis. Discrepancy in the hypothetically expected angle indicates improvement of A-B superexchange intercommunication. Furthermore, magnetic-hysteresis (M-H) and XPS analysis support the claim of enhancement. The presence of the ionic nature of iron and manganese in ferrite is FeII, FeIII, MnII, and MnIV as revealed by the results of XPS. Moreover, XPS assists in an excellent way to understand the properties such as configuration, chemical nature, and average inversion degree of doped ferrite samples. The spin noncollinearity and exquisite interaction amid the sublattice are responsible for the decrease in the saturation and remnant magnetization determined from the hysteresis loop at ambient temperature with maximum magnetic field of 1.8 T.

The Effects of High-Grade Metamorphism on Cr-Spinel from the Archean Sittampundi Complex, South India

We investigated the crystal and structural behavior of Cr-bearing spinels from the Archean chromitites of Sittampundi (India), which had been subjected to very high-grade metamorphism. The structural data show that their oxygen positional parameters are among the highest ever recorded for Cr-bearing spinels with similar Cr# and Mg# and very similar to those found for other Archean occurrences. The general agreement between electron microprobe and Mössbauer data indicates that the analyzed spinels are stoichiometric. It is therefore most likely that the PH2O and Ptotal values as well as both the oxygen fugacity and the temperature reached during high-grade metamorphism inhibited the possibility of the non-stoichiometry of chromites, contrary to what can happen in ophiolites, where non-stoichiometry has recently been documented.

Impact of dysprosium doped (Dy) zinc ferrite (ZnFe2o4) nanocrystals in photo- fenton exclusion of recalcitrant organic pollutant

The issue of effluent, especially organic colorants from several manufacturing units overlays an immense delinquent of the current epoch owing to its effect on oncogenic health hazards. Thus, Rare Earth Metal dysprosium (Dy) doped Zinc Ferrite (ZnFe2O4) were as-synthesized by a facile co-precipitation technique as an effectual nano photocatalyst intended to the amputation of these noxious dyes. The structural, functional, optical, magnetic, and degradation properties of this RE (Dy3+) doped ions were investigated using various characterizations, such as crystallite size (D) and several parameters (cation distribution, oxygen positional parameters, and bond length) were determined using XRD (X-ray diffraction) and it was found that as the dy3+ ion concentration increases the speck size decreased and the grain size remained within nano regime, which intern affects the surface area. From BET analysis it was found that on increasing the doping concentration, the surface area increases which pave a substantial role in the photo-Fenton activity. By using FT-IR (Fourier-transform infrared spectroscopy) various functional parameters (elastic, interionic bonds, ion distribution, etc.) were determined. Raman spectra had no extra peak formation which is seen to have pure phase formation of the as-synthesized samples. HR-TEM (High-Resolution Transmission Electron Microscopy analysis were done to determine the nature of the sample, the as-synthesized magnetic samples exhibit a polycrystalline formation with cubical agglomeration. The magnetic property was very significant for x = 0.10 concentration. As-synthesized (Fe0.9064Zn0.0936) [Fe1.0936Dy0.1Zn0.8064] O4) exhibits a momentous photo – Fenton activity against MB (Methylene blue), its removal efficiency was found to be 97.3% after 45 min. Also, this spinel ferrite acts as a magnetic recyclable catalyst even after 5 cycles with an insignificant lessening of elements and photo-Fenton activity.

Elastic and Structural Properties of Mn2+ Ions Substituted Zn-Co Mixed Ferrites

Magnetic oxides, which are commonly known as ferrites are ferromagnetic in structure. Ferrites have been recognized as one of the most important electromagnetics in modern industry and their processing and application technologies have been improved incessantly in the last 20 years. composition Zn0.5Co0.5-xCdxFe2O4 (x = 0.0, 0.3, 0.5) Cd2+ ions substituted Zn-Co ferrites having have been prepared using the common ceramic technology of double sintering and oxides of AR grade. The preparation of the monophase cubic spinel structure of the ferrite phase is confirmed by X-ray diffraction (XRD) and infrared spectrum analyses. Due to the enormous ionic radius of Cd2+ ions, it was discovered that the lattice constant increased as the cadmium level increased. The bond length, jump length of the tetrahedral (A) site as well as the octahedral [B] site, tetrahedral edge length, shared and unshared octahedral edge length, and other structural parameters were estimated. These parameters included the lattice parameter, X-ray density, cation distribution, ionic site radii, oxygen positional parameter, and theoretical lattice parameter. By contrasting the observed and predicted lattice characteristics, it was possible to confirm the estimated cation distribution of ferrite and is IR, elastic parameters, including both the modulus analysis were estimated

In3+ doped ZnGa2O4 nanoparticles: Difference in the luminescence properties upon optical and electrical excitations

In the present study, influence of In3+ doping on the structural and luminescence properties of ZnGa2O4 nanoparticles has been investigated in detail. In3+ doped ZnGa2O4 nanoparticles with size less than 10 nm have been prepared at a relatively low temperature of 120 °C. From X-ray diffraction (XRD) and photoluminescence (PL) studies, different Ga3+ structural units, with varying number of In3+ as next nearest neighbors (NNN) around Ga3+ in GaO6 octahedra, have been identified and their relative extent is evaluated by assuming a binomial distribution of Ga3+ and In3+ cations in the lattice. The GaO6 octahedra are found to be unaffected by In3+ doping as confirmed by the identical values of oxygen positional parameter “x” derived from Rietveld refinement of the XRD patterns. Alternating current powder electroluminescence (ACPEL) has been demonstrated for the first time from the nanoparticles of undoped and In3+ doped ZnGa2O4. Due to the formation of GaO6 structural units with varying number of In3+ as next near neighbors around Ga3+, tuning of emission wavelength is observed from the nanoparticles upon UV excitation. However, under an applied electric field during electroluminescence (EL) measurements, only regular GaO6 structural units undergo excitation and Ga-O-In linkages mainly act as scattering centers leading to less favorable electrical excitation of corresponding GaO6 structural units. The findings have potential relevance in the area of wide band gap semiconductor technology employing doped ZnGa2O4 nanoparticles.

Structural, thermal, morphological, surface, chemical, and magnetic analysis of Al3+-doped nanostructured mixed-spinel cobalt ferrites

The effect of Al3+ substitution into nanocrystalline cobalt ferrite that was prepared via a thermal treatment method was investigated. The average ferrite nanoparticle diameters are found to be in the range between 5.86 and 15.91 nm when polyvinylpyrrolidone (PVP) was used as a capping agent. The importance of the thermal treatment process in capitulating as-produced aluminum-doped cobalt ferrite on the nanostructured scale is in excellent agreement with the results of structural, thermal, quantitative, dimensional and morphological characterizations, which included X-ray diffraction (XRD), particle size analysis, thermogravimetric analysis (TGA), differential scanning calorimetry (DSC), scanning electron microscopy (SEM) and energy-dispersive X-ray (EDX). The lattice strain and lattice constants were determined by employing the Scherrer and Williamson-Hall extrapolation methods. XRD pattern analysis was used to examine various structural characteristics, which included oxygen positional parameters, radii of octahedral and tetrahedral sites, hopping lengths, bond lengths and bond angles, site bonds, and edge lengths. The disparity in the theoretically anticipated bond angle demonstrates the enhancement of A-B superexchange interactions. This enhancement was supported by the results of Magnetic-Hysteresis (M − H) measured by vibrating-sample magnetometry (VSM) and X-ray photoelectron spectroscopy (XPS) studies. The XPS results demonstrated that iron is present as FeIII and cobalt is present as CoII. XPS analysis represents a powerful tool for investigating the composition, chemical state and inversion degree of doped cobalt ferrites, thereby contributing to the understanding of their properties. The reduction of both saturation magnetization (Ms) and remnant magnetization (Mr), which is demonstrated by the hysteresis loop that was obtained at room temperature (RT) with an ultimate magnetic field of 1.8 T, is due to spin noncollinearity and delicate interactions among sublattices.

Structural and magnetic characterizations of NixCu0.8-x Zn0.2Fe2O4 spinel ferrites

The Ni-Cu-Zn ferrites are one of the most exciting spinel oxides so far because of its diverse applications. In the current study, the ratio of nickel and copper was varied keeping the concentration of zinc constant primarily aiming to examine its effect on cation distribution as well as structural and magnetic properties. The samples were synthesized via the conventional solid state sintering method at a temperature of 1050 °C then subjected to neutron diffraction studies. The magnetic properties were measured using a vibrating sample magnetometer (VSM) which complements the magnetic measurements from the neutron diffraction experiments. The ferromagnetic behaviors of these Ni-Cu-Zn ferrites were explained using the Y-K model and the canting of the magnetic moments were also measured. The lattice parameter ‘a’ was seen to reduce which results from the replacement of large Cu+ ions (0.73 with the smaller ionic radius of (0.69 ). To accommodate a large number of cations in the spinel lattice, the oxygen atoms restructure themselves as a result oxygen position parameter increased. The net magnetic moment per unit formula decreases as the Ni content is increased up to a level, after which the net moment increased.

Effect of cobalt doping on structural parameters, cation distribution and magnetic properties of nickel ferrite nanocrystals

Here, thermal heat treatment method has been used for the synthesis of PVP capped nickel ferrite (NiFe2O4) and cobalt doped nickel (Ni0.5Co0.5Fe2O4) spinel ferrite nanocrystals with the aim of investigating the effect of Co doping on the structural and magnetic properties of NiFe2O4 nanocrystals. XRD analysis confirms the formation of a pure form of FCC nanocrystals of spinel ferrite type, where the average crystallite size has been found to be approximately 17 nm and 19 nm respectively for nickel ferrite (NF) and cobalt doped nickel ferrite (CNF) from XRD. Again, HRTEM study gives the average size for NF and CNF as 20 nm and 25 nm respectively. Further, SAED pattern indicates the polycrystallinity of both the sample, whereas EDX analysis confirms the presence of expected elements in the sample. From XRD data analysis different structural parameters such as lattice spacing, lattice constant, tetrahedral and octahedral ionic radii, oxygen position parameter, average cation radius per molecule, ionic packing coefficients (Pa, Pb), the degree of ionic packing (α), vacancy parameter (β), hopping lengths, and bond lengths etc. have been calculated for both nickel and cobalt doped nickel ferrite nanocrystals. Further, obtained cation distribution for NF and CNF nanocrystals from their XRD pattern analysis shows huge change in the distribution as a result of doping. In addition, FTIR spectral analysis also confirms the phase purity of both the samples. Magnetic characterization shows the improvement of different magnetic parameters due to cobalt doping on nickel, thereby making CNF nanocrystals suitable for different application purposes.