Octahedral Bond Lengths Research Articles

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.

Minimum hysteresis loss and amplified magnetic properties of superparamagnetic Ni–Zn nano spinel ferrite

Nanocrystalline NixZn1-xFe2O4 ferrite was prepared using the microwave-assisted sol-gel auto combustion method. The nanocrystalline ferrite was characterized by powder XRD, SEM, FT-IR, VSM, Mossbauer, magnetic and dielectric study. The lattice constant, tetrahedral radius, octahedral radius, anion parameter, average crystalline size, tetrahedral bond length, octahedral bond length, and deviation parameter have been estimated from XRD and compared with standard results. The magnetic properties of the prepared ferrite were studied and parameters like saturation magnetization, magnetic remnant, magnetic moment, coercivity, and SQR were estimated. The effect of substitution on isomer shift and magnetic exchange interaction between octahedral and tetrahedral sites on magnetic properties were discussed from Mossbauer’s study. It was observed that the isomer shift does not vary appreciably with a concentration of nickel in zinc lattice. Moreover, the exchange interaction between Fe3+ ions at tetrahedral and octahedral sites and the doped nickel ions prefer the octahedral sites that strongly favor the magnetic interactions. The temperature dependence AC susceptibility was measured to know the magnetic phase transition. The dielectric constant and tangent loss are high at lower frequencies, decreasing with frequency and finally becoming almost constant. The dielectric constant ε′ was also found to increase with the increase in Ni2+ content.

Spin–phonon interaction and magnetoelastic coupling associated with unusual cluster-glass states in YFe0.9Cr0.1O3

The magnetic, optical phonon behavior of the polycrystalline YFe0.9Cr0.1O3 (YFC-10), prepared by solid-state reaction route, had been studied via static and ac magnetization measurements and Raman spectroscopic techniques respectively. The results indicated that YFe0.9Cr0.1O3 undergoes unusual cluster-glass transitions at low temperatures viz. Tf1 (SG1) = 108 K (Freez.1) and Tf2 (SG2) = 30 K (Freez.2) coexisting with the long-range weak ferromagnetic (WFM) state. Raman spectroscopic (RS) measurements revealed 12 distinct modes of vibrations at all temperatures with 83–433 K. Interestingly, the freezing transition at Tf1 is found to be accompanied by significant phonon renormalization. From the detailed analysis of the line-shape function of the Raman modes, the anomalous T-variation of the peak position and the linewidths suggests the existence of spin-phonon interaction in the present solid solution. Moreover the temperature dependent synchrotron X-ray diffraction studies between 10 and 300 K revealed the anomalous thermal variation of the lattice parameters and microscopic structural parameters such as super-exchange angles and (Fe/Cr)O6 octahedral bond lengths and bond angles at both the freezing transitions. Overall, the system exhibits the strong magnetoelastic and spin phonon coupling over a broad thermal regime viz. from Liquid. N2 to temperatures above room temperature (RT = 300 K) which makes YFe0.9Cr0.1O3 reliable for application purpose.

Structural and dielectric properties of aluminum-doped GaFeO3

Ga0.9Al0.1FeO3 and Ga0.75Al0.25FeO3 samples were obtained using a solid-state reaction process. Phase analysis indicated that all samples are single phase having an orthorhombic structure. The effect of Al doping on the lattice parameters, the distortions in the tetrahedral and octahedral bond lengths and angles and cation distribution of different ions among the four crystallographic positions in GaFeO3 (GFO) was studied in detail applying Rietveld structural analysis; Al ions substituted Ga mostly at the octahedral site G2 with a small fraction residing at the Fe1 and Fe2 sites. The sample morphology was investigated by high-resolution scanning electron microscopy and the corresponding energy-dispersive x-ray analysis manifested element percentages in accordance with intended values. The influence of the doping amount, the frequency and temperature on the dielectric properties, ac conductivity, complex impedance and complex electric modulus of GFO was also investigated. Nyquist plots for both samples at different temperatures were studied. The activation energy of doped samples is in agreement with the activation energies of double ionized oxygen vacancies; it increased as the amount of Al doping GFO matrix increased.

Effect of annealing on photoluminescence of MgAl1.8Y0.14Eu0.06O4

MgAl2O4 and MgAl1.8Y0.14Eu0.06O4 powders were prepared by sol–gel method and annealed at 600, 800, and 1000 °C. X-ray diffraction patterns confirm the cubic spinel phase with space group Oh7Fd3-m. Increasing the annealing temperature (Ta) resulted in increased octahedral bond lengths and bonding angles resulting in the crystalline phase of the samples. Scanning electron microscopy reveals the micron size flakes morphology and agglomerated grains. The presence of elements such as Mg, Al, Eu, and Y was confirmed by Energy dispersive x-ray spectra. Photoluminescence (PL) was not observed in MgAl2O4 but in the excitation spectra of MgAl1.8Y0.14Eu0.06O4 at emission wavelength 615 nm, both f orbital transitions of Eu3+ ions and charge transfer bands were observed. The intensity of the peak at 392 nm corresponding to the 7F0 → 5L6 transition is strongly dependent on annealing and it is increasing with Ta. Out of 5D0 → 7FJ(= 0, 1, 2, 3, 4) characteristic transitions of Eu3+ ions, the electric dipole transition - 5D0 → 7F2 (618 nm) is prominent in the PL emission spectra. Annealing has further increased the intensity of PL emission spectra. The presence of Eu2+ ions is evident from the broad peak observed around 340 nm (assigned to the 4f65d to 4f7 (8S7/2) transition) in the excitation spectra at emission wavelength 480 nm. The intensity of this peak is decreasing with increasing Ta.

Investigation of new magnetoelastic and magnetic transitions accompanied with magnetoelectric coupling in multiferroic

A new multiferroic solid solution has been developed and characterized for structure, phase transition, magnetoelectric and magnetoelastic coupling. Temperature dependent measurement of dc-magnetization on ceramic shows two magnetic transitions one around 42 K and the second at 130 K. The real part of dielectric permittivity exhibits step like change at the magnetic anomaly temperature (130 K) which indicates the presence of magnetoelectric coupling. The change in the value of dielectric permittivity on the application of magnetic field confirms the presence of magnetoelectric coupling in ceramic. The room temperature polarization (P)-electric field (E) hysteresis loop measurement shows week ferroelectric nature of sample while the magnetization (M) versus magnetic field (H) measurement suggest weakly ferromagnetic character. The ferroelectric nature of sample was further confirmed by calculating remanent polarization using PUND measurement. The Rietveld structural analysis of low temperature x-ray powder diffraction data does not reveal any crystallographic phase transition in terms of peak splitting or new reflections. However, temperature dependence of lattice parameters, tetragonality, unit cell volume, octahedral tilt angle (), bond length and bond angles reveal discontinuous changes at both the magnetic transitions observed in temperature dependence of magnetization. This confirms that both the magnetic anomalies (around 42 K and 130 K) exhibit magnetoelastic coupling accompanied with isostructural transitions.

Rietveld refinement and FTIR spectroscopic studies of Ni2+-substituted Zn-ferrite nanoparticles

Mixed spinel ferrites with stoichiometric equation NixZn1−xFe2O4 (x = 0.5, 0.6, 0.7) were synthesized by co-precipitation technique and consequently heat treated at 800 °C for 2 h. EDX spectra concluded the stoichiometry of elemental composition of present ferrite systems. Rietveld refinement of XRD patterns confirms the cubic spinel structure of the ferrite phase belonging to Fd3m space group. Lattice parameter (8.398–8.387 A) is found to be in non-monotonic variation, whereas crystallite size (17.2–17.5 nm) is increased. From FE-SEM studies, the bigger ferrite nanoparticles (range of 27.9–39.4 nm) are found in the sample of composition x = 0.6. The variation of theoretical tetrahedral and octahedral bond lengths ($$R^{\prime}_{A}$$ and $$R^{\prime}_{B}$$) is quite opposite to the variation of bond lengths (RA and RB) calculated from the Rietveld refinement. The vibrational frequencies in FTIR spectra (ranging from 592 to 385 cm−1) cope with the formation of spinel phase supporting the XRD results. The elastic moduli of present ferrite systems appears to be increasing, but these values are high for the composition x = 0.6. The isotropic nature of present ferrite systems has been revealed from the same value of Poisson ratio obtained for all compositions.

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

Co-Tm nano-spinel ferrite with chemical formula CoTmxFe2−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 Hc, saturation magnetization Ms, remanence Mr, squareness ratio (SQR = Mr/Ms) and magnetic moment nB 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 Ms, Mr and Hc 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 Ms, Mr, and nB 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.

Investigation on structural, electrical and magnetic properties of titanium substituted cobalt ferrite nanocrystallites

The doping of parent compound with selective dopants usually enhances the properties of the parent compound. In this paper, titanium doped cobalt ferrite nanoparticles (Co1−xTixFe2O4 with x = 0–0.075) via the sol-gel route is reported. The effect of titanium ions on the properties of cobalt ferrite is detailed. Structural evolution is confirmed using XRD technique and the titanium ion induced changes are given in terms of lattice constant, grain size, X-ray density, tetrahedral and octahedral hopping length and tetrahedral and octahedral bond length. The X-ray diffraction pattern displayed the formation of cubic inverse spinal structure belonging to the Fd3m space group. FTIR analysis confirmed the presence of characteristic peaks of ferrites around 400 cm−1 and 600 cm−1. Raman spectroscopy revealed reduction in peak intensities of Raman active modes. SEM characterization had shown the formation of well resolved spherical particles. Elemental composition was evaluated by EDAX spectrum. TEM images also confirmed the spherical morphology of the nanocrystallites and crystallite size calculated is in agreement with that calculated from the XRD analysis. The SAED pattern shows uniform fringes of width 0.428 nm belonging (222) plane. The diffraction pattern of HRTEM confirmed cubic spinel structure of the samples. Magnetic properties are evaluated from room temperature hysteresis loops. Increase in the saturation magnetization and coercivity was observed with increasing titanium content. Gradual increase in impedance with the increase in titanium concentration was estimated by impedance spectroscopy.

Fast synthesis, structural, morphology with enhanced magnetic properties of cobalt doped nickel ferrite nanoscale

A series of cobalt substituted nickel ferrite nanoparticles with nominal compositions, Ni(1−x)Co(x)Fe2O4 (x = 0.0, 0.2, 0.4, 0.6, 0.8, 1.0) have been synthesized by gel process. The samples are characterized by X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FTIR), field emission scanning electron microscopy (FESEM) and vibrating sample magnetometer. The XRD spectra revealed that all the samples are of single phase spinel structure and the average size of nanocrystallite was calculated for a sample by the full width at half maximum (FWHM) of the strongest XRD peak. These sizes are small enough to achieve the suitable signal to noise ratio for the high density recording media. The lattice constant (a), X-ray density (ρ x ) and cell volume (V) are also calculated from XRD data. Experimental, theoretical lattice constant (aexp, ath), tetrahedral and octahedral radii (rA and rB), tetrahedral and octahedral bond length (dAx and dBx), tetrahedral edge (dAxE), shared octahedral edge (dBxE) and unshared octahedral edge (dBxEU) of the annealed Ni–Co ferrite nanoparticles increase with the increase in Co doping. Morphology of the samples was investigated by a FE-SEM. The FTIR spectra of the spinel phase calcinated at 600 °C exhibit two prominent fundamental absorption bands in the range of 350–610 cm−1 assigned to the intrinsic stretching vibrations of the metal at the tetrahedral and octahedral sites. The specific saturation magnetization (Ms), remanent magnetization (Mr) and the coercivity (Hc) of the spinel ferrites are further improved by the substitutions of Co+2 ions. The values of Ms for NiFe2O4 and CoFe2O4 are found to be 60.92 and 70.59 emu/g, respectively and Hc are in the range of 452.12–1026 Oe. The process is investigated with simultaneous thermogravimetric-differential thermal analysis (TG–DTA). The role played by the Co ions in improving the structural and magnetic properties are analyzed and understood. Our simple, economic and environmental friendly preparation method may contribute towards the controlled growth of high quality ferrite nanopowders and a potential candidate for recording media application.

Structural and electrical properties of Cu-doped Ni–Zn nanocrystalline ferrites for MLCI applications

Polycrystalline Cu substituted Ni–Zn ferrites with chemical composition Ni[Formula: see text]Zn[Formula: see text]-Cu[Formula: see text]Fe2O4 (x = 0.00 to 0.25 in steps of 0.05) have been prepared by citrate gel autocombustion method. The samples for electrical properties have been sintered at 900[Formula: see text]C for 4 h. The X-ray diffraction patterns of all samples indicate the formation of single phase spinel cubic structure. The value of lattice parameter is decreases with increasing Cu concentration. The estimated cation distribution can be derived from X-ray diffraction intensity calculations and IR spectra. The tetrahedral and octahedral bond lengths, bond angles, cation–cation and cation–anion distances were calculated by using experimental lattice parameter and oxygen positional parameters. It is observed that Cu ions are distributed in octahedral site and subsequently Ni and Fe ions in tetrahedral site. The grain size of all samples has been calculated by Scanning Electron Microscopy (SEM) images. The variations in DC electrical resistivity and dielectric constant have been explained on the basis of proposed cation distribution.

Structural and magnetic investigations: Study of magnetocrystalline anisotropy and magnetic behavior of 0.1% Cu2+ substituted Ni–Zn ferrite nanoparticles

Co-precipitated and 800°C annealed NixCu0.1Zn0.9-xFe2O4 (x = 0.5, 0.6, 0.7) ferrite nano particles were studied by X-ray diffraction, FTIR and FC–ZFC techniques. The presence of Cu2+ ions drastically affects the cation distribution which was obtained by Rietveld refinement. This cation distribution was utilized in interpreting the structural and magnetic properties. The variation in calculated tetrahedral and octahedral bond lengths (RA, RB) and oxygen parameter (U) as a function of Ni2+ ion concentration are explained in terms of cation redistribution given by Rietveld refinement. The variation of tetrahedral and octahedral Fe–O vibrational frequencies observed in FTIR studies are in accordance with the change in RA and RB bond lengths. The metal – oxygen – metal bond angles calculated in the present studies indicates an increase in A–B super exchange interaction as Ni2+ ion concentration is increased. The variation of blocking temperatures (TB) obtained from FC–ZFC studies are in accordance with that expected from Mössbauer studies. The magnetocrystalline anisotropy constant (K) calculated from TB values was found to increase as Ni2+ion concentration is increased. The K value was found to increase for a given Ni2+ ion concentration as the temperature is decreased. The coercive field (Hc) values estimated at 10K were found to decrease as Ni2+ion concentration is increased.

Octahedral distortion, phase structural stability, and microwave dielectric properties in equivalently substituted LaTiNbO6 ceramics

AbstractThe room‐temperature phase composition, microstructural characteristic, and microwave dielectric properties of equivalently substituted LaTiNbO6 ceramics were investigated by means of the Rietveld structural refinement, scanning electron microscopy, and network analyzer. A special interest was focused on the influence of the variation in bond length and octahedral distortion on the phase structural stability. A monoclinic (M) aeschynite phase was obtained in B‐site ions (Ta5+ and [W0.5Ti0.5]5+) substituted LaTiNbO6 ceramics while an orthorhombic (O) aeschynite structure appeared in B‐site ions (Zr4+) or A‐site ions (Ce3+ and Sm3+) substituted LaTiNbO6 ceramics, which owned typical polygonal and short rod‐like grain morphologies, respectively. Compared with the octahedral bond length, a straightforward relation between the phase structural stability and the octahedral distortion was established, in which a reduced octahedral distortion was directly correlated with the destabilization of O or M phases or vice versa, irrespective of the substitution ionic radius. The experimentally observed giant difference in dielectric performance of LaTiNbO6 based ceramics was believed to mainly originate from their distinct phase structure and grain morphology.

Investigation of structural, dielectric and magnetic properties of Ho substituted nanostructured lithium ferrites synthesized via auto-citric combustion route

Abstract A comprehensive study on structural, spectral, magnetic and dielectric properties of holmium substituted (Ho3+) lithium ferrites; Li1.2Co0.4HoxFe2−xO4 (x = 0.00–0.15) synthesized via auto-citric combustion route has been carried out. The annealing temperature essential for complete decomposition of precipitates and spinel phase formation was found around 950 °C which was estimated from thermo-gravimetric analysis (TGA). The development of face centered cubic (FCC) spinel structure was confirmed from X-ray diffraction (XRD) analysis. However, the traces of an ortho phase (HoFeO3) were appeared for x ≥ 0.06 indicating the solubility limit of Ho3+ ions. The lattice constant ′a′ increased from 8.351 to 8.360 A upon Ho addition up to x = 0.06 and it decreased thereafter from 8.360 to 8.352 A. This decrease in lattice constant was attributed to the secondary phase formation revealing segregation of Ho3+ ions at grain boundaries. The porosity was found to decrease from 44 to 23% by the inclusion of Ho3+ ions. Fourier transform infrared spectra (FTIR) exhibited tetrahedral (v1) and octahedral (v2) intrinsic vibrational bands at 627 cm−1 and 479 cm−1 respectively and these bands revealed a shift with increasing Ho concentration. The variations in force constants (Ko and Kt) were calculated and discussed with the tetrahedral (rA) and octahedral (rB) bond length trends. The dielectric parameters have been investigated as a function of composition and frequency. The systematic addition of Ho gradually increased the ac conductivity from 8.97 × 103 to 5.56 × 104 (Ω-cm)−1 up to x = 0.12 and it subsequently decreased for x = 0.15. The complex impedance examination (Cole-Cole plots) confirmed a grain-interior phenomenon, effectively contributing to the dielectric properties. The coercivity was enhanced while the saturation magnetization (Ms) was lessened by the incorporation of Ho3+ ions. The maximum value of coercivity (706 Oe) was obtained for Li1.2Co0.4Ho0.12Fe1.88O4. The improved coercivity may suggest their utilization in perpendicular recording media applications.

Influence of rare earth (Nd+3) doping on structural and magnetic properties of nanocrystalline manganese-zinc ferrite

Ultrafine nanopowders of Mn0.6Zn0.4Fe2-xNdxO4 (x = 0, 0.04, 0.06, 0.08, and 0.1) were prepared using combustion method. The influence of Nd+3 doping on structural parameters, morphological characteristics and magnetic properties were investigated. Formation of pure spinel phase was confirmed using X-ray powder diffraction (XRPD). Nd+3 doping in Mn-Zn ferrite samples have shown remarkable influence on all the properties that were under investigation. An increase in lattice constant commensurate with increasing Nd+3 concentrations was observed in the samples. The crystallite size calculated from XRPD data and grain size observed from Transmission Electron Microscope showed a proportionate decrement with increment in rare earth doping. An increase in mass density, X-ray density, particle strain and decrease in porosity were the other effects noticed on the samples as a result of Nd+3 doping. The corresponding tetrahedral, octahedral bond lengths and bond angles estimated from XRPD data have also shown substantial influence of the Nd+3 doping. Magnetic parameters namely saturation magnetization (MS) and net magnetic moment ηB, estimated using vibrating sample magnetometer (VSM) were found to depend on the Nd+3 doping. Mössbauer spectroscopy was employed to study the magnetic environment of Mössbauer active ions and detection of superparamagnetic behavior in nanocrystalline rare earth ferrite material. The isomer shift values obtained from Mössbauer spectra indicate the presence of Fe+3 ions at tetrahedral site (A-site) and octahedral site (B-site), respectively.

On structural studies and cation distribution of La added Zn-Ni-Mg-Cu spinel nano ferrite

Zn0.75-xNixMg0.15Cu0.1La0.02Fe1.98O4 (x = 0.0, 0.15, 0.30, 0.60, 0.75) was synthesized by sol-gel auto-combustion technique. As-burnt samples were thermally annealed at 500oC for 3 hrs. The as-burnt and annealed powder were characterized by X-ray diffraction (XRD) technique. The lattice constant (aexp), unit cell volume (V) and hopping length at A and B (LA and LB) deceases with increase in Ni2+ content (x). Scherrer's grain diameter (D) for as-burnt and annealed samples respectively ranges between 13.26 - 22.20 nm and 23.61 - 30.93 nm. After annealing the specific surface area of the particles decreases which can be attributed to increase in the particle size. Annealing leads to variation in cation distribution at tetrahedral (A) and octahedral [B] site, which affects theoretical lattice parameter (ath), ionic radii of A- site (rA) and B-site (rB), oxygen positional parameter (u), tetrahedral and octahedral bond length (RA, RB), shared tetrahedral and octahedral edge (dAE, dBE) and Neel's magnetic moment (nBN). The bond angles θ1, θ2, θ3, θ4, θ5 and the distance between the metal ions at tetrahedral/octahedral site and anion (p, q, r) gives information about the A-A, A-B, B-B magnetic interaction. For lower values of Ni content (0.0 ≤ x ≤ 0.3), effective bond length (Reff.) increases with annealing and for higher Ni content (0.30 < x ≤ .75) Reff. decreases.

Swift heavy ion irradiated spinel ferrite: A cheap radiation resistant material

Effect of (80MeV) 16O 6+ ion irradiation on the structural properties and cation distribution of the as-burnt samples (i.e. the samples are without any thermal/sintering treatment) with the following compositions: MnFe2O4, Mn0.5Zn0.5Fe2O4 and ZnFe2O4 prepared by sol–gel auto-combustion technique have been studied through in-situ and ex-situ X-ray diffraction (XRD) technique. Well characterized single phase MnFe2O4 and Mn0.5Zn0.5Fe2O4 samples were irradiated at fluence 1×1011, 1×1012, 1×1013 and 1×1014ions/cm2 to see the effect of the electronic energy loss induced changes in the structural properties and in cation distribution monitored through ex-situ XRD. ZnFe2O4 samples were irradiated with ion fluence values ranging between 1×1011−2×1014ions/cm2 to observe the effect of in-situ XRD on structural properties and cation distribution. Results very clearly depict the redistribution of cations in the samples, which show noticeable changes in: ionic radii of A-site (rA) and B-site (rB), experimental and theoretical lattice parameter (aexp.,ath.), unit cell volume (V), Scherrer’s Grain diameter (D), oxygen positional parameter (u), tetrahedral and octahedral bond length (RA, RB), shared tetrahedral and octahedral edge (dAE,dBE) and bond angles (θ1, θ2, θ3, θ4, θ5). Results are interpreted in terms of irradiation induced changes in the above mentioned parameters.

Structural, Microstructural, and Magnetic Studies on Magnesium (Mg2+)-Substituted CoFe2O4 Nanoparticles

The present work deals with the synthesis and characterizations of magnesium-substituted cobalt ferrite (Co 1−xMg xFe 2O4; x = 0.00, 0.25, 0.50, 0.75, 1.00) nanoparticles by sol-gel auto combustion method. X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FTIR) and scanning electron microscopy (SEM) techniques were used for the characterization of the prepared samples. The magnetic properties were studied through pulse field hysteresis loop technique at room temperature. The XRD patterns of all the samples show the reflection which belongs to the cubic spinel structure. The XRD analysis confirmed the single-phase formation of spinel structure for the present ferrite system. Various structural parameters such as tetrahedral ionic radius (rA), the octahedral ionic radius (rB), theoretical lattice constant (ath), hopping length (LA and LB), tetrahedral bond length (dAL), octahedral bond length (dBL), tetra edge (dAE) and octa edge (dBE) were calculated from the XRD data. The variation of these structural parameters in magnesium composition has been studied. The M-H curves recorded at room temperature exhibit a typical hysteresis loop indicating that the sample exhibits a magnetic nature, which decreases with an increase in Mg content x. The large coercivity (Hc) values indicate a nanocrystalline nature of the present samples. The coercivity, saturation magnetization, remanence magnetization, and magneton number decreases with an increase in Mg content x.

Structural and dielectric studies of Mg2+ substituted Ni–Zn ferrite

AbstractPolycrystalline ferrites having the chemical formula Ni0.65−xZn0.35MgxFe2O4 (0 ⩽ x ⩽ 0.2) were prepared by solid state reaction route in steps of x = 0.04. The effect of incorporation of diamagnetic divalent magnesium at expense of nickel on the structural properties of these ferrites has been studied. The proposed cation distribution was derived from theoretical X-ray diffraction intensity calculations. These intensity calculations were done by varying the concentration of magnesium ions over two sites in the lattice. For a certain amount of magnesium concentration, the calculated and observed X-ray diffraction intensities were found to be in good agreement. Site occupancy of divalent diamagnetic magnesium was established from this cation distribution. The octahedral environment facilitates magnesium to enter the B-site at about 95 % and the remaining 5 % occupy tetrahedral sites (A-sites). The movements of cations between tetrahedral and octahedral sites as a result of magnesium substitution were discussed in the view of structural parameters, such as tetrahedral and octahedral bond lengths, cation-cation and cation-anion distances, bond angles and hopping lengths, which were calculated using experimental lattice constants and oxygen parameters. All structural parameters showed slight deviations from ideal values. Among all magnesium substituted samples, the ones with x = 0.12 exhibited insignificant variation in view of structural properties. Dielectric measurements were conducted at a standard frequency of 1 kHz. Large values of the recorded dielectric constants displayed typical characteristics of bulk ferrites. Both dielectric constant and loss values showed mixed variations, attributed to the loss of zinc ions during the sintering process.

Preparation and crystal structure of [Ru2(μ-Cl)3(P(CH2OH)3)6]Cl

A new water-soluble phosphine Ru complex, [Ru2(μ-Cl)3(P(CH2OH)3)6]Cl, has been prepared from [Ru(PPh3)3Cl2] and P(CH2OH)3 in methanol. The complex was characterized by X-ray analysis. The crystal system is triclinic, space group $P\bar 1$ , a = 9.3659(1) A, b = 13.0976(2) A, c = 16.791(3) A, α = 105.620(5)°, β = 91.114(6)°, γ = 110.193(3)°, V = 1847.3(5) A3, Z = 2. It contains [Ru2(μ-Cl)3(P(CH2OH)3)6]+ and Cl− ions, bound together by hydrogen bonds. Ru has octahedral coordination, with Ru-Cl and Ru-P bond lengths of 2.4815(17)–2.5034(15) and 2.2738(18)–2.2772(18) A, respectively. The RuiRu distance is nonbonding, 3.350(2) A, which is atypical of Ru(II) complexes.