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A Y-type hexagonal ferrite with chemical composition CaBaCo2In0.5Fe11.5O22 was prepared by a sol-gel auto combustion technique. Y-ferrite/PANI nanocomposites were prepared by in situ polymerization of PANI with general formula CaBaCo2In0.5Fe11.5O22 (1-x) + PANI (x) (x = 0.30, 0.50, 0.8, and 1) with nomenclature CF1, CF2, CF3, and P respectively. The samples were characterized by X-ray diffraction (XRD) and electrical and magnetic measurements. X-ray diffraction revealed that Y-type ferrite was successfully prepared in a single phase form. DC resistivity increases with increasing ferrite filler in nanocomposites due to large resistive behavior of ferrite in conducting polymer matrix. The dielectric constant, dielectric loss, and AC conductivity decreases with the increase of ferrite content. The dielectric is high due to interfacial polarization at low frequency, and it is low at high frequency following Maxwell-Wagner model. The coercivity increases with the decrease of ferrite filler content whereas saturation magnetization and remanence decreases which is due to random distribution of ferrite filler particles in PANI matrix. Due to large coercivity and low values of ε′ and ε″, the present samples may be useful in recording media and electromagnetic shielding. [ABSTRACT FROM AUTHOR]

Y-type hexagonal ferrite (Sr 1.8 Sm 0.2 Co 2 Ni 1.50 Fe 10.50 O 22 ) was prepared by a normal microemulsion route. The ferrite/polymer composites thin films are formed at different ferrite ratios in pure polystyrene matrix. The X-ray diffraction analysis shows broad peak at low angles which is due to the PST and the peaks for Y-type ferrite are also observed in composite samples. The peaks become more intense and show less broadening with increasing concentration of ferrite which suggests that crystallinity is improved with the addition of ferrite. DC resistivity of the composites samples is lower than that of the pure PST and decreases by increasing ferrite filler into the polymer. This decrease of resistivity is mainly due to the addition of comparatively less resistive ferrite into the highly insulating polymer matrix of PST. The observed increase in the dielectric constant (permittivity) with increasing concentration ratio of ferrites is mainly due to the electron exchange between Fe 2+ ↔Fe 3+ +e − which consequently results in enhancement of electric polarization as well as dielectric constant. The existence of resonances peaks in the dielectric loss tangent spectra is due to the fact when the external applied frequency becomes equal to the jumping frequency of electrons between Fe 2+ and Fe 3+ . The increasing behavior of the dielectric constant, dielectric loss and AC conductivity with increasing ferrite ratio in PST matrix proposes their versatile use in different technological applications especially for electromagnetic shielding. [ABSTRACT FROM AUTHOR]

Polyaniline was synthesized by chemical polymerization using aniline as monomer, and Y-type hexaferrite with composition (Co 2 Mn 2 Sr 1.66 Nd 0.4 Fe 10 O 22 ) was prepared by co-precipitation assisted by surfactant. Three composites of Polyaniline with different ferrite ratios were prepared by mechanical blending. The synthesized samples were characterized by X-Ray diffraction, Scanning electron microscopy and electrical measurements. The XRD analysis reveals that no second phase was observed in Y-type hexagonal ferrite. In PANI-Ferrite composites, significant changes in resistivity, real and imaginary part of complex permittivity were observed with the increase of ferrite in the polyaniline matrix. At low frequencies the magnitude of dielectric constant and complex permittivity is high with few relaxation peaks. AC conductivity of PANI-Ferrite composites increase with the increase of frequency following Jonscher law. The resistivity and activation energy were found to show similar behavior. [ABSTRACT FROM AUTHOR]

A series of the divalent and trivalent co-substituted Mg 0.5− x Cd x Co 0.5 Cr 0.04 Tb y Fe 1.96− y O 4 spinel ferrite systems (where x =0–0.5 in steps of 0.1 and y =0.00–0.10 in steps 0.02) are synthesized by sol–gel auto combustion method. The product materials were characterized by the thermo gravimetric analysis and differential scanning calorimetry (TGA/DSC), Fourier transform infrared spectra (FTIR), nitrogen adsorption (BET), X-ray diffraction (XRD), scanning electron microscope (SEM), atomic force microscopy (AFM) and vibrating sample magnetometer (VSM). The X-ray diffraction patterns and Fourier transform infrared spectroscopy confirm spinel nanocrystalline phase. The crystallite size is determined by Scherer's formula from 36.6 to 69.4 nm. The X-ray density is found in the range of 5.09–6.43 (g/cm 3 ). The morphological features are studied using scanning electron microscope and AFM. Saturation magnetization ( M s ) and remanence ( M r ) magnetization extracted from M – H loops exhibit the decreasing trends 21.4–16 emu/g and 9.1–6.3 emu/g, respectively. A significant decrease in the intrinsic parameters is observed in the prepared samples due to the weakening of the A–B interaction as iron enters into the tetrahedral A-site. The coercivity lies in the range of 300–869 Oe as a function of co-substitution contents. The coercivity of the sample with x =0.1, y =0.02 was found maximum i.e. 869 Oe. The obtained results suggest that the investigated materials may be potential candidates for high density recording media applications. [ABSTRACT FROM AUTHOR]

Nanocrystalline samples of Ce 3+ substituted Co–Cr ferrite with chemical formula CoCr 0.04 Ce x Fe 1.96− x O 4 (0 ⩽ x ⩽ 0.1) have been synthesized by co-precipitation method and sintered at a temperature of 850 °C for 8 h. The samples were characterized using thermo-gravimetric and differential thermal analysis, X-ray diffraction, Fourier transform infrared spectroscopy, Raman spectroscopy, scanning electron microscopy, atomic force microscopy and vibrating sample magnetometry. The XRD patterns and FTIR spectra confirm that the prepared samples reveal the formation of spinel ferrites. The average particle size was found to be in the range of 30.8–63.7 nm estimated by Scherer formula. The lattice constant varies in the range of 8.352–8.382 Å due to difference in the ionic radii of the substituted cations. IR studies confirm two main absorption bands in the frequency range of 400–800 cm −1 arising due to the tetrahedral (A-site) and octahedral (B-site) stretching vibrations. The elemental analysis as obtained from the EDXS measurement is in close agreement with the expected composition from the stoichiometry of the reactant solutions. The M–H loops show that the saturation magnetization decreased gradually with increasing Ce content, while the coercivity is related to the microstructure of Ce-substituted samples. The obtained results suggest that the investigated materials are potential candidates for magnetic recording media, security, switching and high frequency applications. [ABSTRACT FROM AUTHOR]

Highlights: [•] Single phase ferrites synthesized by chemical co-precipitation. [•] With the increase of Mg concentration the lattice constant was decreased. [•] The grain size of particles was below 100nm. [•] Hc for all the samples revealed that the samples are super paramagnetic. [•] The samples x =0.2, 0.3, 0.5 may be recommended for the hyperthermia applications. [Copyright &y& Elsevier]

Abstract: Effect of Pr–Ni substitution on structural and magnetic properties of Ca0.5Ba0.5−x Pr x Ni y Fe12−y O19 (x=0.00–0.10 and y=0.00–1.00) prepared by the sol–gel auto combustion method were investigated. The XRD analysis confirmed the single phase M-type hexa-ferrite structure. The lattice parameters were found to increase as Pr–Ni content increases, which is attributed to the ionic size of the implicated cations. The Pr–Ni seems to be completely soluble in the lattice. Transmission electron microscopy reveals that the grain size decreases with increase of Pr–Ni substitution. The coercivity and remanent magnetization ranges from 1511 to 1925 (Oe) and 21.4 to 26.5 (emu/g), respectively. The coercivity values of all the samples fall in the range of M-type hexa-ferrites. [Copyright &y& Elsevier]

Highlights: [•] The variation in lattice constant is due to partial solubility of Eu-ions into lattice. [•] The dielectric properties follows Maxwell Weigner model. [•] Impedance measurements revealed that the impedance response is dominated by grain boundary behavior. [•] The ac conductivity showed semiconducting behavior over a wide range of frequency. [ABSTRACT FROM AUTHOR]