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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]

Abstract: Composite ferrite ceramic materials were obtained by mixing sol/gel derived CoFe2O4 and Sr2NiMnFe12O22 nanopowders sintered at 1050°C for 3h. The synthesized samples were characterized by XRD, Scanning Electron Microscopy, FT-IR, electrical resistivity and dielectric measurements. XRD analysis revealed that there is no new phase observed, indicating that no chemical reaction occurs between spinel and hexagonal phases and the intensity of Y-phase gradually decreased by increasing spinel concentration. Crystallite size calculated from XRD data decreased by increasing spinel concentration. Room temperature resistivity and activation energies of the samples increased with increasing spinel concentration. Dielectric constant of pure Y-type hexagonal ferrite decreased by increasing spinel concentration up to ~8.5. At higher frequency further decrease in dielectric constant was observed due to Maxwell-Wagner type relaxation with few resonance peaks beyond 2GHz. Imaginary part of dielectric constant showed the similar behavior with frequency. Low dielectric constant, low dielectric losses and high resistivity make these composite ferrites useful in electromagnetic attenuation materials and microwave devices. [Copyright &y& Elsevier]

Abstract: Nano-sized and single phase W-type hexaferrite (BaCo2Fe16O27) powders synthesized by sol–gel autocombustion method have been investigated. The samples were sintered in a temperature range of 1000–1200°C for 5h. The thermal decomposition behavior of as-prepared powder was studied by thermogravimetry (TG), differential thermal analysis (DTA) and infrared spectra (IR). The structural and magnetic properties of powders were investigated by X-ray diffraction (XRD) and vibrating sample magnetometer (VSM). The grain size calculated by Scherer equation was found in the range of 36–47nm which is small enough to obtain a suitable signal-to-noise ratio in high density recording media. Hysteresis loop measurements show that the coercivity values lie in the range of 210.61–1602.6Oe with increasing sintering temperature. Magnetization studies show a significant increase in the values from 15 to 22emu/g. The dc electrical resistivity is observed to decrease up to a certain value as the temperature increases and then rises at higher temperature. [Copyright &y& Elsevier]