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Polycrystalline samples of a layered magnetic ceramic oxide, Ba2Co2Fe12O22 (Co2Y), doped with Bi2O3 were prepared by the solid state reaction method. The dielectric impedance properties were studied over the range of frequency between 1 Hz–1MHz and in the temperature range of 313–493 K, using the modulus formalism. The impedance plot showed a first semicircle at high frequency which was assigned to the grain intrinsic effect and a second semicircle, at lower frequencies, which corresponds to grain boundary polarization (conduction phenomenon). A complex modulus spectrum was used to understand the mechanism of the electrical transport process, which indicates that a non-exponential type of conductivity relaxation characterizes this material. The values of the activation energy of the compound (calculated both from dc conductivity and the modulus spectrum) are very similar, suggesting that the relaxation process may be attributed to the same type of charge carriers. The dielectric measurements were studied by fitting the electrical modulus with the Havriliak–Negami function, including the conductivity parameters. The study demonstrates that the investigation of dielectric relaxation, conductivity, and loss of the ferrite materials, as a function of temperature, are essential for future microwave absorption applications of this material.

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In this work we report a study of the magnetic behavior of ferrimagnetic oxide CoFe 2 O 4 treated by mechanical milling with different grinding balls. The cobalt ferrite nanoparticles were prepared using a simple hydrothermal method and annealed at 500 o C. The non-milled sample presented coercivity of about 1.9 kOe, saturation magnetization of 69.5 emu/g, and a remanence ratio of 0.42. After milling, two samples attained coercivity of 4.2 and 4.1 kOe, and saturation magnetization of 67.0 and 71.4 emu/g respectively. The remanence ratio M R /M S for these samples increase to 0.49 and 0.51, respectively. To investigate the influence of the microstructure on the magnetic behavior of these samples, we used X-ray powder diffraction (XPD), transmission electron microscopy (TEM), and vibrating sample magnetometry (VSM). The XPD analysis by the Williamson-Hall plot was used to estimate the average crystallite size and strain induced by mechanical milling in the samples.