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Highlights: [•] A series of X-type hexagonal ferrites were prepared by sol–gel method. [•] The XRD analysis showed that the X-type hexagonal structure. [•] The c/a ratio of these samples falls in the range of X-type hexagonal ferrites. [•] The magnetic properties enhances with the increase of Nd–Co contents. [•] The samples show the reflection loss at smaller frequencies. [Copyright &y& Elsevier]

Abstract: The magnetic and microwave characterization of single phase hexaferrites of entirely new composition Ba1-x Sr x Co2AlFe15O27 (x=0.2–1.0) for application in a microwave absorber, have been reported. The samples synthesized by sol–gel method were investigated by differential thermal analyzer, Fourier transform infrared spectroscope, X-ray diffractometer, field emission gun scanning electron microscope, vibrating sample magnetometer and vector network analyzer. Platelet grains exhibit well defined hexagonal shape which is a better shape for microwave absorption. M–H loops for a selected sample were measured for a temperature range of 4.2–400K. Moreover M–H loops for all Sr-substituted samples were also measured at room temperature up to a maximum applied field of 9T. Saturation magnetization values were calculated by the law of approach to saturation. The room temperature coercivity for all the samples is found to be a few hundred oersteds which is necessary for electromagnetic materials and makes these ferrites ideal for microwave devices, security, switching and sensing applications. The complex permittivity, permeability and reflection losses of a selected ferrite–epoxy composite were also investigated over a frequency range of 0.5–13GHz. [Copyright &y& Elsevier]

Abstract: A series of single phased Y-type hexagonal ferrites Sr2Ni2−x Mg x Fe12O22 (x=0.0, 0.1, 0.2, 0.3, 0.4, 0.5) were synthesized by the sol–gel auto combustion method. The effects on structural, magnetic and electrical properties have been investigated by substituting Mg2+ at Ni2+ sites. The X-ray diffraction (XRD) patterns confirm single phase Y-type hexaferrite and various parameters such as lattice constants, cell volume, X-ray density, bulk density and porosity have been calculated from XRD data. The Fourier transform infrared (FTIR) spectra show the characteristics absorption ferrite peaks of the sintered sample. The microstructure was studied by scanning electron microscopy (SEM). All the ferrites show a hexagonal platelet-like shape which is a most suitable shape for microwave absorption. The dielectric constant followed the Maxwell–Wagner interfacial polarization and relaxation peaks were observed in the dielectric loss properties. The room temperature dc electrical resistivity and activation energy were found to decrease for samples x=0.1, 0.2 and increase for the rest of samples hence making these materials suitable for multilayer chip inductors (MLCIs). A soft magnetic behavior was revealed by M–H loops. Saturation magnetization (M s), retentivity (M r), coercivity (H c) and magnetic moment (n B) were found to decrease as the Mg2+ contents increased. [Copyright &y& Elsevier]

Abstract: A series of Al-substituted Co2W hexaferrites BaCo2Al x Fe16 − x O27 (x = 0, 0.2, 0.4, 0.6, 0.8, 1) synthesized by sol-gel autocombustion method have been investigated. The samples were characterized by DTA/TGA analysis, FTIR spectroscopy, X-ray Diffractometer and field emission gun scanning electron microscopy (FEGSEM). Magnetic behavior of a selected sample was examined up to a magnetic field of 9T between a temperature range of 4.2 K–400 K. The values of saturation magnetization were calculated by the law of approach to saturation. The coercivity of the investigated sample has a value of about hundred oersteds at room temperature which is favorable for EM materials. The complex permittivity and complex permeability of a composite sample have been measured in the frequency range of 0.5–13 GHz. Based on the theoretical calculation of reflection loss; the microwave absorption properties have been investigated. The results indicate that the attenuation peak frequency of these compounds can be tuned for the desired frequency by varying the thickness of the absorber. [Copyright &y& Elsevier]