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Nano-composites consisting of polyvinyl alcohol (PVA) immersed with Sr0.7Cr0.3Fe12O19 hexaferrites nanoparticles were successfully synthesized by two-step process. Nanoparticles (Sr0.7Cr0.3Fe12O19) were prepared by the sol–gel auto-combustion method and then embedded with polyvinyl alcohol matrix by the ultrasound in situ emulsion technique. The result indicates that the fabricated nanoparticles were homogeneously diffused in the matrix of PVA. Characterization of the synthesized material was done by the X-ray diffraction, Raman spectra and EDX analysis. The peaks of the XRD pattern become more intense with increasing the ferrite content in the polymer matrix which suggests that the crystallinity was improved with the addition of the ferrite content in the polymer matrix. Crystallite size and cell volume lie in the range of 34–59 nm and 688.83–693.82 nm, respectively. The magnetic field-dependent magnetic properties of the synthesized samples were inspected at room temperature by the vibrating sample magnetometry (VSM). The linearity of Ms, Hc, Mr values and shape of the hysteresis loop clearly indicate that the prepared ferrites nanoparticles were dispersed evenly within the polymer matrix. With the addition of ferrites in polymer composites, saturation magnetization, remanence, and coercivity were found to be enhanced. Saturation magnetization and remanent magnetization ranges from 6–42 emu/g and 4–22 emu/g, respectively, and magnetocrystalline anisotropy ranges from 3.7–5.6 (105 erg/cm3). At low frequency, dielectric constant and dielectric loss are high with few relaxation peaks. Both the real and imaginary parts of permittivity demonstrate increasing trend with the addition of ferrite content in the polymer matrix. AC conductivity of the Ferrite–PVA nano-composites was found to be increased with the increase of frequency following the Joncher's law. The increasing behavior of dielectric parameters with increasing ferrite ratio in PVA is suitable for different applications, especially in energy storage devices. [ABSTRACT FROM AUTHOR]

M-type hexagonal ferrites have been getting considerable attention owing to their promising application in electronic fields. Though, the growth of nanosized M-type hexagonal ferrites is still a big challenge. Herein the fabrication of M-type hexaferrite with nominal composition Ca 1-x Bi x Fe 12-x Co x O 19 (x=0.00, 0.05, 0.10, 0.15, 0.20) with high quality is reported by the sol-gel auto combustion route. The objective of the study is to improve the structural, spectral, dielectric, and magnetic characteristics of M-type hexagonal ferrite which was achieved through the variation of concentration of Cobalt and Bismuth. X-ray diffraction (XRD) patterns confirmed the single-phase M-type hexagonal structure. The crystallite size of all samples was found to be in the range of 42–49 nm. Other parameters such as lattice parameters a & c, unit cell volume, crystallite size, X-ray density, Bulk density, and porosity were also calculated. The doping contents were found to decrease the bulk and X-ray densities while increasing the porosity. Fourier-transform infrared (FTIR) spectra showed the formation of metal-oxygen stretching vibrations that confirmed the formation of hexagonal ferrites. The scanning electron microscopy (SEM) images revealed a regular platelet hexagonal structure and homogeneously distributed grains were examined. The dielectric constant was high at low frequency and then decreased with increasing frequency, while the dielectric loss was decreased appreciably with doping. The saturation magnetization ranged from 15.51 to 38.27 emu/g, coercivity increased from 207.93 to 1359.69 Oe, and the squareness ratio was found to be in the range of 0.19–0.78. The dielectric and magnetic properties of Ca 1-x Bi x Fe 12-x Co x O 19 (x=0.00, 0.05, 0.10, 0.15, 0.20) with the variation of Co and Bi revealed that these materials are good candidates for modern devices. • The samples Ca 1-x Bi x Fe 12-x Co x O 19 results in enhanced structural, dielectric and magnetic properties. • XRD patterns of samples indicate that the peaks match well with the standard patterns of the M-type hexaferrites. • Crystallite size lies in the range of 42–49 nm • At room temperature the conductivity is due to impurity, at higher temperature conductivity is due to polaron hopping. • According to Maxwell–Wagner model the dielectric substance contains heterogeneous structure separated by highly resistant thin grain boundaries [ABSTRACT FROM AUTHOR]

In this work, A series of nanocrystalline Ca–Ba–Co-based Y-type hexaferrite having general chemical formula CaBaCo2-xZnxNdyFe12-yO22 where x = 0.00 to1.0 and y = 0.00 to 0.1 were prepared using the sol–gel autocombustion technique. Prepared samples were characterized by X-ray diffraction (XRD), Fourier transform infrared radiation (FTIR), vibrating sample magnetometer (VSM), and dielectric measurements. XRD analysis of samples having various dopants concentrations in powder system matrix revealed that there was a single-phase pattern of Y-type hexaferrite. The measured structural parameters via lattice constants (a, c), unit cell volume Vcell, X-ray density (dx), bulk density (db), and porosity (P) were calculated through XRD data. FTIR (Fourier transform infrared) spectroscopy analysis showed the locations of ions including their corresponding bonds in the structure of the lattice matrix. It was observed that with increasing the Zn–Nd concentration the values of the dielectric parameters were decreased. At low frequency, due to surface charge polarization, the measurements of dielectric constant and dielectric loss were observed to be higher. Resonance peaks for all examined samples were also observed. Dielectric parameters consisting of impedance and modulus study attributed the presence of grains, while the grain boundaries might play a significant role in conduction mechanism. Magnetic characteristics measured from M–H (Hysteresis loop) curve that was measured from VSM represents that the prepared sample exhibits typical characteristics associated with the ferromagnetic substances. The calculated values for saturation magnetization and coercivity were found in the range from 25.8 to 51.1 emu/g and 0.061–0.063Oe. The increasing Ms and Hc values revealed that the prepared sample powder could be a leading candidate for PMR (perpendicular recording media) applications. Because of suppression of magnetic super exchange interaction anomalous behavior in magnetic parameters of Zn–Nd-doped was observed. The prepared samples with superb structural and magnetic characteristics are capable for high-frequency applications. [ABSTRACT FROM AUTHOR]

[Display omitted] • M type hexaferrites with composition Pb 1-x Cr x Fe 12 O 19 x = (0.0,0.1,0.2,0.3,0.4,0.5) were synthesized by the sol-gel auto combustion technique. • Peaks of the XRD pattern match well with the standard pattern of P63/mmc group with JCPDS card No (43-0002). • Crystallite size lies in the range of 63–53 nm. Lattice parameters, crystallite size and cell volume was found to decrease with the substitution of Cr3+ content. • Dielectric constant and ac conductivity (σ ac) increases gradually with the increase in Chromium doping. Mofreover, Pb 1-x Cr x Fe 12 O 19 with x = 0.2 have exceptional dielectric properties with significant Q-value (4900). • These samples may suitable for high frequency applications such as phase shifter, modulators and also in longitudinal recording media. Chromium substituted M-type hexagonal ferrites with nominal composition Pb 1-x Cr x Fe 12 O 19 where x= (0.0, 0.1, 0.2, 0.3, 0.4, 0.5) were prepared via sol gel route. Structure of the single phase lead hexaferrite was estimated from X-ray diffraction (XRD) analysis. Scanning electron microscopy (SEM) confirmed the formation of hexagonal platelets with an average grain size in the range of 53–63 nm. Crystallite size, lattice parameters and cell volume was found to decrease with the increase of Chromium concentration. Magneto crystalline anisotropy and saturation magnetization has been explored through the law of approach to the saturation magnetization. Saturation magnetization first increased and then found to be maximum (64 emu/g) at 30% of Cr3+ doped lead hexaferrite and minimum coercivity (6.54 KOe) was perceived for this composition. Dielectric constant, dielectric loss, tangent loss, real and imaginary part of electric modulus, ac conductivity and Q-values of the prepared samples were also explained. With the increase of dopant (Cr3+) concentration, dielectric constant was increased gradually. These characteristics are suitable for various applications such as phase shifter, modulators, stealth technologies and also in Multilayer chip inductor. [ABSTRACT FROM AUTHOR]

Abstract: Several aspects of the dielectric behavior of multi-walled carbon nanotube (MWCNT)/acrylonitrile–butadiene–styrene (ABS) nanocomposites were studied. MWCNT/ABS nanocomposites with filler content between 2wt% and 15wt% were prepared by melt mixing and characterized by the impedance technique. The results showed that the dc and ac conductivities increase with increasing dc bias and MWCNT content. The effect of dc bias was more pronounced for nanocomposites with low MWCNT content. The bode diagram of the real impedance for nanocomposites containing 2wt% MWCNT or higher exhibited a frequency independent plateau in the low frequency region revealing that dc conduction is the dominant conduction mechanism. The critical frequency at which ac conductivity becomes frequency dependent increased with increasing dc bias and MWCNT content. [Copyright &y& Elsevier]

The interaction force between a small magnet and a superconducting ring in assumptions of the Meissner state was analyzed using the dipole-dipole interaction model. Two configurations were evaluated: the vertical configuration when the magnetic moment lies parallel to the symmetry axis of the ring and the horizontal when it is perpendicular. The levitation force on the magnet increases by decreasing the distance from the center of the ring up to a maximum value and then decreases down to zero when the magnet is exactly at the center of the ring. The levitation force when the magnet is in the horizontal configuration is mostly higher than that when it is in the vertical configuration. Simulation results were compared with experimental results reported in literature. [ABSTRACT FROM AUTHOR]