Influence of Cr-doping on structural, magnetic and dielectric properties of M-type hexaferrites synthesized using microwave digestion technique

M-type hexaferrite SrCrxFe12-xO19 compounds doped with Cr (x = 0, 1, 2, 3 and 4 at.%) were prepared by microwave digestion system. X-ray diffraction was used to study the structure and crystallization of the samples. The samples are found to have a hexagonal phase, SrFe12O19, as a main phase at 2 theta approximate to 33.144 degrees and 35.618 degrees for x = 0 and 1 respectively, and 32.451 degrees and 34.295 degrees for x >= 2. The Rietveld refined parameters such as the lattice parameters (a = b, c), direct and indirect cell volume, crystallite size and microstrain were investigated. TEM and SEM results showed that the samples have hexagonal shape and grain size range from 126 nm to 379 nm. Magnetization, M, as a function of the applied magnetic field, H, was obtained from the hysteresis loop. The coercive field, H ( C ), saturation, M ( s ) and remnant, M ( r ), magnetization and squareness ration, M ( r )/M ( s ), were extracted from the hysteresis loop results. These results revealed that H ( C ) is inversely proportional with the grains size of the samples but directly proportional with Cr-doping values candidating these compounds to be used in computer hard disk memories applications. M values are inversely proportional with Cr-doping values. The variation of conductivity, sigma, impedance, Z, dielectric constant, epsilon, dielectric loss factor, tan delta and dissipation factor as functions of both AC frequency, F(Hz) and Cr-doping, x, were investigated. The maximum value of the dissipation factor was at x = 2 which equals 8.05 x 10(9) m F-1 when F = 2 x 10(5) Hz. The impedance of the samples behaved as a capacitor reactance that makes our compounds candidate for many crucial dielectric applications.