Investigation of structural, electrical, electrical polarization and dielectric properties of CTAB assisted Ni^sup 2+^ substituted R-type nano-hexaferrites

This paper reports the divalent Ni2+ transition element substituted R-type hexagonal ferrites Sr1-xMn2NixFe4O11 with composition (x = 0, 0.1, 0.2, 0.3) synthesized by sol-gel auto combustion technique. The XRD patterns for all the samples show single phase characteristics. The XRD data was used to calculate the lattice constant a (Å), c (Å), unit cell volume V (Å)3, crystallite size S(nm) and dislocation density D (1/S2). The lattice parameters decreased as the concentration is increased. The range of crystallite size was 11 nm-13 nm. In high density recording media, this small size is proper to obtain the appropriate signal to noise ratio. The observed room temperature (RT) DC electrical resistivity decreased as Ni+2 substitution increased. The conductivity in voltage range of −200 to 200 has been increased. The trend of dielectric constants and dielectric loss factor enhanced with Ni substitution which was due to surface charge polarization. AC conductivity has been enhanced with frequency. In present synthesized material, the conduction process of the material is demonstrated by Cole-Cole graphs which show one semi-circle that influence the grain boundaries. As the Ni+2 concentration is increased the polarization also increased. The increase in dielectric parameters of the synthesized samples with substituents suggests their importance for high frequency applications.