Elucidation of structure and conduction mechanism in Nd-Mn substituted Y-type strontium hexaferrites

Technologically important ferrites magnetic materials with nominal composition “Sr_2-xNd_xCo₂Mn_yFe_12-yO₂₂” (x = 0.0 to 0.1 and y = 0.0 to 1.0) were fabricated by the simple sol-gel method. The X-ray diffraction analysis endorsed the formation of well-defined Y-type hexagonal single phase with crystallite size in range of 38–45 nm. Owing to reduction of Fe³⁺ ions at octahedral site, an increase in DC resistivity was observed from 4.083 × 10⁸ to 2.376 × 10⁹ Ω-cm with the increase in substituents content. The two conduction mechanisms operating in ferri- and paramagnetic regions were shown by Arrhenius plot. It was observed that conduction in ferrimagnetic and paramagnetic regions was governed by the hopping of electrons and polarons, respectively. The decrease in Curie temperature “Tc” (553-423 K) was detected as a factor of Nd-Mn content due to decrease in Fe[sbnd]Fe interaction at octahedral site. The changes in the values of dielectric constant (ε^′), dielectric loss factor (ε^″) and tan loss (δ) follow Maxwell-Wagner model. The relatively high resistivity (2.376 × 10⁹ Ω-cm) and low dielectric constants (2.97 at 1 MHz) for the sample with x = 0.1 and y = 1.0 make this material as an excellent candidates for high frequency microwave devices.