Magnetic and dielectric properties of mixed spinel Ni-Zn ferrites synthesized by citrate-nitrate combustion method

Mixed NixZn1−xFe2O4 (x = 0.1, 0.2, 0.3, 0.4 and 0.5) systems were prepared by a chemical combustion route. This method involves the addition of aqueous nickel nitrate, zinc nitrate, ferric nitrate as oxidizing agents and fuel citric acid as a reducing agent to form a homogeneous redox mixture. The product materials on calcination to 700 °C for 2 h produces nanocrystalline Ni-Zn ferrite with the corresponding average grain size ranging from 53 nm to 71 nm with varying composition. The room temperature magnetization measurements showed that the saturation magnetization (Ms) of Zn ferrite increases with Ni content. Temperature dependent DC resistivity measurements reveal the semiconducting behavior for all the samples. Room temperature dielectric properties viz.; relative dielectric permittivity (ɛr), dielectric loss (tan δ) and AC conductivity (σAC) for all the samples were studied as a function of applied frequency in the range from 20 Hz to 1 MHz. These studies indicate that the relative dielectric permittivity for all the samples shows usual dielectric dispersion which is due to the Maxwell-Wagner type interfacial polarization. The AC conductivity measurement suggests that the conduction is due to small polaron hopping.