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

Mixed Ni(x)Zn(1-x)Je(2)O(4) (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 degrees 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 (M-s) 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 (epsilon(r)), dielectric loss (tan delta) and AC conductivity (sigma(AC)) 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. (C) 2009 Elsevier B.V. All rights reserved.