Electrical Conductivity, Magnetoconductivity and Dielectric Behaviour of (Mg,Ni)-Ferrite below Room Temperature

Abstract

We report a comprehensive study of electrical transport properties of stoichiometric (Mg,Ni)-ferrite in the temperature range 77 ≤ T ≤ 300 K, applying magnetic field upto 1T in the frequency range 20 Hz-1 MHz. After ball milling of MgO, NiO and -Fe 2 O 3 and annealing at 1473 K, a (Mg,Ni)-ferrite phase is obtained. The temperature dependency of dc re-sistivity indicates the prevalence of a simple hopping type charge transport in all the investigated samples. The activa-tion energy decreases by annealing the samples by 1473 K. The dc magnetoresistivity of the samples is positive, which has been explained by using wave function shrinkage model. The frequency dependence of conductivity has been de-scribed by power law and the frequency exponent 's' is found to be anomalous temperature dependent for ball milling and annealing samples. The real part of the dielectric permittivity at a fixed frequency was found to follow the power law  / (f,T)  T n . The magnitude of the temperature exponent 'n' strongly depends on milling time and also on annealing temperature. The dielectric permittivity increases with milling and also with annealing. An analysis of the complex im-pedance by an ideal equivalent circuit indicates that the grain boundary contribution is dominating over the grain con-tribution in conduction process.