Materials Sciences and Applications, 2010, 1, 177-186 doi:10.4236/msa.2010.14028 Published Online October 2010 (http://www.SciRP.org/journal/msa) Copyright © 2010 SciRes. MSA 177 Electrical Conductivity, Magnetoconductivity and Dielectric Behaviour of (Mg,Ni)-Ferrite below Room Temperature Somenath Ghatak 1 , Ajit Kumar Meikap 1 , Manika Sinha 2 , Swapan Kumar Pradhan 2 1 Department of Physics, National Institute of Technology, Deemed University, Durgapur, India; 2 Department of Physics, University of Burdwan, Burdwan, India. Email: meikapnitd@yahoo.com Received March 19 th , 2010; revised June 17 th , 2010; accepted October 9 th , 2010. 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. Keywords: Ferrites, Chemical Synthesis, X-Ray Scattering, Transport Properties 1. Introduction Small ferri-magnetic oxides, technically known as fer- rites have attracted considerable attention not only from a fundamental scientific interest but also from a practical point of view for growing applications in the magnetic, electronic and microwave fields [1-7]. Simultaneous presence of magnetic and dielectric nature of ferrites is vastly exploited in a variety of applications at different frequencies. The special feature of these materials is that the properties can be tailored over wide ranges by appro- priate substitution of various ions in the chemical for- mula unit and control of processing procedures. Ferrites are extensively used in magnetic recording, information storage, colour imaging, bio-processing, magnetic refrig- eration and in magneto optical devices [5-7]. Ferrites also have great promise for atomic engineering of materials with functional magnetic properties. The formation of corrosion product on the out of core surfaces in pressur- ized heavy water reactors (PHWRs) are major problem. Ferrite having spinal structure such as magnetic and nickel etc play a major role to prevent such problem. Thus at- tempts are being made to study the various ferrites to evaluate the impact of substitution of the divalent metal ions to modify the properties of these oxides. Spinals are characterized by a very compact oxygen array with cations in tetrahedral (A) and octahedral (B) coordination and may be described by the IV (A 1-i B i ) VI (B 2-i A i )O 4 structural formula, where IV and VI repre- sent tetrahedrally and octahedrally coordinated sites, A and B are cations with variable valency and i the inver- sion parameter. Normal spinal are those with i = 0, in- verse spinals those with i = 1. Different synthetic roots are employed in preparation of ferrites [8-10]. High energy ball milling is a very suit- able solid state processing technique for the preparation of nanocrystalline ferrite powder exhibiting new and un- usual properties [11-14]. The objectives of the present work are 1) to prepare the Mg-Ni ferrite by ball milling