Theoretical investigation of some hexagonal ferrite ac data

An almost new method has been confirmed for experimentalists to have a first insight into the solid under study, by investigating the Cole-Cole diagrams of both the electric modulus M* and the permittivity epsilon* at different temperatures. All points of M* function at different temperatures of the investigated hexagonal ferrite data have been collected in one semicircular master curve for each composition. This indicates that the studied compositions belong to a category of solids having what we have referred to as an electric stiffness as the dominating property, which is the reciprocal to an electric compliance-this would be the dominating property if the permittivity epsilon* points could be collected in a master curve. In the present work, it has been found that the Cole-Cole diagrams of M* have given some detailed information that are not obviously displayed in the conductivity representation. Moreover, a fitting of the investigated experimental data of the hexagonal ferrites-BaZn2-xMgxFe16O27, where (x=0.0,0.4, 0.8, 1.2, 1.6 and 2)-with Dyre's macroscopic model of ac conductivity has been performed. An indirect method of fitting of the investigated data with the percolation path approximation (PPA) final equation of Dyre's macroscopic model has shown quite satisfactory results especially at relatively low frequencies (f < 10(6) Hz). Whereas for the effective medium approximation (EMA) final equation of Dyre's macroscopic model the fitting has failed in hexagonal ferrites on contrary with a limited success found in a previous work with spinel ferrites. This is attributed to the more complex structure of hexagonal ferrites than that of spinel ferrites which makes the EMA no more suitable. (c) 2007 Elsevier B.V. All rights reserved.