The role of Mg substitution on the micro structure and magnetic properties of BaCoZnW-type hexagonal ferrites

A series of W-type hexagonal ferrites with the composition BaCoZn1-xMgxFe16O27 (0,<=<x,<= 0.6) were prepared by the conventional ceramic method to study their structural and magnetic properties as a function of temperature and composition. The characterization using X-ray diffraction indicated that a hexagonal W-type single-phase structure and the effect of composition on the unit cell parameters, density and porosity was studied. The variation of the magnetic susceptibility (chi(M)) with temperature for all the investigated samples in the temperature range (300-800 K) shows three regions of behavior that was explained on the basis of the distribution of Zn2+ and Mg2+ ions in the lattice and leads to the anomalous behavior of the effective magnetic moment Pert. The Curie temperature indicated that the critical concentration is at x = 0.5. Paramagnetic nature of the samples above the Curie temperature is observed. The Curie Weiss constant theta calculated from the plot of I/(chi M) vs. T (K) is in agreement with the expected value. The effective magnetic moment mu eff decreases with increasing the intensity of magnetic field. The possible mechanisms contributing to these properties are discussed in the text. (C) 2007 Published by Elsevier B.V.