Diffuse phase transition and magnetoelectric effect in (f) Co0.8Ni0.2Fe2O4 + (1-f) PMN-PT particulate composites

Magnetoelectric (ME) materials have ability to convert magnetic energy into the electrical voltage and/or to converts electrical energy into the magnetic energy. The present studies comprise structural, dielectric and electrical properties of (f) Co0.8Ni0.2Fe2O4 + (1 - f) Pb(Mg1/3Nb2/3)(0.67)Ti0.33O3 composites. The presence of both the phases in the composites was confirmed using X-ray diffraction technique. The variations of dielectric constant and loss tangent were studied with frequency at room temperature as well as at higher temperature. Temperature dependent dielectric constant behaviour shows diffuse phase transition in ME composites. The diffuse phase transition can be well described by fitting the Lorentz-type relation epsilon(Delta)/epsilon = 1 + (T-T-Delta)(2)/2 delta(2). In the present case the diffusion is seen to be increases with increasing applied frequency. The dc electrical resistivity measurements were carried out in the temperature range of 300-923 K. Variation of ME voltage coefficient tracks the path of magnetostriction as a function of magnetic field. All the composites show peak behaviour in magnetic field dependent on ME voltage coefficient. (C) 2009 Elsevier B.V. All rights reserved.