Electric properties of Co substituted Ni-Zn ferrites

Nanocrystalline Ni-Co-Zn ferrites have been synthesized by chemical co precipitation method, using oxalate precursors. The phase formation of the sintered ferrite was confirmed by X-ray diffraction study. The lattice parameter 'a' increases with the addition of Co2+ content in the Ni-Zn ferrites. The electrical resistivity (rho) of mixed Ni-Zn ferrites has been studied as a function of varying Co2+ compositions. The resistivity was found to increase with the addition Co content in the Ni-Zn ferrite matrix. The variation of dc resistivity as a function of temperature is almost linear up to the Curie temperature and thereafter a break occurs indicating a change of magnetic ordering from ferrimagnetism to paramagnetism. The values of activation energy in paramagnetic region are found to be greater than those in ferrimagnetic region, which suggests that the process of conduction is affected by the change in magnetic ordering. The dielectric properties were studied as a function of frequency by using an LCR precision meter bridge. It was observed that the dielectric constant (epsilon') and dielectric loss tangent (tan delta) decreases with the substitution of Co2+ content in the Ni-Zn ferrites. (C) 2009 Elsevier B.V. All rights reserved.