Composition, temperature and frequency dependence of dielectric parameters in Ga-substituted Co-Cu mixed ferrites

Abstract

Gallium-substituted Co–Cu mixed ferrites, with different Ga contents, were prepared by a conventional ceramic technique. Single-phase spinel structure was confirmed using X-ray diffraction. The effect of Ga substitution on the structure and dielectric properties of the compounds was studied, where dielectric permittivities (e′, e″) and dielectric loss tangent (tan δ) were measured as a function of frequency and temperature. These parameters were found to be strongly dependent on Ga concentration. The frequency dependence of the dielectric loss tangent showed abnormal behaviour where more than one relaxation peak was observed at different frequencies. This behaviour was attributed to the hopping processes between cation–anion–cation interactions over the octahedral sites in the spinel structure. The Curie temperature Tc determined from measurements of dielectric loss versus temperature was found to decrease with increasing Ga content. (© 2004 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim)