X-ray and IR spectroscopy were carried out for the investigated samples of the general formula Zn1-xCuxCr0.8Fe1.2O4 to assure its formation in the spinel phase. More than one of the absorption peaks was obtained indicating tetrahedral, octahedral and lattice vibration. The magnetic susceptibility of the sample was carried out using Faraday's method at different temperatures as a function of the magnetic field intensity. The obtained data showed that x = 0.7 is the critical concentration of Cu2+ ions in the samples. The values of the calculated effective magnetic moment and other magnetic constants agree well with those reported for the different cations in the prepared samples. The preferences of Zn2+ ions to tetrahedral site and the replacement of Cr3+ ions on the expense of Fe3+ ions on the octahedral site affect directly on the variation of the magnetic susceptibility that will be discussed clearly in the text. (C) 2003 Elsevier B.V. All rights reserved.