The spinel system Zn0.4Co0.6AlxFe2-xO4 (X = 0-0, 0.25, 0.50, 0.75, and 1.0) has been prepared in air at 1300 degreesC by standard solid state sintering method. X-ray and neutron powder diffraction measurements have been performed to characterize the materials. The crystal structure of the system has been found out by refining neutron diffraction data and cubic symmetry corresponding to the space group Fd3m has been confirmed for all the samples of the series. Zn and Al ions exclusively enter into the tetrahedral (A) and octahedral (B) sites, respectively, while Co and Fe ions are distributed over both the A and B sites for the whole compositional range investigated. With increasing x, the occupation of Co gradually increases in A site and that in B site decreases, and the Fe ions gradually decrease in both the sites. The lattice constant decreases and the oxygen position parameter increases with increasing Al content in the system. The moment distributions in the two sublattices for different compositions have also been determined. The magnetization measurements show that the saturation magnetization and the Neel temperature decreases with increasing Al contents and the coercivity decreases initially and then increases when x > 0.75. (C) 2004 Elsevier Ltd. All rights reserved.