Polyaniline (PANI)-Zn0.6Cu0.4Cr0.5Fe1.5O4 nanocomposites with magnetic properties were synthesized by in situ polymerization of aniline in the presence of Zn0.6Cu0.4Cr0.5Fe1.5O4 nanoparticles. The structure and morphologies of nanocomposites were characterized by X-ray diffraction (XRD), infrared spectra, UV-vis absorption spectra, scanning electron microscopy (SEM) and transmission electron microscopy (TEM). The ferromagnetic behaviors of nanocomposites were investigated as a function of the content-of Zn0.6Cu0.4Cr0.5Fe1.5O4 particles. The SEM and TEM images showed that nanocomposites presented the core-shell structure with a magnetic core of ferrite and a conducting shell of PANI. The nanocomposites under applied magnetic field exhibited the hysteresis loops of the ferromagnetic nature. The saturation magnetization and coercivity of nanocomposites varied with the content of Zn0.6Cu0.4Cr0.5Fe1.5O4 particles. (C) 2007 Elsevier Ltd. All rights reserved.