The assembly of silica coated magnetite nanoparticles into chainlike nanostructures is reported in the presence of applied magnetic field. The coating of SiO2 onto the surface of magnetite nanoparticles was successfully conducted with the hydrolysis and condensation of tetraethyl orthosilicate. X-ray diffraction and transmission electron microscopy were used to characterize the microstructure and morphology. Vibrating sample magnetometry reveals that the coercivity is dependent on the coating thickness and can be controlled to a certain extent. (C) 2007 Elsevier Ltd. All rights reserved.