Iron-containing MCM-41 molecular sieves have been successfully synthesized by directly incorporating the metal in the initial synthesis gel. The resulting microstructures were characterized by XRD, UV-vis DR, ICP and N-2 adsorption. Room temperature magnetic properties were evaluated by measuring the magnetization vs. applied magnetic field loops, up to 5 T. The results show that the structural, chemical and magnetic properties of the resulting materials strongly depend on the hydrothermal treatment time and the iron content. The hysteresis loops exhibit para-, superpara- and ferromagnetic contributions in agreement with the iron species distributions. It is found that longer hydrothermal treatments result in a stabilization of the iron into the network and in a refiner effect of the oxide particles. (C) 2013 Elsevier Ltd. All rights reserved.