Microstructure and magnetic properties of iron modified mesoporous silica obtained by one step direct synthesis

• MCM-41 with two Fe-contents has been successfully synthesized by one step method.
• The different Fe-metallic species on the sieves were evidenced by UV–vis.
• Long hydrothermal treatment and low Fe-content enhance superparamagnetic behavior.
• High Fe contents increase the coercivity arising from a major ferromagnetic contribution.
• The magnetic properties strongly depend on hydrothermal treatment time and Fe-content.

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 N2 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.

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