Synthesis, characterization and magnetic properties of iron loaded MCM-48

ELÍAS, V. R.; OLIVA, M.I.; VASCHETTO, E.G.; URRETA, S. E.; EIMER, G. A.; SILVETTI, S. P.

JOURNAL OF MAGNETISM AND MAGNETIC MATERIALS

ELSEVIER SCIENCE BV

Año: 2010 vol. 322 p. 3438 - 3442

0304-8853

Mesoporous molecular sieves of MCM-48 type were loaded with iron by the wet impregnation method, using Fe(III) nitrate or Fe(II) sulfate aqueous solutions as Fe sources, to obtain a magnetic porous composite. The iron loaded materials were characterized by XRD, N2 adsorption and DRUV-vis and compared with the Si-MCM-48 host. Their magnetic properties were studied by measuring the hysteresis loops up to 1.5T at different temperatures (5K-300K) and by magnetization vs temperature curves following the conventional zero field cooling (ZFC) and field cooling (FC) protocols. Materials with high structure regularity and surface area are obtained, which exhibit a mixed paramagnetic and superparamagnetic behavior, arising in isolated iron ions inserted in the host framework, and in small iron oxide clusters or nanoparticles forming inside the pores, respectively. Large („d 8 nm) particles (mainly hematite) grown on the external  surface provide a quite small ferromagnetic contribution to the hysteresis loop.2 adsorption and DRUV-vis and compared with the Si-MCM-48 host. Their magnetic properties were studied by measuring the hysteresis loops up to 1.5T at different temperatures (5K-300K) and by magnetization vs temperature curves following the conventional zero field cooling (ZFC) and field cooling (FC) protocols. Materials with high structure regularity and surface area are obtained, which exhibit a mixed paramagnetic and superparamagnetic behavior, arising in isolated iron ions inserted in the host framework, and in small iron oxide clusters or nanoparticles forming inside the pores, respectively. Large („d 8 nm) particles (mainly hematite) grown on the external  surface provide a quite small ferromagnetic contribution to the hysteresis loop.