SYNTHESIS, CHARACTERIZATION AND MAGNETIC PROPERTIES OF HETEROSTRUCTURES CONTAINING FE IN A MESOPOROUS (MCM-41) HOST MATRIX.

V. R. ELÍAS, M.I. OLIVA, G. A. EIMER , S. G. CASUSCELLI AND S. E. URRETA

San Nicolás, Buenos Aires, Argentina.

Congreso; 7º Congreso de Metalurgia y Materiales SAM-CONAMET; 2007

Comite Organizador

A Fe containing mesoporous material was synthesized by inserting Fe atoms in a Si-MCM-41 molecular sieve host. The samples were prepared by direct hydrothermal synthesis, using an aqueous solution of  iron (III) nitrate as iron source and applying 0 days (S0), 2 days (S2) and 7 days (S7) of synthesis times. The mesostructures were characterized using UV reflectance (DR-UVvis), X-ray diffraction (XRD), infrared transmission (FT-IR) and BET. Magnetization vs. temperature M(T) curves  and hysteresis loops M(H) at temperatures between 5 K and 290 K were measured. XRD patterns indicated that the samples have mesoporous structure and that as the synthesis time increases, the structural ordering diminishes.  The UV-DR spectra showed two bands at 215 and 265 nm in all samples, assigned to the O-2àFe+3 charge transfer transitions involving Fe+3 in tetrahedral coordination.  The samples exhibited a light absorption in the 300-400 nm range, indicating that little clusters could have formed. The M(T) as well as the M/H) curves were consistent with two magnetic contributions, a paramagnetic and a superparamagnetic one. As the synthesis time increased, hysteresis loops with a relatively high apparent coercivity were observed, indicating that the magnetic clusters were no more independent.   Key words: Fe containing mesoporous material; Magnetic properties ; Superparamagnetism