A novel one-step synthesis and characterization of very small maghemite nanoparticles

C.COSIO-CASTAÑEDA; O.MOSCOSO-LONDOÑO; L.M.SOCOLOVSKY; V.BILOVOL; E.J.LEDE; RICARDO MARTÍNEZ GARCÍA

Congreso; X LAW3M - Latin American Workshop on Magnetism; 2013

Very small g-Fe2O3 NPs are obtained through a one-step synthesis at room temperature. The fast neutralization reaction of a Fe3+ solution in a basic medium produces an intermediate phase, presumably two-line ferrihydrite, that in oxidizing conditions is transformed to g-Fe2O3 NPs. The XAFS technique allowed the analysis of the crystallographic variations into g-Fe2O3 NPs as a result of modification in its surface/volume ratio. Mössbauer spectroscopy at 4.2 K confirms the presence of Fe(III) in tetrahedral and octahedral interstices. The specific magnetization (3 K and 300 K, up to 7 T) and temperature dependence of the magnetization (50 Oe by ZFC mode, 2 ≤ T ≤ 300 K) indicate that g-Fe2O3 NPs are in superparamagnetic state with a blocking temperature close to 36 K