Evolution of morphology and magnetic properties in silica/maghemite nanocomposites

Dan Li, Wey Yang Teoh, Robert C. Woodward, John D. Cashion, Cordelia Selomulya, Rose Amal

Research output: Journal Publications and ReviewsRGC 21 - Publication in refereed journalpeer-review

39 Citations (Scopus)

Abstract

The morphological evolution of SiO2/γ-Fe2O 3 nanocomposites was systematically synthesized in a one-step flame spray pyrolysis. Under these conditions, a gradual transformation from discrete γ-Fe2O3 nanoparticles to thin SiO2 coatings, segregated single γ-Fe2O3 core, and multiple γ-Fe2O3 cores within a SiO2 matrix was obtained as a function of SiO2 loading. The presence of SiO 2 up to 13% has a pronounced effect on the j γ-Fe 2O3 crystallite structure (transforming from P4132 to Fd3m space group) and its cationic vacancy ordering.Decrease in the latter was further reflected through the intrinsic magnetic properties of the γ-Fe2O3 cores (i.e., decreasing specific saturation magnetization and increasing coercivity and exchange bias). Deviation from the magnon-type thermal dependence, T3/2 Bloch law, was observed for nanocomposites with SiO2 content above 13%. The Ms vs T curves could be fitted with the sum of an exponential component and a Bloch law component, where the magnitude of the exponential component increased with increasing SiO2 content above 13% SiO2. The thermal dependence of the saturation magnetization for these samples could not be adequately explained by a finite size effect or via freezing of canted spins. © 2009 American Chemical Society.
Original languageEnglish
Pages (from-to)12040-12047
JournalThe Journal of Physical Chemistry C
Volume113
Issue number28
DOIs
Publication statusPublished - 16 Jul 2009
Externally publishedYes

Fingerprint

Dive into the research topics of 'Evolution of morphology and magnetic properties in silica/maghemite nanocomposites'. Together they form a unique fingerprint.

Cite this