Evolution of morphology and magnetic properties in silica/maghemite nanocomposites

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

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Author(s)

  • Dan Li
  • Robert C. Woodward
  • John D. Cashion
  • Cordelia Selomulya
  • Rose Amal

Detail(s)

Original languageEnglish
Pages (from-to)12040-12047
Journal / PublicationJournal of Physical Chemistry C
Volume113
Issue number28
Publication statusPublished - 16 Jul 2009
Externally publishedYes

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.

Citation Format(s)

Evolution of morphology and magnetic properties in silica/maghemite nanocomposites. / Li, Dan; Teoh, Wey Yang; Woodward, Robert C. et al.
In: Journal of Physical Chemistry C, Vol. 113, No. 28, 16.07.2009, p. 12040-12047.

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