||I U P A C
Organizations & People
Pure Appl. Chem. Vol.
72, Nos. 1-2, p. 37-45, 2000
Special Topic Issue on the Theme of
Synthesis of magnetic spinel ferrite CoFe2O4 nanoparticles from
ferric salt and characterization of the size-dependent superparamagnetic
Chao Liu, Adam J. Rondinone, and Z. John Zhang*
*School of Chemistry and Biochemistry, Georgia Institute
of Technology, Atlanta, Georgia 30332-0400, USA
Abstract: The CoFe2O4 nanoparticles have
been synthesized by using a stable ferric salt of FeCl3 with
a micellar microemulsion method. The normal micelles are formed by sodium
dodecyl sulfate (NaDS) in aqueous solutions. The mean size of the nanoparticles
can be controlled from less than 4 nm to about 10 nm through controlling
the concentrations of the reagents. The neutron diffraction in combination
with the Rietveld refinement shows that these CoFe2O4
nanoparticles have a high degree of inversion with 66% of the tetrahedral
sublattice occupied by Fe3+. Magnetic measurements and neutron diffraction
studies demonstrate the superparamagnetic nature of these CoFe2O4
nanoparticles. The size-dependent superparamagnetic properties of CoFe2O4
nanoparticles have also been systematically studied. The blocking temperature
and coercive field of the nanoparticles increase with increasing size
of the nanoparticles. The superparamagnetic behaviors of CoFe2O4
nanoparticles are consistent with the Stoner-Wohlfarth theory of single
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