The magnetic properties of nanoparticles of gamma-Fe2O3 prepared by reverse micelles have been studied by dc magnetization, transverse ac susceptibility, and Mössbauer spectroscopy. The nanoparticles of gamma-Fe2O3 in the nanocomposite (gamma-Fe2O3)80Ag20 exhibit superparamagnetic behavior. The blocking temperatures determined by the three methods indicate the superparamagnetic nature of (gamma-Fe2O3)80Ag20 above 70-80 K and show correlation with measuring time. The average particle diameter obtained by transmission electron microscopy of the gamma-Fe2O3 particles is ~10 nm and that of the Ag particles is ~20 nm. The average particle size determined from the magnetic analyses for the gamma-Fe2O3 particles is ~12 nm. Mössbauer spectra obtained between 4.2 and 295 K clearly reveal the presence of superparamagnetic relaxation at temperatures above ~80 K. The Mössbauer spectra reveal at most 1% of paramagnetic Fe2+ ions in the 295-K spectrum.
J. A. Wiemann et al., "Magnetic Properties of (γ-Fe₂O₃)₈₀Ag₂₀ Nanocomposites Prepared in Reverse Micelles," Journal of Applied Physics, American Institute of Physics (AIP), Jan 2005.
The definitive version is available at http://dx.doi.org/10.1063/1.1847331
Louisiana Board of Regents
Sharp Laboratories of America
Keywords and Phrases
Mössbauer Effect; Coercive Force; Iron Compounds; Magnetic Particles; Magnetic Relaxation; Magnetic Susceptibility; Nanocomposites; Nanoparticles; Partical Size; Silver; Superparamagnetism; Transmission Electron Microscopy
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© 2005 American Institute of Physics (AIP), All rights reserved.