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Selected Works of Takele Seda
Article
Magnetic properties of synthetic six-line ferrihydrite nanoparticles
Physics of the Earth and Planetary Interiors (2006)
  • Yohan Guyodo, University of Minnesota
  • Subir K. Banerjee, University of Minnesota
  • R. Lee Penn, University of Minnesota
  • David Burleson, University of Minnesota
  • Thelma S. Berquo, University of Minnesota
  • Takele Seda, Western Washington University
  • Peter Solheid, University of Minnesota
Link
Abstract
Three synthetic samples of six-line ferrihydrite (Fh5.4, Fh4.1, and Fh3.0), with average particle sizes of 5.4, 4.1, and 3.0 nm (respectively), have been studied by low-temperature magnetic techniques, Mössbauer spectroscopy, transmission electron microscopy, and X-ray absorption spectroscopy. Magnetic data indicate that these nanoparticles are not only antiferromagnetic, but that they also possess a ferromagnetic-like moment due to the presence of uncompensated spins. Both magnetic and Mössbauer data indicate that nanoparticles of six-line ferrihydrite are superparamagnetic at room temperature, with a low-temperature transition between blocked and unblocked magnetic states dependent on average particle size. In particular, low-field magnetic susceptibility data display a peak in amplitude at 45 K (Fh3.0), 55 K (Fh4.1), and 80 K (Fh5.4). Low-temperature induced magnetization data, acquired in magnetic fields up to 5 T, also display clearly a superparamagnetic behavior. These data were tentatively modeled as the sum of two contributions: a linear term due to the antiferromagnetic susceptibility and a nonlinear term due to the uncompensated spins. Model estimates of the magnetization carried by the uncompensated spins (Mnc) show a decrease in Mnc with increasing temperature. Extrapolation of Mnc values down to zero provided an estimate of the Néel temperature for six-line ferrihydrite on the order of 500 K.
Keywords
  • Rock magnetism,
  • Ferrihydrite,
  • Magnetic properties,
  • EXAFS,
  • Mössbauer effect
Disciplines
Publication Date
March 1, 2006
DOI
10.1016/j.pepi.2005.05.009
Publisher Statement
Copyright © 2006 Elsevier B.V.
Citation Information
Yohan Guyodo, Subir K. Banerjee, R. Lee Penn, David Burleson, et al.. "Magnetic properties of synthetic six-line ferrihydrite nanoparticles" Physics of the Earth and Planetary Interiors Vol. 154 Iss. 3 (2006) p. 222 - 233
Available at: http://works.bepress.com/takele-seda/6/