High-Temperature Mössbauer Spectroscopy of Mechanically Milled NiFe2O4
Oxide spinels, in particular those containing iron, often exhibit technically important electrical- and magnetic-properties. We report here on X-ray powder diffraction and Mössbauer studies of nanostructured NiFe2O4 particles prepared by high-energy ball milling from bulk NiFe2O4, which is an inverse spinel. The Mössbauer spectra were recorded in situ at different temperatures in the range of 300–850 K. The Mössbauer spectra of the milled samples show a broad distribution of magnetic hyperfine fields together with a paramagnetic state at room temperature. Initially, at 700 K the spectrum is mainly paramagnetic, but during the process of annealing, magnetic sextets emerge. The treatment results in a significant change in the B/A area ratio of the ferrite. The Neél temperature of the samples is estimated from the B(T) relation to be in the range of 800–850 K.
KeywordsBall Milling Magnetic Hyperfine Field Milled Sample Nickel Ferrite Hyperfine Parameter
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