Helgason, Orn; Ayub, Ibrar; Berry, Frank J. and Crabb, Eleanor
Phase transitions of ruthenium-doped iron oxide studied by Fe-57 Mossbauer spectroscopy at elevated temperatures.
Hyperfine Interactions, 141-142(1-4) pp. 291–295.
The Fe-57 Mossbauer spectra recorded in situ from 5% ruthenium-doped maghemite show parameters typical for maghemite up to 600 K and a hyperfine field distribution indicating that the process of doping is to some extent, inhomogeneous and the materials are formed with a range of particle size. At 700 K a phase transition of maghemite to hematite is detected and further studies show that Ru-doped hematite had a Morin transition temperature at ca. 390 K. Further heating of the sample to 800 K accelerates the maghemite-hematite and broadens the temperature range over which the Morin transition takes place.
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