Magnetic and strustural properties of magnetite-maghemite thermal treatement
Abstract
The purpose of our work is to verify the hypothesis that the transformation of FeOOH (including ferrihydrite) may yield OH substituted maghemite, whereas the mere oxidation of magnetite yields maghemite free of OH. To characterize these different maghemites we applied Rietveld analysis, chemical analysis and rock magnetic measurements on a set of synthetic and of natural samples. All samples were magnetically characterized by the measurement of magnetic susceptibility, ARM and IRM. The magnetic properties provide a sensitive discrimination between the maghemite derived from oxidation of OH-free precursor and from dehydroxylation of OH-containing precursors. The determination of the site occupancies on site A and B in combination with the Fe2+/Fe3+ (Rietveld and chemical nanalysis) ratio in the series magnetite - maghemite showed that an OH-containing precursor phase inherits OH groups to the ferrimagnetic phase during thermal transformation. The amount of OH is significantly higher than in those phases, which stem from OH - free precursors. Therefore, a distinction of the thermally induced pathway from the low - temperature oxidation pathway is possible.
- Publication:
-
EGS - AGU - EUG Joint Assembly
- Pub Date:
- April 2003
- Bibcode:
- 2003EAEJA.....3634S