Magnetization,mössbauer spectroscopy and structural studies of a ferrimagnetic Fe-Oxide formed by heating nontronite in air |
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| Authors: | N Petersen N Schembera E Schmidbauer H Vali |
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| Institution: | 1. Institut f. Allgemeine u. Angewandte Geophysik d. Universit?t München, 8000, München, West Germany
2. Institut f. Angew. Mineralogie d. Techn. Universit?t München, D-8046, Garching, West Germany
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| Abstract: | On heating the paramagnetic clay mineral nontronite for ≈ 30 h at 970 °C in air, a new ferrimagnetic phase forms which was studied by magnetic techniques, microprobe analysis, x-ray diffraction and Mössbauer spectroscopy. The new phase has a Curie temperature T c ≈ 240°C and high magnetic anisotropy at room temperature with a spontaneous magnetization >12 Am2/kg. Semiquantitative microprobe analyses show Fe to be the dominating consistuent. X-ray analysis points to a lattice which may be similar to that of ?-Fe2O3 but differs from it in detail. 57Fe Mössbauer spectra, taken between 78 K and 295 °C, can be deconvoluted into three sextet subpatterns in the ferrimagnetic region which are well resolved at room temperature and exhibit a rather small line width. Above T c, a doublet is visible which is typical for Fe3+ ions. |
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