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| Titel |
Clusters and holes: Exchange networks in hematite-ilmenite solid solutions |
| VerfasserIn |
K. Fabian, S. A. McEnroe, P. Robinson |
| Konferenz |
EGU General Assembly 2009
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| Medientyp |
Artikel
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| Sprache |
Englisch
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| Digitales Dokument |
PDF |
| Erschienen |
In: GRA - Volume 11 (2009) |
| Datensatznummer |
250022141
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| Zusammenfassung |
| Holes and clusters of exchange networks dominate the low-temperature, metastable phase
diagram of the system
(1 - x)Fe2O3 xF eTiO3 (Ilmx ). By
our measurements we have probed and extended the phase diagram of Ishikawa et al. (1985)
in the light of magnetic influences of the random exchange links, which originate either by
replacing random pairs of Fe2+ and Ti4+ ions in the ordered ilmenite lattice by two Fe3+ions
(ordered Ilmx phase), or by randomly replacing two Fe3+ ions in the hematite lattice by a
pair of Fe2+ and Ti4+ ions (disordered Ilmx phase). Now a large dataset is available from
these measurements, and we propose several new ideas to interpret the sometimes unexpected
results. By refining a method of Ishikawa (1967), we analyze the PM’ region of the
phase diagram in terms of a mean field theory of interacting clusters. This allows to
determine cluster sizes and interaction field distribution by inverting hysteresis
measurements of Ilm92 and Ilm97. To understand the relation between ordered
and disordered phases we design a mean field theory to determine Neel and Curie
temperatures of both. An especially interesting finding is that the experimentally
observed intersection of PM-PM’ crossover with the AF phase boundary close
to Ilm97 can be explained by analyzing average exchange interaction strengths. |
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