Abstract
The occurrence of Cr-Al pairs in Mg2SiO4 has been detected by EPR spectroscopy. In the case where Cr3+ replaces Mg at the M2 position three different neighboring Si sites may be substituted by Al3+, which should yield different superhyperfine interactions. A new spectrum is presented which shows the presence of two of these possible pair configurations. An assignment of the spectral features to a specific Cr-Al pair with Cr at M2 from the experimental data alone was not possible, therefore, MSX α cluster calculations have been performed from which the differences in the superhyperfine interaction for the various pair configurations could be obtained. Best agreement with the data of the Cr3+(M2)-Al pair exhibiting the most intense group of lines in the EPR spectrum was obtained for the situation where Al3+ is at the Si position with the shortest distance to M2. The second observed Cr3+(M2)-Al pair, which is significantly weaker in intensity, could not yet be assigned.
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Nagel, S., Rager, H. Hyperfine interactions and spin transfer between Cr3+ and Al3+ in a synthetic single crystal of Mg2SiO4. A theoretical approach to the interpretation of EPR data. Phys Chem Minerals 12, 291–299 (1985). https://doi.org/10.1007/BF00310342
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DOI: https://doi.org/10.1007/BF00310342