Article ID | Journal | Published Year | Pages | File Type |
---|---|---|---|---|
5447425 | Journal of Physics and Chemistry of Solids | 2017 | 38 Pages |
Abstract
The luminescence spectra of Cr3+ in (Mg,Fe2+)5Al(Si3Al)O10(OH)8-clinochlore, a layered silicate compound, are reported to pressures of â¼25 GPa at 298 K: our results encompass emission from single-ions, paired neighbors and vibronic lines. A transition from sharp single Cr3+ ion (R-line) dominated emission to Cr-Cr pair (N-Line) dominated emission is observed under compression. Since Cr atoms are confined to a discrete layer within the structure, efficient Cr-Cr exchange only occurs within a single layer; the distance between the layers is too large for significant interlayer coupling to occur. This 2-dimensional, single-layer arrangement gives rise to three distinguishable Cr3+ nearest neighbor pairs. Neighbor lines are assigned based on ferromagnetic coupling of these three emitting pairs. We observe a decrease in the separation between the split components of the R-line under compression, confirming that the Cr sites become less distorted up to at least â¼11.0 GPa. An increase in overlap between eg orbitals of neighboring Cr-ions (corresponding to delocalization of the excited state) under compression also likely occurs. The R-to N-line transition is fully reversible and hysteresis is not observed, indicating that this transition is purely electronic in nature. The intensity transfer between the single-ion and paired-ion emission changes with a â¼1/4th power law as a function of the Cr-Cr separation.
Keywords
Related Topics
Physical Sciences and Engineering
Materials Science
Electronic, Optical and Magnetic Materials
Authors
Earl III, Quentin Williams,