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Title
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A photosensitive center in photorefractive crystals co-doped with chromium and phosphorus
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Author
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Abstract
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| A trigonal Cr3+ (3d3) defect in sillenite type Bi12SiO20 crystals co-doped with chromium and phosphorus has been identified by means of multi-frequency X-band (9.4 GHz), Q-band (35 GHz) and W-band (94 GHz) electron paramagnetic resonance (EPR). A consistent analysis of the observed spectra and their angular dependence was reached using an S = 3/2 spin Hamiltonian with axial symmetry around a 〈111〉 crystallographic direction, an isotropic g-value g = 1.983, and a zero field splitting parameter B20 = 0.1950 cm−1. The spectra are attributed to a chromium ion in the unusual Cr3+ valence replacing a substitutional Si4+ in tetrahedral oxygen coordination. Evidence is found that the symmetry lowering from tetrahedral to trigonal is not spontaneous but induced by an associated defect, for which a P5+ ion in a nearest-neighbor Si4+ site is the most plausible candidate. Optical excitation results in a reversible charge transfer process directly correlated with a photochromic effect: near-UV light leads to a strong reduction of the Cr3+ EPR signals, and induces a broad band at 675 nm in the absorption spectrum, and both effects are reversed under red light excitation. |
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Language
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English
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Source (journal)
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Journal of applied physics / American Institute of Physics. - New York, N.Y., 1937, currens
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Publication
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New York, N.Y.
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American Institute of Physics
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2011
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ISSN
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0021-8979
[print]
1089-7550
[online]
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DOI
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10.1063/1.3561503
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Volume/pages
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109
:8
(2011)
, p. 083506,1-083506,7
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Article Reference
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083506
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ISI
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000290047000030
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Medium
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E-only publicatie
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Full text (Publisher's DOI)
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