Title A photosensitive $Cr^{3+}$ center in photorefractive $Bi_{12}SiO_{20}$ crystals co-doped with chromium and phosphorus Author Ahmad, Ijaz Marinova, Vera Vrielinck, Henk Callens, Freddy Goovaerts, Etienne Faculty/Department Faculty of Sciences. Physics Publication type article Publication 2011 New York, N.Y. :American Institute of Physics , 2011 Subject Physics Source (journal) Journal of applied physics / American Institute of Physics. - New York, N.Y., 1937, currens Volume/pages 109(2011) :8 , p. 083506,1-083506,7 ISSN 0021-8979 1089-7550 ISI 000290047000030 Carrier E-only publicatie Target language English (eng) Full text (Publishers DOI) Affiliation University of Antwerp Abstract 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. E-info http://gateway.webofknowledge.com/gateway/Gateway.cgi?GWVersion=2&SrcApp=PARTNER_APP&SrcAuth=LinksAMR&KeyUT=WOS:000290047000030&DestLinkType=RelatedRecords&DestApp=ALL_WOS&UsrCustomerID=ef845e08c439e550330acc77c7d2d848 http://gateway.webofknowledge.com/gateway/Gateway.cgi?GWVersion=2&SrcApp=PARTNER_APP&SrcAuth=LinksAMR&KeyUT=WOS:000290047000030&DestLinkType=FullRecord&DestApp=ALL_WOS&UsrCustomerID=ef845e08c439e550330acc77c7d2d848 http://gateway.webofknowledge.com/gateway/Gateway.cgi?GWVersion=2&SrcApp=PARTNER_APP&SrcAuth=LinksAMR&KeyUT=WOS:000290047000030&DestLinkType=CitingArticles&DestApp=ALL_WOS&UsrCustomerID=ef845e08c439e550330acc77c7d2d848 Handle