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Single crystals of KTiOPO4 (KTP) often contain trace amounts of isolated platinum impurities. When present in sufficient concentration, these ions increase the KTP crystal's susceptibility to form gray tracks during frequency doubling of high-power laser beams. Electron paramagnetic resonance (EPR) has been used to characterize three platinum centers in a crystal of KTiOPO4. Initially, the platinum ions are present in nonparamagnetic forms. Exposure to ionizing radiation (i.e., x rays or above-band-gap laser beams) at room temperature converts them into paramagnetic centers. Once formed, these centers are stable for weeks at room temperature; however, their EPR spectra can only be observed at temperatures near or below 30 K. An angular study provided principal values and principal directions for the g matrices and the platinum hyperfine matrices. The Pt(A) center has principal g values of 1.9397, 2.4463, and 2.5900 and is assigned to a Pt3+ ion substituting for a Ti4+ ion. In contrast, the Pt(B) center has principal g values of 1.6019, 1.9754, and 2.7788 and the Pt(C) center has values of 1.4656, 1.8597, and 2.9576. We suggest that these latter two centers are Pt+ ions substituting for K+ ions. © 2000 American Institute of Physics.
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