Electron paramagnetic resonance of platinum impurities in KTiOPO4 crystals

Single crystals of KTiOPO4 (KTP) often contain trace amounts of isolated pl atinum impurities. When present in sufficient concentration, these ions inc rease 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 KTiOPO 4. Initially, the platinum ions are present in nonparamagnetic forms. Expos ure to ionizing radiation (i.e., x rays or above-band-gap laser beams) at r oom temperature converts them into paramagnetic centers. Once formed, these centers are stable for weeks at room temperature; however, their EPR spect ra can only be observed at temperatures near or below 30 K. An angular stud y provided principal values and principal directions for the g matrices and the platinum hyperfine matrices. The Pt(A) center has principal g values o f 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. (C) 2000 American Institute of Physics. [S0021- 8979(00)05812 -6].