Defect model and EPR parameters for the tetragonal Yb3+ center in KTaO3 crystal

The defect model of the tetragonal Yb3+ (at K+ site) center in KTaO3 crystal is suggested, i.e., Yb3+ ion does not occupy the ideal K+ site, but is displaced by an amount Delta Z along one of (100) axes because of the much smaller ionic radius of Yb3+ compared with that of the replaced K+. Based on the defect model, the EPR parameters (g factors g(parallel to), g(perpendicular to) and hyperfine structure constants (171)A(parallel to), (171)A(perpendicular to), (173)A(parallel to), (173)A(perpendicular to)) are calculated by diagonalizing the 14 x 14 complete energy matrix. The calculated values are in agreement with the observed values and the off-center displacement Delta Z (approximate to 0.2 angstrom) is estimated from the calculations. These results are discussed. (C) 2008 Elsevier B.V. All rights reserved.