材料期刊网

The spin Hamiltonian (SH) parameters (g factors g(x), g(y), g(z) and hyperfine structure constants A(x), A(y), A(z)) of the low-symmetry Nb-Li(4+) antisite defect center in the X-ray-irradiated congruent undoped LiNbO3 crystal are calculated from the high-order perturbation formulas of SH parameters for d(1) ions. The calculated results are in reasonable agreement with the experimental values. Some information related to the defect structure of the Nb-Li(4+) center (characterized mainly by the Nb-Li(4+) displacement Delta z from the ideal Li+ site along C-3 axis and the displacement Delta x of O2- ions in the oxygen triangle between Nb-Li(4+) and Nb-Nb(5+)) is obtained from the calculations. These displacements are consistent with the expectation based on the electrostatic interaction and electron cloud overlap. The results are discussed. (C) 2006 Elsevier B.V. All rights reserved.