Investigations of EPR parameters and defect models for three Yb3+ impurity centers in ThO2 and CeO2 crystals

Abstract

The electron paramagnetic resonance (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) and (173)A(perpendicular to)) for three Yb(3+) centers, one cubic (center I) and two trigonal (centers II and III). in ThO(2) and CeO(2) crystals are studied from a complete diagonalization (of energy matrix) method. In the method, the Zeeman and hyperfine interaction terms are added to the classical Hamiltonian and the crystal-field parameters are calculated from the empirical superposition model. From the studies, the EPR parameters for these Yb(3+) centers in ThO(2) and CeO(2) crystals are reasonably explained, the defect model for the trigonal Yb(3+) center II suggested in the previous paper is confirmed and the defect structure of center II are also obtained. The theoretical hyperfine structure constants A of two Yb isotopes for centers II and III are suggested and remain to be checked by further experiments. The results are discussed. (C) 2010 Elsevier B.V. All rights reserved.