Studies of the EPR parameters and defect models for three Er3+ impurity centers in ThO2 crystals.

The electron paramagnetic resonance (EPR) parameters (g factors and hyperfine structure constants of the ground state, and g factors of the first excited state) of three (one cubic and two trigonal) Er(3+) centers in fluoride-type ThO(2) crystal are studied from a diagonalization (of energy matrix) method. In the method, the Zeeman and hyperfine interaction terms are added to the classical Hamiltonian, and a 52 x 52 energy matrix concerning the ground multiplet (4)I(15/2) and the first to third excited multiplets (4)I(13/2), (4)I(11/2) and (4)I(9/2) is established for a 4f(11) ion in trigonal crystal field and under an external magnetic field. From the studies, the EPR parameters for three Er(3+) centers in ThO(2) are reasonably explained, the defect models for the two trigonal Er(3+) centers suggested in the previous paper are confirmed and the defect structures of the two trigonal centers are obtained. The results are discussed.