Studies of the EPR parameters and defect models for three Er 3+ impurity centers in ThO 2 crystals

Abstract

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 × 52 energy matrix concerning the ground multiplet 4I 15/2 and the first to third excited multiplets 4I 13/2, 4I 11/2 and 4I 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.