Investigations of the optical spectra and EPR g-factors for the tetragonal Ce3+centers in YPO4 and LuPO4 crystals

The optical spectral band positions and EPR g-factors (g, g) for the tetragonal Ce3+ centers in YPO4 and LuPO4 crystals with the zircon-structure are calculated using a complete diagonalization (of the energy matrix) method (CDM) related to 4f1 ions in tetragonal symmetry. In this method, the Zeeman interaction term are added to the Hamiltonian in the conventional CDM and so no perturbation calculations are required to obtain the g factors. The crystal-field parameters used in the calculations are obtained from the superposition model in which the local lattice relaxation related to the bonding lengths is considered. The calculated results are in reasonable agreement with the experimental values. It is found that the four observed optical bands for both the systems can be attributed to Ce3+ ions in a tetragonal crystal field.