Investigations on the local structures and the EPR parameters for Er3+ in PbMoO4 and SrMoO4

The local structures and the electron paramagnetic resonance (EPR) parameters g factors gparallel, gperpendicular and the hyperfine structure constants Aparallel and Aperpendicular for Er3+ in PbMoO4 and SrMoO4 are theoretically investigated by using the perturbation formulas of the EPR parameters for a 4f11 ion in tetragonal symmetry. In these formulas, the contributions to the EPR parameters from the second-order perturbation terms and admixtures of different energy levels are considered. Based on the studies, we find that the impurity-ligand bonding angles related to the four-fold axis in the impurity Er3+ centers are reduced by about 1.26 and 1.04 deg. compared with those in host PbMoO4 and SrMoO4 crystals, respectively. The calculated EPR parameters are consistent with the observed values. The validity of the results is discussed