PAC Characterization of 181Ta-implanted Lu and Sm sesquioxides: Non-ionic contributions to the EFG at Ta/Cd impurities in Bixbyites

M. RENTERIA; K. FREITAG; L. A: ERRICO

Durban

Conferencia; 11th International Conference on Hyperfine Interactions; 1998

We present results of PAC experiments on 181Hf-implanted Lu- and Sm-sesquioxides. The hyperfine interactions at 181Ta located at both cation sites of the bixbyite structure were characterized, increasing the electric-field gradient (EFG) data at Ta-impurity sites in these systems. The accumulated EFG data with 181Ta enables a first attempt to investigate the universal character of the empirical correlation between local and ionic contributions to the EFG in binary oxides. In the specific case of the bixbyite group, a factorization of EFG as function of the electronic characteristics of the probe, the geometry of the cation coordination with its nearest (NN) and next-near neighbours (NNN), and the lattice parameter of the sesquioxides is proposed. This factorization explains the experimental EFG results at Ta/Cd sites in bixbyites and is in qualitative agreement with a simplified decomposition of the EFG valence contribution coming from ab-initio calculations.