Hyperfine interactions at ¹⁸¹Hf(→¹⁸¹Ta) impurities implanted in Er₂O₃ and Gd₂O₃: structural and electronic dependence of the EFG in bixbyite sesquioxides

Abstract:

The time-differential-perturbed γ-γ angular-correlation technique (TDPAC) with ion-implanted 181Hf tracers has been applied to study the hyperfine interactions of 181Ta impurities in the cubic bixbyite structure of Er 2 O 3 and Gd 2 O 3 . The TDPAC experiments were performed in air in the temperature range 300-1073 K (in the case of Er 2 O 3 ) and 300-1173 K (in the case of Gd 2 O 3 ). Three electrical-quadrupole interactions were found in each oxide in the whole studied temperature range. Two of them were attributed to the electric-field gradients (EFG) acting on 181Ta probes substitutionally located on the two nonequivalent free-of-defects cation sites of the bixbyite structure. The EFG results are compared with predictions of the point-charge model and discussed together with previous results obtained with the probes 111Cd and 181Ta in other isomorphous sesquioxides. The temperature dependence of the hyperfine parameters for both oxides is also discussed in terms of dilatometric expansion data.