Temperature Dependence of the Hyperfine Interaction at 181Ta in SrHfO3

The temperature dependence of the quadrupole hyperfine parameters covering the temperature range from 293 to 1173 K has been measured at 181Ta probes in SrHfO3 by perturbed angular correlation spectroscopy. A fluctuating distribution of quadrupole interactions model has been applied to interpret the data. At low temperatures above ~300 K a static, asymmetric, and distributed electric quadrupole interaction was detected. At intermediate temperatures (600 K) a different quadrupole interaction appears, characterized by a fluctuating distribution of axially symmetric electric field gradient tensors. Above 873 K, the unique presence of a nuclear spin relaxation machanism shows a second change in the perturbation acting on probes. These changes in the hyperfine interaction are consistent with the structural phase transitions detected by diffraction techniques. The probe effects were also analyzed, comparing 181Ta with 111Cd experiments.