Hyperfine Interactions in the Sr_0.88Ba_0.12HfO₃ Compound

Abstract

The temperature dependence of the hyperfine parameters in a powder sample of the Sr_0.88Ba_0.12HfO₃ compound has been investigated for the first time using perturbed angular correlation spectroscopy. The time spectra were measured as a function of the temperature from 293 to 1273 K. Activated ¹⁸¹Ta nuclei were used as hyperfine probes at the Hf sites. The analysis of the time spectra indicates the presence of two different surroundings for the Ta probes. The most populated site (f ₁≈75% at laboratory temperature) was fitted with the usual static quadrupole hyperfine interactions found in most perovskite-type compounds. The resulting quadrupole frequency is ω _Q ≈24 Mrad/s at this temperature. This frequency continuously decreases to nearly 9 Mrad/s at 1273 K. Its line width temperature dependence displays three regions and the changes observed probably correspond to phase transitions. The other site has a large and temperature independent quadrupole frequency ω _Q ≈120 Mrad/s that reversibly transforms into the first at high temperatures and probably originates from some defect in the structure.