Hyperfine interactions in cubic perovskites

ABO3 perovskites display several physical properties determined by the characteristics of A and B cations. These compounds have cubic structure at high temperature. Lower symmetry cells that are distorted cubes are found at low temperature. Defects modify the properties of these compounds. Under standard conditions oxygen vacancies are produced. Cation substitution also alters the characteristics of perovskites. These materials have been studied by Perturbed Angular Correlation (PAC) spectroscopy and other hyperfine techniques. In this way abundant information is available to determine charge distributions close to probes. In the cubic phase perturbations were detected that are produced by the interaction of probes with defects. To show up these effects we analyze the quadrupole interaction at 181Ta in several compounds: ABO3 with A=Ca, Sr and Ba, BaTi1-xHfxO3 and PbZr1-xTixO3 for 0≤x≤1. Three different quadrupole interactions were found and are interpreted in terms of distinct probe-oxygen vacancy configurations