Hyperfine interactions in the cubic phase of BaTixHf1-xO3

R. E. ALONSO; A.P. AYALA; C. HOROWITZ; P. DE LA PRESA; A. LÓPEZ GARCÍA

FERROELECTRICS

Año: 2002 vol. 274 p. 17 - 28

0015-0193

Abstract The presence of a non-zero hyperfine electric field gradient tensor detected by probes that occupy sites with cubic point group symmetry was observed in many ABO3 perovskite-type compounds. This breakdown of local cubic symmetry is commonly associated with the presence of oxygen vacancies around the probe. This effect in BaTixHf1-xO3, with x=0.70, 0.50, 0.30, 0.10, 0.05 and 0.01 is studied in this work. The cell parameters were obtained at room temperature using XRD spectroscopy. The hyperfine parameters were measured at the 181Ta probe in the B site using Angular Correlation (PAC) spectroscopy as a function of both temperature and composition. As a common trend a static asymmetric and distributed quadrupolar interaction strongly dependent on composition has been observed. The results, together with those corresponding to 1>x³0.75, are analysed using the point-charge model in terms of polarised oxygen vacancies, different covalence of the Ti-O and Hf-O bonds with computational simulation for the lattice positions of cations and oxygen vacancies.