Anomalous pressure dependence of the atomic displacements in the relaxor ferroelectric PbMg1/3Ta2/3O3
Résumé
The crystal structure of the PbMg1/3Ta2/3O3 relaxor ferroelectric was studied under hydrostatic pressure up to 7 GPa by means of powder neutron diffraction. We find a drastic pressure-induced decrease of the lead displacement from the inversion center, which correlates with an increase by 50% of the anisotropy of the oxygen temperature factor. The vibrations of the Mg/Ta are, in contrast, rather pressure insensitive. We attribute these changes being responsible for the previously reported pressure-induced suppression of the anomalous dielectric permittivity and diffuse scattering in relaxor ferroelectrics.