Ab initiostudy of the relation between electric polarization and electric field gradients in ferroelectrics

Abstract

The hyperfine interaction between the quadrupole moment of atomic nuclei and the electric field gradient (EFG) provides information on the electronic charge distribution close to a given atomic site. In ferroelectric materials, the loss of inversion symmetry of the electronic charge distribution is necessary for the appearance of the electric polarization. We present first-principles density functional theory calculations of ferroelectrics such as BaTiO3, KNbO3, PbTiO3 and other oxides with perovskite structures, by focusing on both EFG tensors and polarization. We analyze the EFG tensor properties such as orientation and correlation between components and their relation with electric polarization. This work supports previous studies of ferroelectric materials where a relation between EFG tensors and polarization was observed, which may be exploited to study the ferroelectric order when standard techniques to measure polarization are not easily applied.

Exploiting Radioactive Isotopes: from Pollutant Tracking to Solid State Studies Using a Combined Ab Initio and PAC Approach

“…We combined PAC and DFT methods in a series of studies, with two main materials interests in the topics of magnetic and multiferroic materials, including manganites and Mn pnictides . Further computational work demonstrated the prediction of EFG as a proxy for the spontaneous polarization in ferroelectric oxides, allowing a close comparison with previous experimental results.…”

“…In the following manuscript we will make a review of the use of radioactive isotopes as local probes for solid state physics, and nanotechnology studies, with a particular emphasis on hyperfine interactions, where CICECO team has promoted and participated within the international collaboration at ISOLDE (Isotope mass Separator On‐Line facility) in CERN, a laboratory dedicated to the production of radioactive isotopes…”

Reconciling Local Structure Disorder and the Relaxor State in (Bi1/2Na1/2)TiO3-BaTiO3

“…The size of the EFG depends on the magnitude of the structural distortion that causes it. Three different mechanisms of structural distortion may be responsible for an EFG≠0 in the A-site of BNT-xBT: (1) an asymmetric arrangement of neighboring A-site cations due to dissimilar electric charges of Na + , Ba 2+ and Bi 3+ ; (2) polar displacements of all ions, due to the close relationship between electric polarization and the EFG232425; (3) tilting of oxygen octahedra, which causes a deformation of the oxygen cuboctahedron around the A-site cation and results in an asymmetric charge distribution.…”

Local probing of multiferroics: First-principles study of hyperfine parameters in YMnO3and YMn2O5

“…It should be noted that the magnetic order is simplified in relation to experiment. Still, the results clearly illustrate the atomic scale resolving power of the hyperfine parameters [18,19]. In contrast with YMnO3, here the changes in the EFG are much smaller, only significant at the Mn and some O atoms, which is not surprising, considering, that there is a change of magnetic order while the structure remains the same.…”