Perovskite Crystals: Unique Pseudo-Jahn–Teller Origin of Ferroelectricity, Multiferroicity, Permittivity, Flexoelectricity, and Polar Nanoregions
In a semi-review paper, we show that the local pseudo-Jahn–Teller effect (PJTE) in transition metal B ion center of ABO<sub>3</sub> perovskite crystals, notably BaTiO<sub>3</sub>, is the basis of all their main properties. The vibronic coupling between the ground and excited...
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MDPI AG
2020-11-01
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| Series: | Condensed Matter |
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| Online Access: | https://www.mdpi.com/2410-3896/5/4/68 |
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| author | Isaac B. Bersuker Victor Polinger |
| author_facet | Isaac B. Bersuker Victor Polinger |
| author_sort | Isaac B. Bersuker |
| collection | DOAJ |
| description | In a semi-review paper, we show that the local pseudo-Jahn–Teller effect (PJTE) in transition metal B ion center of ABO<sub>3</sub> perovskite crystals, notably BaTiO<sub>3</sub>, is the basis of all their main properties. The vibronic coupling between the ground and excited electronic states of the local BO<sub>6</sub> center results in dipolar distortions, leading to an eight-well adiabatic potential energy surface with local tunneling or over-the-barrier transitions between them. The intercenter interaction between these dipolar dynamic units results in the formation of the temperature-dependent three ferroelectric and one paraelectric phases with order–disorder phase transitions. The local PJTE dipolar distortion is subject to the presence of sufficiently close in energy local electronic states with opposite parity but the same spin multiplicity, thus limiting the electronic structure and spin of the B(<inline-formula><math display="inline"><semantics><mrow><msup><mi>d</mi><mi>n</mi></msup></mrow></semantics></math></inline-formula>) ions that can trigger ferroelectricity. This allowed us to formulate the necessary conditions for the transition metal perovskites to possess both ferroelectric and magnetic (multiferroic) properties simultaneously. It clarifies the role of spin in the spontaneous polarization. We also show that the interaction between the independently rotating dipoles in the paraelectric phase may lead to a self-assembly process resulting in polar nanoregions and relaxor properties. Exploring interactions of PJTE ferroelectrics with external perturbations, we revealed a completely novel property—<i>orientational polarization in solids—</i>a phenomenon first noticed by P. Debye in 1912 as a possibility, which was never found till now. The hindered rotation of the local dipole moments and their ordering along an external field is qualitatively similar to the behavior of polar molecules in liquids, thus adding a new dimension to the properties of solids—notably, the perovskite ferroelectrics. We estimated the contribution of the orientational polarization to the permittivity and flexoelectricity of perovskite crystals in different limiting conditions. |
| first_indexed | 2024-03-10T15:09:30Z |
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| issn | 2410-3896 |
| language | English |
| last_indexed | 2024-03-10T15:09:30Z |
| publishDate | 2020-11-01 |
| publisher | MDPI AG |
| record_format | Article |
| series | Condensed Matter |
| spelling | doaj.art-e3c9f085816a49599aa64da347ba06362023-11-20T19:31:00ZengMDPI AGCondensed Matter2410-38962020-11-01546810.3390/condmat5040068Perovskite Crystals: Unique Pseudo-Jahn–Teller Origin of Ferroelectricity, Multiferroicity, Permittivity, Flexoelectricity, and Polar NanoregionsIsaac B. Bersuker0Victor Polinger1Department of Chemistry, University of Texas at Austin, Austin, TX 78712-1229, USADepartment of Chemistry, University of Washington, Seattle, WA 98195-1700, USAIn a semi-review paper, we show that the local pseudo-Jahn–Teller effect (PJTE) in transition metal B ion center of ABO<sub>3</sub> perovskite crystals, notably BaTiO<sub>3</sub>, is the basis of all their main properties. The vibronic coupling between the ground and excited electronic states of the local BO<sub>6</sub> center results in dipolar distortions, leading to an eight-well adiabatic potential energy surface with local tunneling or over-the-barrier transitions between them. The intercenter interaction between these dipolar dynamic units results in the formation of the temperature-dependent three ferroelectric and one paraelectric phases with order–disorder phase transitions. The local PJTE dipolar distortion is subject to the presence of sufficiently close in energy local electronic states with opposite parity but the same spin multiplicity, thus limiting the electronic structure and spin of the B(<inline-formula><math display="inline"><semantics><mrow><msup><mi>d</mi><mi>n</mi></msup></mrow></semantics></math></inline-formula>) ions that can trigger ferroelectricity. This allowed us to formulate the necessary conditions for the transition metal perovskites to possess both ferroelectric and magnetic (multiferroic) properties simultaneously. It clarifies the role of spin in the spontaneous polarization. We also show that the interaction between the independently rotating dipoles in the paraelectric phase may lead to a self-assembly process resulting in polar nanoregions and relaxor properties. Exploring interactions of PJTE ferroelectrics with external perturbations, we revealed a completely novel property—<i>orientational polarization in solids—</i>a phenomenon first noticed by P. Debye in 1912 as a possibility, which was never found till now. The hindered rotation of the local dipole moments and their ordering along an external field is qualitatively similar to the behavior of polar molecules in liquids, thus adding a new dimension to the properties of solids—notably, the perovskite ferroelectrics. We estimated the contribution of the orientational polarization to the permittivity and flexoelectricity of perovskite crystals in different limiting conditions.https://www.mdpi.com/2410-3896/5/4/68perovskite crystalsPseudo-Jahn-Teller effectferroelectricitymultiferroicitypermittivityflexoelectricity |
| spellingShingle | Isaac B. Bersuker Victor Polinger Perovskite Crystals: Unique Pseudo-Jahn–Teller Origin of Ferroelectricity, Multiferroicity, Permittivity, Flexoelectricity, and Polar Nanoregions Condensed Matter perovskite crystals Pseudo-Jahn-Teller effect ferroelectricity multiferroicity permittivity flexoelectricity |
| title | Perovskite Crystals: Unique Pseudo-Jahn–Teller Origin of Ferroelectricity, Multiferroicity, Permittivity, Flexoelectricity, and Polar Nanoregions |
| title_full | Perovskite Crystals: Unique Pseudo-Jahn–Teller Origin of Ferroelectricity, Multiferroicity, Permittivity, Flexoelectricity, and Polar Nanoregions |
| title_fullStr | Perovskite Crystals: Unique Pseudo-Jahn–Teller Origin of Ferroelectricity, Multiferroicity, Permittivity, Flexoelectricity, and Polar Nanoregions |
| title_full_unstemmed | Perovskite Crystals: Unique Pseudo-Jahn–Teller Origin of Ferroelectricity, Multiferroicity, Permittivity, Flexoelectricity, and Polar Nanoregions |
| title_short | Perovskite Crystals: Unique Pseudo-Jahn–Teller Origin of Ferroelectricity, Multiferroicity, Permittivity, Flexoelectricity, and Polar Nanoregions |
| title_sort | perovskite crystals unique pseudo jahn teller origin of ferroelectricity multiferroicity permittivity flexoelectricity and polar nanoregions |
| topic | perovskite crystals Pseudo-Jahn-Teller effect ferroelectricity multiferroicity permittivity flexoelectricity |
| url | https://www.mdpi.com/2410-3896/5/4/68 |
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