Ferroelectricity from coupled cooperative Jahn-Teller distortions and octahedral rotations in ordered Ruddlesden-Popper manganates

Abstract

Density functional theory and group theoretical methods are used to explore the origin for ferroelectricity in cation ordered LaSrMnO4 with the Ruddlesden-Popper structure. The equilibrium phase exhibits the polar, P ca21 space group, where small polar displacements of d 4 Mn 3+ coexist with antiferrodistortive octahedral rotations and Jahn-Teller distortions. We find that the octahedral rotations and Jahn-Teller distortion stabilize the polar structure and induce polar displacements through high-order anharmonic interactions among the three modes, making LaSrMnO4 a hybridimproper ferroelectric material. The rotations result from the ionic size mismatch between the A cations and Mn whereas the Jahn-Teller distortions are energetically favored owing to the coupling between the local eg orbital polarization of the two nearest neighboring Mn cations in the two dimensional MnO2 sheets. Our results indicate that anharmonic interactions among multiple centric modes can be activated by cation ordering to induce polar displacements in layered oxides, making it a reliable approach for realizing acentric responses in artificially constructed materials.

Two-dimensional ferroelectricity induced by octahedral rotation distortion in perovskite oxides

“…Therefore, not all soft modes can generate energy gain, which may be related to the fact that the anharmonic effect is not considered in the calculation of phonon band structures. Similar phenomena have also been found in other perovskite and layered perovskite oxides [30,31,40].…”

Learning from data to design functional materials without inversion symmetry

“…In this compound, a combination of A-site and B-site cation ordering work in concert to lift the inversion symmetry. In addition to these compounds, Pb 2 TiO 4 , Ca 2 IrO 4 , Sn 2 SnO 4 , cation-ordered La A NiO 4 ( A =Sr, Ca and Ba) LaSrAlO 4 and LaSrMnO 4 have also been theoretically predicted to have NCS structures 15 24 25 26 27 28 ; however, these results have not been experimentally verified. Recently, the metastable Ca 2 IrO 4 was epitaxially grown on a YAlO 3 substrate in the n =1 RP phase using pulsed laser deposition 29 .…”

Giant exchange bias in the single-layered Ruddlesden-Popper perovskite SrLaCo0.5Mn0.5O4

“…We observed a large difference between the equatorial and apical bonds of Mn/Co-O6 octahedra with bond length 1.92 Å and 2.09 Å respectively, and the difference in bond length is close to 0.17 Å. We may note that Jahn-Teller active LaSrMnO4 has a similar difference in the bond length [26]. The obtained bond lengths (Table S3 supplementary) from the NPD refinement signatures the compression of equatorial and elongation of apical bonds indicating the presence of Jahn Teller active Mn 3+ ion (t2g 3 eg 1 ).…”