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Properties of BaTiO3/BaZrO3 ferroelectric superlattices with competing instabilities | | Alexander I. Lebedev
; | | Date: |
29 Apr 2013 | | Abstract: | Properties of (BaTiO$_3$)$_1$/(BaZrO$_3$)$_n$ ferroelectric superlattices
(SLs) with $n = {}$1--7 grown in the [001] direction are calculated from first
principles within the density functional theory. It is revealed that the
quasi-two-dimensional ferroelectricity occurs in these SLs in the barium
titanate layers with a thickness of one unit cell; the polarization is oriented
in the layer plane and weakly interacts with the polarization in neighboring
layers. The ferroelectric ordering energy and the height of the barrier
separating different orientational states of polarization in these SLs are
sufficiently large to provide the formation of an array of independent
polarized planes at 300 K. The effect of the structural instability on the
properties of SLs is considered. It is shown that the ground state is a result
of simultaneous condensation of the $Gamma_{15}$ polar phonon and phonons at
the $M$ point (for SLs with even period) or at the $A$ point (for SLs with odd
period); it is a polar structure with out-of-phase rotations of the octahedra
in neighboring layers, in which highly polarized layers are spatially separated
from the layers with strong rotations. The competition between the
ferroelectric and structural instabilities in biaxially compressed SLs
manifests itself in that the switching on of the octahedra rotations leads to
an abrupt change of the polarization direction and can cause an improper
ferroelectric phase transition to occur. It was shown that the experimentally
observed $z$-component of polarization in the SLs can appear only as a result
of the mechanical stress relaxation. | | Source: | arXiv, 1304.7596 | | Services: | Forum | Review | PDF | Favorites | |
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