Octahedral Rotation Induced, Antiferroelectric-like Double Hysteresis in Strained Perovskites

Abstract

Antiferroelectrics, which host both polar and antipolar order parameters, are characterized by the double hysteresis loops which are advantageous for various applications such as high-density energy storage. In this study, we investigate the coupling between oxygen octahedral rotations and polarization in well-known perovskites, with a focus on SrTiO$_3$. Using first-principles calculations and symmetry-adapted Landau-Ginzburg-Devonshire theory, we construct an energy landscape to analyze how this coupling shapes polarization-voltage hysteresis behavior. We show that tuning the relative strength of polar and rotational instabilities by exploiting epitaxial strain and layering leads to nontrivial hysteresis behavior. Consequently, the rotation coupling with polarization leads to an expanded search space of materials exhibiting antiferroelectric-like double hysteresis.

Figures (4)

• Figure 1: Strain-dependent ground state properties of SrTiO$_3$. (a) Depiction of the a$^0$a$^0$c$^-$ octahedral rotation, (b) polarization, and (c) $\eta_{zz}$ strain in SrTiO$_3$. (d) Upper panel: Spontaneous polarization (blue) and spontaneous octahedral rotation (red) in the ground state of SrTiO$_3$, with gray data points marking stable local minima. Lower panel: Relative energy for different phases (I4/mcm, P4mm, and I4cm) of SrTiO$_3$, referenced against the parent space group P4/mmm.
• Figure 2: (a) The Kohn-Sham energy surface of SrTiO$_3$ as a function of $P$ and $Q$. (b) Polarization-voltage ($P$-$v$) characteristics of SrTiO$_3$ under varying levels of epitaxial strain. An antiferroelectric (AFE) hysteresis loop emerges at the phase transition between the I4cm and P4mm phases at --1.2% strain. As the strain increases, both ferroelectric and AFE hysteresis are amplified. At --4.8% strain, the saddle point along the $P$ axis transitions into a local minimum. The blue, red, and dotted curves correspond to the stable I4cm phase, the stable P4mm phase, and the metastable I4cm phase, respectively.
• Figure 3: Energy-polarization plot of SrTiO$_3$ as derived from LGD theory under varying epitaxial strain values. The blue, red, and dotted curves represent the stable I4cm phase, stable P4mm phase, and metastable I4cm phase, respectively.
• Figure 4: (a) Coherence-breaking rumpling motions in the 2-octahedral-layer Ruddlesden-Popper (RP) phase perovskite (Sr$_3$Ti$_2$O$_7$) hardens phonon modes associated with a$^0$a$^0$c$^-$ octahedral rotation (R$_2^-$) and polarization ($\Gamma_2^-$), offering additional control over the second-order coefficients $a_2$ and $b_2$. (b) Strain phase diagram of Sr$_{n+1}$Ti$_n$O$_{3n+1}$ for $n$ values from 1 to 4. (c) Most stable phase of Sr$_{n+1}$Ti$_n$O$_{3n+1}$ as a function of epitaxial strain and $n$. (d) Polarization-voltage hysteresis plot of Sr$_3$Ti$_2$O$_7$ at --4% strain.