Bulletin of the American Physical Society
APS March Meeting 2014
Volume 59, Number 1
Monday–Friday, March 3–7, 2014; Denver, Colorado
Session B41: Focus Session: Ferroelectrics and Anti-Ferroelectrics |
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Sponsoring Units: DMP DCOMP Chair: Antonio Cammarata, Drexel University Room: Mile High Ballroom 3C |
Monday, March 3, 2014 11:15AM - 11:27AM |
B41.00001: Structure and Properties Across a Strain-induced Ferri-to-ferroelectric Transition James Rondinelli, Gaoyang Gou We identify a first-order, isosymmetric transition between a ferrielectric (FiE) and ferroelectric (FE) state in $A$-site ordered LaScO$_{3}$/BiScO$_{3}$ and LaInO$_{3}$/BiInO$_{3}$ superlattices using density functional calculations. Such a previously unreported ferroic transition is driven by the easy switching of cation displacements without changing the overall polarization direction or crystallographic symmetry. Epitaxial strains less than 2\% are predicted to be sufficient to transverse the phase boundary, across which we capture a $\sim\!5$X increase in electric polarization. In a fashion similar to Pb-based perovskite ceramics with a morphotropic phase boundary (MPB), we predict an electromechanical response up to 102 pC/N in the vicinity of the FiE-FE phase boundary in multidomain materials. The structural origin of the unanticipated piezoelectric enhancement is explained. [Preview Abstract] |
Monday, March 3, 2014 11:27AM - 11:39AM |
B41.00002: Structural investigations and the effect of strain on lead based double perovskites Brian Abbett, Craig J. Fennie The A$_2 B B^{\prime}$O$_6$ double perovskite structure, in which the $B$ and $B^{\prime}$ ions are ordered (typically in a rocksalt configuration), provides a versatile platform to realize new properties such as multiferroicity. In particular, compounds with a lone-pair cation on the $A$-site, such as $A$=Pb$^{2+}$, and magnetic $B$=Co, Mn, and diamagnetic $B^{\prime}$= Te, Mo, W, Re, cations have been investigated experimentally, but as of yet none have been found to display ferroelectricity, although several are known to be antiferroelectric. Here we present a first-principles study of the structural and dielectric properties of this family of compounds. We resolve any conflicting reports in the literature as to the ground state structure of compounds and predict the ground state structure when no structural data is available. Additionally, we investigate the effect of epitaxial strain on the structural and magnetic properties. [Preview Abstract] |
Monday, March 3, 2014 11:39AM - 11:51AM |
B41.00003: Effect of Epitaxial Strain on the Dynamical Properties of Ferroelectric Perovskites Kevin McCash, Brajesh Mani, Chun-Min Chang, Inna Ponomareva The use of ferroelectric perovskites in device applications is in large part determined by the strain induced by their growth on lattice mismatched substrates. The epitaxial strain resulting from such growth has been shown to dramatically alter the soft-mode dynamics of ferroelectrics. Here we take advantage of first-principles-based molecular dynamics simulations to investigate the soft-mode dynamics in epitaxial PbTiO$_{3}$ films. By calculating the complex dielectric response and extracting the soft-mode frequencies we are able to trace the intrinsic dynamics as a function of temperature and strain. Our simulations show that the interplay of applied and spontaneous strain is critical to the soft-mode dynamics and provides insights into some recent experimental findings. [Preview Abstract] |
Monday, March 3, 2014 11:51AM - 12:03PM |
B41.00004: Frustrated Antiferroelectricity in a Room-Temperature Ferrimagnet: Promising Candidate Toward Multiple State Memory PanShuo Wang, HongJun Xiang Frustration refers to the presence of competing forces that cannot be simultaneously satisfied. However, geometrical frustration in ferroelectrics is highly unusual. Here we show from first-principles calculations that the M-type hexaferrite BaFe$_{12}$O$_{19}$ exhibits frustrated antiferroelectricity, and hence resolve the experimental controversy on the local structure of the trigonal bipyramidal (TBP) site. Due to the electrostatic interaction, the high-spin Fe$^{3+}$ ions at the TBP sites are displaced from the mirror-plane sites to generate local dipole moments along the c axis. Because of the dipole-dipole interactions, the ground state of BaFe$_{12}$O$_{19}$ is a$(2\times 1)$ chain-like antiferroelectric (AFE) phase. Our work indicates that the ferroelectric state is metastable and can be reached by applying an external electric field to the AFE state, and that the FE state can be made stable at room temperature by element substitution or strain engineering. Thus M-type hexaferrites not only provide platform for studying the new physics of the frustrated antiferroelectricity, but also are promising candidates for realizing multiple state memory devices based on the coexistence of the room temperature polar order and strong ferrimagnetic order. [Preview Abstract] |
Monday, March 3, 2014 12:03PM - 12:15PM |
B41.00005: Antiferroelectricity in ZrO$_2$ and related AXY compounds from first principles Sebastian E. Reyes-Lillo, Kevin F. Garrity, Karin M. Rabe The field-induced structural transition in antiferroelectrics has important technological applications in energy-storage capacitors and piezoelectric devices. Recently, antiferroelectricity was reported in zirconia (ZrO$_2$) [1], which is a widely-used material in electronic devices. In this work, we investigate the nature of antiferroelectricity in thin film ZrO$_2$ and related AXY compounds. For ZrO$_2$, we use first principles calculations to provide strong evidence that the experimentally reported field-induced ferroelectric phase is an intrinsic property of ZrO$_2$. Using a Landau type model, we propose a switching mechanism from the nonpolar tetragonal phase to the orthorhombic polar structure, and we show how to access the ferroelectric phase through epitaxial strain. Drawing on these results, we reexamine a wide variety of related AXY compositions as candidates for antiferroelectrics. Physical descriptors that promote optimal functional properties in antiferroelectrics are identified, and results will be presented. \\[4pt] [1]~J. M\"uller~\emph{et al.}, Nano. Lett. 12, 4318 (2012). [Preview Abstract] |
Monday, March 3, 2014 12:15PM - 12:27PM |
B41.00006: Pressure-induced transitions in ferroelectric single-crystal PbZr$_{0.54}$Ti$_{0.46}$O$_{3}$ Muhtar Ahart, R.E. Cohen, Russell J. Hemley Ceramics of PbZr$_{(1-x)}$Ti$_{x}$O$_{3}$ (PZT) are widely used in many modern electromechanical transducers. Because single crystals of these materials are difficult to grow, many intrinsic physical properties have not been well understood. Recent breakthroughs in the growth of PZT single crystals have allowed us to study their fundamental physical properties. Here, we study the pressure induced phase transitions in PbZr$_{0.54}$Ti$_{0.46}$O$_{3}$ single crystal by means of combined high-pressure Raman scattering and x-ray diffraction. Our Raman results indicate that the structural transition at 3 GPa is driven by soft optical phonons, and is accompanied by the appearance of a sharp peak near 370 cm$^{-1}$ above 3 GPa. We also observe a new structural transition occurring above 27 GPa associated with a drastic change of the Raman spectrum. The pressure evolution of the diffraction patterns for PbZr$_{0.54}$Ti$_{0.46}$O$_{3}$ show obvious splitting above 27 GPa, particularly for the pseudo-cubic [111] and [220] diffraction peaks, the results indicate a lowering symmetry transition in PbZr$_{0.54}$Ti$_{0.46}$O$_{3}$. We propose that the second transition is from rhombohedral to orthorhombic induced by a pressure above 27 GPa. [Preview Abstract] |
Monday, March 3, 2014 12:27PM - 1:03PM |
B41.00007: Antiferroelectricity in lead zirconate Invited Speaker: Alexander K. Tagantsev Antiferroelectrics are essential ingredients for widely applied piezoelectric and ferroelectric materials. Despite their technological importance, the reason why materials become antiferroelectric has remained allusive since their first discovery. Experimentally, antiferroelectrics can be recognized as materials that exhibit a structural phase transition between two non-polar phases with a strong dielectric anomaly at the high temperature side of the transition. Despite a widely spread opinion that these materials can be viewed as direct analogues of antiferromagnetics, the so-called anti-polar ionic displacements at the transition do not guaranty the antiferroelectric behavior of the material while the interpretation of such behavior does not require the incorporation of the anti-polar ionic displacements in the scenario. To get insight in the true origin of antiferroelectricity, we studied the lattice dynamics of the antiferroelectric lead zirconate using inelastic and diffuse X-ray scattering techniques and the Brillouin light scattering. Based on our experimental data, we showed that the driving force for antiferroelectricity is a ferroelectric instability. Through flexoelectric coupling, it drives the system to a state, which is virtually unstable against incommensurate modulations. However, the Umklapp interaction allows the system to go directly to the commensurate lock-in phase, leaving the incommensurate phase as a ``missed'' opportunity. By this mechanism the ferroelectric softening is transformed into an antiferroelectric transition. The remaining key parts of the whole scenario are repulsive and attractive biquadratic couplings that suppress the appearance of the spontaneous polarization and induce the anti-phase octahedral rotations in the low-temperature phase. The analysis of the results reveals that the antiferroelectric state is a ``missed'' incommensurate phase, and that the paraelectric to antiferroelectric phase transition is driven by the softening of a single lattice mode via the flexoelectric coupling. These findings resolve the mystery of the origin of antiferroelectricity in lead zirconate and suggest an approach to the treatment of complex phase transitions in ferroics. [Preview Abstract] |
Monday, March 3, 2014 1:03PM - 1:15PM |
B41.00008: Formulation of predictive models for use in first principles design of non-centrosymmetric perovskite oxides Joshua Young, James Rondinelli Because many useful electronic properties such as ferroelectricity arise solely due to the lack of inversion in a material's crystal structure, predictive microscopic models describing how to deterministically remove this symmetry operation can allow for the rapid identification and design of new polar compounds. By understanding how structural distortions influence the connectivity between oxygen polyhedra in solid state oxides, we elucidate a series of geometric design rules necessary to develop polar materials. We then apply these criteria to the family of ABO$_3$ perovskite oxides by systematically investigating how distortions of the corner-connected BO$_6$ polyhedral network influence the A-site environments, resulting in a detailed description of the octahedral rotation patterns and A- and B-site cation ordering arrangements capable of producing centrosymmetric, polar, and enantiomorphic structures. Using this as a guide, we then show how such a method allows for the targeted design of new non-centrosymmetric oxides. We conclude by using these rules in combination with density functional theory calculations to predict a series of rhombohedral (A,A$^\prime$)B$_2$O$_6$ perovskites displaying electric polarizations in their ground state. [Preview Abstract] |
Monday, March 3, 2014 1:15PM - 1:27PM |
B41.00009: Origin of Ferroelectricity in a Family of Polar Oxides: The Dion-Jacobson Phases Nicole Benedek The discovery of octahedral rotation-induced ferroelectricity has expanded the opportunities for designing materials in which the polarization is coupled to (and therefore makes possible the electric field control of) other properties, e.g. magnetism, orbital order, metal-insulator transitions. Recent work has elucidated the microscopic mechanism of octahedral rotation-induced ferroelectricity in two families of layered perovskites: AA$^\prime$B$_2$O$_6$ double perovskites and Ruddlesden-Popper (RP) phases. However, there are many other families of layered perovskites - are there octahedral rotation-induced polar materials among them also? We use symmetry arguments, crystal chemical models and first-principles calculations to elucidate the microscopic origin of ferroelectricity in the Dion-Jacobson (DJ) phases. Although ``on paper'' the phenomenology of the DJ phases appears identical to that of polar double perovskites and RP phases, the crystal chemical details regarding how the polar state emerges are different. We link trends in the magnitude of the induced polarizations to changes in structure and composition and discuss possible phase transition scenarios. Our results add surprising new richness to theories of how polar structures emerge in layered perovskites. [Preview Abstract] |
Monday, March 3, 2014 1:27PM - 1:39PM |
B41.00010: First-principles studies of low tolerance factor perovskites Sung Gu Kang, Craig J. Fennie Most perovskites form in the non-polar \textit{Pnma} structure, however, materials found in the polar subgroup of this structure, e.g., space group \textit{Pna2}$_{1}$, are rare. Here we study from first principles the structural and vibrational properties of twelve materials that span a wide range of tolerance factors (MgSnO$_{\mathrm{3}}$, ZnSnO$_{\mathrm{3}}$, MgTiO$_{\mathrm{3}}$, ZnTiO$_{\mathrm{3}}$, MgGeO$_{\mathrm{3}}$, ZnGeO$_{\mathrm{3}}$, CdSnO$_{\mathrm{3}}$, CaSnO$_{\mathrm{3}}$, CdTiO$_{\mathrm{3}}$, CaTiO$_{\mathrm{3}}$, CdGeO$_{\mathrm{3}}$, and CaGeO$_{\mathrm{3}})$. We illustrate how low tolerance factor materials that have been artificially constrained to the \textit{Pnma} structure do in fact display ferroelectric instabilities. Insight is gained by further studying the energetics for each material in the ilmenite, lithium niobate, and perovskite structures over a wide pressure range. Our first-principles results are shown to correlate with physical descriptors, such as tolerance factor, ionic radii, and electronegativity. The rationalized rules from our data analysis will guide to design the new ferroelectric/functional materials. [Preview Abstract] |
Monday, March 3, 2014 1:39PM - 1:51PM |
B41.00011: Multiferroic Aurivillius Phases: the Case of $\rm Bi_{5}FeTi_{3}O_{15}$ by \textit{Ab Initio} Yael Birenbaum, Claude Ederer The Aurivillius phases form a family of naturally layered-perovskites materials with good ferroelectric properties. $\rm Bi_{5}FeTi_{3}O_{15}$ (BFTO) is perhaps the simplest known member of this family that also incorporates magnetic degrees of freedom. However, due to the low concentration of magnetic cations in similar systems, it is unclear how long-range multiferroic behaviour can be achieved. For example, room temperature ferromagnetism has been reported for $\rm Bi_{5}Co_{0.5}Fe_{0.5}Ti_{3}O_{15}$, in contrast with no magnetic order found in $\rm Bi_{5}CrTi_{3}O_{15}$. To address this question, we establish the ferroelectric and magnetic properties of BFTO, using \textit{ab initio} electronic structure calculations, comparing two commonly used exchange-correlation functionals: PBE and PBEsol. We then discuss a potential site preference for $\rm Fe^{3+}$ and its impact on the polarisation and magnetic couplings. In addition, a brief comparison with $\rm Bi_{5}MnTi_{3}O_{15}$ will be made. [Preview Abstract] |
Monday, March 3, 2014 1:51PM - 2:03PM |
B41.00012: Structure and electronic properties of Zn$_x$Sn$_{1-x}$O$_{2-x}$ Anindya Roy, Yansha Jin, Tonghu Jiang, Michael Falk Using first-principles based hybrid-exchange calculations we look at the structural and electronic properties of Zn-Sn-O system. The oxides represented by Zn$_x$Sn$_{1-x}$O$_{2-x}$ has end members ZnO and SnO$_2$. These relatively well studied, native n-type semiconductors are technologically important. Intermediate oxides corresponding to $x=$2/3 and 1/2 have been synthesized: spinel Zn$_2$SnO$_4$ and rhombohedral ZnSnO$_3$. These mixed oxides are functionally promising for their potential as ferroelectrics, transparent conducting oxides, thermoelectrics etc. Previously, {\it ab initio} calculations investigated the structures, electronic and thermodynamic properties of these mixed oxides. However, we considerably improve our understanding of band gap values and band structure of these compounds using hybrid-exchange method. We also perform band alignment calculations, estimate work function of these intermediate oxides, and compare those values to that of the end members and to the experimental results. The existence of Zn$_2$SnO$_4$ in the spinel structure allows a number of configurations which correspond to normal, partially inverted, or inverted spinel forms. We use cluster expansion method to identify energetically most stable form before calculating other properties. [Preview Abstract] |
Monday, March 3, 2014 2:03PM - 2:15PM |
B41.00013: Semiconducting ferroelectrics for photovoltaics through Zn2+ doping into KNbO3 Fenggong Wang, Ilya Grinberg, Peter Davies, Andrew Rappe Using first-principles calculations, we design and predict six low band gap ferroelectric solid solutions by partially substituting Zn$^{2+}$ for Nb$^{5+}$ into the parent KNbO$_{3}$ material, combined with charge compensations at the $A$-sites by different combinations of higher valence cations (Ba$^{2+}$, Sr$^{2+}$, Pb$^{2+}$ and La$^{3+}$, Bi$^{3+}$). In particular, our HSE06 calculations yield a low band gap of only 2.11 eV for the 75\%KNbO$_{3}-25\%$(Sr$_{1/2}$La$_{1/2}$)(Zn$_{1/2}$Nb$_{1/2}$)O$_{3}$ (KN-SLZN) solid solution, and this can be lowered further by 0.6-0.7 eV upon in-plane compressive strains, allowing for more efficient visible light photovoltaic energy harvesting. The maintaining or enhancing of the polarizations of KN-SLZN provides an efficient charge separation route by the bulk photovoltaic effect that could make the power conversion efficiency (PCE) go beyond the Shockley$-$Queisser limit. We argue that these newly designed low band gap ferroelectric solid solutions can be experimentally synthesized and are promising for photovoltaics. In addition, we demonstrate a new strategy to engineer the band gap while maintaining the polarization of the ferroelectric perovskites, which can be well applied to other systems. [Preview Abstract] |
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