Bulletin of the American Physical Society
2009 APS March Meeting
Volume 54, Number 1
Monday–Friday, March 16–20, 2009; Pittsburgh, Pennsylvania
Session T41: Ferroelectricity and Structural Phase Transitions |
Hide Abstracts |
Sponsoring Units: DMP DCMP Chair: Craig Fennie, Cornell University Room: 413 |
Wednesday, March 18, 2009 2:30PM - 2:42PM |
T41.00001: Strained enabled Ferroelectricity in CaTiO$_{3}$ Thin Films Probed by Nonlinear Optics and Scanning Probe Microscopy Eftihia Vlahos, Amit Kumar, Sava Denev, Charles Brooks, Darrell Schlom, Carl-Johan Eklund, Karin M. Rabe, Craig J. Fennie, Venkatraman Gopalan Calcium titanate, CaTiO$_{3}$ is not a ferroelectric in its bulk form. However, first principles calculations predict that biaxially tensile strained CaTiO$_{3}$ thin films should become ferroelectric.~ Here, we indeed confirm that strained CaTiO$_{3}$ films become ferroelectric with a Curie temperature of $\sim $125K. Optical second harmonic generation (SHG) measurements, polarization studies, and in-situ electric-field measurements for a number of films with different strain values will be presented: CaTiO$_{3}$/DyScO$_{3}$(110), CaTiO$_{3}$/SrTiO$_{3 }$(100),$_{ }$CaTiO$_{3}$/GdScO$_{3}$/NdGaO$_{3}$(110), CaTiO$_{3}$/LaSrAlO$_{3}$(001) as well as for a single crystal CaTiO$_{3}$. From these studies, we conclude that strained CaTiO$_{3}$ films are ferroelectric with a point group symmetry of \textit{mm2}, and show reversible domain switching characteristics under an electric field. We also present results of variable temperature piezoelectric force microscopy for imaging the polar domains in the ferroelectric phase. These results suggest that strain is a valuable tool for inducing polar, long range ferroelectric order in even non-polar ceramic materials such as CaTiO$_{3}$. [Preview Abstract] |
Wednesday, March 18, 2009 2:42PM - 2:54PM |
T41.00002: Potential and piezoelectric response imaging of 180$^{\circ}$ domain of atomically ordered clean surfaces of BaTiO$_{3}$ single crystals in UHV Yukio Watanabe, S. Kaku, D. Matsumoto, S.W. Cheong We report the electrostatic and piezoelectric properties of the clean, free surface of BaTiO$_{3}$ single crystal in ultra high vacuum (UHV) The topographic imaging by AFM confirmed that the surface is atomically wellordered exhibiting clear one-lattice-height atomic steps. The amplitude and the phase image of piezoelectric response microscopy (PFM) identified 180$^{\circ}$ domains. The electrostatic potential mapping by Kelvin force microscopy (KFM) of these domains revealed that the shapes of the domains agreed exactly with the PFM images, which confirms the correctness of the standard 180$^{\circ}$ domain theory and disagrees with closure domains. However, the potential difference of upward and downward domain is approx. 0.1V, which is 100 times smaller than the value estimated by the standard theory. Similar measurements with changing temperature across Curie temperature show that this result cannot be explained by the compensation of the spontaneous polarization by contamination or oxygen deficiency or ionic conduction). The present results suggest that an intrinsic electrostatic shielding mechanism exists for 180$^{\circ}$ domains, which is consistent with the reports of surface electron/hole layers [1]. \\[4pt] [1] Watanabe et al. \textit{PRL}\textbf{86}332(2001);\textit{Ferroelectr.}367, 23(2008) We acknowledge JSPS No.19340084. [Preview Abstract] |
Wednesday, March 18, 2009 2:54PM - 3:06PM |
T41.00003: Magnetic Color Symmetry of Lattice Rotations in a Non-magnetic Material Sava Denev, A. Kumar, M. D. Biegalski, H. W. Jang, C. M. Folkman, A. Vasudevarao, Y. Han, I. M. Reaney, S. Trolier-McKinstry, C.-B. Eom, D. G. Schlom, V. Gopalan Oxygen octahedral rotations are the most common phase transitions in perovskite crystal structures. Here we show that the color symmetry of such pure elastic distortions is isomorphic to magnetic point groups, which allows their probing through distinguishing polar versus magnetic symmetry. We demonstrate this isomorphism using nonlinear optical probing of the octahedral rotational transition in a compressively strained SrTiO$_3$ thin film that exhibits ferroelectric ($4mm$) and antiferrodistortive ($4'mm'$) phases evolving through independent phase transitions. The approach has broader applicability for probing materials with lattice rotations that can be mapped to color groups. [Preview Abstract] |
Wednesday, March 18, 2009 3:06PM - 3:18PM |
T41.00004: Spontaneous polarization and piezoelectricity in polar molecular crystals Ivo Borriello, Giovanni Cantele, Domenico Ninno, Giuseppe Iadonisi Molecular materials with a polar arrangement of the constituent dipoles are good candidates for exhibiting piezoelectric properties, directly related to the \mbox{strain-induced} polarization. The \mbox{metal-organic} molecular crystal (4-dimethylaminopyridyl)bis(acetylacetato)zinc(II) (ZNDA) has been investigated from first principles. The spontaneous polarization and the piezoelectric properties have been studied by means of the modern theory of polarization, focusing on the relation between the piezoelectric properties of the organic crystal and the electronic properties of the polar molecule. [Preview Abstract] |
Wednesday, March 18, 2009 3:18PM - 3:30PM |
T41.00005: Interfaces in ferroelastics: fringing fields, scaling, size and shape effects Turab Lookman We consider the problem of determining the elastic fields and microstructure within a transformable region of size L, in which structural transformations from a parent to a product phase with variants can occur, that is surrounded by a fixed parent matrix. By demanding mechanical equilibrium and strain compatibility at the parent-product interface, we demonstrate that for sufficiently coarse twins the width of the twinned product phase varies as sqrt(L), but this breaks down if L is small enough for the surface and bulk energies to compete. As L decreases further, a transition to a stable checkboard pattern containing the parent and product variants occurs and this subsequently disappears if L is too small. We relate our findings to the behavior of transformations in nanograins of NiTi within an amorphous matrix and nanoscale checkboard microstructure seen in inorganic spinels. Understanding how microstructure emerges from a given configuration of interfaces is a non-trivial task and our overarching theme is to study the interplay of orientations, decaying strain fields, length scaling of energy and dependence of transition on size and shape of a transformable region within a parent matrix. [Preview Abstract] |
Wednesday, March 18, 2009 3:30PM - 3:42PM |
T41.00006: Local Polarization Dynamics and Bias-Induced Phase Transitions in Ferroelectric Relaxors: Time-resolved Spectroscopy and Ergodic Gap Mapping S.V. Kalinin, B. Rodriguez, M.P. Nikiforov, N. Balke, S. Jesse, O.S. Ovchinnikov, A.A. Bokov, Z.-G. Ye Mesoscopic domain structure and dynamics in PMN-PT solis solutions is studied using spatially resolved time- and voltage spectroscopic imaging modes. For compositions close to the MPB, we observe the formation of classical ferroelectric domains with rough self-affine boundaries. In the ergodic phase (PMN and PMN-10PT), the formation of non-classical labyrinthine domain patterns characterized by a single characteristic length scale is observed. The (a) persistence of these patterns well above Tc and (b) the fact that cannot be switched by tip bias suggest that they can be attributed to the frozen polarization component. Spatial variability of polarization relaxation dynamics in PMN-10PT is studied. Local relaxation attributed to the reorientation of polar nanoregions was found to follow stretched exponential dependence, with $\beta \quad \approx $ 0.4, much larger than the macroscopic value determined from dielectric spectra ($\beta $ $\approx $ 0.09). The spatial inhomogeneity of relaxation time distribution with the presence of 100-200 nm ``fast'' and ``slow'' regions is observed. The results are analyzed to map the Vogel-Fulcher temperatures on the nanoscale. The applicability of this technique to map ``ergodic gap'' distribution on the surface is discussed. Research supported by the Division of Materials Science and Engineering, Basic Energy Sciences, U.S. Department of Energy at Oak Ridge National Laboratory, which is managed by UT-Battelle, LLC. [Preview Abstract] |
Wednesday, March 18, 2009 3:42PM - 3:54PM |
T41.00007: Field Dependence of Glassy Freezing in a Relaxor Ferroelectric Matthew Delgado, Eugene Colla, Michael Weissman, Philip Griffin Multi-frequency susceptibility measurements on the cubic relaxor ferroelectric (PbMg$_{1/3}$Nb$_{2/3}$O$_{3})_{0.88}$(PbTiO$_{3})_{0.12}$ were performed at various DC electric field strengths applied along the [111] direction. The temperature-frequency dependences fit the Vogel-Fulcher form, allowing the extraction of a frequency-independent glassy freezing temperature. These Vogel-Fulcher temperatures showed significant reductions in applied fields, following an empirical Gabay-Toulouse form, similar to vector spinglasses. The magnitude of the sensitivity indicates that the glassy state is formed by interactions among the same entities that account for the susceptibility, i.e. the polar nanoregions. This interpretation is supported by data on a powder sample of PbMg$_{1/3}$Nb$_{2/3}$O$_{3}$ (PMN), with grains too small to support large-scale inter-nanoregion cooperativity, in which the Vogel-Fulcher behavior is lost [1]. [1] J. Carreaud et. al., Appl. Phys. Lett. 92, 242902 (2008). [Preview Abstract] |
Wednesday, March 18, 2009 3:54PM - 4:06PM |
T41.00008: The three characteristic Temperatures of Relaxor Dynamics and their Meaning Jean Toulouse In this report, we compare the temperature evolution of several physical properties of the relaxor systems PZN, PMN and KTN. We show that three rather than two characteristic temperatures can be identified, T$_{B}$, T* and T$_{f}$, and discuss their meaning in light of dielectric, Raman and neutron scattering experimental results. [Preview Abstract] |
Wednesday, March 18, 2009 4:06PM - 4:18PM |
T41.00009: Quantum Fluctuation of the Order Parameter in a Structural Phase Transition James L. Smith, S.M. Shapiro, K.A. Modic, J.C. Cooley, E.K.H. Salje, P.B. Littlewood, C.P. Opeil, J.C. Lashley Using a variety of microscopic and bulk-thermodynamic probes (e.g., elastic neutron scattering, inelastic x-ray scattering, specific heat, and pressure-dependent electrical transport), we provide evidence for the presence of a continuous martensitic transition in the binary AuZn system. In Au$_{0.52}$Zn$_{0.48}$ and AuZn, elastic neutron scattering detects new commensurate Bragg peaks (modulation) appearing at $Q$ = (1.33, 0.67, 0) at temperatures corresponding to each sample's martensitic transition temperature, $T_{M}$. The pressure dependence of the transition in each alloy, shows a low-temperature saturation of the order parameter (strain-shuffle) that leads to highly non-linear phase boundaries in temperature-pressure space and to superconductivity in the case of Au$_{0.52}$Zn$_{0.48}$. [Preview Abstract] |
Wednesday, March 18, 2009 4:18PM - 4:30PM |
T41.00010: First principles determination of phase transitions in magnetic shape memory alloys Tilmann Hickel, Matthe Uijttewaal, Joerg Neugebauer Magnetic shape memory alloys have recently attracted a lot of excitement, since they allow shape changes of more then 10\% with a frequency in the kHz regime. The fundamental origin of this property is related to a martensitic phase transition. The material system Ni$_2$MnGa is the most promising candidate for applications, but its operation temperatures and ductility still need to be improved. Hence, an extension of the currently very limited knowledge on the phase diagram is decisive. In order to identify the stable structures and their transitions we performed ab initio calculations of free energies for the austenite, the (modulated) pre-martensite and the unmodulated martensite. Quasiharmonic phonons and fixed-spin magnons are considered, employing density functional theory. Using this approach we were able to successfully describe the phase transition in detail, to reveal the involved delicate interplay of vibrational and magnetic excitations and to accurately determine the transition temperature. The methods are used to interpret the experimental findings and to make predictions for modified material compositions. [Preview Abstract] |
Wednesday, March 18, 2009 4:30PM - 4:42PM |
T41.00011: A fluctuation-based probe to criticality in structural transitions U. Chandni, Arindam Ghosh, H.S. Vijaya, S. Mohan Many natural phenomena, extending from biology to material science, involve slowly driven dissipative systems that are far from thermal equilibrium, triggered only by a slowly varying external field and to which the systems respond through scale-free avalanches in physical observables. In spite of decades of research, experiments are inconclusive whether these systems self organize to the critical state over a broad range of external field, or if there exists a unique critical point that is smudged by a wide critical zone. Here, through the higher order statistics of time dependent avalanches, or noise, in electrical resistivity during temperature-driven martensite transformation in thin nickel-titanium films, we demonstrate for the first time, the existence of a singular `global instability' or divergence of the correlation length as a function of temperature. These results not only establish a mapping of non-equilibrium first order phase transition and equilibrium critical phenomena, but perhaps also call for a re-evaluation of many existing experimental claims of self-organized criticality. References: 1. U. Chandni et.al, Appl. Phys. Lett. 92, 112110 (2008). 2. U. Chandni et. al, arxiv:0811.0102 (2008). [Preview Abstract] |
Wednesday, March 18, 2009 4:42PM - 4:54PM |
T41.00012: Structural phase transformations and dislocations within the Landau theory Roman Gr\"oger, Turab Lookman, Avadh Saxena We propose a two-dimensional model (Gr\"oger et al., PRB78:184101, 2008) that demonstrates how the Landau theory of first order phase transitions can be coupled with plasticity. It is based on Kr\"oner's continuum theory of dislocations that views each dislocation as a source of incompatibility between the components of the elastic strain tensor. This incompatibility then couples to the order parameter that is a local representation of the space group of the crystalline lattice. The order parameter field is obtained by minimizing the free energy and this provides both the stress fields and the Peach-Koehler forces on individual dislocations. The evolution of the dislocation density is then obtained by a Fokker-Planck equation. Updating the dislocation density results in a new estimate of the distribution of strain incompatibilities and this serves as an input to the subsequent minimization of the free energy. This self-consistent procedure thus allows for a simultaneous evolution of the order parameter texture and the density of dislocations. To develop a clear link between the microscopic and mesoscopic dislocation density, the crystal dislocations in individual discrete slip systems are restricted to glide in their well-defined slip planes. Upon cooling, the finite dislocation density gives rise to heterogeneous nucleation of the martensite and thus results in a shift of the transformation temperature. [Preview Abstract] |
Wednesday, March 18, 2009 4:54PM - 5:06PM |
T41.00013: Spontaneous phase transition of nano-sized boron nitride -- A quantum size effect Hongli Dang, Y.G. Shen, Sanwu Wang We report first-principles quantum-mechanical calculations that predict a novel phase transition of nano-sized boron nitride (BN) thin-films. When the thickness of the BN thin-film is below 1.4 nm, a spontaneous phase transition from the diamond-like structure to a graphite phase is predicted. The process would involve no energy barriers. When the thickness of BN increases, on the other hand, energy barriers for the phase transition would appear and gradually increase with the thickness. Calculations show that while the graphite structure has a lower total energy than the corresponding diamond-like structure for the BN thin-film with any thickness, the spontaneous phase transition would occur only when the size is small. We attribute this phenomenon to the quantum size effect. [Preview Abstract] |
Wednesday, March 18, 2009 5:06PM - 5:18PM |
T41.00014: High Pressure Studies of the Metal-Insulator Transition in Pure NiS2 Arnab Banerjee, Yejun Feng, Rafael Jaramillo, Thomas F. Rosenbaum Ni(S,Se)2 is a one of the few Mott-Hubbard systems where a structural phase transition does not preclude quantitative study of the localization of charge at the T = 0 metal-insulator transition. Using diamond anvil cell techniques, we study the corresponding behavior of pure NiS2 at its quantum critical point. We characterize the electronic, magnetic and structural behavior of this model system through a combination of transport and synchrotron scattering techniques, with a particular interest in the effects of disorder at a quantum phase transition. [Preview Abstract] |
Wednesday, March 18, 2009 5:18PM - 5:30PM |
T41.00015: Effect of pressure on the tetragonal distortion in TiH$_{2}$: a first-principles study R. de Coss, R. Quijano, D.J. Singh The transition metal dihydride TiH$_{2}$ present the fluorite structure (CaF$_{2})$ at high temperature but undergoes a tetragonal distortion with c/a$<$1 at low temperature. Early electronic band structure calculations have shown that TiH$_{2}$ in the cubic phase display a nearly flat double degenerated band at the Fermi level. Thus the low temperature tetragonal distortion has been associated to a Jahn-Teller effect. Nevertheless, recently we have show that the instability of fcc-TiH$_{2}$ is likely to be related with a van Hove singularity. In the present work, we have performed \textit{ab-initio} calculations of the electronic structure and the tetragonal distortion for TiH$_{2}$ under pressure (0-30 GPa). We found that the fcc-fct energy barrier and the tetragonal distortion increases with pressure. The evolution of the tetragonal distortion is analyzed in terms of the electronic band structure. This research was supported by Consejo Nacional de Ciencia y Tecnolog\'{\i}a (Conacyt) under Grant No. 49985. [Preview Abstract] |
Follow Us |
Engage
Become an APS Member |
My APS
Renew Membership |
Information for |
About APSThe American Physical Society (APS) is a non-profit membership organization working to advance the knowledge of physics. |
© 2024 American Physical Society
| All rights reserved | Terms of Use
| Contact Us
Headquarters
1 Physics Ellipse, College Park, MD 20740-3844
(301) 209-3200
Editorial Office
100 Motor Pkwy, Suite 110, Hauppauge, NY 11788
(631) 591-4000
Office of Public Affairs
529 14th St NW, Suite 1050, Washington, D.C. 20045-2001
(202) 662-8700