Bulletin of the American Physical Society
APS March Meeting 2016
Volume 61, Number 2
Monday–Friday, March 14–18, 2016; Baltimore, Maryland
Session C30: Novel Ferroic SystemsFocus
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Sponsoring Units: DMP DCMP Chair: R Ramesh, UCBerkeley Room: 329 |
Monday, March 14, 2016 2:30PM - 3:06PM |
C30.00001: Moving Towards Domain Wall Devices in Ferroics Invited Speaker: Marty Gregg Domain walls in ferroelectric, ferroelastic and multiferroic oxides are distinct functional materials in their own right. They can be conducting, or even superconducting, when surrounding domains are insulating [1, 2]; they can demonstrate magnetism when the surrounding bulk is non-magnetic [3] and they can contain ordered electrical dipoles when the matrix containing them is non-polar [4]. Since domain walls can also be created, destroyed, and controllably moved from place to place, there is an amazing opportunity for us to design new forms of devices in which functionality is actively and dynamically deployed (now you see it; now you don't). This is the essence of the emerging field known as ``domain wall nanoelectronics'' [5]. In time, this arena of research could change the way we think of nanoscale functional devices, moving increasingly towards agile circuitry and neuromorphic device architectures. While the control of domain wall injection, movement and annihilation has been developed rather well in the nanomagnetics community (in race-track [6] and domain wall logic [7] research), similar research has not been widely performed in nanoscale ferroelectrics, ferroelastics and multiferroics. This talk will discuss progress that has been made to date and the way in which nanomagnetics research can be used as a source of inspiration. Site-specific domain wall injection and motion control in both proper and improper ferroelectrics using inhomogeneous electric and elastic fields, as well as dielectric patterning in uniaxial ferroelectrics, will be specifically considered [8]. As will be shown, sufficient control has been developed to allow the creation of a diode for domain wall motion in ferroelectrics, for example. [1] J. Seidel \textit{et al.} Nat. Mater., \textbf{8}, 229 (2009); J. Guyonnet \textit{et al.} Adv. Mater., \textbf{23}, 5377 (2011); P. Maksymovych, \textit{et al.} Nano Lett., \textbf{11}, 1906 (2011); T. Sluka \textit{et al.} Nat. Commun., \textbf{4}, 1808 (2013); [2] A. Aird, E. K. H. Salje, J.Phys.:Condens. Matter, \textbf{10}, L377 (1998); [3] S. Farokhipoor \textit{et al.}, Nature \textbf{515}, 379 (2014); [4] S. Van Aert \textit{et al.} Adv. Mater., \textbf{24}, 523 (2012); [5] G. Catalan \textit{et al.} Rev Mod Phys \textbf{84}, 119 (2012); [6] S. S. P. Parkin, M. Hayashi {\&} L. Thomas, Science \textbf{320}, 190--194 (2008); [7] D. A. Allwood \textit{et al.} Science \textbf{309}, 1688--1692 (2005). [8] J. R. Whyte \textit{et al.}, Adv Mat, \textbf{26}, 293 (2014); J. R. Whyte \textit{et al.}, J. Appl. Phys. \textbf{116}, 066813 (2014); J. R. Whyte \textit{et al.}, Nat. Commun. \textbf{6}, 7361 (2015); R. G. P. McQuaid \textit{et al.} Nat. Commun. (under review 2015). [Preview Abstract] |
Monday, March 14, 2016 3:06PM - 3:18PM |
C30.00002: Epitaxial Thin Films of Y doped HfO$_{\mathrm{2}}$ Claudy Serrao, Asif Khan, Ramesh Ramamoorthy, Sayeef Salahuddin Hafnium oxide (HfO$_{\mathrm{2}})$ is one of a few metal oxides that is thermodynamically stable on silicon and silicon oxide. There has been renewed interest in HfO$_{\mathrm{2}}$ due to the recent discovery of ferroelectricity and antiferroelectricity in doped HfO$_{\mathrm{2}}$. Typical ferroelectrics -- such as strontium bismuth tantalate (SBT) and lead zirconium titanate (PZT) -- contain elements that easily react with silicon and silicon oxide at elevated temperatures; therefore, such ferroelectrics are not suited for device applications. Meanwhile, ferroelectric HfO$_{\mathrm{2}}$ offers promise regarding integration with silicon. The stable phase of HfO$_{\mathrm{2}}$ at room temperature is monoclinic, but HfO2 can be stabilized in the tetragonal, orthorhombic or even cubic phase by suitable doping. We stabilized Y-doped HfO2 thin films using pulsed laser deposition. The strain state can be controlled using various perovskite substrates and controlled growth conditions. We report on Y-doped HfO2 domain structures from piezo-response force microscopy (PFM) and structural parameters via X-ray reciprocal space maps (RSM). We hope this work spurs further interest in strain-tuned ferroelectricity in doped HfO2. [Preview Abstract] |
Monday, March 14, 2016 3:18PM - 3:30PM |
C30.00003: Ab initio study of ZrO2 monolayers epitaxial on Si Mehmet Dogan, Divine Kumah, Charles Ahn, Frederick Walker, Sohrab Ismail-Beigi Growing thin films of crystalline metal oxides on semiconductors has been of much scientific interest because of their applications in electronic devices. One research goal is to achieve ferroelectricity in a crystalline and thin oxide film that is epitaxial on a semiconductor. This would enable the realization of non-volatile field-effect transistors where the state is encoded in the polarization direction of the oxide. We study oxides that are not ferroelectric in the bulk but become ferroelectric as an ultra-thin film on a semiconductor. Recent advances in epitaxial growth methods permit fabrication of such systems. We use density functional theory to study the interface between ZrO$_{2}$ monolayers and Si (001). These monolayers have multiple metastable states. We present an analysis of these configurations and energy barriers between them. We consider the likely experimental situation where different configurations coexist to form a multi-domain system, and investigate domain dynamics. Furthermore, we demonstrate that the ZrO$_{2}$ monolayers can be used as a buffer layer to induce ferroelectricity in perovskite oxides such as SrTiO$_{3}$ on Si. We also show that these monolayers modify the transport properties of Si which would allow for the desired device applications. [Preview Abstract] |
Monday, March 14, 2016 3:30PM - 3:42PM |
C30.00004: Ferroelectric to paraelectric transition in YCrO$_{\mathrm{3}}$ revisited Rajeev Gupta, Ashish Mall, Ashish Garg X-ray diffraction (XRD) and Raman spectroscopy measurements are used to explore the origin of ferroelectricity in the orthorhombic ferroelectric oxide ,YCrO$_{\mathrm{3}}$. Temperature dependent XRD studies carried out up to 900K and subsequent Reitveld refinement of the data shows that there is no evidence of any structural phase transition in YCrO$_{\mathrm{3}}$ across the ferroelectric to paraelectric phase transition at T$_{\mathrm{c}} \quad =$ 470K. Temperature dependent unpolarized Raman spectroscopy measurements, from 300 K to 600 K, were carried out to investigate structural changes near Tc locally within the material. All Raman modes below 600 cm$^{\mathrm{-1}}$ were assigned to phonon modes of Pnma structure and for further analysis of the Raman data, the line shape parameters were obtained by fitting a Lorentzian function to each peak. Surprisingly, despite absence of observation of any structural change in XRD measurements,YCrO$_{\mathrm{3}}$ shows a strong anomalous temperature variation near T$_{\mathrm{c}}$ in the peak positions and line widths for selected modes as a function of temperature. It is believed that YCrO$_{\mathrm{3}}$ is an improper ferroelectric and ferroelectricity arises due to local rotations of CrO$_{\mathrm{6}}$ octahedra leading to non-centrosymmetricity. Our results seem to suggest that YCrO$_{\mathrm{3}}$ undergoes an iso-structural transition across T$_{\mathrm{c}}$. [Preview Abstract] |
Monday, March 14, 2016 3:42PM - 3:54PM |
C30.00005: Phase Transitions in Nanoscale SrTiO$_{\mathrm{3}}$ Tian Yu, Han Zhang, Mark Croft, Megan Scofield, Dara Bobb-Semple, Jing Tao, Cherno Jaye, Daniel Fisher, Stanislaus Wong, Trevor Tyson Free standing SrTiO$_{\mathrm{3}}$ has recently been shown to be polar for \textasciitilde 10 nm particles (APL 105, 091901 (2014)). We have conducted pressure dependent x-ray diffraction on monodispersed nanoscale samples with varying particle size. Distinctly different behavior is found in the diffraction patterns for sample with reduced size. The nature of the low temperature polar state under pressure will be discussed. The results are compared with reported work on bulk SrTiO$_{\mathrm{3.\thinspace }}$This work is supported by DOE Grant DE-FG02-07ER46402. [Preview Abstract] |
Monday, March 14, 2016 3:54PM - 4:06PM |
C30.00006: High-pressure synthesis of predicted oxynitride perovskite: Yttrium Silicon Oxynitride (YSiO$_{2}$N) Muhtar Ahart, M. Somayazulu, Rajasekarakumar Vadapoo, R. E. Cohen We synthesized the previously predicted [1] polar oxynitride perovskite in a diamond anvil cell with laser heating. YSiO$_{2}$N was predicted to have the polar $P$4mm structure with an effective spontaneous polarization of 130 $\mu $C/cm$^{2}$. A mixture of Yttrium nitride (YN) and amorphous Silicon dioxide (SiO$_{2})$ were loaded into a diamond anvil cell and laser heated at or above 1200 C at 12 GPa. The run products were investigated by x-ray diffraction, Raman spectroscopy, and second harmonic generation, for their phase and structural properties. The x-ray diffraction pattern (a $=$ 3.235 {\AA}, c $=$ 4.485 {\AA}) shows the phase formation of YSiO$_{2}$N and matches with the diffraction pattern derived from the first-principle predicted lattice parameters. However, minor unknown peaks are on the diffraction pattern indicating of the co-existence of other unknown phases. Further study of Raman spectroscopy observes the theoretically predicted modes, and second harmonic generation shows strong non-linear optical signal, which confirms the polar properties of YSiO$_{2}$N. [1] R. Caracas and R. E. Cohen, Appl. Phys. Lett. 91, 092902 (2007). [Preview Abstract] |
Monday, March 14, 2016 4:06PM - 4:18PM |
C30.00007: Ferroelectricity in corundum derivatives Meng Ye, David Vanderbilt The search for new ferroelectric (FE) materials holds promise for broadening our understanding of FE mechanisms and extending the range of application of FE materials. The known FE materials LiNbO$_3$ can be regarded as derived from the $A_2$O$_3$ corundum structure with cation ordering. Here we consider more general binary ($AB$O$_3$) and ternary ($A_2BB'$O$_6$) corundum derivatives as an extended class of potential FE materials, motivated by the fact that some members of this class have recently been synthesized. There are four structure types for these corundum derivatives, and the number of cation combinations is enormous, but in many cases the energy barriers for polarization reversal may be too large to allow FE behavior. Here we present a first-principles study of the polar structure, coherent FE barrier, and domain-wall switching barrier for a representative set of polar corundum derivatives, allowing us to identify several potentially new FE materials. We also discuss the conditions under which ferroelectricity is compatible with magnetic ordering. Finally, we identify several empirical measures that can provide a rule of thumb for estimating the barrier energies. Our results should assist in the experimental search for new FE materials in the corundum derivative family. [Preview Abstract] |
Monday, March 14, 2016 4:18PM - 4:30PM |
C30.00008: The origin of hyper-ferroelectricity in Li$B$O$_3$ ($B$=V, Nb, Ta, Os) Lixin He, Pengfei Li, Xinguo Ren, G-C Guo The electronic and structural properties of Li$B$O$_3$ ($B$=V, Nb, Ta, Os) are investigated via first-principles methods. We show that Li$B$O$_3$ are belong to the recently proposed hyperferroelectrics, i.e., they all have unstable longitudinal optical phonon modes. Especially, the ferroelectric-like instability in the metal LiOsO$_3$ is a limiting case of a hyperferroelectrics, whose optical dielectric constant goes to infinity. We further show via an effective Hamiltonian that in contrast to normal proper ferroelectricity, in which the ferroelectric instability usually comes from long range coulomb interactions, the hyperferroelectric instability is due to the structure instability driven by the short range interactions. This could happen in systems with large ion size mismatches, which therefore provides a useful guidance in searching for novel hyperferroelectrics. [Preview Abstract] |
Monday, March 14, 2016 4:30PM - 4:42PM |
C30.00009: Ferroelectric switching pathways in Ca$_{\mathrm{3}}$Ti$_{\mathrm{2}}$O$_{\mathrm{7}}$ from first principles Elizabeth Nowadnick, Andrew Mulder, Craig Fennie Hybrid improper ferroelectricity, where polarization can be induced via a trilinear coupling to two non-polar order parameters (in this case octahedral rotations), has recently been experimentally demonstrated in the n$=$2 Ruddlesden-Popper compound Ca$_{\mathrm{3}}$Ti$_{\mathrm{2}}$O$_{\mathrm{7}}$. The observation of an unexpectedly low ferroelectric switching barrier and abundant structural domains suggests that these domains may be critical to the switching process. Key issues that remain to be understood include what are the specific structural properties of Ca$_{\mathrm{3}}$Ti$_{\mathrm{2}}$O$_{\mathrm{7}}$ that enable this low-energy switching, and how these properties could be further optimized. To address these questions, we analyze the possible ferroelectric switching pathways that can be facilitated by the presence of orthorhombic twin domains and vertical stacking faults in the n$=$2 Ruddlesden-Popper structure of Ca$_{\mathrm{3}}$Ti$_{\mathrm{2}}$O$_{\mathrm{7}}$. Utilizing first principles methods, we calculate the energy barriers of the various switching pathways and study the evolution of the octahedral rotation and polar order parameters during these switching processes. These results offer insight into what is the likely switching mechanism in Ca$_{\mathrm{3}}$Ti$_{\mathrm{2}}$O$_{\mathrm{7}}$, and which order parameter is primarily responsible for controlling the energy barriers. [Preview Abstract] |
Monday, March 14, 2016 4:42PM - 4:54PM |
C30.00010: An efficient ab-initio approach for the anharmonic properties of structurally complex ceramics Liang-Feng Huang, James M. Rondinelli In the conventional quasiharmonic method for the simulation of crystal anharmonic properties (e.g., thermal expansion and thermomechanics), the phonon spectra of about ten (or more) volumes have to be calculated, which is often computationally prohibitive for complex ceramics with large unit cells. In this work, we describe an efficient alternative method, i.e., a self-consistent quasiharmonic approximation (SC-QHA) method, where the phonon modes of only two or three volumes are necessary. At the same time, it provides a convenient framework to analyze the microscopic origins underlying the anharmonic properties. We successfully apply the SC-QHA method to the hybrid improper ferroelectric Ca3Ti2O7 to explain the recent experimentally measured thermal expansion data [Senn, Phys. Rev. Lett., 114, 0(2015)], and related lattice dynamical properties in an efficient manner. [Preview Abstract] |
Monday, March 14, 2016 4:54PM - 5:06PM |
C30.00011: Polarization Domain Switching of Improper Hybrid Ferroelectric (Ca,Sr)$_{3}$Ti$_{2}$O$_{7}$ Crystals Seong Joon Lim, Bin Gao, Jaewook Kim, Fei-Ting Huang, Sang-wook Cheong The observation of switchable polarization loops at room temperature in (Ca,Sr)$_{3}$Ti$_{2}$O$_{7}$, induced by improper hybrid ferroelectricity, has drawn much attention. Since the ferroelectric polarization directly couples with structural distortions (oxygen octahedral tilting and rotation) in hybrid improper ferroelectrics, the energy barrier for polarization switching is predicted to be large, and the observation of ferroelectric polarization loops was a surprise. Furthermore, the observed complexity of the domain wall configuration in (Ca,Sr)$_{3}$Ti$_{2}$O$_{7}$ may complicate the domain wall motion or the domain nucleation for polarization switching. Thus, it is imperative to understand the mechanism and dynamics of polarization domain switching. Particularly, it has to be clarified if polarization switching occurs through 90$^{\circ}$ or 180$^{\circ}$ switching. Comparing piezoresponse force microscope and polarized optical microscope images before and after applying electric fields consecutively, we explored the mechanism and dynamics of polarization domain switching. [Preview Abstract] |
Monday, March 14, 2016 5:06PM - 5:18PM |
C30.00012: Conducting Ferroelectric Walls, Domain Topology, and Domain Switching Kinetics in a Hybrid Improper Ferroelectric Sang-Wook Cheong \textbf{Charged polar interfaces such as charged ferroelectric domain walls or heterostructured interfaces of ZnO/(Zn,Mg)O and LaAlO}$_{\mathbf{3}}$\textbf{/SrTiO}$_{\mathbf{3}}$\textbf{, across which the normal component of electric polarization changes suddenly, can host large two-dimensional conduction. Charged ferroelectric domain walls can be highly conducting but energetically unfavored; however, they were found to be mysteriously abundant in hybrid improper ferroelectric (Ca,Sr)}$_{\mathbf{3}}$\textbf{Ti}$_{\mathbf{2}}$\textbf{O}$_{\mathbf{7}}$\textbf{ single crystals. }\textbf{From the exploration of antiphase domain boundaries, which are hidden in piezoresponse force microscopy, using dark-field electron microscopy, we have explored the macroscopic topology of polarization domains and antiphase domains. We found that the macroscopic domain topology is directly responsible for the presence of charged domain walls, and is closely related with the polarization domain switching mechanism in }\textbf{(Ca,Sr)}$_{\mathbf{3}}$\textbf{Ti}$_{\mathbf{2}}$\textbf{O}$_{\mathbf{7}}$\textbf{.} [Preview Abstract] |
Monday, March 14, 2016 5:18PM - 5:30PM |
C30.00013: Exploration of the ferroelectric properties of a new Titanium-based compound Remi Federicci, Florin Popa, Luc Brohan, Benoit Baptiste, Keevin Beneut, Poala Giura, Fabio Finocchi, Abhay Shukla, Brigitte Leridon Even though ferroelectric materials are well known and widely used in many applied fields, the families of compounds exhibiting ferroelectricity are just a few. Among them, BaTiO3 and its substitution-related compounds play a major role and have been widely investigated. We present here an experimental study on a new titanium-based perovskite structure. The synthesis and structural characterization (through XRD and Raman spectroscopy) of this material will be exposed, in excellent agreement with DFT calculations. We will demonstrate possible ferroelectricity at room temperature and discuss the probable microscopic mechanisms at play in this material. [Preview Abstract] |
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