Bulletin of the American Physical Society
APS March Meeting 2016
Volume 61, Number 2
Monday–Friday, March 14–18, 2016; Baltimore, Maryland
Session S30: Theory of Ferroic SystemsFocus

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Sponsoring Units: DMP Chair: Steve Johnson, ETHZ Room: 329 
Thursday, March 17, 2016 11:15AM  11:27AM 
S30.00001: New design strategy for realizing multiferroic materials Danilo Puggioni, Gianluca Giovannetti, Massimo Capone, James Rondinelli Ferroelectricity is a property that only insulating materials can exhibit. % For this reason, nearly all searches for new multiferroic compounds, those simultaneously exhibiting ferroelectric and magnetic order, have focused on \emph{insulating} magnetic oxides. % Here, we propose a different approach: Start from a \emph{conducting} oxide with broken inversion symmetry and search for routes to induce longrange magnetic order [1]. % Using densityfunctional and dynamical meanfield theories, we investigate the electronic properties of the polar metallic oxide LiOsO$_3$. % We show that a multiferroic state can be engineered by enclosing LiOsO$_3$ between an insulating material, LiNbO$_3$. % We predict that the 1/1 superlattice of LiOsO$_3$ and LiNbO$_3$ exhibits strong coupling between magnetic and ferroelectric degrees of freedom with a ferroelectric polarization of 41.2 $\mu$Ccm$^{2}$, Curie temperature of 927\,K, and N\'eel temperature of 379\,K. % Our results show that one can start with polar metallic oxides to make multiferroics.\\[1em] [1] D.\ Puggioni \emph{et al}, Phys.\ Rev.\ Lett.\ \textbf{115}, 087202 (2015). [Preview Abstract] 
Thursday, March 17, 2016 11:27AM  11:39AM 
S30.00002: Crystal structure and electronic properties of bulk and thinfilm brownmillerite oxides Joshua Young, James Rondinelli The equilibrium structure and functional properties exhibited by brownmillerite oxides (general formula $A_2B_2$O$_5$), a family of perovskitederived structures with alternating layers of $B$O$_6$ octahedra and $B$O$_4$ tetrahedra arising from ordered arrangements of oxygen vacancies, is dependent on a variety of competing crystalchemistry factors. Using first principles electronic structure calculations, we investigate two antiferromagnetic brownmillerite ferrites, Sr$_2$Fe$_2$O$_5$ and Ca$_2$Fe$_2$O$_5$, and find that the stability of the equilibrium ground state is governed by complex interactions among several structural descriptors, including ionic size, distortions of nominally regular oxygen octahedral, and inplane and outofplane separation of tetrahedral chains. Furthermore, we find that these same effects control the preferred oxygen vacancy orientation under epitaxial strain, a tunable parameter which also strongly influences the magnitude of the electronic band gap via an asymmetricvacancy alignment dependent response. Finally, we show that $A$site cation ordering in these materials can lift inversion symmetry, providing a potential new route to room temperature multiferroics. [Preview Abstract] 
Thursday, March 17, 2016 11:39AM  11:51AM 
S30.00003: Unveiling hidden ferrimagnetism and giant magnetoelectricity in polar magnet Fe$_{2}$Mo$_{3}$O$_{8}$ Yazhong Wang, Gheorghe L. Pascut, Bin Gao, Trevor A. Tyson, Kristjan Haule, Valery Kiryukhin, SangWook Cheong Polar magnets, belonging to the polar crystallographic symmetry groups and containing magnetic ions, can exhibit nontrivial magnetoelectric (ME) effects below magnetic ordering temperatures due to the broken time reversal and space inversion symmetries. Monodomain polar single crystals can often be grown, and eliminate the need for any poling procedures to reveal the possible ME response. Here, we report a giant ME effect in a polar magnet Fe$_{2}$Mo$_{3}$O$_{8}$ at temperature as high as 60 K. Polarization jumps of 0.3 $\mu $C/cm$^{2}$~and repeated mutual control of ferroelectric and magnetic moments with differential ME coefficients on the order of 10$^{4\, }$ps/m are achieved. The sign of the ME coefficients can be switched by changing the direction of the applied ``bias'' magnetic field. Importantly, no electric or magnetic poling is needed, as necessary for applications. Using first principles calculations, we show that exchange striction is the leading mechanism responsible for the observed ME effect. [Preview Abstract] 
Thursday, March 17, 2016 11:51AM  12:27PM 
S30.00004: Theory of colossal magnetoelectric response near spinflop transition in Ni3TeO6 Invited Speaker: Sergey Artyukhin The manipulation of magnetic ordering with applied electric fields is of pressing interest for new spintronic and information storage applications. Recently, such magnetoelectric control was realized in multiferroics [1]. However, their magnetoelectric switching is often accompanied by significant hysteresis, resulting from a large barrier, separating different ferroic states. Hysteresis prevents robust switching, unless the applied field overcomes a certain value (coercive field). I will discuss the role of a switching barrier on magnetoelectric control, in particular, in a collinear antiferromagnetic and pyroelectric Ni3TeO6 [2,3]. The barrier between two magnetic states in the vicinity of a spinâ€“flop transition is almost flat, and thus small changes in external electric/magnetic fields allow to switch the ferroic state through an intermediate state in a continuous manner, resulting in a colossal magnetoelectric response. This colossal magnetoelectric effect resembles the large piezoelectric effect at the morphotropic phase boundary in ferroelectrics. [1] T. Kimura, T. Goto, H. Shintani et al., Nature 426, 5 (2003) [2] Y.S. Oh, S. Artyukhin J. J. Yang et al., Nature Communications 5, 3201 (2014) [3] J. W. Kim, S. Artyukhin, E.?D. Mun et al., Phys. Rev. Lett. 115, 137201 (2015) [Preview Abstract] 
Thursday, March 17, 2016 12:27PM  12:39PM 
S30.00005: Multiferroic behavior at a spin state transition Vivien Zapf, Shalinee Chikara, John Singleton, Shizeng Lin, Cristian Batista, Brian Scott, Nathan Smythe Traditionally, multiferroic behavior is studied in materials with coexisting longrange orders, such as ferromagnetism and ferroelectricity. Here we present multiferroic behavior at a spinstate transition (SST). SSTs, for example, the S $=$ 1 to S $=$ 2 transition in Mn$^{\mathrm{3+}}$ can become cooperative magnetostructural phase transitions due to structural coupling between ions. SSTs are accompanied by change in the orbital occupation and hence, strongly coupled to the lattice and charge degrees of freedom. They are a dominant functionality in metalorganic materials, persisting up to room temperature in some compounds. We demonstrate that a magnetic SST can induce ferroelectricity. We study a Mnbased metalorganic system in which a threefold degenerate dynamic JahnTeller effect at high temperatures vanishes when the temperature is lowered, and the system drops into a lower spin state. Application of a magnetic field restores the high spin JahnTelleractive state and allows the Jahn Teller distortions to order cooperatively, creating a dielectric constant change and a net electric polarization. We use high magnetic fields at the NHMFL to study the magnetic and electric behavior of this system across a significant fraction of its TH phase space, and compare to theoretical modeling. [Preview Abstract] 
Thursday, March 17, 2016 12:39PM  12:51PM 
S30.00006: ABSTRACT WITHDRAWN 
Thursday, March 17, 2016 12:51PM  1:03PM 
S30.00007: Spin polarized electronic states and spin textures at the surface of oxygendeficient SrTiO$_3$ Harald O. Jeschke, Michaela Altmeyer, Marcelo Rozenberg, Marc Gabay, Roser Valenti We investigate the electronic structure and spin texture at the (001) surface of SrTiO$_3$ in the presence of oxygen vacancies by means of {\it ab initio} density functional theory (DFT) calculations of slabs. Relativistic nonmagnetic DFT calculations exhibit Rashbalike spin winding with a characteristic energy scale $\sim 10$ meV. However, when surface magnetism on the Ti ions is included, bands become spinsplit with an energy difference $\sim 100$ meV at the $\Gamma$ point. This energy scale is comparable to the observations in SARPES experiments performed on the twodimensional electronic states confined near the (001) surface of SrTiO$_3$. We find the spin polarized state to be the ground state of the system, and while magnetism tends to suppress the effects of the relativistic Rashba interaction, signatures of it are still clearly visible in terms of complex spin textures. [Preview Abstract] 
Thursday, March 17, 2016 1:03PM  1:15PM 
S30.00008: Electronic structure studies on competing phases of Aurivillius Bi$_4$Ti$_3$O$_{12}$ using firstprinciples calculations FuChang Sun, Sanjeev Nayak, Deepam Maurya, Shashank Priya, S. Pamir Alpay The low temperature ferroelectric to high temperature paraelectric phase transition in bismuth titanate (Bi$_4$Ti$_3$O$_{12}$) has been experimentally observed at Curie temperature (T$_C$) around 675 $^{\circ}$C. The firstprinciples calculations using density functional theory as implemented in the Vienna \textit{ab initio} simulation package (VASP) with generalized gradient approximation (GGA) for the exchangecorrelation interaction are performed to investigate this monoclinic (\textit{b}1\textit{a}1) to tetragonal (\textit{I}4/\textit{mmm}) crystal structural transition. We further, provide discussion of the band structure and the TiO orbital hybridization, in addition to the frequency dependent dielectric and optical properties of Bi$_4$Ti$_3$O$_{12}$ due to the potential applications in the electronic devices. [Preview Abstract] 
Thursday, March 17, 2016 1:15PM  1:27PM 
S30.00009: ABSTRACT WITHDRAWN 
Thursday, March 17, 2016 1:27PM  1:39PM 
S30.00010: Microscopic description of oxide perovskites and automated highthroughput analysis of their energy landscape Giovanni Pizzi, Andrea Cepellotti, Boris Kozinsky, Nicola Marzari Even if ferroelectric materials like BaTiO$_3$ or KNbO$_3$ have been used for decades in a broad range of technological applications, there is still significant debate in the literature concerning their microscopic behavior. For instance, many perovskite materials display a hightemperature cubic phase with zero net polarization, but its microscopic nature is though still unclear, with some materials displaying a very complex energy landscape with multiple local minima. In order to investigate and clarify the microscopic nature of oxide perovskites, we perform a study on a set of about 50 representative ABO$_3$ systems. We use spacegroup techniques to systematically analyze all possible local displacement patterns that are compatible with a net paraelectric phase, but can provide local nonzero ferroelectric moments. The energetics and the stability of these patterns is then assessed by combining the spacegroup analysis with DFT calculations. All calculations are managed and analyzed using our highthroughput platform AiiDA (www.aiida.net) [1]. Using this technique, we are able to describe the different classes of microscopic models underlying the perovskite systems. [1] G. Pizzi et al., Comp. Mat. Sci 111, 218230 (2016). [Preview Abstract] 
Thursday, March 17, 2016 1:39PM  1:51PM 
S30.00011: Temperaturedependent phase transition of ferroelectric perovskites: A WangLandauDFT approach Simuck Yuk, Ying Wai Li, Markus Eisenbach, Valentino Cooper Since the discovery of ferroelectricity in perovskite oxides, considerable efforts have been devoted to understanding their phase transition behaviors in terms of temperature, pressure, and composition. Such materials have regularly been used in transducer and actuator applications. As our first step to make accurate predictions of the crystal phases of more complex oxides such as Pb(Zr$_{x}$Ti$_{1x})$O$_{3}$, we have used the WangLandau (WL) algorithm and density functional theory (DFT) to examine the temperaturedependent phase transition of PbTiO$_{3}$, BaTiO$_{3}$, and KNbO$_{3}$. DFT was employed to evaluate the energetics of important crystalstructure candidates, which were later used as the input for WL algorithm. In addition, we examine how the choice of exchangecorrelation functionals affects our predictions of the relevant phase transition temperatures. [Preview Abstract] 
Thursday, March 17, 2016 1:51PM  2:03PM 
S30.00012: First Principle Studies of Electromechanical Properties in MnDoped BaTiO$_3$ Hiroyuki Takenaka, R.E. Cohen We are performing density functional calculations to elucidate the electromechanical properties for Mndoped BaTiO$_3$ with an oxygen vacancy, applying electric field perpendicular to polarization directions. We find that local dipole switching and lattice changes take place at 3MV/m. Spontaneous polarization along x is 0.251 C/m$^2$ and $c/a$ ratio changes from 1.021 to 1.000. This indicates that coercive field of Mndoped BaTiO$_3$ increases as were experimentally reported since our results for pure BaTiO$_3$ exhibit onset of the switching and changes at 0.8 MV/m. We report our computational dielectric constant and strain as a function of electric field for Mndoped BaTiO$_3$. [Preview Abstract] 
Thursday, March 17, 2016 2:03PM  2:15PM 
S30.00013: Towards an understanding of antiferroelectricity in PbZrO$_3$ from first principles Brian M. Abbett, Karin M. Rabe, Craig J. Fennie For decades, PbZrO$_3$ has been referred to as the prototypical antiferroelectric. According to a recent analysis, an essential requirement for antiferroelectricity is that there is a polar phase almost degenerate with the nonpolar ground state. Indeed, as previously reported, firstprinciples calculations show that the polar $R3c$ structure of PbZrO$_3$ is only 1 meV per formula unit higher in energy than the nonpolar ground state $Pbam$ structure. Here, we explore the question of how these two structures, which seem to be only distantly related, can be so close in energy. Using firstprinciples methods we investigate the energy landscape of PbZrO$_3$. We introduce a simple structural model that both describes the relevant, lowenergy, structural motifs and captures the gross energy landscape relating to both structures. We use this model (and test with direct firstprinciples calculations) to explore a possible switching path between the nonpolar ground state and the metastable polar structure. Our results provide insight into why PbZrO$_3$ is antiferroelectric, which may prove useful in identifying new antiferroelectric materials. [Preview Abstract] 
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