Bulletin of the American Physical Society
APS March Meeting 2021
Volume 66, Number 1
Monday–Friday, March 15–19, 2021; Virtual; Time Zone: Central Daylight Time, USA
Session R53: Multiferroics, Magnetoelectrics, Spin-Electric Coupling, and Ferroelectrics -4Live
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Sponsoring Units: DMP DCOMP GMAG Chair: Zahra Hooshmand, University of Texas at El Paso |
Thursday, March 18, 2021 8:00AM - 8:12AM Live |
R53.00001: Perturbative approach to electrocaloric effects Monica Graf, Jorge Iniguez The electrocaloric (EC) effect is the temperature change an insulator material undergoes upon the application of an electric bias. This phenomenon has been widely studied due to its potential as an alternative refrigeration technology. However, we still lack on a unified way to explain normal (increase of temperature under electric bias) and inverse (decrease of temperature) EC effects. In this work we show that, by expressing EC temperature and entropy changes as Taylor series of the applied electric field, one can qualitatively predict and explain all EC effects observed in ferroelectric and antiferroelectric materials. As an example, we present results obtained through second-principles simulations on prototype ferroelectric PbTiO3. |
Thursday, March 18, 2021 8:12AM - 8:24AM Live |
R53.00002: Deep Learning of Accurate Force Field of Ferroelectric HfO2 Jing Wu, Yuzhi Zhang, Linfeng Zhang, Shi Liu The emergence of ferroelectricity in HfO2-based thin films opens up exciting opportunities of using ferroelectrics at the nanoscale. The performance of ferroelectric-based electronics depends on dynamical responses to external stimuli. We developed a deep neural network-based interatomic force field of HfO2, enabling molecular dynamics simulations of this silicon-compitable ferroelectrics at large time and length scales. The development of an accurate model potential using first-principles data is greatly facilitated by a concurrent learning procedure. The model potential predicts a wide range of materials properties such as elastic constants and moduli, equations of states, phonon spectra, and solid-solid phase transition barriers accurately. The temperature-driven ferroelectric-paraelectric phase transition is reproduced with isobaric-isothermal ensemble molecular dynamics simulations. |
Thursday, March 18, 2021 8:24AM - 8:36AM Live |
R53.00003: Electron-electron correlations and Higher Harmonic generation in perovskite BaTiO3 Didarul Alam, Naseem Ud, Shima Gholam Mirzaeimoghadar, Michael Chini, Volodymyr Turkowski We apply the Dynamical Mean-Field Theory+Time-Dependent Density-Functional Theory (DMFT+TDDFT) approach to study the role of strong electron-electron correlations in the high-order harmonic (HH) spectra in perovskite BaTiO3. In DMFT+TDDFT, the response of the system to a perturbation is analyzed with TDDFT with the exchange-correlation kernel derived from the charge susceptibility for the effective Hubbard model by using DMFT, i.e. by including time-resolved on-site electron-electron interactions. We calculated the HH spectrum of the system at different values of the field strength and of the local Coulomb repulsion U. It was found that at high field strengths the number of harmonics in the spectrum increases with the increase of U, the center-of-weight of the spectrum moves to higher harmonics, and the even harmonics become dominating. The spectrum has a strong angle dependence in the case of moderate correlations, while at stronger correlations the angle dependence is much less pronounced. These results can be used to quantify the strength of the electron correlation effects in the material with spectroscopic measurements. |
Thursday, March 18, 2021 8:36AM - 8:48AM Live |
R53.00004: Methods of Manipulating and Dynamics of Ferroic Order in BiFeO3 Eric Parsonnet, Lucas Caretta, Alexander David Qualls, Tanay Gosavi, Dmitri Nikonov, Chia-Ching Lin, Ian Young, Jeffrey Bokor, Lane Wyatt Martin, Ramamoorthy Ramesh
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Thursday, March 18, 2021 8:48AM - 9:00AM Live |
R53.00005: Switchable photovoltaic properties in PZT epitaxial thin films Komalika Rani Ferroelectric thin films are investigated for their potential in photovoltaic applications, due to large open-circuit voltage and switchable photovoltaic effect. The photocurrent can be controlled by the direction of the ferroelectric polarization, allowing in theory to achieve a 100% switchability of the photocurrent with the polarization, which is of great interest for potential photoferroelectric memory devices. However, it is not always achievable in capacitor devices. In this work, a careful study of the switchability of the PV properties of epitaxial lead zirconate titanate thin films has been conducted in order to investigate the role played by the ferroelectric polarization. 100 nm thick PZT films were grown using pulsed laser deposition and integrated into capacitor geometry between SrRuO3 bottom and Pt top electrodes and the photoinduced current in the PZT devices was studied under UV illumination, in different polarization states. A voltage pulse protocol was used to pole the device under increasing electric fields to reach different electrical states while measuring their polarization value. These results revealed the critical role of the depolarizing field as the driving force for the photocurrent and allowed us to extract the screening efficiency of electrodes. |
Thursday, March 18, 2021 9:00AM - 9:12AM Live |
R53.00006: Enhanced Tunneling Electroresistance in MoS2-Hf0.5Zr0.5O2-W Heterojunctions Pradeep Chaudhary, Pratyush P Buragohain, Anastasia Chouprik, Alexey Lipatov, Alexander Sinitskii, Andrei Zekenvich, Alexei Gruverman A reproducibly large tunneling electroresistance (TER) effect resulting from the ferroelectric (FE) polarization reversal is of the great importance for the development of efficient ferroelectric tunnel junctions (FTJs). Recently, it has been demonstrated that incorporation of a semiconducting electrode into the FTJ allowed enhancement of the TER magnitude by several orders of magnitude. Here, we report the polarization-controlled TER of up to 105 % in Hf0.5Zr0.5O2 (HZO) based FTJs employing 2D MoS2 as a top electrode. The resistive switching effect induced by polarization reversal could be explained by the Fowler-Nordheim tunneling mechanism. Enhancement of the TER effect stems from the polarization-mediated accumulation or depletion of the electrons at the MoS2/HZO interface that alters the effective barrier profile seen by the conduction electrons. The obtained results may facilitate fabrication of high performance non-volatile resistive memory devices for information storage systems. |
Thursday, March 18, 2021 9:12AM - 9:24AM Live |
R53.00007: Multiscale Electric Field Imaging in Ferroelectric Vortices Christopher Addiego, Wenpei Gao, Xiaoqing Pan The discovery of polarization vortices in PbTiO3/SrTiO3 superlattices [1] has drawn significant interest due to their unique structure. For example, previous studies of the electric field in these vortex structures using a large probe size revealed the presence of confined regions of negative capacitance within the lattice [2]. However, changing the length scale of measurement can reveal new properties in materials. Using a highly convergent electron probe in a scanning transmission electron microscope with sub-Å resolution, we have studied the electric field at the scale of individual atoms and unit cells, revealing a different pattern in the local electric field than what is observed when using a nanometer scale probe. We find that the atomic scale electric field pattern follows the same vortex structure as the atomic dipole distribution while the nanometer scale electric field does not. This divergence in the electric field patterns results from the highly convergent probe interacting with the charge dipoles of individual unit cells which do not generate a coherent shift in the larger nanometer scale probe. |
Thursday, March 18, 2021 9:24AM - 9:36AM Live |
R53.00008: Band-Mott mixing hybridizes the gap in Fe2Mo3O8 Kiman Park, Gheorghe Pascut, Ghanashyam Khanal, Michael O Yokosuk, Xianghan Xu, Bin Gao, Matthias Gutmann, Alexander Litvinchuk, Valery D Kiryukhin, Sang-Wook Cheong, David Vanderbilt, Kristjan Haule, Janice Musfeldt We combine optical spectroscopy and first-principles electronic structure calculations to reveal the microscopic character of the charge gap in polar magnet Fe2Mo3O8. Iron occupation on the octahedral site draws the gap strongly downward compared to the Zn parent compound, whereas occupation on the tetrahedral site creates a narrow resonance near the Fermi energy that emanates from a flat Mott-like state due to screening of the local moment - similar to expectations for a Zhang-Rice singlet. We discuss this unusual hybridization in terms of orbital occupation and character as well as the structure-property relationships that can be unveiled in various metal-substituted systems (Ni, Mn, Co, Zn). |
Thursday, March 18, 2021 9:36AM - 9:48AM Live |
R53.00009: Theoretical investigation of ferroelectric switching in La-doped BiFeO3 Natalya Fedorova, Dmitri Nikonov, Ian Young, Jorge Iniguez We combine phenomenological Landau-Devonshire (LD) theory and density functional theory (DFT) to investigate the effect of La doping on the structural and dynamic properties of LaxBi1-xFeO3 (LBFO). First, we compute the parameters of the LD potential via an expansion relative to the reference cubic phase as a function of all the relevant degrees of freedom: polarization, antiphase rotations of oxygen octahedra, and strain. For several concentrations of La (x = 0, 1/8 and 1/4), we determine the LD coefficients by requiring that we accurately reproduce the DFT energies and the distortion amplitudes for a set of relevant LBFO polymorphs. Then, we utilize this LD potential in Landau-Khalatnikov simulations of ferroelectric switching in LBFO, to predict how La doping affects the trajectories and the electric field thresholds of switching. |
Thursday, March 18, 2021 9:48AM - 10:00AM Live |
R53.00010: Optimization of artificial antiferroelectrics from second-principles simulations Hugo Aramberri, Natalya Fedorova, Jorge Iniguez Under appropriate conditions, ferroelectrics are known to display ultra-short-period, highly-ordered stripe domain structures that are evocative of antipolar order in antiferroelectric materials. Such states originate so as to minimize the electrostatic energy of the ferroelectric subject to open-circuit-like boundary conditions (as e.g. in the thin PbTiO3 layers of short-period PbTiO3/SrTiO3 superlattices); hence, it follows that the application of an external electric field – i.e., the control of the electrostatic boundary conditions – should allow us to access a strongly polarized state, and thus obtain genuinely antiferroelectric-like behavior. We have used second-principles simulations to pursue this concept, by investigating the antiferroelectric-like properties of PbTiO3/SrTiO3 superlattices and exploring to what extent they can be optimized through the design parameters allowed by these complex materials (e.g., layer thickness, epitaxial strain). In this talk I will summarize our most recent findings. |
Thursday, March 18, 2021 10:00AM - 10:12AM Live |
R53.00011: Atomistic calculations of elastocaloric effects in ferroelectric materials Diana Elisa Murillo Navarro, Mónica Graf, Jorge Iniguez Elastocaloric effects (i.e., the change in temperature due to the application or removal of a mechanical stress) in ferroelectric materials could provide us with an alternative to current – and very polluting – cooling technologies. Ferroelectric phase transitions – as, e.g., in prototype materials like PbTiO3 – have an elastic transformation associated to them, which could potentially give rise to strong elastocaloric effects. Here we introduce a theoretical approach to compute and analyze the elastocaloric response from atomistic simulations and present our results for PbTiO3. Our results reveal several unusual features (i.e., strong anisotropy of the elastocaloric response, the possibilty to choose its sign) that we discuss in detail. |
Thursday, March 18, 2021 10:12AM - 10:24AM Live |
R53.00012: Polarized Raman spectroscopy on epitaxial barium titanate thin films on silicon Sebastian Schmitt, Israel Ibukun Olaniyan, Cesar Magen, Sylvie Schamm-Chardon, Catherine A Dubourdieu Silicon (Si)-integrated thin barium titanate (BTO) films can be used in the design of CMOS compatible ferroelectric (FE) nano-electronic building blocks for future information technology. Material properties as well as the orientation of the FE domains in the BTO films are key for the functionality of the targeted devices. In addition to assessing material properties like crystal structure, composition and strain, Raman spectroscopy permits to investigate the FE domain orientation in BTO thin films. However, except when using a deep UV laser source, Raman spectra from thin oxides on Si are superimposed by strong Raman scattering from the Si substrate. Here we show, how a proper alignment of sample axis, polarizers and analyzers permits to fully suppress Raman scattering from the Si substrate and enables the recording of polarized Raman spectra from thin BTO films on Si. Raman spectra were collected for 5-20 nm BTO films grown on Si by molecular beam epitaxy under various processing conditions and will be discussed in comparison to the Raman response of a bulk, unstrained and stoichiometric BTO single crystal. The crystal structure and FE domain orientation of the BTO films are investigated and correlated to the information gained from scanning transmission electron microscopy. |
Thursday, March 18, 2021 10:24AM - 10:36AM Live |
R53.00013: Atomic and Electronic Structure Changes Underlying Votex Polarization Domains in Hexagonal RMnO3 Trevor Tyson, Sizhan Liu, Jerzy T. Sadowski, Matthew Newville, Antonio Lanzirotti, Sang-Wook Cheong Hexagonal phase RMnO3 systems exhibit polarization domains with complex vortex patterns with density depending on the cooling rate from the high-temperature paraelectric phase. Detailed polarization mapping is compared with spatially dependent structural and spectroscopic measurements to relate variations in the domain patterns with local atomic and electronic structure. Structural measurements reveal variations on the length scale of the changes in polarization. The hard x-ray measurements were complemented by soft x-ray and low energy electron microscopy measurements to probe surface potential variations. |
Thursday, March 18, 2021 10:36AM - 10:48AM Live |
R53.00014: Reversible Redox Properties of Multiferroic Sr1-xBaxMn1-yTiyO2+d Elena Krivyakina, Stanislaw Kolesnik, Cheng Li, Bogdan Dabrowski, Stephan Rosenkranz, Omar Chmaissem We report the phase transformations under various conditions of manganese-based multiferroic perovskite materials with 6% titanium-doping at the magnetic B site in Sr1-xBaxMn1-yTiyO2+d (with d ~ 0.4 – 1). A multiferroic perovskite material of the composition Sr0.4Ba0.6Mn0.94Ti0.06O2+d, was studied by in-situ TOF neutron diffraction under oxidizing and reducing conditions. Oxygen partial pressure dependence of the system’s structure at high temperature was investigated using POWGEN at the SNS, ORNL facility. A fully oxygenated precursor of the same composition was subjected to consequent redox annealing cycles from which we observed a reversible sequence of phase transformations. Slow annealing of an oxygen-deficient material (d ~ 0.4), on the other hand, under controlled oxygen partial pressure conditions give evidence for the presence of a miscibility gap with phase separation consisting of two coexisting phases having oxygen stoichiometries d ~ 0.4 and d ~ 1.0. Further, our results shed light on the suppression of the intermediate oxygen ordered states previously observed with the parent SrMnO2+d material. |
Thursday, March 18, 2021 10:48AM - 11:00AM On Demand |
R53.00015: Angular Dependence of Surface Energy with Crystal Directions of LiNbO3 (110) for Nano-BondingTM to Si and α-quartz SiO2 Abbie Elison, Mohammed Sahal, Shefali Prakash, Srivatsan Swaminathan, Riley Rane, Brian Baker, Saaketh R Narayan, Jacob Kintz, Aliya Yano, Alex L. Brimhall, Lauren Puglisi, Robert J Culbertson, Nicole Herbots LiNbO3 is a piezo-electric that, when mono-lithically integrated to Si-based materials, yields voice activated chips. |
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