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 E53: Multiferroics, Magnetoelectrics, Spin-Electric Coupling, and Ferroelectrics - 2Live
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Sponsoring Units: DMP GMAG Chair: Mark Pederson, University of Texas at El Paso |
Tuesday, March 16, 2021 8:00AM - 8:12AM On Demand |
E53.00001: Sum-frequency excitation of coherent magnons Derek Wang, Dominik Juraschek, Prineha Narang Ultrashort laser pulses can coherently excite quasiparticles with macroscopically large amplitudes. Coherent excitation of magnons is conventionally achieved through Raman scattering processes, in which the difference-frequency components of the driving field are resonant with the magnon frequency. Here, we describe mechanisms by which the sum-frequency components of the driving field can be used. We numerically simulate the spin-precession amplitudes that impulsive stimulated and ionic Raman scattering processes and their sum-frequency counterparts are able to induce in a model antiferromagnet with realistic experimental opto- and phono-magnetic coupling coefficients. We show that the sum-frequency excitation is possible via the (phonon) inverse Cotton-Mouton effect, but not the (phonon) inverse Faraday effect. These sum-frequency mechanisms operate at lower excitation energies than conventional techniques, and they complete the map of dynamical spin control pathways by the means of Raman-type mechanisms. |
Tuesday, March 16, 2021 8:12AM - 8:24AM Live |
E53.00002: Impact of intrinsic defects on ferroelectric polarization in YFeO3 Konstantin Klyukin, Shuai Ning, Caroline Anne Ross, Bilge Yildiz Multiferroic materials have experienced a vast interest due to their inherent coupling between electric and magnetic degrees of freedom offering a high potential for memory applications. Because of fundamental limitations, only a small set of materials demonstrate both ferromagnetic and ferroelectric properties at room temperatures. Defect and strain engineering opens a promising route to discover novel multiferroic materials by inducing ferroelectricity in paraelectric materials having magnetic ions. Although bulk YFeO3 (YFO) has a centrosymmetric crystal structure, our recent experimental investigations indicated that epitaxial YFO thin films can become ferroelectric. We attribute the ferroelectric behavior to the presence of point defects that introduce a dipole moment polarizing the surrounding regions. In this work, we investigate a variety of intrinsic defects in YFO by means of DFT calculations and the Berry phase approach. Our calculations demonstrate that yttrium antisite defects YFe can break the inversion symmetry causing a switchable polarization up to ~7 μC/cm2. In addition, we predict that rare-earth antisite defects will also induce the formation of ferroelectric regions in other RFeO3 orthoferrites (R=Lu, Yb etc). |
Tuesday, March 16, 2021 8:24AM - 8:36AM Live |
E53.00003: Origin of antiferroelectricity in NaNbO3 Niloofar Hadaeghi, Hongbin Zhang To figure out the origin of antiferroelectricity in NaNbO3, we performed in-depth investigation combining symmetry analysis and density functional theory (DFT) calculation. The primary distortion modes driving the phase transition from the paraelectric (PE) Pm-3m phase to the antiferroelectric (AFE) Pbcm phase are identified to be R5-, T2 and Δ5. The adiabatic potential energy surface reveals that the R5- and T2 modes lead to more energy gain than the Δ5 mode. It also shows that the coexistence of R5- and Δ5 modes, and T2 and Δ5 modes cooperate to stabilize the AFE phase as well as the trilinear coupling term. To elucidate the electronic driving force of the PE-AFE phase transition, symmetry analysis on the possible couplings between the electronic and vibrational states is carried out following the pseudo Jahn-Teller effect (PJTE) theory, and the adiabatic potential energy surface cross sections are evaluated based on the unfolded band structures. It is observed that the Δ5 mode is created by the coupling of T2u and T2g electronic states by PJTE, while R5- and T2 modes are more responsible to stabilize the AFE phase. This paves the way to identify the descriptors from the electronic structure for the displacive phase transitions and materials design in future studies. |
Tuesday, March 16, 2021 8:36AM - 8:48AM Live |
E53.00004: Prediction of exotic magnetic states in quasi-one-dimensional iron selenide compound Na2FeSe2 bradraj pandey, Ling-Fang Lin, Rahul Soni, Nitin Kaushal, Jacek Herbrych, Gonzalo Alvarez, Elbio Dagotto Motivated by recent progress in preparing alkali-metal compounds, we present the magnetic and |
Tuesday, March 16, 2021 8:48AM - 9:00AM Live |
E53.00005: Phonon Anharmonicity in Tunable Quantum Paraelectrics Xing He, Dipanshu Bansal, Douglas L Abernathy, Barry Winn, Songxue Chi, Lynn A Boatner, Olivier Delaire The quantum paraelectric behavior and strongly anharmonic lattice dynamics in SrTiO3 and KTaO3 have attracted interest for decades. By tunning temperature, doping, and external field, quantum paraelectric materials can cross multiple phase transitions and approach a ferroelectric quantum critical point (QCP). Besides the ferroelectric soft mode and phase transition, recent research also revealed unusual thermal transport properties such as thermal Hall effects in SrTiO3 and KTaO3, as well as superconductivity, which motivate detailed studies of lattice dynamics. In particular, understanding phonon anharmonicity near a QCP is crucial to rationalizing the properties of quantum paraelectrics. We used inelastic neutron scattering and first-principle simulations to probe the temperature, electric field, and doping effects on phonons in SrTiO3 and KTaO3. Our experiments reveal striking intensity changes, as well as phonon damping and shifts, reflecting strong acoustic-optic phonon coupling which are reproduced by our calculations. These results provide direct insights into the behaviors of phonon eigenvectors and ionic interactions. |
Tuesday, March 16, 2021 9:00AM - 9:12AM Live |
E53.00006: Amorphous to crystal phase transition for organic ferroelectrics revealed by in situ hysteresis loop measurements. Yifan Yuan, Xiaoshan Xu 2-methylbenzimidazole (MBI) films are deposited on the interdigitated electrodes at low temperatures by physical vapor deposition. Dielectric hysteresis loops are investigated in situ during the deposition and warming process. The loops indicate that the amorphous to crystal phase transition and the transition temperature increases as the film thickness increase. |
Tuesday, March 16, 2021 9:12AM - 9:24AM Live |
E53.00007: Domain fluctuations in a ferroelectric low-strain BaTiO3 thin film Jianheng Li, Louie Zhong, Rahul Jangid, FNU Meera, Geoffery I Rippy, Kenneth Ainslie, Chris Kohne, Arnoud Everhardt, Beatriz Noheda, Yugang Zhang, Andrei Fluerasu, Sylvia Matzen, Roopali Kukreja The intriguing prospect of ferroelectric materials is that they possess spontaneous electric polarization that can be altered with applied electric fields, enabling numerous device applications including non-volatile memories, actuators, and sensors. Ferroelectric domain reconfiguration plays an important role in manipulating polarization switching behavior and the dynamical properties of the ferroelectric thin films. In this study, we utilized X-ray photon correlation spectroscopy to probe ordered a/c domain dynamics and fluctuations across a/b to a/c domain transformation and Curie temperature. Our studies show that the a/b to a/c domain transformation is accompanied by a decrease in fluctuation timescales, and an increase in intensity and correlation length. Surprisingly, domain fluctuations are observed up to 25 °C above the transformation, concomitant with the growth of a/c domains and coexistence of both domain types. A further increase in temperature brings the system closer to the Curie temperature resulting in the observance of a/c domain fluctuations. The observed time evolution and reconfiguration of domain patterns highlight the role played by phase coexistence and elastic boundary conditions in altering fluctuations timescales in ferroelectric thin films. |
Tuesday, March 16, 2021 9:24AM - 9:36AM Live |
E53.00008: Designing layered two dimensional Van der Waals multiferroics and polar metals Swamynadhan M. J., Saurabh Ghosh We have employed first-principles density functional theory calculations to investigate the electric, magnetic and electronic properties of ABP2S6 (A = Cu, Ni; B = Cr, Mn) two dimensional (2D) transition metal phosphorous chalcogenides (TMPC). We have investigated four (TMPCs) compounds namely CuCrP2S6 (CCPS), CuMnP2S6 (CMPS), NiCrP2S6 (NCPS) and NiMnP2S6 (NMPS) and reported unusual anti/ferroelectric (AFE/FE) and electronic properties. We have found a more stable ferroelectric state is in the Van der Waals (VdW) gap with higher polarization compared to the usual ferroelectric phase. We report CMPS and NMPS as polar half metals whereas NMPS can undergo metal-to-insulator transition driven by the polar distortion. At 300K, by performing molecular dynamic simulations, we have discovered a hybrid ’inter-intra’ antiferroelectric switching within the VdW gap for CCPS. The origin of such switching is found to be the relative displacement of the layers with respect to each other. The reported VdW FE/AFE 2D layered TMPC systems and thus can be considered as potential piezoelectric materials. |
Tuesday, March 16, 2021 9:36AM - 9:48AM Live |
E53.00009: Hexagonal ABC polar metals from first principles Konrad Genser, Karin M Rabe Ternary ABC intermetallic compounds exhibit a rich variety of crystal structures and electronic properties. In this work, we study the structural energetics and band structures of real and hypothetical hexagonal ABC intermetallic phases, using first principles calculations to determine the structural parameters and the bands in each phase. We use this dataset to analyze and model the bands near the Fermi level in metallic examples to classify the systems considered and to connect to experimental measurements on known hexagonal ABC phases. The possibility of switchability of the polar distortion in these polar metals by appropriate applied fields and stresses offers the promise of functional optical and transport properties, with examples to be discussed. |
Tuesday, March 16, 2021 9:48AM - 10:00AM Live |
E53.00010: Role of structure, energetics, and electronic structure in determining the pressure response of octahedral rotations in Ruddlesden-Popper layered perovskites Sriram Poyyapakkam Ramkumar, Elizabeth A Nowadnick Octahedral rotations are ubiquitous in perovskite oxides and couple closely to their electronic and magnetic properties. Whereas the pressure response of octahedral rotations in ABO3 perovskites has been well studied, the impact of pressure on layered perovskites such as the n=2 Ruddlesden-Popper (RP) phase A3B2O7 is much less explored. In this work, we use a combination of group theoretic analysis, density functional theory calculations, and Landau free energy expansions to explore how octahedral rotations in a family of A3B2O7 RP materials respond to applied pressure. Contrasting with the pressure response of octahedral rotations in ABO3 perovskites, which often can be classified by the charge state of the A- and B-site cations, we find that each A32+B24+O7 material that we investigate exhibits a distinct behavior under pressure. We identify the key ingredients that determine the evolution of octahedral rotations in RPs under pressure, and show that it is determined by an interplay of the structural and electronic degrees of freedom. Our results offer insight into how to tune the structure and properties such as ferroelectricity in layered perovskites. |
Tuesday, March 16, 2021 10:00AM - 10:12AM Live |
E53.00011: Thermal expansion in Ruddlesden-Popper and perovskite sulfides Nathan Koocher, James M Rondinelli The thermal expansion of materials affects the capability, performance, and lifetime of materials operating in variable thermal conditions. Previously ferroelectric Ca3Ti2O7 with the layered Ruddlesden-Popper (RP) structure (n=2 member of An+1BnO3n+1) was shown to exhibit pressure-tunable negative thermal expansion (NTE) and a pressure-independent softening of the bulk modulus due to a quasi-two-dimensional vibration [Huang et al, Phys. Rev. Lett. 117, 115901 (2016)], whereas nonpolar RP strontium titanates did not exhibit NTE [Huang et al, Chem. Mater. 30, 7100 (2018)]. Here, we analyze structural lattice dynamical, and thermodynamic properties of d0 Ruddlesden-Popper and perovskite sulfides using the self-consistent quasi-harmonic approximation with density functional theory. We relate the thermal expansion coefficient and bulk modulus to the number of octahedral units and type of octahedral connectivity present in the respective materials. This local structure understanding may help design thermal expansion property in other chemistries. |
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