Bulletin of the American Physical Society
APS March Meeting 2018
Volume 63, Number 1
Monday–Friday, March 5–9, 2018; Los Angeles, California
Session L23: Multiferroic Oxide HeterostructuresFocus
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Sponsoring Units: GMAG DMP DCOMP Chair: Pu Yu, Tsinghua University Room: LACC 402B |
Wednesday, March 7, 2018 11:15AM - 11:51AM |
L23.00001: Atomic-resolution Imaging of Functional Electronic Inversion Layers at Ferroelectric Domain Walls Invited Speaker: Julia Mundy Ferroelectric domain walls hold great promise as functional two-dimensional materials because of their unusual electronic properties. Particularly intriguing are the so-called charged walls where a polarity mismatch causes local, diverging electrostatic potentials requiring charge compensation and hence a change in the electronic structure. These walls can exhibit significantly enhanced conductivity and serve as a circuit path. Here we use atomic-resolution STEM-EELS to directly probe the charge transfer at these charged ferroelectric domain walls in ErMnO3. Our direct quantification of the charge transfer to the domain boundary gives insight into the the formation—and eventual activation—of an inversion layer that acts as the channel for the charge transport. The findings provide new insight into the domain-wall physics in ferroelectrics and foreshadow the possibility to design elementary digital devices for all-domain-wall circuitry. |
Wednesday, March 7, 2018 11:51AM - 12:03PM |
L23.00002: In-situ imaging of electric field-induced ferroelastic domain motion in SrTiO3 Blai Casals, Andrea Schiaffino, Arianna Casiraghi, Sampo J. Hämäläinen, Diego López González, Sebastiaan van Dijken, Massimiliano Stengel, Gervasi Herranz SrTiO3 displays superconductivity, incipient ferroelectricity and can host two-dimensional electron gases (2DEGs). These phenomena occur below the cubic-to-tetragonal transition, where ferroelastic twins emerge as a result of the lower symmetry and have a strong impact on all the aforementioned properties, To shed light on these issues, we exploited the magnetoelastic coupling caused by the imprinting of ferroelastic domains into magnetostrictive films on SrTiO3. With this approach we imaged the spatial distribution of ferroelastic twins under the action of in-situ applied electric fields and revealed the expected anisotropic dielectric behavior of tetragonal SrTiO3. Based on first-principles and Landau theory, we associate the observed anisotropy to the emergence of an antiferroelectric (AFE) lattice instability of the Ti ions that couples to polar and AFD lattice modes. The appearance of this coupling also solves the longstanding issue of the origin of the R-point infrared-active phonon which previously was generically assigned to the back-folding of the Brillouin zone in the tetragonal phase. Our study foresees the emergence of antiferroelectric instabilities in other oxide perovskites, a prediction that deserves further research in the lattice dynamics of these materials. |
Wednesday, March 7, 2018 12:03PM - 12:15PM |
L23.00003: Structure, magnetic, and electronic properties in epitaxial Ca1-xSrxMn7O12 films Amanda Huon, Alexander Grutter, Julie Borchers, Michael Fitzsimmons, Ho Nyung Lee, Steven May The quadruple perovskite CaMn7O12 has garnered attention over the years due to the interesting physics in this unique crystal structure. Mn ions are simultaneously present on both the A- and B-site, with both Mn3+ and Mn4+ ions on the B-site. Due to the presence of different sites of the Mn ions in this complex oxide, this perovskite exhibits an array of collectively ordered states: spin, orbital, charge, and lattice. Here, we present a detailed study on the synthesis of epitaxially grown Ca1-xSrxMn7O12 thin films by utilizing x-ray diffraction, neutron diffraction, transport, and magnetometry approaches to understand the underlying physics present in the magnetic and electronic properties. This talk will focus on how the charge-ordering and magnetic-ordering transitions are altered through Sr doping (x) and due to the influence of growth parameters. |
Wednesday, March 7, 2018 12:15PM - 12:27PM |
L23.00004: Electronic and magnetic structure of thin film of biferroic YCrO3 Banabir Pal, Xiaoran Liu, Fangdi Wen, Mikhail Kareev, Elke Arenholz, Jak Chakhalian Thin films of YCrO3 were synthesized using pulsed laser deposition (PLD) technique in order to investigate the effect of reduced dimensionality on the electronic and magnetic structure of this biferroic system. Each thin film was characterized using a combination of in-situ RHEED, AFM, XPS, and XRD techniques establishing both epitaxial and stoichiometric growth. Polarization dependent Cr L3,2 edge XAS measurements which probes the orbital configuration of the Cr 3d states, showed a distinct X-ray linear dichroism (XLD) signal signifying the unexpected splitting of the Cr t2g states in this system. Additionally temperature dependent Cr L3,2 edge X-ray magnetic linear dichroism (XMLD) studies exhibit the appearance of new magnetic ground states indicating a modified magnetic interaction between Cr atoms in lower dimensions. |
Wednesday, March 7, 2018 12:27PM - 12:39PM |
L23.00005: First-principles investigation of the temperature dependent lattice dynamics in multiferroic CuFeO2 Santosh KC, Feng Ye, Tsuyoshi Kimura, Valentino Cooper CuFeO2 is a canonical magnetic-driven multiferroic with a triangular lattice network. It forms in the delafossite structure with space group R3-m at room temperature and undergoes a crystallographic phase transition to a monoclinic space group, C2/m, below the antiferromagnetic transition ~ 11 K. Using density functional theory (DFT), we examined the evolution of the coupling between the atomic and magnetic structure as a function of crystal symmetry. Phonon dispersion indicates a strong spin-lattice coupling which is driven mostly by differences in crystal symmetry of the high temperature and low temperature phases. Moreover, the phonon dynamics allowed us to determine that CuFeO2 has long-range antiferromagnetic ordering. Our results for the calculated phonon dispersion are in good agreement with the experimentally observed phonon spectra. |
Wednesday, March 7, 2018 12:39PM - 12:51PM |
L23.00006: Tuning Functionalities in Bi1-xMxFeO3(M=La,Sr) bulk systems and BiFeO3/La1-xSrxMnO3 Heterostructure: A First-Principles Based Study Ayana Ghosh, Hongchul Choi, Dennis Trujillo, Serge Nakhmanson, Pamir Alpay, Jian-Xin Zhu In past decades, design of novel multi-functional materials and heterostructures has gained much interest in the scientific community for their applications in developing interface-based magnetoelectric and information-storage devices. However, the science behind atomistic mechanisms of magnetoelectric coupling, and charge-controlled electronic phenomena are yet to be determined. With an aim to solidify the theoretical understanding of these multiferroic properties, we have studied electronic and magnetic properties of bulk systems such as |
Wednesday, March 7, 2018 12:51PM - 1:03PM |
L23.00007: Ferroelectricity-induced interfacial ferromagnetism in non-magnetic heterostructures W. X. Zhou, H. Wang, Tula Paudel, H. J. Wu, Thirumalai Venkatesan, Stephen Pennycook, Evgeny Tsymbal, J. S. Chen, Ariando Ariando We show, through deliberate interfacial electronic structure modification, ferroelectricity induced room-temperature interfacial ferromagnetism with perpendicular magnetic anisotropy in Pt at the Pt/BaTiO3 interface in a nominally non-magnetic Pt/BaTiO3/SrTiO3 (001) heterostructure. The average magnetic moment of a 2 nm Pt thin film on 20 unit cells of BaTiO3 at 300 K is ~0.4 mB/Pt. Our first-principles calculations, as well as scanning transmission electron microscopy measurements indicate that the interfacial electronic structure modification induced by the polarization of BaTiO3 and Pt substitution of Ti at the Pt/BaTiO3 interface is responsible for the unusual ferromagnetism in Pt. The general concept of interfacial electronic structure modification provides an innovative route to induce interfacial room-temperature ferromagnetism in a nominally non-magnetic material. |
Wednesday, March 7, 2018 1:03PM - 1:15PM |
L23.00008: Effects of the Size of the Rare Earth Ions on the Magnetism in h-RFeO3 Kishan Sinha, Yaohua Liu, Huibo Cao, Xiao Wang, Xiaozhe Zhang, Xuemei Cheng, Xiaoshan Xu Hexagonal ferrites (h-RFeO3, R: rare earth) are multiferroic materials that exhibit spontaneous magnetic and ferroelectric polarizations simultaneously. We have prepared epitaxial h-RFeO3 thin films for different R and studied their magnetic transition temperature TN and the saturation magnetic moments. We found that, when the size of the rare-earth ion is reduced, the magnetic transition temperature may become significantly higher (e.g. TN»125 and 200 K for h-YbFeO3 and h-ScFeO3 respectively), while the magnetic moment on the Fe ions becomes smaller. We attribute this significant increase of TN to the enhanced interlayer exchange interactions due to the larger lattice distortion caused by the reduced size of the rare earth ion. |
Wednesday, March 7, 2018 1:15PM - 1:27PM |
L23.00009: Size Effects on the Magnetism of Multiferroic BiFeO3 Nanoparticles Rogério de Sousa, Marc Allen, Ian Aupiais, Maximilien Cazayous We present a theory of the mechanisms that are responsible for the observation of enhanced ferromagnetism and the destruction of the cycloid in nanoparticles of the room temperature magnetoelectric multiferroic bismuth ferrite (BiFeO3). We consider the role of uncompensated spins at the surface, the impact of surface-induced magnetic anisotropy, and the RKKY interaction mediated by the surface charge density in the ferroelectric nanoparticles. The competing interactions give rise to rich magnetic phase diagrams as a function of size and chemical doping, opening up many opportunities for engineering the magnetic state of bismuth ferrite. |
Wednesday, March 7, 2018 1:27PM - 1:39PM |
L23.00010: Engineering a multiferroic monodomain in BiFeO3 films through magnetoelastic control Noah Waterfield Price, Roger Johnson, Wittawat Saenrang, Jonathan Schad, Francis Chmiel, Alessandro Bombardi, Francesco Maccherozzi, Sarnjeet Dhesi, Chang-Beom Eom, Paolo Radaelli The presence of domains in ferroic materials can diminish their macroscopic properties and hence their usefulness in device applications. This effect is particularly limiting in multiferroic materials such as BiFeO3, which combine magnetic, ferroelectric and ferroelastic orders, and tend to grow with numerous domain variants in all three sectors. Here, we present the use of strain and electric fields to control the magnetic domain population in (111)-BiFeO3 films. This orientation maximises the out-of-plane polarisation but generally results in a texture of magnetic domains. By exploiting the magnetoelastic coupling between the magnetic and crystal structures, and measuring the resulting magnetic domain populations by magnetic x-ray and neutron diffraction, we demonstrate the use of substrate strain to engineer a ferroelastic, ferroelectric, and magnetic monodomain, coherent over an entire 1-micron-thick BiFeO3 film. We further demonstrate the coupling of the magnetic structure to the ferroelectric polarisation by showing the cycloidal rotation direction (magnetic polarity) is inverted upon 180-degree switching of the polarisation. |
Wednesday, March 7, 2018 1:39PM - 2:15PM |
L23.00011: Imaging, controlling and harnessing non-collinear magnetism in perovskite oxides Invited Speaker: Manuel Bibes In magnetic perovskite oxides ABO3, first-neighbour antiferromagnetic super-exchange interactions usually dominate, but may coexist with other terms such as ferromagnetic double-exchange or Dzyaloshinskii-Moriya interactions at B-O-B and A-O-A bonds. This often produces non-collinear spin configurations leading to weak ferromagnetism or to spatially modulated spin structures. A prototypical non-collinear magnetic oxide is multiferroic BiFeO3 that shows a cycloidal order with a 64 nm period in the bulk. In this talk, I will show how epitaxial strain can be used to tailor the magnetic order of BiFeO3 thin films and present real-space images of the cycloidal structure, as well as its manipulation by an electric field In a second part I will discuss how magnetic spin texture can influence the Hall response in strongly correlated oxide thin films. |
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