Bulletin of the American Physical Society
Annual Meeting of the APS Four Corners Section
Volume 62, Number 17
Friday–Saturday, October 20–21, 2017; Fort Collins, CO
Session C2: Condensed Matter and Materials I |
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Chair: Sangita Kalarickal, Seagate Technology Room: Lory Student Center 304 |
Friday, October 20, 2017 10:30AM - 10:54AM |
C2.00001: Many faces of lithium metal under pressure Invited Speaker: Shanti Deemyad Even at zero temperature lattice of lithium remains far from static. In periodic table lithium is the first element immediately after helium and the lightest metal. While fascinating quantum nature of condensed helium is suppressed at high densities, because of the presence of long range interactions in metallic systems, lithium is expected to adapt more quantum solid behavior under compression. Physics of dense lithium offers a rich playground to look for new emergent quantum phenomena in condensed matter. In this talk I will discuss the physics of ultra-light materials under extreme pressures and will present some of our studies on quantum contributions to the structural and electronic phase transitions of lithium, and will present our results on the resolving the long lasting mystery of lithium ground state [Preview Abstract] |
Friday, October 20, 2017 10:54AM - 11:06AM |
C2.00002: Octahedral Tilting from Organic Cations in Defect-Ordered Hybrid Perovskites Annalise Maughan, Alex Ganose, Andrew Candia, Juliette Granger, David Scanlon, James Neilson Perovskite semiconductors such as methylammonium lead iodide (CH$_3$NH$_3$PbI$_3$) are a technologically-relevant family of materials, finding applications in field-effect transistors, light-emitting diodes, and low-cost photovoltaics, yet materials such as methylammonium lead iodide present significant concerns for toxicity and material stability. Defect-ordered perovskites provide a platform to study optical and electronic behavior in materials with improved toxicity and stability outlooks relative to lead-containing counterparts. We have prepared the series of vacancy-ordered double perovskites $A_2$SnI$_6$, where \textit{A}~=~Cs$^+$, CH$_3$NH$_3^+$, and CH(NH$_2$)$_2^+$. While Cs$_2$SnI$_6$ exhibits moderate electronic conductivity, incorporation of CH$_3$NH$_3^+$ and CH(NH$_2$)$_2^+$ reduces carrier mobility across the series. We correlate the observed trends in carrier mobility with rotational disorder and anharmonicity of the [SnI$_6$] octahedral units, which is enhanced through hydrogen bond formation in the hybrid (CH$_3$NH$_3$)$_2$SnI$_6$ and (CH(NH$_2$)$_2$)$_2$SnI$_6$ compounds. These studies provide an avenue to explore the influence of organic-inorganic coupling on the properties of perovskite-based materials for emerging optical and electronic applications. [Preview Abstract] |
Friday, October 20, 2017 11:06AM - 11:18AM |
C2.00003: First-Principles Study of Hydrogen Trapping in Electrolytic Manganese Dioxide Birendra Ale Magar, Timothy N. Lambert, Jonathon Duay, Babu Chalamala, Igor Vasiliev Alkaline Zn/MnO$_{2}$ batteries hold great promise for electrical energy storage due to their high energy density, non-toxicity, and low cost. At a low depth of discharge, the reduction reaction in the Zn/MnO$_{2}$ battery cathode is governed by hydrogen trapping in the solid phase of $\gamma$-MnO$_{2}$. We applied ab initio computational methods based on density functional theory to study the mechanism of hydrogen insertion into the pyrolusite and ramsdellite tunnels of $\gamma$-MnO$_{2}$. Our calculations were carried out using the Quantum ESPRESSO electronic structure code combined with Vanderbilt ultrasoft pseudopotentials. We found that the trapped hydrogen initially occupied the 2$\times$1 ramsdellite tunnels of $\gamma$-MnO$_{2}$. Our study showed that the insertion of hydrogen into the 1$\times$1 pyrolusite tunnels induced significant structural distortions leading to the breakdown of the crystal structure of $\gamma$-MnO$_{2}$. These results could explain the presence of groutite and the absence of manganite among the reaction products of partially reduced $\gamma$-MnO$_{2}$. [Preview Abstract] |
Friday, October 20, 2017 11:18AM - 11:30AM |
C2.00004: Magnetic Ordering of Magnetite Nanoparticles (Fe3O4) Brittni Newbold, Karine Chesnel, Dalton Griner, Dallin Smith, Kamden Jones We are studying the magnetic ordering in magnetite (Fe3O4) nanoparticle assemblies. Samples of these nanoparticle assemblies were put through x-ray resonant magnetic scattering which produced scattering images. These images provide information about the magnetic ordering of the particles. The scattering patterns are reduced to 1D scattering profiles. By fitting these scattering profiles with a model, we are determining specific magnetic orderings present in the assemblies and their associated weights. We analyze such scattering images to determine the weight of each magnetic order in the nanoparticle assemblies as a function of magnetic field and temperature. Specifically, I analyze samples at 300 K and at 280 K to determine the amount of anti-ferromagnetic contribution as the field value approaches 0 Oe. This research can have application in the medical field. [Preview Abstract] |
Friday, October 20, 2017 11:30AM - 11:42AM |
C2.00005: Emergent multiferroic phase in Barium Hexaferrite nanopowders Richard Mbatang, E Enriquez, A Chen, E Fohtung A subset of multiferroic materials known as magnetoelectrics, where multiferroic ordering is achieved due to proximity effects from magnetic and ferroelectric ordered phases, have attracted a great amount of interest in the last decade.~The ability to modulate electric properties by a magnetic field and magnetic properties by an electric field could be crucial in the fabrication of new memory devices with low power consumption. A lot of effort is being put in the design of new single phase magnetoelectric materials with optimum magnetoelectric coupling and high temperature. This talk will focus on the connections between structural, electrical and magnetic properties of Barium Hexaferite nanopowders. The magnetoelectric coupling of these materials has been explored by studying magnetic-field control of electric polarization, which may be important for low-power electronics. [Preview Abstract] |
Friday, October 20, 2017 11:42AM - 11:54AM |
C2.00006: Partial helical order in Fe$_{\mathrm{3}}$PO$_{\mathrm{7}}$ Colin Sarkis, Michael Tarne, Huibo Cao, James R. Neilson, Kate A. Ross For most magnetic systems, a particular ground state is chosen at low enough temperatures. For partially ordered states, there exists an extended manifold of possible ordering wavevectors available, from which the system cannot pick a unique solution, and instead shows short range order. Partial order has been observed, for example, in the Skrymion-lattice hosting materials MnSi and Fe$_{\mathrm{1-x}}$Co$_{\mathrm{x}}$Si, and in the latter it was shown to be the precursor to the Skyrmion lattice phase. Polycrystalline iron phosphate oxide (Fe$_{\mathrm{3}}$PO$_{\mathrm{7}})$ has been previously shown to host nanosized antiferromagnetic helical domains, implying a large number of topological defects are present below T$_{\mathrm{N}} \quad =$ 163 K. Here we present Neutron Diffraction data on single crystal Fe$_{\mathrm{3}}$PO$_{\mathrm{7}}$ which definitively shows partial order as evidenced by a continuous ring of scattering instead of well-defined Bragg peaks. This can be understood in terms of the competition between J$_{\mathrm{1}}$ (nearest neighbor) and J$_{\mathrm{2}}$ (next nearest neighbor) interactions in a Heisenberg model, which produces a quasi-degenerate manifold of ordering wavevectors. The partial order appears to be linked to the presence of topological defects, but at this point the origin of the latter is not well understood. [Preview Abstract] |
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