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 E3: Condensed Matter and Materials III |
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Chair: Jinke Tang, University of Wyoming Room: Lory Student Center 372 |
Friday, October 20, 2017 1:20PM - 1:32PM |
E3.00001: Discovery of a New Quantum Dimer Magnet in a Strongly Spin-Orbit Coupled Material Gavin Hester, Hari Nair, Tim Reeder, Jeff Quilliam, Jamie Neilson, Gabrielle Sala, Kate Ross Various novel phases of matter have been discovered in the search for a quantum spin liquid and research on high-temperature superconductivity. One such state is the quantum dimer magnet, which consists of entangled electrons forming spin singlets in a solid. A phenomenon occurs in these materials called Bose-Einstein condensation (BEC), most famously observed in ultracold gases, that is bounded by lower and upper critical fields. Many compounds based on 3d magnetic cations have been found that exhibit a quantum dimer state with BEC. We have found a new realization of this state in Yb$_{\mathrm{2}}$Si$_{\mathrm{2}}$O$_{\mathrm{7}}$, which is of interest due to its high spin-orbit coupling, which leads to anisotropic exchange. Specific heat data shows a field-dependent Schottky-like anomaly peaked near 1 K and a low temperature transition to the BEC phase that appears at the first critical field. Single crystal inelastic neutron scattering was performed using the Cold Neutron Chopper Spectrometer at Oak Ridge National Laboratory. Changes in elastic and inelastic data occur at the same critical fields as specific heat measurements. However, these critical fields are much smaller than observed in known systems due to magnetism arising from 4f electrons, giving easier access to the full field vs. temperature phase diagram. [Preview Abstract] |
Friday, October 20, 2017 1:32PM - 1:44PM |
E3.00002: Transport and magnetic properties of thin films fabricated by magnetron sputtering Hiroto Kato, Ty Newhouse-Illige, Hamid Almasi, Weigang Wang Magnetron sputtering is a widely used technique for fabricating various thin film structures. We will present the design and construction of an ultra-high vacuum magnetron sputtering system. By avoiding the use of O-ring seals and using small chambers as the enclosure, the system maintains UHV efficiently and keeps the pumping time short. The small system size also worked economically well. This system has three sputtering guns for depositing metals or oxides. All sputtering guns are capable of accepting 1.5 and 2-inch targets. The designs have the capability of heating samples up to 800C while being sputtered and transferring the sample into another chamber without exposing samples to air. These greatly enhance our ability of thin film growth and reduce a risk of cross-contamination of systems or within a system. We will discuss the structural, magnetic and transport properties of the thin films fabricated by this system. [Preview Abstract] |
Friday, October 20, 2017 1:44PM - 1:56PM |
E3.00003: Pair Distribution Function (PDF) analysis of Barium Hexaferrite (BaFe12O19) nanocrystals Binod Paudel, Katharine L. Page, Daniel P. Olds, Edwin Fohtung Complex Ferroic Oxides such as Barium Hexaferrite is a multiferroic that can be driven far from equilibrium by external perturbations such heat, light, electric and magnetic fields. Four primary ferroic orders namely toroidal, dipole, elastic and magnetic moments can be tuned at the microscopic level and used in the design of novel devices and functional properties. It is critical to study the morphology and structural properties of Barium Hexaferrite nanocrystals to understand the origin of enhanced properties such as a large uniaxial anisotropy with the easy magnetization direction along the c-axis, high dielectric properties etc. Conventional crystallography doesn't accomplish the structure determination of nanocrystals due to the lack of long range ordering and the structural information contained on the local level is not unraveled through this technique even though it gives the average structure. Here, we used the pair distribution function (PDF) technique to investigate the structure on short, medium and long-range order. The analysis of Barium Hexaferrite is done by fitting the PDF data taken at two different temperatures (300K and 315K) with the idealized model PDF for three different r-ranges and the structural changes of the sample between these temperatures are also searched. [Preview Abstract] |
Friday, October 20, 2017 1:56PM - 2:08PM |
E3.00004: Glassy Behavior in a Crystalline Lattice: Substituted Hybrid Perovskites Eve Mozur, Annalise Maughan, Yongqiang Cheng, Ashfia Huq, Niina Jalarvo, Luke Daemen, James Neilson Hybrid perovskites are at the forefront of research for the next generation of semiconductors for solar cells, even though the fundamental physics behind their electronic properties are not well understood. The presence of a dynamic organic cation is typically thought to localize charge carriers, but hybrid perovskites preform competitively with conventional semiconductors. Therefore, many questions remain about the influence of an organic cation on the dynamics, structure, and phase behavior of a crystalline framework. We have characterized the crystallographic and dynamic behavior of the series (CH$_3$NH$_3$)$_{1-x}$Cs$_x$PbBr$_3$. Cs$^+$ substitution leads to the formation of an orientational glass, which can be described as a disordered molecular sublattice coupled to a periodic inorganic framework. We attribute the glassiness of the lattice to geometric strain at the substituted site. In (CH$_3$NH$_3$)$_{0.8}$Cs$_{0.2}$PbBr$_3$, a reentrant phase transition allows us to map the strain onto the cuboctahedral void, in terms of the shape of the cuboctahedral void and the organic cation orientation. Our results enable a better understanding of the complex energy landscape of hybrid perovskites, which is essential to building theoretical models to enable technological innovation. [Preview Abstract] |
Friday, October 20, 2017 2:08PM - 2:20PM |
E3.00005: Magnetron Sputtering of Arsenic Doped Zinc Oxide Thin Films Micah Shelley, John Colton, J. Ryan Peterson, Gary Renlund, David Allred Zinc Oxide (ZnO) is a wide band gap semiconductor (3.37 eV) with potential applications in LEDs and military technology. ZnO has native n-type defects, making production of p-type material difficult. In order to form p-type material we have deposited arsenic doped ZnO thin films (\textasciitilde 25 microns) by radio frequency magnetron sputtering of a ZnO target onto sapphire substrates coated with evaporated zinc arsenide (ZnAs). Annealing has been employed to improve sample structure. Thin film growth has been refined through characterization by x-ray diffraction techniques, Seebeck effect measurements, and photoluminescence. We will report on the quality of the thin films produced. [Preview Abstract] |
Friday, October 20, 2017 2:20PM - 2:32PM |
E3.00006: Magnetic Properties of Vanadium Oxide/Ferromagnetic hybrid composites Logan Sutton, Joshua Lauzier, Jose de la Venta The temperature dependence of the coercivity and magnetization of vanadium oxide/ferromagnet composite powders was studied. The vanadium oxides VO2 and V2O3 exhibit a well-known temperature induced Structural Phase Transition (SPT). When incorporated in ferromagnetic/vanadium oxide hybrid systems, the SPT of the oxide induces an inverse magnetoelastic effect that strongly modifies the coercivity and magnetization of ferromagnetic films (1) and powder composites (2). In this work different combinations of vanadium oxide and ferromagnetic powders were ball-milled and sintered to form a powder composite. Magnetic properties were measured using a Vibrating Sample Magnetometer. The milling and sintering conditions allow tuning of the magnetic properties. For some sintering conditions, irreversibility in the coercivity is observed after the first cycle of the thermally induced phase transformation. These results indicate that properties of vanadium oxide/ferromagnet composite hybrid powders are strongly affected by the strain induced SPT and that it is possible to control the magnetic properties by tuning the sintering conditions. 1. J. de la Venta el al Applied Physics Letters 104, 062410 (2014) 2. C. Urban et al 109, 112401 (2016) [Preview Abstract] |
Friday, October 20, 2017 2:32PM - 2:44PM |
E3.00007: Droplet Manipulation to Detect Surface Tesnion Sanli Movafaghi, Wei Wang, Ari Metzger, Desiree Williams, John Williams, Arun Kota Droplet manipulation on super-repellent surfaces has been widely studied using different methods because droplets exhibit high mobility, minimal contamination and minimal sample loss on such surfaces. However, to the best of our knowledge, there are no studies that employ super-repellent surfaces to sort droplets based on surface tension. In this work, we synthesized tunable superomniphobic surfaces with fluorinated, flower-like TiO$_{\mathrm{2}}$ nanostructures. We demonstrate that the surface chemistry of our superomniphobic surfaces can be tuned using UV irradiation. This allows us to systematically tune the mobility of droplets with different surface tensions on our superomniphobic surfaces. Each of these surfaces with same surface texture, but different solid surface energy allows certain high surface tension liquid droplets to freely roll past the surface while ``trapping'' other low surface tension liquid droplets due to adhesion. Leveraging this selective mobility of droplets based on their surface tension, we fabricated a simple device with precisely tailored discrete surface energy domains that, for the first time, can sort droplets by their surface tension. The novelty of our work lies in the design of discrete and tunable superomniphobic domains as well as the ability of the device to sort droplets by surface tension. We envision that our droplet sorting device will enable inexpensive and analytical devices for personalized point-of-care diagnostic platforms. [Preview Abstract] |
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