Bulletin of the American Physical Society
2020 Annual Meeting of the APS Four Corners Section (Virtual)
Volume 65, Number 16
Friday–Saturday, October 23–24, 2020; Albuquerque, NM (Virtual)
Session E03: Condensed Matter Physics IILive
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Chair: Benjamin Frandsen, BYU |
Friday, October 23, 2020 2:00PM - 2:24PM Live |
E03.00001: Exploring the Rich Physics of Triangular Lattice Antiferromagnets with Neutron Scattering Invited Speaker: Benjamin Frandsen In geometrically frustrated magnets, the spatial arrangement of magnetic moments on a lattice prevents competing magnetic interactions from being simultaneously satisfied, often leading to exotic magnetic behavior. The canonical example of geometrical frustration consists of antiferromagnetically coupled spins populating a triangular lattice. Here, we explore the compound TmMgGaO$_{\mathrm{4}}$, which hosts Ising-like Tm$^{\mathrm{3+}}$ magnetic moments on a perfect triangular lattice. Using magnetic pair distribution function analysis of neutron scattering data, we study the short-range magnetic correlations present at low temperatures. The results suggest a surprising connection to a topological Kosterlitz-Thouless transition at low temperature, showcasing the rich behavior observed in geometrically frustrated magnets. [Preview Abstract] |
Friday, October 23, 2020 2:24PM - 2:36PM Live |
E03.00002: Abrupt structural transition in V 2 O 3 revealed by pair distribution function analysis Ethan Fletcher, Benjamin Frandsen, Kentaro Higashi, Hiroshi Kageyama V$_{\mathrm{2}}$O$_{\mathrm{3}}$ is a popular system for studying Mott insulators, which are materials that are driven into an insulating state by strong electron correlations. Despite decades of research, a complete understanding of the metal-insulator transition in V$_{\mathrm{2}}$O$_{\mathrm{3}}$ has not been conclusively established. Here, we present comprehensive atomic and magnetic pair distribution function (PDF) analyses of V$_{\mathrm{2}}$O$_{\mathrm{3}}$ using both x-ray and neutron total scattering measurements, shedding new light on the mechanism of the transition from the point of view of short-range structural and magnetic correlations on both sides of the transition. We observe an abrupt structural transition with no hint of short-range monoclinic distortions above the transition temperature. This lack of structural fluctuations above the transition contrasts with the known presence of magnetic fluctuations in the high-temperature state, suggesting that the lattice degree of freedom plays a secondary role behind the spin degree of freedom in the transition mechanism. [Preview Abstract] |
Friday, October 23, 2020 2:36PM - 2:48PM Live |
E03.00003: Useful Predictions of Materials Begin with Accurate Band Integration Jeremy Jorgensen, Tom Sederberg, Gus Hart Technologies are often limited by the properties of available materials, and so discovering materials with superior properties will advance technology. We are able to simulate many possible materials and predict their properties with computers and scientific software. The properties of materials are obtained by integrating the material's electronic band structure. The electronic band structure is qualitatively a collection of intersecting sheets. Efforts have been made to separate the sheets to simplify calculations of properties of materials. We mathematically describe the electronic band structure, answer the question: ``Are the electronic energy sheets separable?", and study the role intersecting sheets play in the calculations of properties of materials. [Preview Abstract] |
Friday, October 23, 2020 2:48PM - 3:00PM Live |
E03.00004: Machine Learning Utilization for Temperature Predictions from Photoluminescence Properties of CdTe Quantum Dots Marissa Iraca Minute temperature changes in biological systems can result in the unraveling of DNA sequences or cause mutations. When studying these biological samples within a microfluidic device, a sensor that can detect these minute changes in temperature is necessary. A sensitive temperature detector was developed by training a neural network with spectral and time-resolved photoluminescence data. This data was recorded with corresponding temperature from a cadmium telluride quantum dot sample that emitted at around 808nm. The photoluminescence data was used as an input and the corresponding temperature was used as an output when training the neural network. Using the trained neural network, temperature predictions within a mean absolute error of 0.599 K were achieved. [Preview Abstract] |
Friday, October 23, 2020 3:00PM - 3:12PM |
E03.00005: Ab Initio Study of the Influence of Structural Defects on the Electrochemical Properties of MnO$_{\mathrm{2}}$ in Rechargeable Zn/MnO$_{\mathrm{2}}$ Alkaline Batteries Nirajan Paudel, Birendra Magar, Timothy Lambert, Igor vasiliev The performance of MnO$_{\mathrm{2}}$ electrodes in rechargeable solid-state alkaline Zn/MnO$_{\mathrm{2\thinspace }}$batteries can be enhanced by nanostructuring and by introducing cation and oxygen vacancies into the crystal structure of MnO$_{\mathrm{2}}$. However, the mechanism of this enhancement has not been investigated in detail. We apply \textit{ab initio} density functional computational methods to study the mechanism of hydrogen ion insertion into the structures of $\beta $-, R-, and $\gamma $-MnO$_{\mathrm{2}}$ polymorphs containing cation vacancies, oxygen vacancies, and surfaces. Our calculations show that the presence of bulk defects and surfaces significantly changes the binding energies of hydrogen ions inserted into the crystal structures of MnO$_{\mathrm{2}}$ polymorphs. The results of our study show that surfaces and structural defects have a strong influence on the electrochemical properties of MnO$_{\mathrm{2}}$. [Preview Abstract] |
Friday, October 23, 2020 3:12PM - 3:24PM |
E03.00006: The effect of x-ray illumination on magnetic domain memory in [Co/Pd] / IrMn multilayers Colby Walker, Mason Parkes, David Keavney, Eric Fullerton, karine Chesnel We are studying the effect that illumination by coherent x-rays may have on magnetic domain memory (MDM) in a [Co / Pd] / IrMn multilayers. MDM is the ability of the magnetic domains to retain their exact same domain topology upon field cycling. Earlier studies have suggested that under higher dose of x-ray illumination, the material may lose its existing MDM. To investigate this potential effect, we have used both x-ray resonant magnetic scattering (XRMS) along with magneto-transport measurements to track the exchange bias while the sample is illuminated with x-rays. Magneto-transport is here used to measure the hysteresis loop of our multilayers material from which we can measure the exchange bias and its possible alteration. A loss of exchange bias would indicate that the x-rays illumination dose may alter the strength of the exchange couplings and ultimately the amount of MDM. Knowing if a loss of exchange bias has occurred requires collecting magneto-transport data as well as XRMS data and correlating the observed changes under various dose of x-ray illumination. I will show magneto-transport results obtained in the presence and in the absence of x-ray illumination, that provides with preliminary answers. [Preview Abstract] |
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