Bulletin of the American Physical Society
APS March Meeting 2018
Volume 63, Number 1
Monday–Friday, March 5–9, 2018; Los Angeles, California
Session A06: Undergraduate Research IUndergraduate
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Sponsoring Units: APS SPS Chair: Crystal Bailey, American Physical Society Room: LACC 153A |
Monday, March 5, 2018 8:00AM - 8:12AM |
A06.00001: Fabrication of High–Quality Croconic Acid thin films Erika Sanchez Ferroelectric materials have demonstrated diverse technological applications, with thin films of particular interest. Croconic Acid, an organic ferroelectric, is promising due to its economic, scalable production and large ferroelectric polarization. The films are prepared in a thermal deposition chamber under an ultrahigh vacuum system at a pressure of at least 1×10^-7 Torr. The bulk material is heated at about 130°C to 140°C. During the deposition, electric field guidance is utilized in order to promote the alignment of Croconic Acid molecules as they make their way to an ultra-flat substrate. Here we present results on room temperature growth of Croconic Acid thin films using two different methods to create an electric field in order to achieve a high quality smooth surface film. One method was using a mesh screen and the other was using a metal washer in order to create an electric field, each of an equal strength of 2kV. Atomic force microscopy was used to assess film thickness and surface structure and roughness. |
Monday, March 5, 2018 8:12AM - 8:24AM |
A06.00002: Fabrication and characterization of magnetic-vortex microdiscs for applying force in mechanobiological systems Cassie Wang, Andy Clark, Zhongying Yan, Baiyi Kong, Xuemei Cheng Applying controlled, localized force in 3D mechano-biological systems has been a technical hurdle for probing cell mechanics. Bio-functionalized magnetic microdiscs have been used to apply force to cancer cells triggering apoptosis because of the advantage of a near zero stray field magnetic vortex configuration that prevents agglomeration when in solution.[1] In this work, we have fabricated discs with diameters ranging from 0.5 – 10 μm through lithography and sputtering. To guide the design of the microdiscs for biological applications, micromagnetic simulations, formulated with the Landau-Lifshitz equation, were performed using MUMAX3. Atomic force microscopy, small angle x-ray reflectivity, and scanning electron microscopy results confirm the desired characteristics of the discs. |
Monday, March 5, 2018 8:24AM - 8:36AM |
A06.00003: Synthesis and Characterization of Iron Oxide Nanotubes for Targeted Hyperthermia and Drug Delivery Jason Cardarelli, Raja Das, Manh-Huong Phan, Hariharan Srikanth Iron oxide nanoparticles have been studied for magnetic hyperthermia and targeted drug delivery applications due to their tunable magnetic properties and biocompatibility. However, the low heating efficiency (evaluated as Specific Absorption Rate - SAR) of these magnetic particles hinders their practicality. It has recently been shown that increasing the anisotropy of the nanoparticles by synthesizing one-dimensional (1D) nanorods with high saturation magnetization (SM), their SAR value increases significantly. We propose 1D magnetic nanotubes due to an enhanced surface area compared to nanorods. Crystalline, tunable aspect ratio Fe3O4 nanotubes have been synthesized using a hydrothermal method. Magnetic measurements show a clear Verwey transition and a high SM at 300 K, confirming a high quality of the nanotubes. Calorimetric experiments on the nanotubes dispersed in water (1mg/mL) show a large SAR value of 400 W/g in an AC magnetic field of 800 Oe. Our study shows the potential of using Fe3O4 nanotubes as a multifunctional tool for targeted hyperthermia and drug delivery. |
Monday, March 5, 2018 8:36AM - 8:48AM |
A06.00004: Studying the Synthesis of Few-Layer CVD h-BN for Graphene Devices Stanley Liu, Stephen Gilbert, Alex Zettl Hexagonal boron nitride’s (h-BN) high in-plane mechanical strength and chemical inertness support its role in many applications including protective coatings, transparent membranes and deep ultraviolet emitters. In particular, h-BN has a unique role as a dielectric layer when paired with graphene due to its similar lattice spacing and large bandgap. In order to optimize these effects, we need control over the properties of h-BN films, including layer number, grain size and crystal quality. Chemical vapor deposition (CVD) synthesis of h-BN has been the subject of intense research. Here we outline the growth dynamics of few-layer single crystal h-BN. We report the role of conditions such as cooling rate, hydrogen flow and catalyst temperature and characterize our films using scanning electron microscopy to study the overall growth mechanism. |
Monday, March 5, 2018 8:48AM - 9:00AM |
A06.00005: Synthesis and Magnetic Characterization of Cerium Orthoferrite CeFe1-xCrxO3 Jesus Perez, Josefa Gregorio, Stephen Tsui The rare-earth orthoferrites RFeO3(R being a rare earth metal) have been extensively investigated for their magnetic properties, in particular the spin reorientation (SR) transition whereby the net magnetic moment due to the spin configuration rotates in response to changing temperature. |
Monday, March 5, 2018 9:00AM - 9:12AM |
A06.00006: Structural and Magnetic Characterization of HoFexV1-xO3 Josefa Gregorio, Jesus Perez, Alejandro Zafra, Lorena Aguirre, Stephen Tsui We investigate the synthesis, structure, and magnetic behavior of the orthoferrivanadate compound HoV1-xFexO3, a chemically doped variant of HoFeO3 which is known to have an electronic spin reorientation (SR) transition at low temperature. Our results show that the SR temperature is increased by V substitution, likely due to the V interfering with the Fe-Fe interactions.The crystal structure was obtained using X-ray diffraction, and the magnetic properties were characterized via vibrating sample magnetometry. |
Monday, March 5, 2018 9:12AM - 9:24AM |
A06.00007: Exchange Bias of Py-Based Ferromagnetic Multilayers Compared to Their Alloy Frank Schooner, Kristen Repa, Casey Miller The objective of this experiment is to compare the exchange bias of a Py-based alloy film with several multilayer structures with both total thickness and net magnetization equal to the alloy. Samples were made via DC magnetron sputtering using permalloy (Py=Ni0.8Fe0.2) and Py0.8Cu0.2 as the ferromagnets in equal proportions to create an overall alloy of Py0.9Cu0.1 with a total thickness of 20 nm. The films are exchange biased by an 8 nm layer of IrMn and capped with a 5 nm layer of Ta to avoid oxidation. Py0.9Cu0.1 (20 nm)/IrMn vs. [Py0.8Cu0.2(t)/ Py(t)]X/IrMn, where x ranges from 2 to 20 and t is chosen such that 2t*x = 20nm. In this presentation we discuss the results of magnetometry by comparing MOKE and VSM measurements to understand how the multilayer structures differ from the alloy. |
Monday, March 5, 2018 9:24AM - 9:36AM |
A06.00008: Computational Optimization of Monte-Carlo Simulation of Magnetic Ising Models Patrick Gemperline, David Jonathan Morris, David Gerberry Sodium cobaltate has versatile characteristics that have been studied as potentially being used as a battery cathode, good thermoelectric material, and a superconductor when hydrated. Mobile sodium ions in NaxCoO2 can occupy two energetically different neighboring sites in the crystal structure. By mapping the neighboring sites onto Ising spins we are able to study the ground-state structures using Monte-Carlo simulations. In addition to general computational optimizations, various sampling methods of parameter space (i.e. uniform grid, Monte Carlo sampling and Latin Hypercube sampling) are compared to show how computational efficiency can be improved while retaining the completeness of the simulation results. |
Monday, March 5, 2018 9:36AM - 9:48AM |
A06.00009: Charge Offset Drift in Silicon Single Electron Devices: Geometrical Considerations Erick Ochoa, Binhui Hu, Daniel Sanchez, Justin Perron, Michael Stewart Single electron devices (SEDs) have applications in metrology and quantum computing. Using SEDs necessitates stability in the operating point. The low-frequency stability of a SED can be quantified with a measurement of charge offset drift. One of the difficulties that arises with these types of measurements is differentiating between drift inherent in the device and extrinsic drift caused by the measurement setup. To this end, measurements of nominally identical devices were carried out using different cryogenic and electronic systems. In addition to verifying that the measured drifts are the result of the SEDs, our measurements confirm a gate design dependence of charge offset drift. Combined with the previously observed materials dependence this design dependence provides the first steps toward a more complete picture of what influences low-frequency charge noise in SEDs. |
Monday, March 5, 2018 9:48AM - 10:00AM |
A06.00010: Abstract Withdrawn
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Monday, March 5, 2018 10:00AM - 10:12AM |
A06.00011: Theory of Multi-band Indirect K-edge Bimagnon Resonant Inelastic X-ray Scattering Spectrum Sean Mongan, Trinanjan Datta, Zengye Huang, Dao-Xin Yao Magnetic correlations can give rise to two electron spin-flip (bimagnon) excitations in a quantum Heisenberg magnet. In recent years Resonant Inelastic X-ray Scattering (RIXS) has emerged as a powerful spectroscopic technique to study elementary excitations, including bimagnon processes, across the entire Brillouin zone in strongly correlated materials. Utilizing linear spin wave theory, I will describe our research effort to compare and contrast the results of the RIXS response of a bicollinear antiferromagnet (α-FeTe) and the block collinear antiferromagnet (K2Fe4Se5) system, respectively. We will highlight the various features of the intraband and interband RIXS scattering channels, including the presence or absence of multi-peak structures. The number of peaks provide a clue on the various bimagnon excitation processes that can be supported both in and within the acoustic and optical magnon branches present in the material. |
Monday, March 5, 2018 10:12AM - 10:24AM |
A06.00012: Development of a New Pressure Measuring Technique for Examining Pressure Gradients in Solid Helium Aleksandar Tadic, Michael Ray Recent solid helium experiments have shown interesting, unexpected effects that occur within the solid, such as the appearances of pressure differences between the edges of the solid [1]. In order to explore these effects, we are developing new methods to measure pressure gradients inside of the solid sample. We have performed preliminary tests of a resistive sensor at liquid nitrogen temperature. Measurements of the sensor's response were made up to 31 bars, and while the force sensor is seen to react to the pressure change, further noise reduction is required in order to increase the precision of measurements. |
Monday, March 5, 2018 10:24AM - 10:36AM |
A06.00013: Dancing Our Way to Mars Through Physics Justine Walker, John Lindner, Kim Tritt How does gravity affect the efficiency of dance movements? We expect the fundamentals of various dance forms to change drastically at Earth, Mars, and lunar gravity. The efficacy of movements are altered in lower gravities by changes in natural oscillation frequencies and a dancer’s kinesphere. We simulate lower gravities using a pulley counterweight system connected to a dancer in a two-point harness. The dancer moves on a treadmill (non-stationary movements) or a force mat (stationary movements). Quantitatively, we compare motion tracking data from two perpendicular cameras for each dancer and movement at the three gravities. Qualitatively, we consider the dancers’ feedback and our choreographic experiences in relation to post-modern dance. As physicists we thereby better understand the mechanics of the human body in various gravities, beyond the walking-running transition. Engineers can incorporate our results when creating space habitats. Earth-based choreographers can create dances inspired by our lower gravity experiments. Our work highlights obstacles and opportunities for movement in space colonies, which will expand our understanding both of movement and of what it means to be human. |
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