Bulletin of the American Physical Society
APS March Meeting 2014
Volume 59, Number 1
Monday–Friday, March 3–7, 2014; Denver, Colorado
Session F3: Undergraduate Research - Society of Physics Students IV |
Hide Abstracts |
Sponsoring Units: SPS Chair: Crystal Bailey, American Physical Society Room: 107 |
Tuesday, March 4, 2014 8:00AM - 8:12AM |
F3.00001: Design of Rectangular Coils for Control of Magnetic Fields Ryan Daniels, Changgong Zhou Over the last decade, cylindrical cross-section (CCS) coils have encompassed the majority of studies (i.e., ``Double-Helix'' coils): predominantly for use in particle accelerators (Goodzeit et al., Rochford et al., and Tominaka et al.). In this study, we investigate single and double-layered rectangular cross-section (RCS) coils of different inclination angles. RCS coils are a novel design, which does not require special machining of grooves on supporting structure for precise assembly of coils, and may lead to cost reduction. Numerical calculation of the field based on Biot-Savart's Law is conducted using Mathematica. Our goal is to generate a static and controllable time-varying magnetic field using a special configuration of four RCS coils, and impose the field on magnetic nanoparticles levitated by optical forces to study their behavior. The calculation provides guidance for optimizing the magnetic field in this application. Our current results indicate that the configuration produces highly uniform and controllable magnetic fields in the region where the nanoparticles are levitated. [Preview Abstract] |
Tuesday, March 4, 2014 8:12AM - 8:24AM |
F3.00002: Magnetic Phase Transitions in Intercalated Dichalcogenide Nanostructures Corbyn Mellinger, Corey Cooling, Kayla Boyle, Paul Shand, Tim Kidd, Laura Strauss Nanostructured Mn-intercalated TaS$_{\mathrm{2}}$ was prepared with a nominal Mn concentration of 23.5{\%}. Powder x-ray diffraction confirms incorporation on Mn in the Van der Waals gaps between TaS$_{\mathrm{2}}$ layers. AC susceptibility measurements in a DC bias field indicate the sample displays paramagnetic behavior down to its Curie-Weiss temperature of 75 K. An Arrott plot confirms the transition to the ferromagnetic state, with critical exponent $\beta $ larger than expected for the Heisenberg 3D model. Further analysis of the AC susceptibility indicates a transition to cluster-glass state around 40 K, indicated by Vogel-Fulcher analysis near the transition temperature. We believe the difference from expected critical exponent values to be due to the proximity of the ferromagnetic and cluster-glass transitions. [Preview Abstract] |
Tuesday, March 4, 2014 8:24AM - 8:36AM |
F3.00003: Field Directed Ordering in Magnetic Nanocrystal Structures Stuart Lawson, Joshua Wright, Robert Meulenberg Iron oxide nanocrystals (NCs) have been the focus of intense research owing to the observation of tunable magnetic properties which could lead to advances in many fields including magnetic storage devices and medicine. We have been targeting the use of iron oxide NCs as magnetoresistance (MR) based sensors using ordered NC arrays. In this work, we will present our efforts toward using external magnetic fields to induce intraparticle ordering in iron oxide NC drop cast films. We use x-ray diffraction to analyze effects of the external fields on the NC array structure, while using SQUID magnetometry to probe the effects of NC interactions on the magnetic properties of iron oxide NCs ranging from 5 - 20 nm in diameter. MR measurements suggest large changes in the MR ratio can be achieved using the directed ordering approach for NC arrays. Our work could provide new avenues towards the fabrication of new magnetic devices. [Preview Abstract] |
Tuesday, March 4, 2014 8:36AM - 8:48AM |
F3.00004: Temperature Dependence of the Spin Hall Effect in Perpendicularly Magnetized Magnetic Materials Shuoying Yang, Weifeng Zhang, Salvatore Mesoraca, Aakash Pushp, Timothy Phung, See-hun Yang, X.M. Cheng, Stuart S.P. Parkin The spin Hall effect (SHE) and spin torque generated from it have been of great interest recently due to their potential use in future spintronic memory and logic devices. A solid understanding of the detailed mechanisms behind SHE is key to effectively utilizing and enhancing this effect. In this work, we report the experimental study of switching perpendicularly magnetized magnetic layers using the spin torque from SHE. Multilayers with the repeated units consisting of normal metal (Pt or Ta)/ ferromagnet with perpendicular magnetic anisotropy (CoFeB, CoNiCo, or Co) were deposited on Si substrates by sputtering deposition. Magnetoresistance and Hall resistance of the samples were measured by the Quantum Design PPMS DynaCool system with the field up to 6 tesla at various temperatures ranging from 10 K to 300 K. The spin Hall angle, calculated by comparing the field dependence of Hall resistance measured with the currents of the same magnitude but opposite directions, depends linearly on temperature. The contributions of the skew-scattering and side-jump mechanisms to SHE have been quantitatively separated. [Preview Abstract] |
Tuesday, March 4, 2014 8:48AM - 9:00AM |
F3.00005: Distortions in 2p4d Partial Fluorescence yield for 4d elements Alexander Price, Frank de Groot, Trinanjan Datta X-ray absorption spectroscopy (XAS) is a standard tool to determine the electronic structure of molecules and materials. CTM4XAS and CTM4RIXS are semi-empirical programs to analyze transition metal L$-$ and M$-$ edge transitions by evaluating the effects of crystal field and charge transfer parameters on the atomic multiplets. We compute and compare the XAS and the fluorescence yield (FY) XAS, of the 3d and 4d transition metal ions. In the case of 2p edges of 3d elements Auger decay dominates and sets the time scale. The 2p3d X$-$ray emission spectra (XES) accounts for approximately 80\% of the radiative decay. The 2p3d partial FY is distorted and because it dominates the FY, the total FY is also distorted. For the 4d elements the 2p4d XES decay is approximately 10\% of 2p3d XES decay, implying that (the energy-constant) core-core XES and Auger channels dominate the decay. The computed 2p4d partial FY$-$XAS spectra are different from the 2p XAS. Although 2p4d partial FY is distorted, the total FY is not because it is dominated by 2p3d XES. We also find that the 2p3s and 2p4s XES channels contribute less than 1\% and can be neglected. [Preview Abstract] |
Tuesday, March 4, 2014 9:00AM - 9:12AM |
F3.00006: Structural and Electrical Properties of Thin Films of Electron-doped Mixed-Valent Rare Earth Manganites Zoey Warecki, Grace Yong, David Schaefer, Rajeswari Kolagani Research in thin films of mixed valent rare earth manganese oxides has largely been focused on hole-doped manganites that exhibit colossal magnetoresistance. Hole doped manganites are derived from trivalent rare earth manganese oxides, where the hole doping (introduction of Mn$^{\mathrm{4+}}$ ions to replace the Mn$^{\mathrm{3+}}$ ions) is the result of substitution of the trivalent rare earth site (such as La$^{\mathrm{3+}})$ by a divalent alkaline earth element (such as Ca$^{\mathrm{2+}})$. In contrast, electron doped manganites can be obtained by introducing Mn$^{\mathrm{3+}}$ ions to replace Mn$^{\mathrm{4+}}$ ions in an alkaline earth manganese oxide. We are currently investigating the properties of electron-doped manganites which are derived from CaMnO$_{\mathrm{3}}$. We use Pulsed Laser Deposition to grow these epitaxial thin films. One way to introduce electron carriers in the film is by creating an oxygen poor environment during the deposition, causing the film composition to be of the form Ca$^{\mathrm{2+}}$Mn$^{\mathrm{4+}}_{\mathrm{1-2x}}$Mn$^{\mathrm{3+}}_{\mathrm{2x}}$O$^{\mathrm{2\thinspace -}}_{\mathrm{3-x}}$. Another method is by substitution of the Ca$^{\mathrm{2+}}$ site by rare earth elements of valency 3$+$ or higher (such as Ce$^{\mathrm{4+}}$ or Ho$^{\mathrm{4+}})$ to introduce electron carriers. We will report our study of the structural, electrical, and magneto-transport properties of electron doped manganite thin films, focusing on the sensitivity of these properties to growth parameters. [Preview Abstract] |
Tuesday, March 4, 2014 9:12AM - 9:24AM |
F3.00007: Fluid Manipulation Utilizing Electrowetting Techniques Laura Kaiser, Laura Pyrak-Nolte The fraction of the pore space in rock occupied by a given fluid is called saturation. The relationship between saturation and capillary pressure for porous media is hysteretic between imbibition and drainage cycles. If the wetting phase saturation increases, the capillary pressure follows an imbibition curve, and, if the wetting phase saturation decreases, the capillary pressure follows the drainage curve. Due to this hysteresis, researchers have suggested that there is a third variable that should be considered called interfacial area per volume that removes the ambiguity in the capillary pressure - saturation relationship. Before the relationship can be explored in more detail, we first must be able to manipulate the saturation internally rather than externally. We used electrowetting techniques to manipulate the contact angle of a salt water drop. This technique affects the interfacial energy and, therefore, enables manipulation of the contact angles and saturation. Once mastered, the technique could be used to explore the effect of interfacial area per volume on micromodel systems. [Preview Abstract] |
Tuesday, March 4, 2014 9:24AM - 9:36AM |
F3.00008: Understanding the Cytoxicity of Permalloy Microdisks Aleksandra Karapetrova, Elena Rozhkova, Valentin Novosad, Philip Gach Nanomagnetic materials offer exciting opportunities when attempting remote control of biological processes. For example, ferromagnetic microdisks are able to induce apoptosis via magnetomechanical stimulus. The rotation of the disks occurs under an alternating magnetic field. A spin vortex state is formed in the microdisk that gives them the ability to not congregate in the absence of magnetic field but to be mechanically responsive in the presence of field. Iron-nickel Permalloy disks are fabricated using optical lithography and metal deposition. The disks can be made with a layer of gold on the top and bottom sides for the purpose of surface functionalization such that fluorescent dyes and biological compounds can be bound. Since the magnetic core of the disks consists of a transition metal alloy, there is a possibility of reactive oxidative species (ROS) forming in aqueous solution by a Fenton reaction. The chemical stability of disks not coated with a gold layer were studied. ROS formation was detected using fluorescent probe hydroxyphenyl fluorescein, X-ray fluorescence microscopy, and Inductively Coupled Plasma-Mass Spectrometry (ICP-MS). No significant levels of hydroxyl radicals were detected at neutral pH. However, X-Ray fluorescence and ICP-MS did detect leaching. [Preview Abstract] |
Tuesday, March 4, 2014 9:36AM - 9:48AM |
F3.00009: Influence of Crowding on Polymer Conformations in Polymer-Nanoparticle Mixtures: Monte Carlo Simulations Wei Kang Lim, Alan R. Denton Within the cytoplasm and nucleoplasm of eukaryotic cells, a complex mixture of macromolecules (biopolymers, such as proteins and RNA) and smaller molecules share a tightly restricted space. In this crowded environment, hard nanoparticles exclude volume to softer biopolymer coils, restricting protein and RNA conformations and folding pathways. At sufficiently high concentrations, nanoparticle crowding also can affect phase stability, inducing aggregation or separation into polymer-rich and polymer-poor phases. Through Monte Carlo simulations, we explore the impact of crowding on polymer conformations and phase behavior in a coarse-grained model of polymer-nanoparticle mixtures. Neglecting polymer self-interactions, we exploit the random-walk geometry of ideal coils to model the polymers as effective ellipsoids whose shapes fluctuate according to the probability distribution of the gyration tensor. Accounting for penetration of polymers by smaller nanoparticles, we calculate the crowding-induced shift in the polymer shape distribution. We compare our results with predictions of a free-volume theory and available experimental data. [Preview Abstract] |
Tuesday, March 4, 2014 9:48AM - 10:00AM |
F3.00010: Microwave Directional Coupler for Quantum Measurement Victoria Xu, Chris Macklin, Andrew Eddins, Irfan Siddiqi We present the design of a 20dB single-section directional coupler using two edge-coupled, conductor-backed coplanar waveguides (CPW). We begin with an electromagnetic analysis of the physical mechanisms that allow two waveguides to form a directional coupler. Based on the coplanar waveguide geometry used for the coupler, we experienced inherently limited directivity in the performance, and we discuss the mechanisms by which we optimize for directivity despite geometric limitations. After laying out the theory behind CPW directional couplers, an electromagnetic analysis of our simulated design is presented. Two iterations of designs were fabricated. The final directional coupler yields simulated and measured performance even beyond the level of our design goals. At the center frequency of 6 GHz, our coupler showed comparable performance to commercial directional couplers. The 20-dB directional coupler serves as a solid-state equivalent of a 99/1 beam splitter for microwave photons, and will further enable on-chip experiments in quantum measurement. [Preview Abstract] |
Tuesday, March 4, 2014 10:00AM - 10:12AM |
F3.00011: Non-linear Multidimensional Optimization for use in Wire Scanner Fitting Alyssa Henderson, Balsa Terzic, Alicia Hofler To ensure experiment efficiency and quality from the Continuous Electron Beam Accelerator at Jefferson Lab, beam energy, size, and position must be measured. Wire scanners are devices inserted into the beamline to produce measurements which are used to obtain beam properties. Extracting physical information from the wire scanner measurements begins by fitting Gaussian curves to the data. This study focuses on optimizing and automating this curve-fitting procedure. We use a hybrid approach combining the efficiency of Newton Conjugate Gradient (NCG) method with the global convergence of three nature-inspired (NI) optimization approaches: genetic algorithm, differential evolution, and particle-swarm. In this Python-implemented approach, augmenting the locally-convergent NCG with one of the globally-convergent methods ensures the quality, robustness, and automation of curve-fitting. After comparing the methods, we establish that given an initial data-derived guess, each finds a solution with the same chi-square- a measurement of the agreement of the fit to the data. NCG is the fastest method, so it is the first to attempt data-fitting. The curve-fitting procedure escalates to one of the globally-convergent NI methods only if NCG fails, thereby ensuring a successful fit. This method allows for the most optimal signal fit and can be easily applied to similar problems. [Preview Abstract] |
Tuesday, March 4, 2014 10:12AM - 10:24AM |
F3.00012: Simulating FinFET Self-Heating for Device Reliability James Ham, Lincoln Carr, Carole Graas The continual scaling of transistors has led to sharp gradients in temperature (from ballistic transport of carriers) that result in new difficulties modeling device reliability. Current device-level thermal simulations do not track phonon populations, which are necessary to understand damage from high temperatures in scaled devices. A model for simulating highly localized hot spots due to an optical phonon bottle-neck near the channel/drain interface of a device operating in a ballistic transport regime will be presented. Various expansions of the Boltzmann transport equation (spherical harmonic expansion and methods of moments) are compared to a hydrodynamic model for device thermal simulations. We will discuss the post-processing technique for arriving at phonon populations from technology computer aided design (TCAD) simulations. [Preview Abstract] |
Tuesday, March 4, 2014 10:24AM - 10:36AM |
F3.00013: Scanning capacitance microscopy using a relaxation oscillator Marie Pahlmeyer, Andrew Hankins, Sam Tuppan, Woo-Joong Kim We have performed scanning capacitance microscopy using a relaxation oscillator. Calibrations using precision capacitors indicate a sensitivity on the order of 0.05 pF, stabilizing in under 0.1s. Surface topography of metallic structures, such as machined grooves and coins, can be readily obtained either in the constant-height (non-contact) or tapping (contact) mode. Spatial resolution of sub-50 $\mu$ micron has been achieved. [Preview Abstract] |
Follow Us |
Engage
Become an APS Member |
My APS
Renew Membership |
Information for |
About APSThe American Physical Society (APS) is a non-profit membership organization working to advance the knowledge of physics. |
© 2024 American Physical Society
| All rights reserved | Terms of Use
| Contact Us
Headquarters
1 Physics Ellipse, College Park, MD 20740-3844
(301) 209-3200
Editorial Office
100 Motor Pkwy, Suite 110, Hauppauge, NY 11788
(631) 591-4000
Office of Public Affairs
529 14th St NW, Suite 1050, Washington, D.C. 20045-2001
(202) 662-8700