Bulletin of the American Physical Society
Inaugural Fall 2009 Meeting of the Prairie Section of the APS
Volume 54, Number 17
Thursday–Saturday, November 12–14, 2009; Iowa City, Iowa
Session F2: Condensed Matter Physics I |
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Chair: Giovanni Vignale, University of Missouri Room: IMU 243 (Ballroom) |
Friday, November 13, 2009 11:30AM - 12:06PM |
F2.00001: A Multispectroscopic Structural Study of Lead Silicate Glasses over an Extended Range of Compositions Invited Speaker: A series of lead silicate glasses, spanning the broadest reported range of lead contents (up to 83 molar percent PbO), were prepared, on which the following spectroscopic observations were made: $^{29}$Si magic angle spinning NMR, MS-TOF, Raman and FTIR. For bulk, splat-quenched samples, infra-red results indicate that the lever rule (Q$^{n} \rightarrow $ Q$^{n-1})$ is approximately followed until about 60 molar percent PbO, though with considerable dissociation of the stoichiometric groups into silicate units with lesser and greater numbers of non-bridging oxygens as shown in the equilibrium relation 2Q$^{n} \rightarrow $ Q$^{n+1}$ + Q$^{n-1}$. For roller-quenched samples, NMR data are consistent with a statistical distribution up to this lead concentration. Above 60 molar percent PbO, added oxygen remains associated with lead to form a separate lead oxide glass network. The evidence for this comes from each of the spectroscopic techniques employed. A quantitative distribution of PbO is given. [Preview Abstract] |
Friday, November 13, 2009 12:06PM - 12:18PM |
F2.00002: Controlling the spin-orbit amplitude in a non-flat quantum well Oleg Chalaev, Giovanni Vignale Using the inverse-scattering theory, we adjust the wave functions of a quantum well so that electrons occupying two lowest subbands conserve their spin projection, while the electrons occupying the third subband experience Rashba spin-orbit interaction. Shifting the Fermi level in the well with an external gate, one can drastically change the strength of the spin-orbit interaction felt by electrons. Such system can work as a spin-orbit trigger which has two states: (i) when the spin projection $s_z$ is a constant and (ii) when the spin precesses due to the spin-orbit interaction. [Preview Abstract] |
Friday, November 13, 2009 12:18PM - 12:30PM |
F2.00003: Characterization of PLZT Thin Films Hasitha Ganegoda, Carlo Segre, Beihai Ma, Lidens Cheng, Jeff Terry Ferroelectric lead lanthanum zirconate titanate (Pb$_{1.12}$La$_{0.08}$Zr$_{0.52}$Ti$_{0.48}$) of various thickness ($\sim $50-300nm) were fabricated by spin-coating metallo-organic solutions on Pt/TiO/SiO2/Si substrates, followed by heat treatment. The films were observed to be uniform and polycrystalline in nature. Slight modifications to the processing technique yielded either metallic or non-metallic samples. Increasing metallicity in the reaction products of the film may be one of the key factors that result in high leakage current in film-on-foil capacitors, which is detrimental to their operation as high voltage capacitors. In order to understand the mechanisms that resulted in metallic films, we utilized synchrotron radiation techniques for characterization. The samples were investigated using x-ray diffraction, photoemission, absorption spectroscopy, and resistance. Our preliminary measurements have shown interdiffusion of the metal foil into some of the thin films. Photoemission measurements show single peaks for Pb and Zr in the thinnest sample while thicker samples exhibit splitting for each of these peaks suggesting the existence of Pb and Zr in more than one chemical environment. [Preview Abstract] |
Friday, November 13, 2009 12:30PM - 12:42PM |
F2.00004: Magnetic impurities in Graphene: Electronic structure and RKKY interaction Mohammad Sherafati, Sashi Satpathy Graphene, a recently produced allotrope of carbon, is formed in a two-dimensional honeycomb structure and is a material of considerable current interest because of the possibilities in nano-device applications. Because of its unique linearly-dispersive band structure, graphene can have properties very different from any other two-dimensional material. We will present the nature of magnetic interaction between two magnetic impurities such as Fe placed on single layer graphene sheet. Results will be presented from detailed ab-initio electronic structure calculations as well as simple models incorporating the linear dispersion and compared to the results of the standard Ruderman-Kittel-Kasuya-Yosida model. It is shown that the linearly-dispersive band structure plays a significant role in determining the magnetic interaction between iron atoms. [Preview Abstract] |
Friday, November 13, 2009 12:42PM - 12:54PM |
F2.00005: Mechanisms of Laser Induced Modification of Lead and Barium Vanadate Glasses Mario Affatigato, Ruhil Dongol, Landon Tweeton, Cory Faris, Steve Feller We report on our investigations on the mechanisms for structural and morphological change in lead and barium vanadate glasses modified by 785 nm laser irradiation. The fundamental process is thermal in nature, leading to phase decomposition, phase changes, and mass transport in the center of the irradiated region, as well as the formation of lead- or barium-rich debris zones. Crystallization is also a consequence of the exposure to the laser light. We further report on pre-irradiation experiments in which low-power exposure above a determined energy threshold results in structural changes that bridge the gap between the amorphous state and the ultimate crystalline arrangement. Finally, we discuss the application of the laser irradiation in the making of vanadate microspheres. [Preview Abstract] |
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