Bulletin of the American Physical Society
2007 APS Four Corners Section/SPS Zone 16 Joint Fall Meeting
Volume 52, Number 14
Friday–Saturday, October 19–20, 2007; Flagstaff, Arizona
Session G1: Condensed Matter: Structure Characterization |
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Chair: David Cornelison, Northern Arizona University Room: Chemistry (Bldg. 20) Room 224 |
Saturday, October 20, 2007 8:15AM - 8:27AM |
G1.00001: AFM and TEM Studies on the Phase Transition of Micro and Nanocrystalline Films of Vanadium Dioxide Felipe Rivera, Mike Clemens, Brady Cox, Robert Davis, Richard Vanfleet Bulk crystalline vanadium dioxide undergoes an insulator (semiconductor) to metal phase transition near 68 degrees Celsius, and consequently has potential electronic and optical applications. Solid crystalline thin films and isolated particles up to 1 micron in size were produced through an anneal process of an amorphous thin film. The phase transition in these films and particles was studied using capacitive AFM measurements and with electron microscopy. A geometric enhancement was observed in the capacitance measurements of these films. [Preview Abstract] |
Saturday, October 20, 2007 8:27AM - 8:39AM |
G1.00002: Mapping of GeSbTe Thin Film Electrical Properties with Conductive AFM Jordan Brocious, Colin Inglefield, David Bobela, Thomas Herring, P. Craig Taylor The phase-change material system GeSbTe (GST) is currently used for optical data storage, however many details of the mechanism governing the phase change are not understood. GST's optical properties and electrical conductivities differ between the amorphous and crystalline phases. For instance, the electrical conductivity in the amorphous phase can be $\sim $10$^{3}$ times smaller than electrical conductivity in the crystalline phase. Thin films of Ge$_{2}$Sb$_{2}$Te$_{5 }$ and other alloys were created by a RF sputtering technique, which is known to produce amorphous samples. Crystalline regions were created after growth by localized laser heating. We characterized these films with Conductive Atomic Force Microscopy, which provides physical and electrical topography images. From this characterization we have identified sparse $\sim $100 nm highly conductive regions in the overall low-conductivity amorphous material. Although the laser treatment does not result in a uniformly conductive film, conductive regions in the treated material are significantly denser and larger. [Preview Abstract] |
Saturday, October 20, 2007 8:39AM - 8:51AM |
G1.00003: Electronic properties of single crystalline UNi$_{0.39}$Rh$_{0.61}$Al Farzana Nasreen, Sami El Khatib, Alexander Andreev, Alex Lacerda, Heinrich Nakotte U(Ni,Rh)Al alloys crystallize in the hexagonal ZrNiAl structure. Here, we report on measurements on a single-crystalline member of this series, namely UNi$_{0.39}$Rh$_{0.61}$Al. Similar to other members of this series, this compound exhibits highly anisotropic properties with the easy magnetization direction along the $c$-axis. We report in the results of electrical resistance, magnetoresistance and thermal expansion as a function of temperature (2-300 K) and applied magnetic field (0-18 T). The results provide strong evidence for antiferromagnetic ordering at T$_{N} \le $ 15 K followed by a ferromagnetic transition around 7 K. A magnetic B-T phase diagram for UNi$_{0.39}$Rh$_{0.61}$Al is proposed. [Preview Abstract] |
Saturday, October 20, 2007 8:51AM - 9:03AM |
G1.00004: X-ray diffuse scattering from a ferroelectric relaxor Va Yee Vue, Branton J. Campbell Piezoelectric relaxor crystals of PZN-4.5{\%}PT, a solid solution of Pb(Zn$_{1/3}$Nb$_{2/3})$O$_{3}$ and PbTiO$_{3}$ perovskites, displays a remarkably-high piezoelectric response of 4500 pC/N. In recent years, PZN-PT has become a popular ceramics for a variety of applications. While the underlying physics is largely unknown, it has been hypothesized that nano-scale polar regions (NPRs) are responsible for the large piezoelectric response in PZN-PT. If NPRs exist, it would be very helpful to structurally characterize them. We have collected a 3D volume of high-energy x-ray diffuse scattering data, and developed an NPR model that explains many of our experimental observations. The work may allow us to better understand and possibly even enhance the useful properties of this material. [Preview Abstract] |
Saturday, October 20, 2007 9:03AM - 9:15AM |
G1.00005: Hybridization effects and magnetism in UPdSn Karunakar Kothapalli, Sami el-khatib, Heinz Nakotte, Ekkehard Bruck We report on the dependence of the interatomic distances in the intermetallic compound UPdSn as determined from the neutron diffraction data done on HIPD at Los Alamos spallation neutron source. The U-U distance gives a measure of the direct 5$f$-5$f $overlap. The U-Pd and U-Sn distances give a measure of 5$f$-ligand hybridization. Using the Rietveld refinement method, we were able to determine the interatomic distances in the range 15K-300K. The interatomic distances are found to decrease with decreasing temperature until the compound exhibits antiferromagnetic order around 40K. A second transition occurs around 25K. [Preview Abstract] |
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