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Full-Text Articles in Physics

Diffraction Paradox: An Unusually Broad Diffraction Background Marks High Quality Graphene, Shen Chen, Michael Horn-Von Hoegen, Patricia A. Thiel, Michael C. Tringides Oct 2019

Diffraction Paradox: An Unusually Broad Diffraction Background Marks High Quality Graphene, Shen Chen, Michael Horn-Von Hoegen, Patricia A. Thiel, Michael C. Tringides

Chemistry Publications

The realization of the unusual properties of two-dimensional (2D) materials requires the formation of large domains of single-layer thickness, extending over the mesoscale. It is found that the formation of uniform graphene on SiC, contrary to textbook diffraction, is signaled by a strong bell-shaped component (BSC) around the (00) and G(10) spots (but not around the substrate spots). The BCS is also seen on graphene grown on metals, because a single uniform graphene layer can be also grown with large lateral size. It is only seen by electron diffraction but not with x-ray or He scattering. Although the origin ...


Energetics Of Cu Adsorption And Intercalation At Graphite Step Edges, Yong Han, Ann Lii-Rosales, Michael C. Tringides, James W. Evans, Patricia A. Thiel Mar 2019

Energetics Of Cu Adsorption And Intercalation At Graphite Step Edges, Yong Han, Ann Lii-Rosales, Michael C. Tringides, James W. Evans, Patricia A. Thiel

Chemistry Publications

To assess the energetics of Cu intercalation on defective graphite, the chemical potentials and binding energies for Cu at graphite step edges are calculated for three main configurations: an isolated atom, a chain, and an atom attached to a chain. As expected, for Cu interacting directly with a graphite step edge, the strength of interaction depends on the stability of the step, with Cu binding more strongly at a less-stable step. However, the relationship is reversed when considering binding of a Cu atom attached to a chain. Taken together, these trends mean that if the graphite step is less stable ...


Kinetics, Energetics, And Size Dependence Of The Transformation From Pt To Ordered Ptsn Intermetallic Nanoparticles, Minda Chen, Yong Han, Tian Wei Goh, Rong Sun, Raghu V. Maligal‐Ganesh, Yuchen Pei, Chia‐ Kuang Tsung, James W. Evans, Wenyu Huang Jan 2019

Kinetics, Energetics, And Size Dependence Of The Transformation From Pt To Ordered Ptsn Intermetallic Nanoparticles, Minda Chen, Yong Han, Tian Wei Goh, Rong Sun, Raghu V. Maligal‐Ganesh, Yuchen Pei, Chia‐ Kuang Tsung, James W. Evans, Wenyu Huang

Chemistry Publications

The outstanding catalytic activity and chemical selectivity of intermetallic compounds make them excellent candidates for heterogeneous catalysis. However, the kinetics of their formation at the nanoscale is poorly understood or characterized, and precise control of their size, shape as well as composition during synthesis remains challenging. Here, using well-defined Pt nanoparticles (5 nm and 14 nm) encapsulated in mesoporous silica, we study the transformation kinetics from monometallic Pt to intermetallic PtSn at different temperatures by a series of time-evolution X-ray diffraction studies. Observations indicate an initial transformation stage mediated by Pt surface-controlled intermixing kinetics, followed by a second stage with ...


Squeezed Nanocrystals: Equilibrium Configuration Of Metal Clusters Embedded Beneath The Surface Of A Layered Material, Scott E. Julien, Ann Lii-Rosales, Kai-Tak Wan, Yong Han, Michael C. Tringides, James W. Evans, Patricia A. Thiel Jan 2019

Squeezed Nanocrystals: Equilibrium Configuration Of Metal Clusters Embedded Beneath The Surface Of A Layered Material, Scott E. Julien, Ann Lii-Rosales, Kai-Tak Wan, Yong Han, Michael C. Tringides, James W. Evans, Patricia A. Thiel

Chemistry Publications

Shapes of functional metallic nanocrystals, typically synthesized either free in solution or supported on surfaces, are key for controlling properties. Here, we consider a novel new class of metallic nanocrystals, copper islands embedded near the surface of graphite, which can be considered a model system for metals embedded beneath surfaces of layered materials, or beneath supported membranes. We develop a continuum elasticity (CE) model for the equilibrium shape of these islands, and compare its predictions with experimental data. The CE model incorporates appropriate surface energy, adhesion energies, and strain energy. The agreement between the CE model and the data is ...


Reverse-Engineering Of Graphene On Metal Surfaces: A Case Study Of Embedded Ruthenium, Ann Lii-Rosales, Yong Han, Ka Man Yu, Dapeng Jing, Nathaniel Anderson, David Vaknin, Michael C. Tringides, James W. Evans, Michael S. Altman, Patricia A. Thiel Oct 2018

Reverse-Engineering Of Graphene On Metal Surfaces: A Case Study Of Embedded Ruthenium, Ann Lii-Rosales, Yong Han, Ka Man Yu, Dapeng Jing, Nathaniel Anderson, David Vaknin, Michael C. Tringides, James W. Evans, Michael S. Altman, Patricia A. Thiel

Chemistry Publications

Using scanning tunneling microscopy, x-ray photoelectron spectroscopy, and x-ray absorption spectroscopy, we show that Ru forms metallic nanoislands on graphite, covered by a graphene monolayer. These islands are air-stable, contain 2–4 layers of Ru, and have diameters on the order of 10 nm. To produce these nanoislands two conditions must be met during synthesis. The graphite surface must be ion-bombarded, and subsequently held at an elevated temperature (1000–1180 K) during Ru deposition. A coincidence lattice forms between the graphene overlayer and the Ru island top. Its characteristics—coincidence lattice constant, corrugation amplitude, and variation of carbon lattice appearance ...


Spatial–Temporal Spectroscopy Characterizations And Electronic Structure Of Methylammonium Perovskites, Zhaoyu Liu, K. C. Bhamu, Liang Luo, Satvik Shah, Joong-Mok Park, Di Cheng, Men Long, Rana Biswas, F. Fungara, Ruth Shinar, Joseph Shinar, Javier Vela, Jigang Wang Jul 2018

Spatial–Temporal Spectroscopy Characterizations And Electronic Structure Of Methylammonium Perovskites, Zhaoyu Liu, K. C. Bhamu, Liang Luo, Satvik Shah, Joong-Mok Park, Di Cheng, Men Long, Rana Biswas, F. Fungara, Ruth Shinar, Joseph Shinar, Javier Vela, Jigang Wang

Chemistry Publications

Using time-resolved laser-scanning confocal microscopy and ultrafast optical pump/THz probe spectroscopy, we measure photoluminescence and THz-conductivity in perovskite micro-crystals and films. Photoluminescence quenching and lifetime variations occur from local heterogeneity. Ultrafast THz-spectra measure sharp quantum transitions from excitonic Rydberg states, providing weakly bound excitons with a binding energy of ~13.5 meV at low temperatures. Ab-initio electronic structure calculations give a direct band gap of 1.64 eV, a dielectric constant ~18, heavy electrons, and light holes, resulting in weakly bound excitons, consistent with the binding energies from experiment. The complementary spectroscopy and simulations reveal fundamental insights into perovskite ...


Theoretical Prediction Of Crystallization Kinetics Of A Supercooled Lennard-Jones Fluid, K. G. S. H. Gunawardana, Xueyu Song May 2018

Theoretical Prediction Of Crystallization Kinetics Of A Supercooled Lennard-Jones Fluid, K. G. S. H. Gunawardana, Xueyu Song

Chemistry Publications

The first order curvature correction to the crystal-liquid interfacial free energy is calculated using a theoretical model based on the interfacial excess thermodynamic properties. The correction parameter (δ), which is analogous to the Tolman length at a liquid-vapor interface, is found to be 0.48 ± 0.05 for a Lennard-Jones (LJ) fluid. We show that this curvature correction is crucial in predicting the nucleation barrier when the size of the crystal nucleus is small. The thermodynamic driving force (Δμ) corresponding to available simulated nucleation conditions is also calculated by combining the simulated data with a classical density functional theory ...


Defect-Mediated, Thermally-Activated Encapsulation Of Metals At The Surface Of Graphite, Yinghui Zhou, Ann Lii-Rosales, Minsung Kim, Mark Wallingford, Dapeng Jing, Michael C. Tringides, Cai-Zhuang Wang, Patricia A. Thiel Feb 2018

Defect-Mediated, Thermally-Activated Encapsulation Of Metals At The Surface Of Graphite, Yinghui Zhou, Ann Lii-Rosales, Minsung Kim, Mark Wallingford, Dapeng Jing, Michael C. Tringides, Cai-Zhuang Wang, Patricia A. Thiel

Chemistry Publications

We show that 3 metals – Dy, Ru, and Cu – can form multilayer intercalated (encapsulated) islands at the graphite (0001) surface if 2 specific conditions are met: Defects are introduced on the graphite terraces to act as entry portals, and the metal deposition temperature is well above ambient. Focusing on Dy as a prototype, we show that surface encapsulation is much different than bulk intercalation, because the encapsulated metal takes the form of bulk-like rafts of multilayer Dy, rather than the dilute, single-layer structure known for the bulk compound. Carbon-covered metallic rafts even form for relatively unreactive metals (Ru and Cu ...


Polar Intermetallics Pr5co2ge3 And Pr7co2ge4 With Planar Hydrocarbon‐Like Metal Clusters, Qisheng Lin, Kaiser Aguirre, Scott M. Saunders, Timothy A. Hackett, Yong Liu, Valentin Taufour, Durga Paudyal, Sergey L. Bud’Ko, Paul C. Canfield, Gordon J. Miller Aug 2017

Polar Intermetallics Pr5co2ge3 And Pr7co2ge4 With Planar Hydrocarbon‐Like Metal Clusters, Qisheng Lin, Kaiser Aguirre, Scott M. Saunders, Timothy A. Hackett, Yong Liu, Valentin Taufour, Durga Paudyal, Sergey L. Bud’Ko, Paul C. Canfield, Gordon J. Miller

Chemistry Publications

Planar hydrocarbon‐like metal clusters may foster new insights linking organic molecules with conjugated π–π bonding interactions and inorganic structures in terms of their bonding characteristics. However, such clusters are uncommon in polar intermetallics. Herein, we report two polar intermetallic phases, Pr5Co2Ge3 and Pr7Co2Ge4, both of which feature such planar metal clusters, namely, ethylene‐like [Co2Ge4] clusters plus the concatenated forms and polyacene‐like [Co2Ge2]n ribbons in Pr5Co2Ge3, and 1,2,4,5‐tetramethylbenzene‐like [Co4Ge6] cluster in Pr7Co2Ge4. Just as in the related planar organic structures, these metal–metalloid species are dominated by covalent bonding interactions. Both ...


Crystal Structure, Homogeneity Range And Electronic Structure Of Rhombohedral Γ-Mn5al8, Srinivasa Thimmaiah, Zachary Tener, Tej N. Lamichhane, Paul C. Canfield, Gordon J. Miller Jul 2017

Crystal Structure, Homogeneity Range And Electronic Structure Of Rhombohedral Γ-Mn5al8, Srinivasa Thimmaiah, Zachary Tener, Tej N. Lamichhane, Paul C. Canfield, Gordon J. Miller

Chemistry Publications

The γ-region of the Mn–Al phase diagram between 45 and 70 at.% Al was re-investigated by a combination of powder and single crystal X-ray diffraction as well as EDS analysis to establish the distribution of Mn and Al atoms. Single crystals of γ-Mn5–x Al8+x were grown using Sn-flux at 650 °C. The crystal structure, atomic coordinates and site occupancy parameters of γ-Mn5−x Al8+x phases were refined from single crystal X-ray data. The γ-Mn5-x Al8+x phase adopts the rhombohedral Cr5Al8-type structure rather than a cubic γ-brass structure. The refined compositions from two crystals extracted ...


Tailoring Nanoscale Morphology Of Polymer: Fullerene Blends Using Electrostatic Field, Moneim Elshobaki, Ryan S. Gebhardt, John Carr, William Lindemann, Wenjie Wang, Eric Grieser, Swaminathan Venkatesan, Evan Ngo, Ujjal Bhattacharjee, Joseph Strzalka, Zhang Jiang, Qiquan Qiao, Jacob W. Petrich, David Vaknin, Sumit Chaudhary Jan 2017

Tailoring Nanoscale Morphology Of Polymer: Fullerene Blends Using Electrostatic Field, Moneim Elshobaki, Ryan S. Gebhardt, John Carr, William Lindemann, Wenjie Wang, Eric Grieser, Swaminathan Venkatesan, Evan Ngo, Ujjal Bhattacharjee, Joseph Strzalka, Zhang Jiang, Qiquan Qiao, Jacob W. Petrich, David Vaknin, Sumit Chaudhary

Chemistry Publications

To tailor the nanomorphology in polymer/fullerene blends, we study the effect of electrostatic field (E-field) on the solidification of poly(3-hexylthiophene-2, 5-diyl) (P3HT):[6,6]-phenyl-C61-butyric acid methyl ester (PC60BM) bulk heterojunction (BHJ). In addition to control; wet P3HT:PC60BM thin films were exposed to E-field of Van de Graaff (VDG) generator at three different directions—horizontal (H), tilted (T), and vertical (V)—relative to the plane of the substrate. Surface and bulk characterizations of the field-treated BHJs affirmed that fullerene molecules can easily penetrate the spaghetti-like P3HT and move up and down following the E-field. Using E-field treatment ...


Superconducting Properties Of Rh 9 In 4 S 4 Single Crystals, Udhara S. Kaluarachchi, Qisheng Lin, Weiwei Xie, Valentin Taufour, S. L. Bud’Ko, Gordon J. Miller, Paul C. Canfield Jan 2016

Superconducting Properties Of Rh 9 In 4 S 4 Single Crystals, Udhara S. Kaluarachchi, Qisheng Lin, Weiwei Xie, Valentin Taufour, S. L. Bud’Ko, Gordon J. Miller, Paul C. Canfield

Chemistry Publications

The synthesis and crystallographic, thermodynamic, and transport properties of single crystalline Rh9In4S4 were studied. The resistivity, magnetization, and specific heat measurements all clearly indicate bulk superconductivity with a critical temperature, Tc∼2.25 K. The Sommerfeld coefficient γ and the Debye temperature (ΘD) were found to be 34 mJ mol−1 K−2 and 217 K, respectively. The observed specific heat jump, ΔC/γTc=1.66, is larger than the expected BCS weak coupling value of 1.43. Ginzburg-Landau (GL) ratio of the low-temperature GL-penetration depth, λGL≈5750 Å, to the GL-coherence length, ξGL≈94 Å, is large: κ ∼60 ...


Oxygen Trapped By Rare Earth Tetrahedral Clusters In Nd4feos6: Crystal Structure, Electronic Structure, And Magnetic Properties, Qisheng Lin, Valentin Taufour, Yuemei Zhang, Max Wood, Thomas Drtina, Sergey L. Bud’Ko, Paul C. Canfield, Gordon J. Miller Sep 2015

Oxygen Trapped By Rare Earth Tetrahedral Clusters In Nd4feos6: Crystal Structure, Electronic Structure, And Magnetic Properties, Qisheng Lin, Valentin Taufour, Yuemei Zhang, Max Wood, Thomas Drtina, Sergey L. Bud’Ko, Paul C. Canfield, Gordon J. Miller

Chemistry Publications

Single crystals of Nd4FeOS6 were grown from an Fe–S eutectic solution. Single crystal X-ray diffraction analysis revealed a Nd4MnOSe6-type structure (P63mc, a=9.2693(1) Å, c=6.6650(1)Å, V=495.94(1) Å3, Z=2), featuring parallel chains of face-sharing [FeS6×1/2]4− trigonal antiprisms and interlinked [Nd4OS3]4+ cubane-like clusters. Oxygen atoms were found to be trapped by Nd4 clusters in the [Nd4OS3]4+ chains. Structural differences among Nd4MnOSe6-type Nd4FeOS6and the related La3CuSiS7− and Pr8CoGa3-type structures have been described. Magnetic susceptibility measurements on Nd4FeOS6 suggested the dominance of antiferromagnetic interactions at low ...


Β-Mn-Type Co8+Xzn12–X As A Defect Cubic Laves Phase: Site Preferences, Magnetism, And Electronic Structure, Weiwei Xie, Srinvasa Timmaiah, Jagat Lamal, Jing Liu, Thomas W. Heitmann, Dante Quirinale, A. I. Goldman, Vitalij K. Pecharsky, Gordon J. Miller Jan 2013

Β-Mn-Type Co8+Xzn12–X As A Defect Cubic Laves Phase: Site Preferences, Magnetism, And Electronic Structure, Weiwei Xie, Srinvasa Timmaiah, Jagat Lamal, Jing Liu, Thomas W. Heitmann, Dante Quirinale, A. I. Goldman, Vitalij K. Pecharsky, Gordon J. Miller

Chemistry Publications

The results of crystallographic analysis, magnetic characterization, and theoretical assessment of β-Mn-type Co–Zn intermetallics prepared using high-temperature methods are presented. These β-Mn Co–Zn phases crystallize in the space group P4132 [Pearson symbol cP20; a = 6.3555(7)–6.3220(7)], and their stoichiometry may be expressed as Co8+xZn12–x [1.7(2) < x < 2.2(2)]. According to a combination of single-crystal X-ray diffraction, neutron powder diffraction, and scanning electron microscopy, atomic site occupancies establish clear preferences for Co atoms in the 8c sites and Zn atoms in the 12d sites, with all additional Co atoms replacing some Zn atoms, a result that can be rationalized by electronic structure calculations. Magnetic measurements and neutron powder diffraction of an equimolar Co:Zn sample confirm ferromagnetism in this phase with a Curie temperature of ∼420 K. Neutron powder diffraction and electronic structure calculations using the local spin density approximation indicate that the spontaneous magnetization of this phase arises exclusively from local moments at the Co atoms. Inspection of the atomic arrangements of Co8+xZn12–x reveals that the β-Mn aristotype may be derived from an ordered defect, cubic Laves phase (MgCu2-type) structure. Structural optimization procedures using the Vienna ab initio simulation package (VASP) and starting ...


Rhombohedrally Distorted Γ-Brasses Cr1−Xfexga, Hyujin Ko, Olivier Gourdon, Delphine Gout, Eun-Deok Mun, Srinivasa Thimmaiah, Gordon J. Miller Jan 2010

Rhombohedrally Distorted Γ-Brasses Cr1−Xfexga, Hyujin Ko, Olivier Gourdon, Delphine Gout, Eun-Deok Mun, Srinivasa Thimmaiah, Gordon J. Miller

Chemistry Publications

A series of rhombohedrally distorted γ-brass structures containing a mixture of magnetically active 3d elements, Cr and Fe, Cr1−xFexGa, is investigated crystallographically. These structures consist of chains of trans-face-sharing Ga-centered transition metal icosahedra. Neutron powder diffraction specifically on Cr0.5Fe0.5Ga, which could be prepared as a single phase material, gave lattice constants (11 K) a = 12.5172(2) Å and c = 7.8325(2) Å and a refined composition of Cr0.502(6)Fe0.498Ga = Cr6.523Fe6.477Ga13 and revealed partial ordering ...


Variation Of The Magnetic Ordering In Gdt2zn20 (T=Fe, Ru, Os, Co, Rh And Ir) And Its Correlation With The Electronic Structure Of Isostructural Yt2zn20, Shuang Jia, Ni Ni, G. D. Samolyuk, A. Safa-Sefat, K. Dennis, Hyunjin Ko, Gordon J. Miller, Sergey L. Bud'ko, Paul C. Canfield Jan 2008

Variation Of The Magnetic Ordering In Gdt2zn20 (T=Fe, Ru, Os, Co, Rh And Ir) And Its Correlation With The Electronic Structure Of Isostructural Yt2zn20, Shuang Jia, Ni Ni, G. D. Samolyuk, A. Safa-Sefat, K. Dennis, Hyunjin Ko, Gordon J. Miller, Sergey L. Bud'ko, Paul C. Canfield

Chemistry Publications

Magnetization, resistivity, and specific heat measurements were performed on solution-grown single crystals of six GdT2Zn20 (T=Fe, Ru, Os, Co, Rh, and Ir) compounds, as well as on their Y analogs. For the Gd compounds, the Fe column members manifest a ferromagnetic (FM) ground state (with an enhanced Curie temperature TC for T=Fe and Ru), whereas the Co column members manifest an antiferromagnetic (AFM) ground state. Thermodynamic measurements on YT2Zn20 revealed that the enhanced TC for GdFe2Zn20 and GdRu2Zn20 can be understood within the framework of Heisenberg moments embedded in a nearly ferromagnetic Fermi liquid. Furthermore, electronic structure calculations ...


The Coloring Problem In Intermetallics: Bonding And Properties Of Tb3zn3.6al7.4 With The La3al11 Structure Type, Mi-Kyung Han, Emilia Morosan, Paul C. Canfield, Gordon J. Miller Jan 2005

The Coloring Problem In Intermetallics: Bonding And Properties Of Tb3zn3.6al7.4 With The La3al11 Structure Type, Mi-Kyung Han, Emilia Morosan, Paul C. Canfield, Gordon J. Miller

Chemistry Publications

Single crystals of the new compound Tb3Zn3.6(1)Al7.4(1) were obtained from Al and Zn-rich ternary solutions. The title compound crystallizes in the orthorhombic La3Al11 structure type (space group Immm (No. 71), Z = 2; a = 4.2334(1) Å, b = 9.9725(3) Å, c = 12.4659(1) Å). The inverse susceptibility above ca. 50 K shows Curie-Weiss behavior, and a metamagnetic transition is apparent in the T = 2 K field-dependent magnetization around Hc ∼ 20 kG. The resistivity increases with temperature in a roughly linear fashion, indicating the metallic ...


Crystallographic, Electronic, And Magnetic Studies Of Ζ2-Gam (M = Cr, Mn Or Fe):  Trends In Itinerant Magnetism, Olivier Gourdon, Sergey L. Bud'ko, Darrick Williams, Gordon J. Miller Jan 2004

Crystallographic, Electronic, And Magnetic Studies Of Ζ2-Gam (M = Cr, Mn Or Fe):  Trends In Itinerant Magnetism, Olivier Gourdon, Sergey L. Bud'ko, Darrick Williams, Gordon J. Miller

Chemistry Publications

This study of the crystal structure, electronic structure, and magnetic properties of the ζ2-GaM (M = Cr, Mn or Fe) alloys is motivated by the recent reinvestigation of the crystallographic Al8Cr5 structure type of ζ2-GaMn. The isostructural compounds ζ2-GaFe and ζ2-GaCr have been refined using X-ray powder diffraction as well as neutron powder diffraction for ζ2-GaFe. Their structures have been refined using the space group Rm, with cell parameters a = 12.625(8) Å and c = 7.785(10) Å for ζ2-GaCr and a ...


Anomalous Temperature-Dependent Transport In Ybni2b2c And Its Correlation To Microstructural Features, M.A. Avila, Y.Q. Wu, C.L. Condron, Sergey L. Bud'ko, M. J. Kramer, Gordon J. Miller, Paul C. Canfield Jan 2004

Anomalous Temperature-Dependent Transport In Ybni2b2c And Its Correlation To Microstructural Features, M.A. Avila, Y.Q. Wu, C.L. Condron, Sergey L. Bud'ko, M. J. Kramer, Gordon J. Miller, Paul C. Canfield

Chemistry Publications

We address the nature of the ligandal disorder leading to local redistributions of Kondo temperatures, manifested as annealing-induced changes in the transport behavior of the heavy fermion system YbNi2B2C. The anomalous transport behavior was fully characterized by temperature dependent resistivity measurements in an extended range of 0.4


Anisotropy And Large Magnetoresistance In The Narrow-Gap Semiconductor Fesb2, Cedomir Petrovic, J.W. Kim, Sergey L. Bud'ko, A. I. Goldman, Paul C. Canfield, Wonyoung Choe, Gordon J. Miller Jan 2003

Anisotropy And Large Magnetoresistance In The Narrow-Gap Semiconductor Fesb2, Cedomir Petrovic, J.W. Kim, Sergey L. Bud'ko, A. I. Goldman, Paul C. Canfield, Wonyoung Choe, Gordon J. Miller

Chemistry Publications

A study of the anisotropy in magnetic, transport, and magnetotransport properties of FeSb2 has been made on large single crystals grown from Sb flux. Magnetic susceptibility of FeSb2 shows diamagnetic to paramagnetic crossover around 100 K. Electrical transport along two axes is semiconducting, whereas the third axis exhibits a metal-semiconductor crossover at temperature Tcr which is sensitive to current alignment and ranges between 40 and 80 K. In H=70kOe semiconducting transport is restored for T<300K, resulting in large magnetoresistance [ρ(70kOe)−ρ(0)]/ρ(0)=2200% in the crossover temperature range.


A New Look At Bonding In Trialuminides:  Reinvestigation Of Taal3, C.L. Condron, Gordon J. Miller, Joel D. Strand, Sergey L. Bud'ko, Paul C. Canfield Jan 2003

A New Look At Bonding In Trialuminides:  Reinvestigation Of Taal3, C.L. Condron, Gordon J. Miller, Joel D. Strand, Sergey L. Bud'ko, Paul C. Canfield

Chemistry Publications

Single crystals of TaAl3 were grown at high temperatures from an Al-rich, binary solution. TaAl3 adopts the D022 structure type, space group I4/mmm with a = 3.8412(5) Å, c = 8.5402(17) Å, and Z = 2. The structure type, which is the preferred structure for all group 5 trialuminides and TiAl3 as well as the high-temperature form of HfAl3, is a binary coloring of the face-centered-cubic (fcc) arrangement. The distribution of Ta atoms creates a three-dimensional network of vertex and edge-sharing square pyramids of Al atoms. Temperature-dependent electrical resistivity and magnetic susceptibility ...


The Intermetallic Compound Gd6ta4al43, Cathie L. Condron, Joel D. Strand, Paul C. Canfield, Gordon J. Miller Jan 2003

The Intermetallic Compound Gd6ta4al43, Cathie L. Condron, Joel D. Strand, Paul C. Canfield, Gordon J. Miller

Chemistry Publications

The elements Gd (99.999%; Ames Laboratory), Ta (99.999%; Ames Laboratory), and Al (99.98%; Alfa) were combined in the atomic ratio Gd6Ta4Al100 in a 2 ml alumina crucible. The crucible was placed into a fused silica tube and a second crucible, filled with SiO2 wool, was placed inverted on top of the first. The tube was sealed under 1/5 atm Ar and placed into a box furnace. The mixture was heated to 1463 K in 3 h, kept at 1463 K for 2 h, and then cooled to 1173 K over ...


Decoupling Of The Magnetic And Structural Transformations In Er5si4, Vitalij K. Pecharsky, Alexandra O. Pecharsky, Yurij Mozharivskyj, Karl A. Gschneidner Jr., Gordon J. Miller Jan 2003

Decoupling Of The Magnetic And Structural Transformations In Er5si4, Vitalij K. Pecharsky, Alexandra O. Pecharsky, Yurij Mozharivskyj, Karl A. Gschneidner Jr., Gordon J. Miller

Chemistry Publications

Er5Si4 is a member of the R5(Si4−xGex) family of alloys, where R=rare earth metal. Many of these compounds display a strong coupling between the magnetic and crystal lattices. In the naturally layered R5(Si4−xGex) materials, inter- and intralayer interactions can be controlled by chemical and physical means; thus their physical properties can be tailored within wide limits. The Er5Si4 is unique in that the temperature dependent structural sequence is opposite that of other representatives of this family. The magnetism of Er5Si4 is reflective of its exceptional place within the series.