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Iowa State University

Series

Metallurgy

Physics and Astronomy

2009

Articles 1 - 5 of 5

Full-Text Articles in Physics

Flux Growth At Ambient Pressure Of Millimeter-Sized Single Crystals Of Lafeaso, Lafeaso1−Xfx, And Lafe1−Xcoxaso, J.-Q. Yan, Shibabrata Nandi, Jerel L. Zarestky, W. Tian, Andreas Kreyssig, Brandt A. Jensen, A. Kracher, Kevin W. Dennis, Robert J. Mcqueeney, Alan I. Goldman, R. William Mccallum, Thomas A. Lograsso Dec 2009

Flux Growth At Ambient Pressure Of Millimeter-Sized Single Crystals Of Lafeaso, Lafeaso1−Xfx, And Lafe1−Xcoxaso, J.-Q. Yan, Shibabrata Nandi, Jerel L. Zarestky, W. Tian, Andreas Kreyssig, Brandt A. Jensen, A. Kracher, Kevin W. Dennis, Robert J. Mcqueeney, Alan I. Goldman, R. William Mccallum, Thomas A. Lograsso

Ames Laboratory Publications

Millimeter-sized single crystals of LaFeAsO, LaFeAsO1−xFx, and LaFe1−xCoxAsO were grown in NaAs flux at ambient pressure. The detailed growth procedure and crystal characterizations are reported. The as-grown crystals have typical dimensions of3×4×0.05–0.3 mm3 with the crystallographic c-axis perpendicular to the plane of the platelike single crystals. Various characterizations confirmed the high quality of our LaFeAsO crystals. Co and F were introduced into the lattice leading to superconductingLaFe1−xCoxAsO and LaFeAsO1−xFx single crystals, respectively. This growth protocol ...


Single-Crystal Neutron Diffraction Study Of Short-Range Magnetic Correlations In Tb5ge4, W. Tian, Andreas Kreyssig, Jerel L. Zarestky, L. Tan, Shibabrata Nandi, Alan I. Goldman, Thomas A. Lograsso, Deborah L. Schlagel, Karl A. Gschneidner Jr., Vitalij K. Pecharsky, Robert J. Mcqueeney Oct 2009

Single-Crystal Neutron Diffraction Study Of Short-Range Magnetic Correlations In Tb5ge4, W. Tian, Andreas Kreyssig, Jerel L. Zarestky, L. Tan, Shibabrata Nandi, Alan I. Goldman, Thomas A. Lograsso, Deborah L. Schlagel, Karl A. Gschneidner Jr., Vitalij K. Pecharsky, Robert J. Mcqueeney

Ames Laboratory Publications

We present a single-crystal neutron diffraction study of the magnetic short-range correlations in Tb5Ge4 which orders antiferromagnetically below the Neel temperature TN≈92 K. Strong diffuse scattering arising from magnetic short-range correlations was observed in wide temperature ranges both below and above TN. The antiferromagnetic ordering in Tb5Ge4 is described to consist of strongly coupled ferromagnetic block layers in the ac plane that stack along the b axis with weak antiferromagnetic interlayer coupling. Diffuse scattering was observed along both a∗ and b∗ directions indicating three-dimensional short-range correlations. Moreover, the q dependence of ...


In Situ High Energy X-Ray Synchrotron Diffraction Study Of The Synthesis And Stoichiometry Of Lafeaso And Lafeaso1−Xfy, R. William Mccallum, J.-Q. Yan, Gustav E. Rustan, E. D. Mun, Yogesh Singh, S. Das, R. Nath, Sergey L. Bud'ko, Kevin W. Dennis, David C. Johnston, Paul C. Canfield, Matthew J. Kramer, Andreas Kreyssig, Thomas A. Lograsso, Alan I. Goldman Jun 2009

In Situ High Energy X-Ray Synchrotron Diffraction Study Of The Synthesis And Stoichiometry Of Lafeaso And Lafeaso1−Xfy, R. William Mccallum, J.-Q. Yan, Gustav E. Rustan, E. D. Mun, Yogesh Singh, S. Das, R. Nath, Sergey L. Bud'ko, Kevin W. Dennis, David C. Johnston, Paul C. Canfield, Matthew J. Kramer, Andreas Kreyssig, Thomas A. Lograsso, Alan I. Goldman

Ames Laboratory Publications

The reaction path for the synthesis of LaFeAsO and LaFeAsO1−xFy by solid state reaction was studied by in situ high temperature x-ray diffraction technique and differential thermal analysis in the temperature interval 100 °C ⩽ T ⩽ 1150 °C. Starting with LaAs, Fe2O3, Fe, and LaF3 as precursors, the results show that the synthesis is characterized by three temperature intervals: (1) Below 500 °C the sequential reduction of Fe2O3 and Fe3O4takes place through the oxidization of LaAs. Below 400 °C, Fe2O3 is reduced to ...


Single-Crystal Growth, Crystallography, Magnetic Susceptibility, Heat Capacity, And Thermal Expansion Of The Antiferromagnetic S=1 Chain Compound Cav2o4, A. Niazi, Sergey L. Bud'ko, Deborah L. Schlagel, J.-Q. Yan, Thomas A. Lograsso, Andreas Kreyssig, S. Das, Shibabrata Nandi, Alan I. Goldman, A. Honecker, R. William Mccallum, M. Reehuis, O. Pieper, B. Lake, David C. Johnston Mar 2009

Single-Crystal Growth, Crystallography, Magnetic Susceptibility, Heat Capacity, And Thermal Expansion Of The Antiferromagnetic S=1 Chain Compound Cav2o4, A. Niazi, Sergey L. Bud'ko, Deborah L. Schlagel, J.-Q. Yan, Thomas A. Lograsso, Andreas Kreyssig, S. Das, Shibabrata Nandi, Alan I. Goldman, A. Honecker, R. William Mccallum, M. Reehuis, O. Pieper, B. Lake, David C. Johnston

Ames Laboratory Publications

The compound CaV2O4 contains V+3 cations with spin S=1 and has an orthorhombic structure at room temperature containing zigzag chains of V atoms running along the c axis. We have grown single crystals of CaV2O4 and report crystallography, static magnetization, magnetic susceptibility χ, ac magnetic susceptibility, heat capacity Cp, and thermal expansion measurements in the temperature T range of 1.8–350 K on the single crystals and on polycrystalline samples. An orthorhombic-to-monoclinic structural distortion and a long-range antiferromagnetic (AF) transition were found at sample-dependent temperatures TS≈108–145 K ...


Low Temperature Heat Capacity Of Fe1−Xgax Alloys With Large Magnetostriction, J. M. Hill, Robert J. Mcqueeney, Ruqian Wu, Kevin W. Dennis, R. William Mccallum, Mianliang Huang, Thomas A. Lograsso Jan 2009

Low Temperature Heat Capacity Of Fe1−Xgax Alloys With Large Magnetostriction, J. M. Hill, Robert J. Mcqueeney, Ruqian Wu, Kevin W. Dennis, R. William Mccallum, Mianliang Huang, Thomas A. Lograsso

Ames Laboratory Publications

The low temperature heat capacity Cp of Fe1−xGax alloys with large magnetostriction has been investigated. The data were analyzed in the standard way using electron (γT) and phonon (βT3) contributions. The Debye temperature ΘD decreases approximately linearly with increasing Ga concentration, consistent with previous resonant ultrasound measurements and measured phonon dispersion curves. Calculations of ΘD from lattice dynamical models and from measured elastic constants C11,C12, and C44 are in agreement with the measured data. The linear coefficient of electronic specific heat γ remains relatively constant as the Ga concentration ...