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Displaying 51 - 75 of 78

Spin Liquid State in the S = 1/2 Triangular Lattice Ba 3 CuSb 2 O 9

April 6, 2011
Author(s)
H. D. Zhou, E. S. Choi, G. Li, L. Balicas, C. R. Wiebe, Yiming Qiu, John R. Copley, Jason S. Gardner
Spin liquids remain one of the most important objects of study in modern solid state physics as model systems of quantum magnetism. In this paper, we report the synthesis and characterization of a new spin liquid candidate, Ba 3CuSb 2O 9, which has a

Neutron Scattering Study of a Quasi-2D Spin-1/2 Dimer System Piperazinium Hexachlorodicuprate Under Hydrostatic Pressure

November 22, 2010
Author(s)
Tao Hong, Chris Stock, I. Cabrera, Collin L. Broholm, Yiming Qiu, Juscelino Leao, Sarah Poulton, John R. Copley
We report inelastic neutron scattering study of a quasi-two-dimensional S=1/2 dimer system Piperazinium Hexachlorodicuprate under hydrostatic pressure. The spin gap δ becomes softened with the increase of the hydrostatic pressure while the bandwidth of the

Localized Diffusive Motion on Two Different Time Scales in Solid Alkane Nanoparticles

October 11, 2010
Author(s)
Siao-Kwan Wang, E. Mamontov, Mengjun Bai, F.Y. Hansen, Haskell Taub, John R. Copley, Victoria Garcia Sakai, Goran Gasparovic, Timothy Jenkins, Madhu Sudan Tyagi, Kenneth W. Herwig, David B. Neumann, Wouter Montfrooij, U.G. Volkmann
High-energy-resolution quasielastic neutron scattering on three complementary spectrometers has been used to investigate molecular diffusive motion in solid nanoparticles of the alkane n-C 32H^66^. Nontranslational molecular diffusive motion in the plastic

Coexisting Magnetic Order and Cooperative Paramagnetism in the Stuffed Pyrochlore Tb 2+x Ti 2-2x Nb x O 7

February 18, 2010
Author(s)
Benjamin Ueland, Jason S. Gardner, A. J. Williams, M. L. Dahlberg, J.G. Kim, Yiming Qiu, John R. Copley, P. Schiffer, R J. Cava
Neutron scattering and magnetization measurements have been performed on the stuffed pyrochlore system Tb 2+xTi 2-2xNb xO 7. We find that despite the introduction of chemical disorder and increasingly antiferromagnetic interactions, cooperative

Itinerant spin excitations near the hidden order transition in URu2Si2

April 22, 2009
Author(s)
J. A. Janik, H. D. Zhou, Y.-J. Jo, L. Balicas, G. J. MacDougall, G. M. Luke, J. D. Garrett, K. J. McClellan, E. D. Bauer, J. L. Sarrao, Yiming Qiu, John R. Copley, Z. Yamani, W. J. Buyers, C. R. Wiebe
By means of neutron scattering we show that the high-temperature precursor to the hidden order state of the heavy fermion superconductor URu 2Si 2 exhibits heavily damped incommensurate paramagnons whose strong energy dispersion is very similar to that of

Study of hydrogen diffusion in superprotonic ionic conductors, MHXO4, by m+SR and QENS

February 21, 2009
Author(s)
Yutaka Ikedo, Hiroshi Nozaki, Masashi Harada, Jun Sugiyama, Taku J. Sato, Yasumitsu Matsuo, Kusuo Nishiyama, James S. Lord, Yiming Qiu, John R. Copley
In order to clarify the mechanism of high proton conductivity (σH+) for superprotonic ionic conductors, MHXO4, where M=Cs and Rb, X=S and Se, muon-spin rotation and relaxation (μ+SR) and quasi-elastic neutron scattering (QENS) measurements have been

Neutron Scattering Study of the Excitation Spectrum of Solid Helium At Ultra-low Temperatures

October 1, 2008
Author(s)
Elizabeth Blackburn, John Goodkind, Sunil K. Sinha, Collin Broholm, John R. Copley, Ross W. Erwin
There has been a resurgence of interest in the properties of Solid Helium due to the recent discovery of non-classical rotational inertia (NCRI) in solid 4He by Chan and coworkers below 200 mK which they have interpreted as a transition to a "supersolid"

Neutron-scattering study of the oxypnictide superconductor LaFeAsO 0.87 F 0.13

August 26, 2008
Author(s)
Yiming Qiu, M. Kofu, Wei Bao, S.-H. Lee, Qingzhen Huang, Taner N. Yildirim, John R. Copley, Jeffrey Lynn, T. Wu, G. Wu, X. H. Chen
The recently discovered superconductor LaO0.87F0.13FeAs (TC≈26 K) was investigated using the neutron-scattering technique. No spin-density-wave (SDW) order was observed in the normal state or in the superconducting state, both with and without an applied
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