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Physics

Condensed matter

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Displaying 1051 - 1075 of 1253

Structure and Degeneracy of Vortex Lattice Domains in Pure Superconducting Niobium: A Small-Angle Neutron Scattering Study

January 27, 2009
Author(s)
Mark Laver, E M. Forgan, C Bowell, C D. Dewhurst, S Ramos, A B. Abrahamsen, D. K. Christen, D Fort, S Muhlbauer, J Kohlbrecher, R Cubitt
High-purity niobium exhibits a surprisingly rich assortment of vortex lattice (VL) structures for fields applied parallel to a fourfold symmetry axis, with all observed VL phases made up of degenerate domains that spontaneously break some crystal symmetry

3:1 Magnetization Plateau and Suppression of Ferroelectric Polarization in an Ising Chain Multiferroic

January 26, 2009
Author(s)
Y.-J. Jo, Seoungsu Lee, E. Choi, H. Yi, William D. Ratcliff, Y. Choi, V. Kiryukhin, S.-W. Cheong, L. Balicas
Ferroelectric Ising chain magnet Ca3Co2−xMnxO6 (x≃0.96) was studied in magnetic fields of up to 33 T. Magnetization and neutron-scattering measurements reveal successive metamagnetic transitions from the zero-field ↑↑↓↓ spin configuration to the ↑↑↑↓ state

Origin and Tuning of the Magnetocaloric Effect in the Magnetic Refrigerant Mn1.1Fe0.9(P0.8Ge0.2)

January 26, 2009
Author(s)
Danmin Liu, Ming Yue, Jiuxing Zhang, T. M. McQueen, Jeffrey Lynn, Xiaolu Wang, Ying Chen, Jiying Li, R. J. Cava, X. Liu, Zaven Altounian, Qingzhen Huang
Neutron-diffraction and magnetization measurements have been carried out on a series of samples of the magnetorefrigerant Mn1+yFe1−yP1−xGex. The data reveal that the ferromagnetic and paramagnetic phases correspond to two very distinct crystal structures

Striped Domains at the Pentacene:C 60 Interface

January 12, 2009
Author(s)
Dan B. Dougherty, W Jin, J Cullen, J Reutt-Robey, Steven W. Robey
STM observations of the initial growth stages of the first layer of pentacene on a monolayer film of C60 on Ag(111) are presented. Pentacene films nucleate and grow with molecules standing up at the Pentacene:C60 interface similar to the well known thin

Spin Correlations in the Geometrically Frustrated Pyrochlore Tb 2 Mo 2 O 7

December 31, 2008
Author(s)
D. K. Singh, J. S. Helton, S. Chu, T. Han, C. Bonnoit, Sung Chang, Hye J. Kang, Jeffrey W. Lynn, Y. S. Lee
We report neutron scattering studies of the spin correlations of the geometrically frustrated py- rochlore Tb 2Mo 2O 7using single crystal samples. Elastic diffuse peaks are observed at low temperatures, indicating short-range ordering of the Tb 3+ moments

Neutron-Diffraction Measurements of Magnetic Order and a Structural Transition in the Parent BaFe2As2 Compound of FeAs-Based High-Temperature Superconductors

December 17, 2008
Author(s)
Qingzhen Huang, Yiming Qiu, Wei Bao, Mark Green, Jeffrey Lynn, Y. C. Gasparovic, T. Wu, G. Wu, X. H. Chen
The recent discovery of superconductivity in (Ba,K)Fe2As2, which crystallizes in the ThCr2Si2 (122) structure as compared with the LnFeAsO (Ln is lanthanide) systems that possess the ZrCuSiAs (1111) structure, demonstrates the exciting potential of the

Pressure-induced volume-collapsed tetragonal phase of CaFe 2 As 2 as seen via neutron scattering

November 24, 2008
Author(s)
A. Kreyssig, Mark Green, Y. Lee, G. D. Samolyuk, Pawel Zajdel, Jeffrey Lynn, S. L. Bud'ko, M. S. Torikachvili, N. Ni, S. Nandi, Juscelino Leao, Sarah Poulton, D. N. Argyriou, B. N. Harmon, R. J. McQueeny, P. C. Canfield, A. I. Goldman
Recent investigations of the superconducting iron-arsenide families have highlighted the role of pressure, be it chemical or mechanical, in fostering superconductivity. Here we report that CaFe2As2 undergoes a pressure-induced transition to a nonmagnetic

Josephson phase qubit circuit for the evaluation of advanced tunnel barrier materials

November 21, 2008
Author(s)
Jeffrey S. Kline, Haohua Wang, Seongshik Oh, John M. Martinis, David P. Pappas
We have found that crystalline Josephson junctions have critical current density control problems which decrease circuit yield. We present a qubit circuit designed to accommodate a factor-of-five variation in critical current density for the evaluation of

Unusual Heavy-mass Nearly Ferromagnetic State with a Surprisingly Large Wilson Ratio in Double Layered Ruthenates (Sr 1-x Ca x ) 3 Ru 2 O 7

November 14, 2008
Author(s)
Z Qu, L Spinu, H Q. Yuan, V Dobrosavljevic, Wei Bao, Jeffrey Lynn, M Nicklas, J Peng, T J. Liu, F Fobes, E Flesch, Z Q. Mao
We report a very unusual heavy-mass nearly ferromagnetic state with a surprisingly large Wilson ratio Rw (e.g., Rw 700 for x = 0.2) in double layered ruthenates (Sr 1- xCa x) 3Ru 2O 7. This state does not evolve into a long-range ferromagnetic order

Surviving the Transition

October 31, 2008
Author(s)
Kristian Helmerson
Observations of the birth of a superfluid have uncovered details of the microphysics of phase transitions. Whether these results can be used to model such trnsitions in the early Universe is an open question.

Structural and magnetic phase diagram of CeFeAsO1- xFx and its relation to high-temperature superconductivity

October 26, 2008
Author(s)
Jun Zhao, Qingzhen Huang, Clarnia dela Cruz, Shiliang Li, Jeffrey Lynn, Ying Chen, Mark Green, G. F. Chen, Z. C. Li, J. L. Luo, N. L. Wang, Pengcheng Dai
Recently, high-transition-temperature (high-Tc) superconductivity was discovered in the iron pnictide RFeAsO1−xFx (R, rare-earth metal) family of materials. We use neutron scattering to study the structural and magnetic phase transitions in CeFeAsO1−xFx as

Collective dynamics in the Heisenberg pyrochlore antiferromagnet Gd 2 Sn 2 O 7

October 22, 2008
Author(s)
J. R. Stewart, Jason Gardner, Yiming Qiu, G. Ehlers
Gd2Sn2O7 is believed to be a good approximation to a Heisenberg antiferromagnet on a pyrochlore lattice with exchange and dipole-dipole interactions. The system is known to enter a long-range ordered ground state (the "Palmer Chalker" state) below Tc = 1 K

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"

Ultra-high resolution alpha particle spectroscopy using calorimetry

September 23, 2008
Author(s)
Robert D. Horansky, Joel N. Ullom, James A. Beall, Gene C. Hilton, Kent D. Irwin, Don Dry, Beth Hastings, Stephen Lamont, Clifford R. Rudy, Michael W. Rabin
Calorimetry has been used since the late 1700?s to measure the heat output of physical processes ranging from chemical reactions to the respiration of organisms . Calorimetry is performed by measuring the temperature change caused by heat release into a

Signature of magnetic phase separation in the ground state of Pr 1 - x Ca x MnO 3

August 27, 2008
Author(s)
Hao Sha, F Ye, Pengcheng Dai, J. A. Fernandez-Baca, D Mesa, Jeffrey Lynn, Y Tomioka, Y Tokura, Jiandi Zhang
Neutron scattering has been used to investigate the evolution of long- and short-range charge-ordered (CO), ferromagnetic, and antiferromagnetic (AF) correlations in single crystals of Pr1−xCaxMnO3. The existence and population of spin clusters as

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

Magnetic order of the iron spins in NdFeAsO

August 21, 2008
Author(s)
Ying Chen, Jeffrey Lynn, Jiying Li, G. J. Li, G. F. Chen, J. L. Luo, N. L. Wang, Pengcheng Dai, Clarnia dela Cruz, H. A. Mook
Polarized and unpolarized neutron diffraction measurements have been carried out to investigate the iron magnetic order in undoped NdOFeAs. Antiferromagnetic order is observed below 141(6) K, which is in close proximity to the structural distortion

Ferromagnetism in CuO-ZnO multilayers

July 28, 2008
Author(s)
C. Sudakar, K. Pradmanabhan, R Naik, G Lawes, Brian Kirby, Sanjiv Kumar, V. M. Naik
We investigated the magnetic properties of CuO–ZnO heterostructures to elucidate the origin of the ferromagnetic signature in Cu doped ZnO. The CuO and ZnO layer thickness were varied from 15 to 150 nm and from 70 to 350 nm⁠, respectively. Rutherford
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