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Physics

Condensed matter

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Displaying 1051 - 1075 of 1242

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

Electric field control of the magnetic state in Bi Fe O3 single crystals

May 12, 2008
Author(s)
Seoungsu Lee, William D. Ratcliff, S.-W. Cheong, V. Kiryukhin
Single crystals of multiferroic BiFeO 3 were investigated using neutron scattering. Application of an electric field reversibly switches ferroelastic domains, inducing changes in the magnetic structure which follows rotation of the structural domains. In

Shear Thinning Near the Critical Point of Xenon

April 17, 2008
Author(s)
Robert F. Berg, Michael R. Moldover, M Yao, G A. Zimmerli
We measured shear thinning, a viscosity decrease ordinarily associated with complex liquids, near the critical point of xenon. The data span the range of reduced shear rates: 0.001 < γτ < 700, where γτ is the shear rate scaled by the relaxation time τ of

Residual Multiparticle Entropy Does Not Generally Change Sign Near Freezing

April 13, 2008
Author(s)
William P. Krekelberg, Vincent K. Shen, Jeffrey R. Errington, Thomas M. Truskett
The residual multiparticle entropy (RMPE) of two- and three-dimensional fluids changes sign near the freezing line, providing a quasi-universal one-phase rule for the location of the liquid-solid transition. We present new simulation results ford

Operation of an X-ray transition-edge sensor cooled by tunnel junction refrigerators

January 19, 2008
Author(s)
Nathan A. Tomlin, James A. Beall, Gene C. Hilton, Kent D. Irwin, Galen O'Neil, Dan Schmidt, Leila R. Vale, Joel Ullom
We demonstrate successful cooling of an X-ray transition-edge sensor (TES) using solid-state refrigerators based on normal-metal/insulator/superconductor (NIS) tunnel junctions. Above the TES transition temperature (Tc), we use Johnson noise thermometry to

Cosputtered Amorphous Nb_xSi_1-x Barriers for Josephson-Junction Circuits

December 1, 2006
Author(s)
Burm Baek, Paul D. Dresselhaus, Samuel P. Benz
Cosputtered Amorphous NbxSi1-x has been developed as a barrier material for Josephson junction array circuits. This material is not only promising as a normal-metal barrier for state-of-the-art Josephson voltage standard circuits, but the capability of

Scanning Tunneling Microscope - Web Page

November 1, 2006
Author(s)
Marilyn E. Jacox, John William Gadzuk
The scanning tunneling microscope [STM] is widely used in both industrial and fundamental research to obtain atomic-scale images of metal surfaces. It provides a three-dimensional profile of the surface which is very useful for characterizing surface

Thermally Assisted Atom Transfer on Surfaces

February 1, 2006
Author(s)
John William Gadzuk
The low-temperature rates for site-to-site transfer of single atoms and molecules adsorbed on surfaces have been determined in recent scanning tunneling microscopy (STM) studies within the temperature regime where the dominant transfer mechanism changes
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