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Displaying 26 - 50 of 78

Spin Jam Induced by Quantum Fluctuations in a Frustrated Magnet

September 15, 2015
Author(s)
Junjie Yang, Anjana Samarakoon, Sachith Dissanayake, Hiroaki Ueda, Israel Klich, Daniel M Pajerowski, Nicholas Butch, Qingzhen Huang, John R. Copley, Seung-Hun Lee
Since the discovery of spin glasses in dilute magnetic systems, their study has been largely focused on understanding randomness and defects as the driving mechanisms. However, it has been theoretically suggested that different mechanism. However, it has

Competition Between the Inter- and Intra-sublattice Interactions in Yb 2 V 2 O 7

February 27, 2015
Author(s)
Z. L. Dun, J. Ma, H. B. Cao, Yiming Qiu, John R. Copley, T. Hong, M. Matsuda, J. G. Cheng, M. Lee, E. S. Choi, S. Johnston, H. D. Zhou
We studied single crystals of Yb 2V 2O 7 using dc and ac susceptibility measurements, elastic and inelastic neutron scattering measurements, and linear spin wave theory. The experimental data shows a ferromagnetic ordering of V 4+ ions at 70 K, a short

Strong Competition between Orbital-ordering and Itinerancy in a Frustrated Spinel Vanadate

January 26, 2015
Author(s)
J. Ma, J. H. Lee, S. E. Hahn, Tao Hong, H. B Cao, A. A. Aczel, Z. L. Dun, M. B. Stone, W. Tian, Yiming Qiu, John R. Copley, H. D. Zhou, R. S. Fishman, M. Matsuda
The crossover from localized- to itinerant-electron behavior is associated with many intriguing phenomena such as metal-insulator transitions [1], colossal magnetoresistance [2], and superconductivity in heavy fermion [3] and Fe-based materials [4]

Temperature and Magnetic Field Dependence of Spin-Ice Correlations in the Pyrochlore Magnet Tb^2^Ti 2 O 7

July 23, 2014
Author(s)
K. Fritsch, E. Kermarrec, Kathryn Aileen Ross, Yiming Qiu, John R. Copley, D. Pomaranski, J. B. Kycia, H. A. Dabkowska, B. D. Gaulin
We present a parametric study of the diffuse magnetic scattering at (1/2, 1/2, 1/2}) positions in reciprocal space, ascribed to a frozen antiferromagnetic spin ice state in single crystalline Tb 2Ti 2O 7. Our high-resolution neturon scattering measurements

Incoherent Quasielastic Neutron Scattering Study of the Relaxation Dynamics in Molybdenum-Oxide Based Keplerate Type Nanocages

June 19, 2014
Author(s)
Antonio Faraone, Emiliano Fratini, Somenath Garai, Achim Muller, Madhu Sudan Tyagi, Timothy Jenkins, Eugene Mamontov, Rick L. Paul, John R. Copley, Piero Baglioni
The single particle relaxation dynamics of hydrogen atoms in different oxomolybdate Keplerate type nanocages characterized by a (metal) 30 icosidodecahedron and a size of {approximately equal}25 A were studied using Incoherent Quasielastic Neutron

Boson Peak in Deeply Cooled Confined Water: A Possible Way to Explore the Existence of the Liquid-to-Liquid Transition in Water

June 13, 2014
Author(s)
Zhe Wang, Kao-Hsiang Liu, Peisi Le, Mingda Li, Wei-Shan Chiang, Juscelino Leao, John R. Copley, Madhu Sudan Tyagi, Andrey Podlesnyak, Alexander I. Kolesnikov, Chung-Yuan Mou, Sow-Hsin Chen
The Boson peak in deeply-cooled water confined in nanopores is studied with inelastic neutron scattering. We show that the emergence of the Boson peak is correlated to the Widom line below 1600 bar. Above 1600 bar, the situation is different and from this

Order by Disorder Spin Wave Gap in the XY Pyrochlore Magnet Er 2 Ti 2 O 7

February 4, 2014
Author(s)
Kathryn Aileen Ross, Yiming Qiu, John R. Copley, H. A. Dabkowska, B. D. Gaulin
The recent determination of a robust spin Hamiltonian for the anti-ferromagnetic XY pyrochlore Er 2Ti 2O 7 reveals a most convincing case of the ¿order by quantum disorder¿ (ObQD) mechanism for ground state selection. This mechanism relies on quantum

Intertwining of Frustration with Magneto-Elastic Coupling in the Multiferroic LuMnO 3

December 25, 2013
Author(s)
Shin-ichiro Yano, Despina Louca, Songxue Chi, Masaaki Matsuda, Yiming Qiu, John R. Copley, Sang-Wook Cheong
Residual magnetic frustration in the multiferroic LuMNO 3 may be key towards understanding magneto-elastic coupling in hexagonal manganites. Critical magnetic scattering present well above the magnetic ordering temperature Τ N persists below, as observed

Successive Phase Transitions and Extended Spin-Excitation Continuum in the S=1/2 Triangular-Lattice Antiferromagnet Ba 3 CoSb 2 ) 9

December 26, 2012
Author(s)
H. D. Zhou, Cenke Xu, A. M. Hallas, H. J. Silverstein, C. R. Wiebe, I. Umegaki, J. Q. Yan, T. P. Murphy, J.-H. Park, Yiming Qiu, John R. Copley, Jason S. Gardner, Y. Takano
Using magnetic, thermal and neutron measurements on single-crystal samples, we show that Ba 3CoSb 2O 9 is a spin-1/2 triangular-lattice antiferromagnet with easy-axis anisotropy and two magnetic phase transitions bracketing an intermediate up-up-down phase

Magnetic Order and Fluctuations in the Presence of Quenched Disorder in the Kagome Staircase System (Co 1-x Mg x ) 3 V 2 O 8

November 21, 2012
Author(s)
K. Fritsch, Zahra Yamani, S. Chang, Yiming Qiu, John R. Copley, M. Ramazanoglu, H. A. Dabkowska, B. D. Gaulin
Co 3V 2O 8 is an orthorhombic magnet in which S=3/2} magnetic moments reside on two crystallographically inequivalent Co 2+ sites, which decorate a stacked, buckled version of the two dimensional kagome lattice, the stacked kagome staircase. The magnetic

Coherent Dynamics of meta-Toluidine Investigated by QuasiElastic Neutron Scattering

March 14, 2012
Author(s)
Antonio Faraone, Kunlun Hong, Larry Kneller, Michael Ohl, John R. Copley
The coherent dynamics of a typical fragil glass former, meta-toluidine, was investigated at the molecular level using QuasiElastic Neutron Scattering, with Time-of-Flight and Neutron Spin Echo spectrometers. It is well known that the static structure

Magnetic Excitations in the Geometric Frustrated Multiferroic CuCrO 2

September 28, 2011
Author(s)
M. Frontzek, J. T. Haraldsen, A. Podlesnyak, M. Matsuda, A. D. Christianson, R. S. Fishman, A. S. Sefat, Yiming Qiu, John R. Copley, S. Barilo, S. V. Shiryaev, G. Ehlers
In this paper detailed neutron scattering measurements of the magnetic excitation spectrum of CuCrO6d2^ in the ordered state below T N1 = 24.2 K are presented. The spectra are analyzed using a model Hamiltonian which includes interlayer-exchanged up to the
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