Z. Yamani
National Research Council
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Featured researches published by Z. Yamani.
Nature Physics | 2007
C. R. Wiebe; J. A. Janik; Gregory John MacDougall; G. M. Luke; J.D. Garrett; H. D. Zhou; Y. J. Jo; L. Balicas; Y. Qiu; J. R. D. Copley; Z. Yamani; W. J. L. Buyers
Gapped itinerant spin excitations account for missing entropy in the hidden-order state of URu 2 Si 2
Physical Review Letters | 2008
A. D. Christianson; M. D. Lumsden; Manuel Angst; Z. Yamani; Wei Tian; Rongying Jin; E. A. Payzant; Stephen E Nagler; B. C. Sales; David Mandrus
We present single crystal neutron diffraction measurements on multiferroic LuFe(2)O(4). Magnetic reflections are observed below transitions at 240 and 175 K indicating that the magnetic interactions in LuFe(2)O(4) are three-dimensional in character. The magnetic structure is refined as a ferrimagnetic spin configuration below the 240 K transition. Below 175 K a significant broadening of the magnetic peaks is observed along with the buildup of a diffuse component to the magnetic scattering.
PLOS ONE | 2013
Clare L. Armstrong; Drew Marquardt; Hannah Dies; Norbert Kučerka; Z. Yamani; John Katsaras; An-Chang Shi; Maikel C. Rheinstädter
Rafts, or functional domains, are transient nano- or mesoscopic structures in the exoplasmic leaflet of the plasma membrane, and are thought to be essential for many cellular processes. Using neutron diffraction and computer modelling, we present evidence for the existence of highly ordered lipid domains in the cholesterol-rich (32.5 mol%) liquid-ordered () phase of dipalmitoylphosphatidylcholine membranes. The liquid ordered phase in one-component lipid membranes has previously been thought to be a homogeneous phase. The presence of highly ordered lipid domains embedded in a disordered lipid matrix implies non-uniform distribution of cholesterol between the two phases. The experimental results are in excellent agreement with recent computer simulations of DPPC/cholesterol complexes [Meinhardt, Vink and Schmid (2013). Proc Natl Acad Sci USA 110(12): 4476–4481], which reported the existence of nanometer size domains in a liquid disordered lipid environment.
Physical Review Letters | 2012
Chetan Dhital; Z. Yamani; Wei Tian; J. Zeretsky; Athena S. Sefat; Ziqiang Wang; R. J. Birgeneau; Stephen D. Wilson
We report neutron scattering experiments probing the influence of uniaxial strain on both the magnetic and structural order parameters in the parent iron pnictide compound, BaFe2As2. Our data show that modest strain fields along the in-plane orthorhombic b axis can affect significant changes in phase behavior simultaneous to the removal of structural twinning effects. As a result, we demonstrate in BaFe2As2 samples detwinned via uniaxial strain that the in-plane C4 symmetry is broken by both the structural lattice distortion and long-range spin ordering at temperatures far above the nominal (strain-free) phase transition temperatures. Surprising changes in the magnetic order parameter of this system under relatively small strain fields also suggest the inherent presence of magnetic domains fluctuating above the strain-free ordering temperature in this material.
Physical Review Letters | 2012
J. S. De Groot; Karol Marty; M. D. Lumsden; A. D. Christianson; Stephen E Nagler; Shilpa Adiga; Wouter J. H. Borghols; Karin Schmalzl; Z. Yamani; S. R. Bland; R. T. de Souza; U. Staub; W. Schweika; Y. Su; Manuel Angst
We present a detailed study of magnetism in LuFe(2)O(4), combining magnetization measurements with neutron and soft x-ray diffraction. The magnetic phase diagram in the vicinity of T(N) involves a metamagnetic transition separating an antiferro- and a ferrimagnetic phase. For both phases the spin structure is refined by neutron diffraction. Observed diffuse magnetic scattering far above T(N) is explained in terms of near degeneracy of the magnetic phases.
Physical Review Letters | 2012
Huiqian Luo; Rui Zhang; Mark Laver; Z. Yamani; Meng Wang; Xingye Lu; Miaoyin Wang; Yanchao Chen; Shiliang Li; Sung Chang; Jeffrey W. Lynn; Pengcheng Dai
Superconductivity in the iron pnictides develops near antiferromagnetism, and the antiferromagnetic (AF) phase appears to overlap with the superconducting phase in some materials such as BaFe(2-x)T(x)As2 (where T=Co or Ni). Here we use neutron scattering to demonstrate that genuine long-range AF order and superconductivity do not coexist in BaFe(2-x)Ni(x)As2 near optimal superconductivity. In addition, we find a first-order-like AF-to-superconductivity phase transition with no evidence for a magnetic quantum critical point. Instead, the data reveal that incommensurate short-range AF order coexists and competes with superconductivity, where the AF spin correlation length is comparable to the superconducting coherence length.
Physical Review Letters | 2014
Laura Toppozini; Sebastian Meinhardt; Clare L. Armstrong; Z. Yamani; Norbert Kučerka; Friederike Schmid; Maikel C. Rheinstädter
Rafts, or functional domains, are transient nano-or mesoscopic structures in the plasma membrane and are thought to be essential for many cellular processes such as signal transduction, adhesion, trafficking, and lipid or protein sorting. Observations of these membrane heterogeneities have proven challenging, as they are thought to be both small and short lived. With a combination of coarse-grained molecular dynamics simulations and neutron diffraction using deuterium labeled cholesterol molecules, we observe raftlike structures and determine the ordering of the cholesterol molecules in binary cholesterol-containing lipid membranes. From coarse-grained computer simulations, heterogenous membranes structures were observed and characterized as small, ordered domains. Neutron diffraction was used to study the lateral structure of the cholesterol molecules. We find pairs of strongly bound cholesterol molecules in the liquid-disordered phase, in accordance with the umbrella model. Bragg peaks corresponding to ordering of the cholesterol molecules in the raftlike structures were observed and indexed by two different structures: a monoclinic structure of ordered cholesterol pairs of alternating direction in equilibrium with cholesterol plaques, i.e., triclinic cholesterol bilayers.
Soft Matter | 2012
Clare L. Armstrong; Matthew A. Barrett; Laura Toppozini; Norbert Kučerka; Z. Yamani; John Katsaras; G. Fragneto; Maikel C. Rheinstädter
Lateral nanostructures in membranes, so-called rafts, are believed to strongly influence membrane properties and functions. The experimental observation of rafts has proven difficult as they are thought to be dynamic structures that likely fluctuate on nano- to microsecond time scales. Using neutron diffraction we present direct experimental evidence for the co-existence of gel and fluid lipid domains in a single-component phospholipid membrane made of DPPC as it undergoes its main phase transition. The coherence length of the neutron beam sets a lower limit for the size of structures that can be observed. Neutron coherence lengths between 30 and 242 A used in this study were obtained by varying the incident neutron energy and the resolution of the neutron spectrometer. We observe Bragg peaks corresponding to co-existing nanometer sized structures, both in out-of-plane and in-plane scans, by tuning the neutron coherence length. During the main phase transition, instead of a continuous transition that shows a pseudo-critical behavior, we observe the co-existence of gel and fluid domains.
Physical Review B | 2009
Stephen D. Wilson; Z. Yamani; C. R. Rotundu; Byron Freelon; Edith Bourret-Courchesne; R. J. Birgeneau
We present the results of an investigation of both the magnetic and structural phase transitions in a high quality single crystalline sample of the undoped, iron pnictide compound BaFe
Physical Review Letters | 2013
Xingye Lu; H. Gretarsson; Rui Zhang; X. Liu; Huiqian Luo; Wei Tian; Mark Laver; Z. Yamani; Young-June Kim; Andriy H. Nevidomskyy; Qimiao Si; Pengcheng Dai
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