oalib

Publish in OALib Journal

ISSN: 2333-9721

APC: Only $99

Submit

Any time

2020 ( 34 )

2019 ( 227 )

2018 ( 241 )

2017 ( 242 )

Custom range...

Search Results: 1 - 10 of 144402 matches for " B. Fak "
All listed articles are free for downloading (OA Articles)
Page 1 /144402
Display every page Item
Polarization analysis of the inelastic magnetic scattering in Sr2RuO4
B. Fak,S. Raymond,F. Servant,P. Lejay,J. Flouquet
Physics , 2003,
Abstract: The spin fluctuations in the normal state of the unconventional superconductor Sr2RuO4 have been studied using inelastic neutron scattering with polarization analysis on single crystals. We find that the spin fluctuations are anisotropic with chi_c/chi_ab=2.0 (0.4). No evidence for Q-independent or nearly-ferromagnetic spin fluctuations are found in the energy range 4-22 meV, in contradiction with NMR measurements.
Inflection point in the magnetic field dependence of the ordered moment of URu2Si2 observed by neutron scattering in fields up to 17 T
F. Bourdarot,B. Fak,K. Habicht,K. Prokes
Physics , 2002, DOI: 10.1103/PhysRevLett.90.067203
Abstract: We have measured the magnetic field dependence of the ordered antiferromagnetic moment and the magnetic excitations in the heavy-fermion superconductor URu2Si2 for fields up to 17 Tesla applied along the tetragonal c axis, using neutron scattering. The decrease of the magnetic intensity of the tiny moment with increasing field does not follow a simple power law, but shows a clear inflection point, indicating that the moment disappears first at the metamagnetic transition at ~40 T. This suggests that the moment m is connected to a hidden order parameter Phi which belongs to the same irreducible representation breaking time-reversal symmetry. The magnetic excitation gap at the antiferromagnetic zone center Q=(1,0,0) increases continuously with increasing field, while that at Q=(1.4,0,0) is nearly constant. This field dependence is opposite to that of the gap extracted from specific-heat data.
Comment on "Magnetic field effects on neutron diffraction in the antiferromagnetic phase of UPt3"
B. Fak,N. H. van Dijk,A. S. Wills
Physics , 2001, DOI: 10.1103/PhysRevB.66.216401
Abstract: Moreno and Sauls [Phys. Rev. B 63, 024419 (2000)] have recently tried to reanalyze earlier neutron scattering studies of the antiferromagnetic order in UPt3 with a magnetic field applied in the basal plane. In their calculation of the magnetic Bragg peak intensities, they perform an average over different magnetic structures belonging to distinct symmetry representations. This is incorrect. In addition, they have mistaken the magnetic field direction in one of the experiments, hence invalidating their conclusions concerning the experimental results.
Reply to: Comment by S.-L. Drechsler et al. (arXiv:1006.5070v2)
M. Enderle,B. Fak,H. -J. Mikeska,R. K. Kremer
Physics , 2011,
Abstract: In a comment on arXiv:1006.5070v2, Drechsler et al. claim that the frustrated ferromagnetic spin-1/2 chain LiCuVO4 should be described by a strong rather than weak ferromagnetic nearest-neighbor interaction, in contradiction with their previous work. Their comment is based on DMRG and ED calculations of the magnetization curve and the magnetic excitations. We show that their parameters are at odds with the magnetic susceptibility and the magnetic excitation spectrum, once intensities are taken into account, and that the magnetization curve cannot discriminate between largely different parameter sets within experimental uncertainties. We further show that their new exact diagonalization results support the validity of the RPA-approach, and strongly reinforce our conclusion on the existence of a four-spinon continuum in LiCuVO4, see Enderle et al., Phys. Rev. Lett. 104 (2010) 237207.
Roton-Phonon Interactions in Superfluid 4He
B. Fak,T. Keller,M. E. Zhitomirsky,A. L. Chernyshev
Physics , 2012, DOI: 10.1103/PhysRevLett.109.155305
Abstract: High-resolution neutron resonance spin-echo measurements of superfluid 4He show that the roton energy does not have the same temperature dependence as the inverse lifetime. Diagrammatic analysis attributes this to the interaction of rotons with thermally excited phonons via both four- and three-particle processes, the latter being allowed by the broken gauge symmetry of the Bose condensate. The distinct temperature dependence of the roton energy at low temperatures suggests that the net roton-phonon interaction is repulsive.
Neutron scattering studies of the spin ices Ho2Ti2O7 and Dy2Ti2O7 in applied magnetic field
T. Fennell,O. A. Petrenko,B. Fak,J. S. Gardner,S. T. Bramwell,B. Ouladdiaf
Physics , 2005, DOI: 10.1103/PhysRevB.72.224411
Abstract: Neutron diffraction has been used to investigate the magnetic correlations in single crystals of the spin ice materials Ho2Ti2O7 and Dy2Ti2O7 in an external magnetic field applied along either the [001] or [1-10] crystallographic directions. With the field applied along [001] a long range ordered groundstate is selected from the spin ice manifold. With the field applied along [1-10] the experiments show that the spin system is separated into parallel (alpha) and perpendicular (beta) chains with respect to the field. This leads to partial ordering and the appearance of quasi-one-dimensional magnetic structures. In both field orientations this frustrated spin system is defined by the appearance of metastable states, magnetization plateaux and unusually slow, field regulated dynamics.
The Onconeural Antigen cdr2 Is a Novel APC/C Target that Acts in Mitosis to Regulate C-Myc Target Genes in Mammalian Tumor Cells
Kevin J. O'Donovan,Jennifer Diedler,Graeme C. Couture,John J. Fak,Robert B. Darnell
PLOS ONE , 2012, DOI: 10.1371/journal.pone.0010045
Abstract: Cdr2 is a tumor antigen expressed in a high percentage of breast and ovarian tumors and is the target of a naturally occurring tumor immune response in patients with paraneoplastic cerebellar degeneration, but little is known of its regulation or function in cancer cells. Here we find that cdr2 is cell cycle regulated in tumor cells with protein levels peaking in mitosis. As cells exit mitosis, cdr2 is ubiquitinated by the anaphase promoting complex/cyclosome (APC/C) and rapidly degraded by the proteasome. Previously we showed that cdr2 binds to the oncogene c-myc, and here we extend this observation to show that cdr2 and c-myc interact to synergistically regulate c-myc-dependent transcription during passage through mitosis. Loss of cdr2 leads to functional consequences for dividing cells, as they show aberrant mitotic spindle formation and impaired proliferation. Conversely, cdr2 overexpression is able to drive cell proliferation in tumors. Together, these data indicate that the onconeural antigen cdr2 acts during mitosis in cycling cells, at least in part through interactions with c-myc, to regulate a cascade of actions that may present new targeting opportunities in gynecologic cancer.
Inelastic neutron scattering studies of the quantum frustrated magnet clinoatacamite, $γ$-Cu2(OD)3Cl, a proposed valence bond solid (VBS)
A. S. Wills,T. G. Perring,S. Raymond,B. Fak,J. -Y. Henry,M. Telling
Physics , 2009, DOI: 10.1088/1742-6596/145/1/012056
Abstract: The frustrated magnet clinoatacamite, $\gamma$-Cu$_2$(OH)$_3$Cl, is attracting a lot of interest after suggestions that at low temperature it forms an exotic quantum state termed a Valence Bond Solid (VBS) made from dimerised Cu$^{2+}$ ($S=1/2$) spins.\cite{Lee_clinoatacamite} Key to the arguments surrounding this proposal were suggestions that the kagom\'e planes in the magnetic pyrochlore lattice of clinoatacamite are only weakly coupled, causing the system to behave as a quasi-2-dimensional magnet. This was reasoned from the near 95$^\circ$ angles made at the bridging oxygens that mediate exchange between the Cu ions that link the kagom\'e planes. Recent work pointed out that this exchange model is inappropriate for $\gamma$-Cu$_2$(OH)$_3$Cl, where the oxygen is present as a $\mu_3$-OH.\cite{Wills_JPC} Further, it used symmetry calculations and neutron powder diffraction to show that the low temperature magnetic structure ($T<6$ K) was canted and involved significant spin ordering on all the Cu$^{2+}$ spins, which is incompatible with the interpretation of simultaneous VBS and N\'eel ordering. Correspondingly, clinoatacamite is best considered a distorted pyrochlore magnet. In this report we show detailed inelastic neutron scattering spectra and revisit the responses of this frustrated quantum magnet.
Spin correlation in kagomé ice state: neutron scattering study of the dipolar spin ice Dy_{2}Ti_{2}O_{7} under magnetic field along [111]
Y. Tabata,H. Kadowaki,K. Matsuhira,Z. Hiroi,N. Aso,E. Ressouche,B. Fak
Physics , 2006, DOI: 10.1016/j.jmmm.2006.10.479
Abstract: We have investigated the kagom\'{e} ice state in the frustrated pyrochlore oxide Dy_{2}Ti_{2}O_{7} under magnetic field along a [111] axis. Spin correlations have been measured by neutron scattering and analyzed by Monte-Carlo simulation. The kagom\'{e} ice state, which has a non-vanishing residual entropy well established for the nearest-neighbor spin ice model by the exact solution, has been proved to be realized in the dipolar-interacting spin ice Dy_{2}Ti_{2}O_{7} by observing the characteristic spin correlations. The simulation shows that the long-range interaction gives rise to only weak lifting of the ground state degeneracy and that the system freezes within the degenerate kagom\'{e} ice manifold .
Anomalous spin distribution in the superconducting ferromagnet UCoGe studied by polarized neutron diffraction
K. Prokes,A. de Visser,Y. K. Huang,B. Fak,E. Ressouche
Physics , 2010, DOI: 10.1103/PhysRevB.81.180407
Abstract: We report a polarized neutron diffraction study conducted to reveal the nature of the weak ferromagnetic moment in the superconducting ferromagnet UCoGe. We find that the ordered moment in the normal phase in low magnetic fields (B // c) is predominantly located at the U atom and has a magnitude of about 0.1 muB at 3 T, in agreement with bulk magnetization data. By increasing the magnetic field the U moment grows to about 0.3 muB in 12 T and most remarkably, induces a substantial moment (about 0.2 muB) on the Co atom directed antiparallel to the U moment. The anomalous polarizability of the Co 3d orbitals is unique among uranium intermetallics and might reflect the proximity to a magnetic quantum critical point of UCoGe in zero field.
Page 1 /144402
Display every page Item


Home
Copyright © 2008-2017 Open Access Library. All rights reserved.