All Publications

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11,643 items found (19 items not approved), displaying 51 to 60.[First/Prev] 2, 3, 4, 5, 6, 7, 8, 9 [Next/Last]

Instruments / Technical Area	Publication Details	Published
	Hysteresis effect in FePd magnetic stripes studied by coherent soft X-ray resonant magnetic scattering K Chesnel , G. Van Der Laan , F. Livet , Guillaume Beutier , A Marty , M Belakhovsky , A Haznar , Steve Collins Journal Of Synchrotron Radiation 11, 469-475 DOI: 10.1107/S090904950402309X PMID: 15496734 Show Abstract ▼ Abstract: An FePd thin film sample, showing magnetic stripe domains as imaged by magnetic force microscopy, has been measured by soft X-ray resonant magnetic scattering in reflection geometry. Illumination with coherent radiation, produced by inserting a 20 mum pinhole in front of the sample, leads to a magnetic speckle pattern in the scattered intensity that gives access to the domain morphology. Application of an in-plane magnetic field for a few seconds gives a strong change in the observed intensity fluctuations, which indicates a large degree of variation between the two patterns taken before and after field exposure. From the speckle pattern we calculate a degree of coherence of beta = 0.5 for the incident beam.	Nov 2004
Vacuum	Ionization of sputtered metals in high power pulsed magnetron sputtering Johan Bohlmark , Jones Alami , Chris Christou , Arutiun P. Ehiasarian , Ulf Helmersson Journal Of Vacuum Science & Technology A: Vacuum, Surfaces, And Films 23 (1), 18-22 DOI: 10.1116/1.1818135 Show Abstract ▼ Abstract: The ion to neutral ratio of the sputtered material have been studied for high power pulsed magnetron sputtering and compared with a continuous direct, current (dc) discharge using the same experimental setup except for the power source. Optical emission spectroscopy (OES) was used to study the optical emission from the plasma through a side window. The emission was shown to be dominated by emission from metal ions. The distribution of metal ionized states clearly differed from the distribution of excited states, and we suggest the presence of a hot dense plasma surrounded by a cooler plasma. Sputtered material was ionized close to the target and transported into a cooler plasma region where the emission was also recorded. Assuming a Maxwell-Boltzmann distribution of excited states the emission from the plasma was quantified. This showed that the ionic contribution to the recorded spectrum was over 90% for high pulse. powers. Even at relatively low applied pulse powers, the recorded spectra were dominated by emission from ions. OES analysis of the discharge in a continuous dc magnetron discharge was also made, which demonstrated much lower ionization. (C) 2005 American Vacuum Society.	Nov 2004
Diagnostics	Diamond Storage Ring Optical And X-Ray Diagnostics Cyrille Thomas , Guenther Rehm BEAM INSTRUMENTATION WORKSHOP 2004: Eleventh Beam Instrumentation Workshop DOI: 10.1063/1.1831146 Show Abstract ▼ Abstract: This paper gives an overview of the optical and X-ray diagnostics for the 3-GeV stored electron beam of the DIAMOND storage ring. The specification and the requirement for the diagnostics are given in detail. The diagnostics are performed using the properties of the synchrotron radiation from two bending magnets in the visible and in the X-ray range. Four measurements will provide information on the beam longitudinal distribution, the relative energy spread, the transverse size, and emittance of the beam.	Nov 2004
Diagnostics	Acquisition of Diagnostic Screen and Synchrotron Radiation Images Using IEEE1394 Digital Cameras Guenther Rehm BEAM INSTRUMENTATION WORKSHOP 2004: Eleventh Beam Instrumentation Workshop DOI: 10.1063/1.1831175 Show Abstract ▼ Abstract: In the LINAC, booster synchrotron and transfer lines of DIAMOND a number of screens (YAG:Ce and OTR) as well as synchrotron radiation ports will be used to acquire information about the transverse beam distribution. Digital IEEE1394 cameras have been selected for their range of sensor sizes and resolutions available, their easy triggering to single events, and their noise-free transmission of the images into the control system. Their suitability for use under influence of high-energy radiation has been verified. Images from preliminary tests at the SRS Daresbury are presented.	Nov 2004
	Phase transitions, noncollinear magnetism, and magnetoelectric symmetry in gadolinium tetraboride S. W. Lovesey , J. Fernández Rodríguez , J. A. Blanco Rodriguez , P. J. Brown Physical Review B 70 DOI: 10.1103/PhysRevB.70.172414 Show Abstract ▼ Abstract: Resonant x-ray Bragg diffraction data for gadolinium tetraboride (GdB4), gathered at the Gd L3 edge above and below a transition temperature TN=42K, is shown to imply that a structural phase transition occurs at temperatures above the onset of long-range magnetic order in the Gd moments. Specifically, the room-temperature tetragonal structure P4∕mbm would appear to change to orthorhombic P21212, which is a continuous structural phase transition in Landau and renormalization-group theories. Below TN, a configuration of Gd moments is established, which is consistent with the magnetic Shubnikov group P21212, where moments are constrained to lie in the plane normal to the c axis. The crystal structure and magnetic point symmetry (222) inferred, is one of the class of 58 magnetic groups that can show the magnetoelectric effect.	Nov 2004
	Phonon effects in resonant “forbidden” reflections V. E. Dmitrienko , E. Ovchinnikova , K. Ishida , J. Kokubun , A. Kirfel , S. Collins , D. Laundy , A. P. Oreshko , D. Cabaret Physica Status Solidi (c) 1 (11), 3081 - 3084 DOI: 10.1002/pssc.200405396 Show Abstract ▼ Abstract: The influence of atomic vibrations on the ”forbidden” Bragg reflections, excited near absorption edges owing to anisotropic resonant X-ray scattering, is discussed. It is shown that in spite of the difference of X-rays and phonons energies the “forbidden” reflections can be extremely sensitive to the atomic vibrations and their correlations. The numerical calculations are performed taking into account the correlations of atomic thermal displacements, which give an adequate description of the thermal growth of the 600 forbidden reflection in Ge and describe drastic changes of the “forbidden” reflections spectra in ZnO	Nov 2004
Theoretical Physics	Direct and quantitative determination of the orbital ordering in CeB Yoshi Tanaka , U Staub , K Katsumata , S. W Lovesey , J. E Lorenzo , Y Narumi , V Scagnoli , S Shimomura , Y Tabata , Y Onuki , Y Kuramoto , A Kikkawa , T Ishikawa , H Kitamura EPL (Europhysics Letters) 68 (5), 671 - 677 DOI: 10.1209/epl/i2004-10271-9 Show Abstract ▼ Abstract: Results of non-resonant X-ray Bragg diffraction by CeB6 are reported. This material has been described in terms of a simple antiferro-quadrupolar order below TQ = 3.2 K. We determine for the first time, directly and quantitatively the orbital ordering in this material. In particular, we find direct evidence for a simultaneous ordering of a quadrupole (QP) and a hexadecapole (HDP) moments below TQ. From a strong dependence of the Bragg intensity on applied magnetic field in phase II, we conclude that octupole (OP) moments are induced and are coupled to the QP and HDP moments. When spontaneous magnetic dipole order sets in below TN = 2.4 K (phase III), a large enhancement of the Bragg intensity confirms the coupling between the dipole and the QP, OP and HDP moments.	Dec 2004
	X-ray high-resolution diffraction using refractive lenses Michael Drakopoulos , A. Snigirev , Irina Snigireva , Jorg Schilling Applied Physics Letters 86 (1) DOI: 10.1063/1.1843282 Show Abstract ▼ Abstract: Refractive x-raylenses have recently been applied for imaging and scanning microscopy with hard x rays. We report the application of refractive lenses in an optical scheme for high-resolution x-ray diffraction, performed at a high brilliance synchrotron radiation source. An experimental proof of principle and a theoretical discussion are presented. In particular, we observe the x-ray diffraction pattern from a two-dimensional photonic crystal with 4.2μm periodicity, which normally is employed to scatter light in the infrared.	Dec 2004
	Dhesi et al. Reply: S. Dhesi , H. Durr , M. Munzenberg , W. Felsch Physical Review Letters 94 (3) DOI: 10.1103/PhysRevLett.94.039702 Show Abstract ▼ Abstract: .... raise three objections regarding the analysis in our Letter. First, Lorenzo et al. claim that the second order peak could arise from nonmagnetic effects such as magnetoelastic strain fields. Second, that the second order peak could arise from magnetic effects, but caused by an unequal distribution of spinup and spin-down domains. Third, that the shift with incidence angle of the second order peak might not arise from x-ray standing wave fields. In the following we refute these claims and show that the analysis given in our Letter remains valid.	Jan 2005
Theoretical Physics	Orbital Dynamics of the 4f Shell in DyB2C2 U. Staub , A. Mulders , O. Zaharko , S. Janssen , T. Nakamura , S. W. Lovesey Physical Review Letters 94 (3) DOI: 10.1103/PhysRevLett.94.036408 PMID: 15698297 Show Abstract ▼ Abstract: For the first time, fluctuations in the Dy quadrupole (orbital) moment have been observed in DyB2C2 using inelastic neutron scattering. The observed quasielastic response is decomposed into two components, one reflecting transitions within the doublets (narrow) and the other transitions between the doublets (broad) of the effective Dy quartet ground state. The widths of the narrow and broad components are shown to arise from fluctuations in the magnetic dipole and the electric quadrupole moments, respectively.	Jan 2005

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