Magnetic x-ray-scattering study of uranium arsenide

McWhan, D. B.; Vettier, C.; Isaacs, Ellen; Ice, G. E.; Siddons, D. P.; Hastings, J. B.; Peters, Charles C.; Vogt, O.

doi:10.1103/physrevb.42.6007

Cited by 130 publications

(54 citation statements)

References 28 publications

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“…The enhancement factor depends on the density of final states uncovered by the exchange splitting and the factor of 50 for Ho pales into insignificance compared with faction of 10 6 observed in studies of UAs [13] (see Fig. 3), other actinides and transuranium compounds where there is a high density of atom-like 5d states.…”

Section: Resonant Exchange X-ray Scatteringmentioning

confidence: 99%

X-Ray Magnetic Scattering

Cooper

1992

Acta Phys. Pol. A

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Magnetic X-ray diffraction with synchrotron radiation is now an established technique for studies of antiferromagnets. The problems associated with the small magnetic scattering cross-section being alleviated by the dramatic enhancements found near absorption edges through resonant exchange scattering. The technique is particularly useful for those materials that require high wavevector resolution to reveal the structural phase transitions that accompany the magnetic ordering process or those that are difficult to investigate with neutrons, (e.g. samarium, for which recent results are presented). In the actinides the work is also motivated by the objective of performing an empirical separation of the spin and orbital components of magnetisation. Diffraction studies of ferromagnets require circular polarised radiation and suffer from the superposition of the small magnetic signal and the charge scattering; to date Lave methods have proved more successful than monochromatic beam studies. Ferro-and ferrimagnets can also be studied by Compton (inelastic) scattering but the cross-section is less well established: considerable effort has been directed to determining whether orbital magnetisation can be measured in these experiments and results on HoFe2 now indicate this is not so. Magnetic Compton profiles provide information about the momentum distribution of electrons with unpaired spins, and this, together with magnetisation data can provide the basis for the separation of spin and orbital magnetisation.

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Section: Resonant Exchange X-ray Scatteringmentioning

confidence: 99%

X-Ray Magnetic Scattering

Cooper

1992

Acta Phys. Pol. A

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“…We will concentrate on a review of the first experimental evidence for resonant scattering in holmium [35]. Then, we will present the dramatic enhancement discovered at the Μ edges of uranium in UAs [36], followed by the extension of this technique to physical problems involving magnetic order and phase transitions near surfaces.…”

Section: L2 Resonant Scatteringmentioning

confidence: 99%

“…First, nonresonant scattering studies will be presented that deal with the details of magnetic ordering in holmium [28,32] and magnetic superlattices [33], the separation of L versus S in holmium [7] and the use of white beam diffraction experiments to extract magnetic form faction [34]. Then, resonant magnetic scattering applications will be discnssed; we will concentrate on the cases of holmium [35] and UAs [36]. The resonant magnetic X-ray scattering technique can be extended to investigations of magnetic phase transitions, surface ordering, mixed valence materials, etc.…”

Section: Magnetic X-ray Scattering Experimentsmentioning

confidence: 99%

“…In the soft X-ray range below 3 keV (L edges of 3d metals), only reflectivity or X-ray absorption experiments can be performed. Resonant magnetic X-ray diffraction has been performed on most rare-earth metals [40][41][42] and intermetallics [43], on some d compounds [44,45] and a large variety of actinides [8,36,46,47]. We will concentrate on a review of the first experimental evidence for resonant scattering in holmium [35].…”

Section: L2 Resonant Scatteringmentioning

confidence: 99%

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Magnetic X-Ray Scattering

Vettier

1994

Acta Phys. Pol. A

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It was proposed in the 1950's that X-rays could be used to probe magnetization densities. After some experimental demonstrations of the technique, applications have shown that tle use of magnetic X-ray scattering c o m -b i n e d w i t h s y n c h r o t r o n r a d i a t i o n c a n l e a d t o i m p o r t a n t n e w d i s c o v e r i e s i n the magnetism of solid materials. Several important features have emerged, especially the resonant magnetic X-ray scattering: large enhancements of scattered intensities, site and species selectivity, X-ray energy and polarization dependence. These properties make it possible to study new phenomena: details of magnetic structures of materials including micro-crystals, new aspects of magnetic plase transitions and surface magnetism.

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“…Because the M absorption edge energies are much lower than those of L edges but increase with atomic number, uranium, the heaviest stable element, stands as the natural candidate to study. Indeed, there is both experimental and theoretical evidence for very strong anomalous scattering at the M IV and M V edges of uranium (5)(6)(7)(8).…”

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confidence: 99%

Multiwavelength anomalous diffraction analysis at the M absorption edges of uranium

Liu¹,

Ogata²,

Hendrickson³

2001

Proc. Natl. Acad. Sci. U.S.A.

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The multiwavelength anomalous diffraction (MAD) method for phase evaluation is now widely used in macromolecular crystallography. Successful MAD structure determinations have been carried out at the K or L absorption edges of a variety of elements. In this study, we investigate the anomalous scattering properties of uranium at its MIV (3.326 Å) and MV (3.490 Å) edge. Fluorescence spectra showed remarkably strong anomalous scattering at these edges (f ‫؍‬ ؊70e, f ‫؍‬ 80e at the MIV edge and f ‫؍‬ ؊90e, f ‫؍‬ 105e at the M V edge), many times higher than from any anomalous scatterers used previously for MAD phasing. However, the large scattering angles and high absorption at the low energies of these edges present some difficulties not found in typical crystallographic studies. We conducted test experiments at the MIV edge with crystals of porcine elastase derivatized with uranyl nitrate. A four-wavelength MAD data set complete to 3.2-Å Bragg spacings was collected from a single small frozen crystal. Analysis of the data yielded satisfactory phase information (average difference of 0 T ؊ 0 A for replicated determinations is 32°) and produced an interpretable electron-density map. Our results demonstrate that it is practical to measure macromolecular diffraction data at these edges with current instrumentation and that phase information of good accuracy can be extracted from such experiments. We show that such experiments have potential for the phasing of very large macromolecular assemblages.MAD ͉ protein crystallography ͉ resonance scattering ͉ x-ray absorption X -ray absorption increases sharply as the energy of incident x-rays meets the transition energy needed to excite an electron from an atomic orbital into the continuum. A prominent peak of absorption, known as a ''white line,'' can also appear at an absorption edge. These features enhance the intrinsic atomic absorption to produce a very rapid change with respect to wavelength in the vicinity of the absorption edge. White line features result from the stimulated resonant transition of an electron from a bound atomic state to an unoccupied molecular orbital. A resonant modulation of x-ray scattering accompanies the dispersion of x-ray absorption; these anomalous scattering increments to the normal scattering include an imaginary part, fЈЈ, that is proportional to the x-ray absorption spectrum and a real part, fЈ, that is related to fЈЈ by the Kramers-Kronig dispersion integral. The method of multiwavelength anomalous diffraction (MAD) takes advantage of such anomalous dispersion of x-ray scattering to accomplish de novo phasing of macromolecular crystal structures (1). In a MAD experiment, diffraction data are measured at several different wavelengths chosen in the vicinity of the absorption edge of a certain anomalous scatterer present in the crystal. This approach contrasts with the more conventional multiple isomorphous replacement (MIR) method, in which data sets are collected at the same single wavelength from native and different heavy-atom derivative...

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Magnetic x-ray-scattering study of uranium arsenide

Cited by 130 publications

References 28 publications

X-Ray Magnetic Scattering

X-Ray Magnetic Scattering

Magnetic X-Ray Scattering

Multiwavelength anomalous diffraction analysis at the M absorption edges of uranium

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