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Sample records for resonant x-ray magnetic

  1. Element Selective X-ray Detected Magnetic Resonance

    SciTech Connect

    Goulon, J.; Rogalev, A.; Wilhelm, F.; Jaouen, N.; Goulon-Ginet, C.; Goujon, G.; Youssef, J. Ben; Indenbom, M. V.

    2007-01-19

    Element selective X-ray Detected Magnetic Resonance (XDMR) was measured on exciting the Fe K-edge in a high quality YIG thin film. Resonant pumping at high microwave power was achieved in the nonlinear foldover regime and X-ray Magnetic Circular Dichroism (XMCD) was used to probe the time-invariant change of the magnetization {delta}Mz due to the precession of orbital magnetization densities of states (DOS) at the Fe sites. This challenging experiment required us to design a specific instrumentation which is briefly described.

  2. Resonant magnetic scattering of polarized soft x rays

    SciTech Connect

    Sacchi, M.; Hague, C.F.; Gullikson, E.M.; Underwood, J.

    1997-04-01

    Magnetic effects on X-ray scattering (Bragg diffraction, specular reflectivity or diffuse scattering) are a well known phenomenon, and they also represent a powerful tool for investigating magnetic materials since it was shown that they are strongly enhanced when the photon energy is tuned across an absorption edge (resonant process). The resonant enhancement of the magnetic scattering has mainly been investigated at high photon energies, in order to match the Bragg law for the typical lattice spacings of crystals. In the soft X-ray range, even larger effects are expected, working for instance at the 2p edges of transition metals of the first row or at the 3d edges of rare earths (300-1500 eV), but the corresponding long wavelengths prevent the use of single crystals. Two approaches have been recently adopted in this energy range: (i) the study of the Bragg diffraction from artificial structures of appropriate 2d spacing; (ii) the analysis of the specular reflectivity, which contains analogous information but has no constraints related to the lattice spacing. Both approaches have their own specific advantages: for instance, working under Bragg conditions provides information about the (magnetic) periodicity in ordered structures, while resonant reflectivity can easily be related to electronic properties and absorption spectra. An important aspect common to all the resonant X-ray scattering techniques is the element selectivity inherent to the fact of working at a specific absorption edge: under these conditions, X-ray scattering becomes in fact a spectroscopy. Results are presented for films of iron and cobalt.

  3. X-ray resonant reflection from magnetic multilayers: Recursion matrix algorithm

    SciTech Connect

    Stepanov, S. A.; Sinha, S. K.

    2000-06-01

    Recursion equations for 2x2 scattering matrices have been derived to calculate resonant x-ray reflection from magnetic multilayers. The solution has been basically reduced to that found in Stepanov et al, Phys. Rev. B 57, 4829 (1998) for grazing incidence x-ray diffraction from crystalline multilayers. (c) 2000 The American Physical Society.

  4. Magnetic x-ray linear dichroism in resonant and non-resonant Gd 4f photoemission

    SciTech Connect

    Mishra, S.; Gammon, W.J.; Pappas, D.P.

    1997-04-01

    The enhancement of the magnetic linear dichroism in resonant 4f photoemission (MLDRPE) is studied from a 50 monolayer film of Gd/Y(0001). The ALS at beamline 7.0.1 provided the source of linearly polarized x-rays used in this study. The polarized light was incident at an angle of 30 degrees relative to the film plane, and the sample magnetization was perpendicular to the photon polarization. The linear dichroism of the 4f core levels is measured as the photon energy is tuned through the 4d-4f resonance. The authors find that the MLDRPE asymmetry is strongest at the resonance. Near the threshold the asymmetry has several features which are out of phase with the fine structure of the total yield.

  5. Magnetic symmetries in neutron and resonant x-ray Bragg diffraction patterns of four iridium oxides

    NASA Astrophysics Data System (ADS)

    Lovesey, S. W.; Khalyavin, D. D.; Manuel, P.; Chapon, L. C.; Cao, G.; Qi, T. F.

    2012-12-01

    The magnetic properties of Sr2IrO4, Na2IrO3, Sr3Ir2O7 and CaIrO3 are discussed, principally in the light of experimental data in recent literature for Bragg intensities measured in x-ray diffraction with enhancement at iridium L-absorption edges. The electronic structure factors we report, which incorporate parity-even and acentric entities, serve the immediate purpose of making full use of crystal and magnetic symmetry to refine our knowledge of the magnetic properties of the four iridates from resonant x-ray diffraction data. They also offer a platform on which to interpret future investigations, using dichroic signals, resonant x-ray diffraction and neutron diffraction, for example, as well as ab initio calculations of electronic structure. Unit-cell structure factors, suitable for x-ray Bragg diffraction enhanced by an electric dipole-electric dipole (E1-E1) event, reveal exactly which iridium multipoles are visible, e.g., a magnetic dipole parallel to the crystal c-axis (z-axis) and an electric quadrupole with yz-like symmetry in the specific case of CaIrO3. Magnetic space-groups are assigned to Sr2IrO4, Sr3Ir2O7 and CaIrO3, namely, PIcca, PAban and Cm‧cm‧, respectively, in the Belov-Neronova-Smirnova notation. The assignment for Sr2IrO4 is possible because of our new high-resolution neutron diffraction data, gathered on a powder sample. In addition, the new data are used to show that the ordered magnetic moment of an Ir4+ ion in Sr2IrO4 does not exceed 0.29(4) μB. Na2IrO3 has two candidate magnetic space-groups that are not resolved with currently available resonant x-ray data.

  6. Extended reciprocal space observation of artificial spin ice with x-ray resonant magnetic scattering

    NASA Astrophysics Data System (ADS)

    Perron, J.; Anghinolfi, L.; Tudu, B.; Jaouen, N.; Tonnerre, J.-M.; Sacchi, M.; Nolting, F.; Lüning, J.; Heyderman, L. J.

    2013-12-01

    Soft x-ray resonant magnetic scattering is an element-sensitive technique that enables the characterization of the magnetic properties of a wide variety of systems. Here we apply this technique to study lithographically produced artificial spin ice, a particular class of magnetically frustrated systems comprising arrays of nanomagnets. Using a CCD detector we can access a large fraction of the reciprocal space at once, allowing us to easily distinguish the signatures of the magnetic ground-state ordering. Comparing the dichroic signal at the position of the Bragg peaks with model calculations based on the kinematical theory of x-ray diffraction, we are able to determine the number of reversed moments as a function of applied magnetic field for each of the two sublattices. This study demonstrates the benefit of having direct access to a significant fraction of the reciprocal space, and opens the way towards more sophisticated x-ray based experiments on artificial spin ice such as scattering of coherent x-ray beams to explore the dynamics of thermally activated systems.

  7. Single-pulse resonant magnetic scattering using a soft x-ray free-electron laser

    SciTech Connect

    Gutt, C.; Streit-Nierobisch, S.; Stadler, L.-M.; Faeustlin, R. R.; Treusch, R.; Feldhaus, J.; Weckert, E.; Vartanyants, I. A.; Gruebel, G.; Pfau, B.; Guenther, C. M.; Koennecke, R.; Eisebitt, S.; Froemter, R.; Kobs, A.; Stickler, D.; Oepen, H. P.; Grunze, M.; Rosenhahn, A.; Wilhein, T.

    2010-03-01

    We report on single-pulse resonant magnetic scattering experiments using soft x-ray pulses generated by the free-electron laser FLASH at DESY. We could record a magnetic diffraction pattern from a Co/Pt multilayer sample at the Co M{sub 2,3} edge with a single 30-fs-long FEL pulse. The analysis of the magnetic small-angle scattering signal for subsequent pulses indicates a threshold energy density below which there is no indication that the magnetic properties of the sample might be altered.

  8. X-ray and magnetic resonance imaging fusion for cardiac resynchronization therapy.

    PubMed

    Choi, Jinwoo; Radau, Perry; Xu, Robert; Wright, Graham A

    2016-07-01

    Cardiac Resynchronization Therapy (CRT) can effectively treat left ventricle (LV) driven Heart Failure (HF). However, 30% of the CRT recipients do not experience symptomatic benefit. Recent studies show that the CRT response rate can reach 95% when the LV pacing lead is placed at an optimal site at a region of maximal LV dyssynchrony and away from myocardial scars. Cardiac Magnetic Resonance (CMR) can identify the optimal site in three dimensions (3D). 3D CMR data can be registered to clinical standard x-ray fluoroscopy to achieve an optimal pacing of the LV. We have developed a 3D CMR to 2D x-ray image registration method for CRT procedures. We have employed the LV pacing lead on x-ray images and coronary sinus on MR data as landmarks. The registration method makes use of a guidewire simulation algorithm, edge based image registration technique and x-ray C-arm tracking to register the coronary sinus and pacing lead landmarks. PMID:27025953

  9. Perpendicular magnetic anisotropy in ultrathin Co|Ni multilayer films studied with ferromagnetic resonance and magnetic x-ray microspectroscopy

    NASA Astrophysics Data System (ADS)

    Macià, F.; Warnicke, P.; Bedau, D.; Im, M.-Y.; Fischer, P.; Arena, D. A.; Kent, A. D.

    2012-11-01

    Ferromagnetic resonance (FMR) spectroscopy, x-ray magnetic circular dichroism (XMCD) spectroscopy and magnetic transmission soft x-ray microscopy (MTXM) experiments have been performed to gain insight into the magnetic anisotropy and domain structure of ultrathin Co|Ni multilayer films with a thin permalloy layer underneath. MTXM images with a spatial resolution better than 25 nm were obtained at the Co L3 edge down to an equivalent thickness of Co of only 1 nm, which establishes a new lower boundary on the sensitivity limit of MTXM. Domain sizes are shown to be strong functions of the anisotropy and thickness of the film.

  10. Technology Preview: X-Ray Fused With Magnetic Resonance During Invasive Cardiovascular Procedures

    PubMed Central

    Gutiérrez, Luis F.; de Silva, Ranil; Ozturk, Cengizhan; Sonmez, Merdim; Stine, Annette M.; Raval, Amish N.; Raman, Venkatesh K.; Sachdev, Vandana; Aviles, Ronnier J.; Waclawiw, Myron A.; McVeigh, Elliot R.; Lederman, Robert J.

    2009-01-01

    Background We have developed and validated a system for real-time X-ray fused with magnetic resonance imaging, MRI (XFM), to guide catheter procedures with high spatial precision. Our implementation overlays roadmaps—MRI-derived soft-tissue features of interest—onto conventional X-ray fluoroscopy. We report our initial clinical experience applying XFM, using external fiducial markers, electrocardiogram (ECG)-gating, and automated real-time correction for gantry and table movement. Methods This prospective case series for technical development was approved by the NHLBI Institutional Review Board and included 19 subjects. Multimodality external fiducial markers were affixed to patients’ skin before MRI, which included contrast-enhanced, 3D T1-weighted, or breath-held and ECG-gated 2D steady state free precession imaging at 1.5T. MRI-derived roadmaps were manually segmented while patients were transferred to a calibrated X-ray fluoroscopy system. Image spaces were registered using the fiducial markers and thereafter permitted unrestricted gantry rotation, table panning, and magnification changes. Static and ECG-gated MRI data were transformed from 3D to 2D to correspond with gantry and table position and combined with live X-ray images. Results Clinical procedures included graft coronary arteriography, right ventricular free-wall biopsy, and iliac and femoral artery recanalization and stenting. MRI roadmaps improved operator confidence, and in the biopsy cases, outperformed the best available alternative imaging modality. Registration errors were increased when external fiducial markers were affixed to more mobile skin positions, such as over the abdomen. Conclusion XFM using external fiducial markers is feasible during X-ray guided catheter treatments. Multimodality image fusion may prove a useful adjunct to invasive cardiovascular procedures. PMID:18022851

  11. Plain X-ray, computed tomography and magnetic resonance imaging findings of telangiectatic osteosarcoma: a case report

    PubMed Central

    Koutoulidis, Vasilios; Koureas, Andreas; Moulopoulos, Lia; Gouliamos, Athanasios

    2009-01-01

    An 18-year-old male patient presented with chronic nonspecific pain of three months located at his left proximal tibia. The patient was admitted to our department for plain X-ray, computed tomography and magnetic resonance imaging examination. Plain X-ray and computed tomography revealed a geographic lytic lesion at the medial aspect of the proximal tibia. Biopsy of the lesion showed telangiectatic osteosarcoma. Image findings of all modalities are presented. PMID:19918488

  12. A complete software application for automatic registration of x-ray mammography and magnetic resonance images

    SciTech Connect

    Solves-Llorens, J. A.; Rupérez, M. J. Monserrat, C.; Lloret, M.

    2014-08-15

    Purpose: This work presents a complete and automatic software application to aid radiologists in breast cancer diagnosis. The application is a fully automated method that performs a complete registration of magnetic resonance (MR) images and x-ray (XR) images in both directions (from MR to XR and from XR to MR) and for both x-ray mammograms, craniocaudal (CC), and mediolateral oblique (MLO). This new approximation allows radiologists to mark points in the MR images and, without any manual intervention, it provides their corresponding points in both types of XR mammograms and vice versa. Methods: The application automatically segments magnetic resonance images and x-ray images using the C-Means method and the Otsu method, respectively. It compresses the magnetic resonance images in both directions, CC and MLO, using a biomechanical model of the breast that distinguishes the specific biomechanical behavior of each one of its three tissues (skin, fat, and glandular tissue) separately. It makes a projection of both compressions and registers them with the original XR images using affine transformations and nonrigid registration methods. Results: The application has been validated by two expert radiologists. This was carried out through a quantitative validation on 14 data sets in which the Euclidean distance between points marked by the radiologists and the corresponding points obtained by the application were measured. The results showed a mean error of 4.2 ± 1.9 mm for the MRI to CC registration, 4.8 ± 1.3 mm for the MRI to MLO registration, and 4.1 ± 1.3 mm for the CC and MLO to MRI registration. Conclusions: A complete software application that automatically registers XR and MR images of the breast has been implemented. The application permits radiologists to estimate the position of a lesion that is suspected of being a tumor in an imaging modality based on its position in another different modality with a clinically acceptable error. The results show that the

  13. X-Ray Detected Magnetic Resonance: A Unique Probe of the Precession Dynamics of Orbital Magnetization Components

    PubMed Central

    Goulon, Jośe; Rogalev, Andrei; Goujon, Gérard; Wilhelm, Fabrice; Ben Youssef, Jamal; Gros, Claude; Barbe, Jean-Michel; Guilard, Roger

    2011-01-01

    X-ray Detected Magnetic Resonance (XDMR) is a novel spectroscopy in which X-ray Magnetic Circular Dichroism (XMCD) is used to probe the resonant precession of local magnetization components in a strong microwave pump field. We review the conceptual bases of XDMR and recast them in the general framework of the linear and nonlinear theories of ferromagnetic resonance (FMR). Emphasis is laid on the information content of XDMR spectra which offer a unique opportunity to disentangle the precession dynamics of spin and orbital magnetization components at given absorbing sites. For the sake of illustration, we focus on selected examples in which marked differences were found between FMR and XDMR spectra simultaneously recorded on ferrimagnetically ordered iron garnets. With pumping capabilities extended up to sub-THz frequencies, high-field XDMR should allow us to probe the precession of orbital magnetization components in paramagnetic organometallic complexes with large zero-field splitting. Even more challenging, we suggest that XDMR spectra might be recorded on selected antiferromagnetic crystals for which orbital magnetism is most often ignored in the absence of any supporting experimental evidence. PMID:22272105

  14. Investigations of the (R)nickel germanide intermetallic compounds by X-ray resonant magnetic scattering

    NASA Astrophysics Data System (ADS)

    Kim, Jong-Woo

    2005-11-01

    The x-ray magnetic scattering (XRMS) intensities of the Gd, Tb, Dy, Ho, Er, and Tm L2,3 edges were investigated using two isostructural samples [Gd1/4Tb1/4Dy1/4Ho 1/4]Ni2Ge2 and [Gd1/3Er1/3Tm 1/3]Ni2Ge2 in order to elucidate systematics in the underlying resonance process. Taken together with theoretical linearized augmented planewave (LAPW) calculations employing LDA + U, we found that the XRMS intensity at the heavy rare-earth L edges is strongly related to the 4f-5d exchange interaction and that the branching ratio arises from the effects of spin orbit coupling in the 5d band. For Gd, the 4f-5 d exchange interaction is large and dominant over not only the spin orbit coupling but also other interactions. Therefore, the XRMS intensity of Gd L3 and L2 edges most closely reflects the state of 4f moments. In the pure GdNi2Ge2 compound, large antiferromagnetic (AFM) domains were found, comparable to the x-ray beam size. Single domain scattering was measured carefully with a very small beam size for various azimuth angles and temperatures. From this measurement, a second transition at 16 K in bulk measurements was identified as a transformation from a collinear squared-up structure at high temperature, to a tilted helical structure below 16 K. Since the XRMS scattering cross-section is strongly dependent on the magnetic moment direction, the AFM domain structure was imaged by the XRMS intensity. From single domain scattering data, the ratio of the spin moments in the collinear and the spiral structure of GdNi2Ge2 at the second magnetic transition temperature were derived and used to estimate the magnetic anisotropy energy of Gd. Surprisingly, the estimated magnetic anisotropy energy of Gd in this compound is much higher than that of pure Gd metal (about a order of magnitude). This is expected to be the effect of the anisotropy in 5d conduction band. More theoretical study is necessary to understand this observation.

  15. X-ray Resonant Scattering Study of the Magnetic Phase Diagram of Multiferroic TbMnO3

    SciTech Connect

    Wilkins, S.B.; Walker, H.C.; Ewings, R.A.; Fabrizi, F.; Mannix, D.; Mazzoli, C.; Paolasini, L.; Prabhakaran, D.; Boothroyd, A.T.; McMorrowa, D.F.

    2009-10-15

    We present the magnetic phase diagram of multiferroic TbMnO{sub 3} for H {parallel} b determined using X-ray resonant scattering at the Tb L{sub 3}-edge. Investigations of two different magnetic domains, C-type and F-type, demonstrate very similar behavior in high applied magnetic fields, with a low temperature incommensurate to commensurate transition at H {approx_equal} 4.5 T, concurrent with the polarization flop observed in bulk magnetoelectric measurements.

  16. Phonon effects on x-ray absorption and nuclear magnetic resonance spectroscopies

    NASA Astrophysics Data System (ADS)

    Nemausat, Ruidy; Cabaret, Delphine; Gervais, Christel; Brouder, Christian; Trcera, Nicolas; Bordage, Amélie; Errea, Ion; Mauri, Francesco

    2015-10-01

    In material sciences, spectroscopic approaches combining ab initio calculations with experiments are commonly used to accurately analyze the experimental spectral data. Most state-of-the-art first-principles calculations are usually performed assuming an equilibrium static lattice. Yet, nuclear motion affects spectra even when reduced to the zero-point motion at 0 K. We propose a framework based on density-functional theory that includes quantum thermal fluctuations in theoretical x-ray absorption near-edge structure (XANES) and solid-state nuclear magnetic resonance (NMR) spectroscopies and allows to well describe temperature effects observed experimentally. Within the Born-Oppenheimer and quasiharmonic approximations, we incorporate the nuclear motion by generating several nonequilibrium configurations from the dynamical matrix. The averaged calculated XANES and NMR spectral data have been compared to experiments in MgO. The good agreement obtained between experiments and calculations validates the developed approach, which suggests that calculating the XANES spectra at finite temperature by averaging individual nonequilibrium configurations is a suitable approximation. This study highlights the relevance of phonon renormalization and the relative contributions of thermal expansion and nuclear dynamics on NMR and XANES spectra on a wide range of temperatures.

  17. Quantitative imaging of cell-permeable magnetic resonance contrast agents using x-ray fluorescence.

    PubMed

    Endres, Paul J; Macrenaris, Keith W; Vogt, Stefan; Allen, Matthew J; Meade, Thomas J

    2006-01-01

    The inability to transduce cellular membranes is a limitation of current magnetic resonance imaging probes used in biologic and clinical settings. This constraint confines contrast agents to extracellular and vascular regions of the body, drastically reducing their viability for investigating processes and cycles in developmental biology. Conversely, a contrast agent with the ability to permeate cell membranes could be used in visualizing cell patterning, cell fate mapping, gene therapy, and, eventually, noninvasive cancer diagnosis. Therefore, we describe the synthesis and quantitative imaging of four contrast agents with the capability to cross cell membranes in sufficient quantity for detection. Each agent is based on the conjugation of a Gd(III) chelator with a cellular transduction moiety. Specifically, we coupled Gd(III)-diethylenetriaminepentaacetic acid DTPA and Gd(III)-1,4,7,10-tetraazacyclododecane-1,4,7,10-tetraacetic acid with an 8-amino acid polyarginine oligomer and an amphipathic stilbene molecule, 4-amino-4'-(N,N-dimethylamino)stilbene. The imaging modality that provided the best sensitivity and spatial resolution for direct detection of the contrast agents is synchrotron radiation x-ray fluorescence (SR-XRF). Unlike optical microscopy, SR-XRF provides two-dimensional images with resolution 10(3) better than (153)Gd gamma counting, without altering the agent by organic fluorophore conjugation. The transduction efficiency of the intracellular agents was evaluated by T(1) analysis and inductively coupled plasma mass spectrometry to determine the efficacy of each chelate-transporter combination. PMID:17150161

  18. Static magnetic proximity effect in Pt /Ni1 -xFex bilayers investigated by x-ray resonant magnetic reflectivity

    NASA Astrophysics Data System (ADS)

    Klewe, C.; Kuschel, T.; Schmalhorst, J.-M.; Bertram, F.; Kuschel, O.; Wollschläger, J.; Strempfer, J.; Meinert, M.; Reiss, G.

    2016-06-01

    We present x-ray resonant magnetic reflectivity (XRMR) as a very sensitive tool to detect proximity induced interface spin polarization in Pt/FM heterostructures. Different XRMR experiments are carried out and the results are evaluated for their dependence on the magneto-optical depth profile, the photon energy, the optical parameters, and the ferromagnetic material. We demonstrate that a detailed analysis of the reflected x-ray intensity gives insight into the spatial distribution of the spin polarization of a nonmagnetic metal across the interface to a ferromagnetic layer. The evaluation of the experimental results with simulations based on optical data from ab initio calculations provides the induced magnetic moment per Pt atom in the spin-polarized volume adjacent to the ferromagnet. For a series with different ferromagnetic materials consisting of Pt/Fe, Pt/Ni33Fe67 , Pt/Ni81Fe19 (permalloy), and Pt/Ni bilayers we find the largest spin polarization in Pt/Fe and a much smaller magnetic proximity effect in Pt/Ni. Additional XRMR experiments with varying photon energy are in good agreement with the theoretical predictions for the energy dependence of the magneto-optical parameters and allow identifying the optical dispersion δ and absorption β across the Pt L3-absorption edge.

  19. A theoretical framework for absorption (dichroism) and the resonance-enhanced scattering of x-rays by magnetic materials: I

    NASA Astrophysics Data System (ADS)

    Lovesey, Stephen W.; Balcar, Ewald

    1996-12-01

    The scattering length common to the attenuation coefficient and cross-sections for the resonance-enhanced scattering of x-rays suffers from a dependence on a spectrum of virtual, intermediate states which contain next to no useful information about the environment of the atoms. It is the dependence of the scattering length on intermediate states that sets the x-ray techniques apart from neutron scattering and other techniques which directly probe properties of magnetic materials, and limits the usefulness of physical intuition in the interpretation of empirical x-ray data. As a step toward a legible interpretation, in a language of standard atomic variables, an investigation is reported of a modified scattering length constructed to possess a structure similar to the scattering length for magnetic neutron scattering, namely, it has the mathematical structure of a spherical tensor operator, to which all Racah's methods for electrons in an open valence shell can be applied. In the process of reaching this goal, the influence of the intermediate states on the scattering length is reduced by summing over a limited set of quantum numbers for the intermediate states. Topics covered in the investigation include the attenuation coefficient for x-rays passing through a foil of magnetic material, dichroism, and the cross-sections for resonance-enhanced elastic (Bragg) and inelastic scattering of x-rays by magnetic materials. The treatment of polarization in the primary beam admits states of partial polarization, described by a Stokes vector. Both jj-coupling and Russell - Saunders coupling schemes for the valence states are explored.

  20. X-Ray Magnetic Resonance Fusion to Internal Markers and Utility in Congenital Heart Disease Catheterization

    PubMed Central

    Dori, Yoav; Sarmiento, Marily; Glatz, Andrew C.; Gillespie, Matthew J.; Jones, Virginia M.; Harris, Matthew A.; Whitehead, Kevin K.; Fogel, Mark A.; Rome, Jonathan J.

    2012-01-01

    Background X-ray magnetic resonance fusion (XMRF) allows for use of 3D data during cardiac catheterization. However, to date, technical requirements have limited the use of this modality in clinical practice. We report on a new internal-marker XMRF method that we have developed and describe how we used XMRF during cardiac catheterization in congenital heart disease. Methods and Results XMRF was performed in a phantom and in 23 patients presenting for cardiac catheterization who also needed cardiac MRI for clinical reasons. The registration process was performed in <5 minutes per patient, with minimal radiation (0.004 to 0.024 mSv) and without contrast. Registration error was calculated in a phantom and in 8 patients using the maximum distance between angiographic and 3D model boundaries. In the phantom, the measured error in the anteroposterior projection had a mean of 1.15 mm (standard deviation, 0.73). The measured error in patients had a median of 2.15 mm (interquartile range, 1.65 to 2.56 mm). Internal markers included bones, airway, image artifact, calcifications, and the heart and vessel borders. The MRI data were used for road mapping in 17 of 23 (74%) cases and camera angle selection in 11 of 23 (48%) cases. Conclusions Internal marker–based registration can be performed quickly, with minimal radiation, without the need for contrast, and with clinically acceptable accuracy using commercially available software. We have also demonstrated several potential uses for XMRF in routine clinical practice. This modality has the potential to reduce radiation exposure and improve catheterization outcomes. PMID:21536785

  1. [Characterization of biochar by X-ray photoelectron spectroscopy and 13C nuclear magnetic resonance].

    PubMed

    Xu, Dong-yu; Jin, Jie; Yan, Yu; Han, Lan-fang; Kang, Ming-jie; Wang, Zi-ying; Zhao, Ye; Sun, Ke

    2014-12-01

    The wood (willow branch) and grass (rice straw) materials were pyrolyzed at different temperatures (300, 450 and 600 °C) to obtain the biochars used in the present study. The biochars were characterized using elementary analysis, X-ray photoelectron spectroscopy (XPS) and solid state 13C cross-polarization and magic angle spinning nuclear magnetic resonance spectroscopy (13C NMR) to illuminate the structure and composition of the biochars which were derived from the different thermal temperatures and biomass. The results showed that the H/C, O/C and (O+N)/C ratios of the biochars decreased with the increase in the pyrolysis temperatures. The surface polarity and ash content of the grass-derived biochars were higher than those of the wood-derived biochars. The minerals of the wood-derived biochars were mainly covered by the organic matter; in contrast, parts of the mineral surfaces of the grass-derived biochars were not covered by organic matter? The 13C NMR of the low temperature-derived biochars revealed a large contribution of aromatic carbon, aliphatic carbon, carboxyl and carbonyl carbon, while the high temperature-derived biochars contained a large amount of aromatic carbon. Moreover, the wood-derived biochars produced at low heat treatment temperatures contained more lignin residues than grass-derived ones, probably due to the existence of high lignin content in the feedstock soures of wood-derived biochars. The results of the study would be useful for environmental application of biochars. PMID:25881450

  2. Electronic and magnetic properties of manganite thin films with different compositions and its correlation with transport properties: An X-ray resonant magnetic scattering study

    DOE PAGESBeta

    Singh, Surendra; Freeland, J. W.; Fitzsimmons, M. R.; Jeen, H.; Biswas, A.

    2014-12-08

    Here, we present x-ray resonant magnetic dichroism and x-ray resonant magnetic scattering measurements of the temperature dependence of magnetism in Pr-doped La-Ca-Mn-O films grown on (110) NdGaO3 substrates. We observed thermal hysteresis of the ferromagnetism in one film that also showed large thermal hysteresis of ~18K in transport measurements. While in a second film of a different nominal chemistry, which showed very small thermal hysteresis ~3K in transport measurements, no thermal hysteresis of the ferromagnetism was observed. As a result, these macroscopic properties are correlated with evolution of surface magnetization across metal insulator transition for these films as observed bymore » soft x-ray resonant magnetic scattering measurements.« less

  3. Electronic and magnetic properties of manganite thin films with different compositions and its correlation with transport properties: An X-ray resonant magnetic scattering study

    SciTech Connect

    Singh, Surendra; Freeland, J. W.; Fitzsimmons, M. R.; Jeen, H.; Biswas, A.

    2014-12-14

    Here, we present x-ray resonant magnetic dichroism and x-ray resonant magnetic scattering measurements of the temperature dependence of magnetism in Pr-doped La-Ca-Mn-O films grown on (110) NdGaO{sub 3} substrates. We observed thermal hysteresis of the ferromagnetism in one film that also showed large thermal hysteresis of ∼18 K in transport measurements. While in a second film of a different nominal chemistry, which showed very small thermal hysteresis ∼3 K in transport measurements, no thermal hysteresis of the ferromagnetism was observed. These macroscopic properties are correlated with evolution of surface magnetization across metal insulator transition for these films as observed by soft x-ray resonant magnetic scattering measurements.

  4. Electronic and magnetic properties of manganite thin films with different compositions and its correlation with transport properties: An X-ray resonant magnetic scattering study

    SciTech Connect

    Singh, Surendra; Freeland, J. W.; Fitzsimmons, M. R.; Jeen, H.; Biswas, A.

    2014-12-08

    Here, we present x-ray resonant magnetic dichroism and x-ray resonant magnetic scattering measurements of the temperature dependence of magnetism in Pr-doped La-Ca-Mn-O films grown on (110) NdGaO3 substrates. We observed thermal hysteresis of the ferromagnetism in one film that also showed large thermal hysteresis of ~18K in transport measurements. While in a second film of a different nominal chemistry, which showed very small thermal hysteresis ~3K in transport measurements, no thermal hysteresis of the ferromagnetism was observed. As a result, these macroscopic properties are correlated with evolution of surface magnetization across metal insulator transition for these films as observed by soft x-ray resonant magnetic scattering measurements.

  5. Resonant inelastic scattering in dilute magnetic semiconductors by x-ray fluorescence spectroscopy

    SciTech Connect

    Lawniczak-Jablonska, K. |; Jia, J.J.; Underwood, J.H.

    1997-04-01

    As modern, technologically important materials have become more complex, element specific techniques have become invaluable in studying the electronic structure of individual components from the system. Soft x-ray fluorescence (SXF) and absorption (SXA) spectroscopies provide a unique means of measuring element and angular momentum density of electron states, respectively, for the valence and conducting bands in complex materials. X-ray absorption and the decay through x-ray emission are generally assumed to be two independent one-photon processes. Recent studies, however have demonstrated that SXF excited near the absorption threshold generate an array of spectral features that depend on nature of materials, particularly on the localization of excited states in s and d-band solids and that these two processes can no be longer treated as independent. Resonant SXF offers thus the new way to study the dynamics of the distribution of electronic valence states in the presence of a hole which is bound to the electron low lying in the conduction band. This process can simulate the interaction between hole-electron pair in wide gap semiconductors. Therefore such studies can help in understanding of transport and optics phenomena in the wide gap semiconductors. The authors report the result of Mn and S L-resonant emission in Zn{sub 1{minus}x}Mn{sub x}S (with x=0.2 and 0.3) and MnS as the energy of exciting radiation is tuned across the Mn and S L{sub 3,2} absorption edge, along with the resonant excited spectra from elemental Mn as a reference.

  6. Years of Magnetic X-Ray Dichroism

    NASA Astrophysics Data System (ADS)

    van der Laan, Gerrit

    A historical overview of magnetic x-ray dichroism is presented. I describe the first theoretical and experimental results that have led to the development of this powerful technique for element-specific magnetometry. The theoretical progress of the sum rules is also described, starting with the spinorbit sum rule for the isotropic spectrum which led on to the spin and orbital moment sum rules for x-ray magnetic circular dichroism. The latter has been particularly useful to understand the magnetic anisotropy in thin films and multilayers. Further developments of circular dichroism in (resonant) photoemission and Auger, as well as x-ray detected optical activity, also are summarized. Currently, magnetic x-ray dichroism finds a wide application in x-ray spectroscopy and imaging for the study of magnetic materials and it is considered to be one of the most important discoveries in the field of magnetism in the last few decennia. It is hard to imagine modern research into magnetism without the aid of polarized x-rays.

  7. Application of polarized neutron reflectometry and x-ray resonant magnetic reflectometry for determining the inhomogeneous magnetic structure in Fe/Gd multilayers.

    SciTech Connect

    Kravtsov, E. A.; Haskel, D.; te Velthuis, S. G. E.; Jiang, J. S.; Kirby, B. J.

    2010-01-01

    The evolution of the magnetic structure of multilayer [Fe (35 {angstrom})/Gd (50 {angstrom}){sub 5}] with variation in temperature and an applied magnetic field was determined using a complementary approach combining polarized neutron and X-ray resonant magnetic reflectometry. Self-consistent simultaneous analysis of X-ray and neutron spectra allowed us to determine the elemental and depth profiles in the multilayer structure with unprecedented accuracy, including the identification of an inhomogeneous intralayer magnetic structure with near-atomic resolution.

  8. Nanocrystalline tin oxide: Possible origin of its weak ferromagnetism deduced from nuclear magnetic resonance and X-ray photoelectron spectroscopies

    NASA Astrophysics Data System (ADS)

    Zhang, Feng; Lian, Yadong; Gu, Min; Yu, Ji; Tang, Tong B.; Sun, Jian; Zhang, Weiyi

    2016-09-01

    Nanocrystalline tin oxide was fabricated, with molar ratio O/Sn determined as 1.40, 1.55, 1.79, 1.92 and 1.96 from X-ray photoelectron spectroscopy. They displayed weak ferromagnetism, the sample with O/Sn = 1.55 showing the maximum saturation magnetization reaching almost 8 ×10-3 emu /g at room temperature. 119Sn nuclear magnetic resonance allowed the deduction, based on four resolved resonance peaks, that their Sn ions had four possible coordination numbers, namely 3, 4, 5 and 6. The relative fraction of 4-coordinated cations was the one found to bear positive linear correlation with saturation magnetization of the sample. It is surmised that magnetism in tin oxide results mainly from 4-coordination Sn ions, of valance about +3, as estimated from the binding energies of their 3d photoelectron emission levels.

  9. Molecular structure of di-aryl-aldimines by multinuclear magnetic resonance and X-ray diffraction

    NASA Astrophysics Data System (ADS)

    Montalvo-González, Rubén; Ariza-Castolo, Armando

    2003-08-01

    The complete 1H, 13C and 15N NMR analyses for a series of 25 diaryl-aldimines containing phenyl, pyridyl, pyrazolone and furanyl moieties are described herein. Detailed evaluation of substituent chemical shift and coupling constant effects showed that interaction between the lone pair of the pyrazolone carbonyl group or the nitrogen of 2-substitued pyridines with the aldimine hydrogen increases the 1J CH value and shifts the resonance signal for this hydrogen to high frequency, in the 1H NMR spectra. The X-ray crystal structure analysis of pyrazolone substituted aldimines evidenced the planarity of the aryl groups which are conjugated with the CN double bond. In the case of the N-(2-pyridinemethylene)-1,5-dimethyl-2-phenyl-1,2-dihydro-pyrazol-3-one, two rotamers were observed in the same unit cell.

  10. X-rays and magnetism.

    PubMed

    Fischer, Peter; Ohldag, Hendrik

    2015-09-01

    Magnetism is among the most active and attractive areas in modern solid state physics because of intriguing phenomena interesting to fundamental research and a manifold of technological applications. State-of-the-art synthesis of advanced magnetic materials, e.g. in hybrid structures paves the way to new functionalities. To characterize modern magnetic materials and the associated magnetic phenomena, polarized x-rays have emerged as unique probes due to their specific interaction with magnetic materials. A large variety of spectroscopic and microscopic techniques have been developed to quantify in an element, valence and site-sensitive way properties of ferro-, ferri-, and antiferromagnetic systems, such as spin and orbital moments, and to image nanoscale spin textures and their dynamics with sub-ns time and almost 10 nm spatial resolution. The enormous intensity of x-rays and their degree of coherence at next generation x-ray facilities will open the fsec time window to magnetic studies addressing fundamental time scales in magnetism with nanometer spatial resolution. This review will give an introduction into contemporary topics of nanoscale magnetic materials and provide an overview of analytical spectroscopy and microscopy tools based on x-ray dichroism effects. Selected examples of current research will demonstrate the potential and future directions of these techniques. PMID:26288956

  11. A Comparison of Rapid-Scanning X-Ray Fluorescence Mapping And Magnetic Resonance Imaging to Localize Brain Iron Distribution

    SciTech Connect

    McCrea, R.P.E.; Harder, S.L.; Martin, M.; Buist, R.; Nichol, H.

    2009-05-26

    The clinical diagnosis of many neurodegenerative disorders relies primarily or exclusively on observed behaviors rather than measurable physical tests. One of the hallmarks of Alzheimer disease (AD) is the presence of amyloid-containing plaques associated with deposits of iron, copper and/or zinc. Work in other laboratories has shown that iron-rich plaques can be seen in the mouse brain in vivo with magnetic resonance imaging (MRI) using a high-field strength magnet but this iron cannot be visualized in humans using clinical magnets. To improve the interpretation of MRI, we correlated iron accumulation visualized by X-ray fluorescence spectroscopy, an element-specific technique with T1, T2, and susceptibility weighted MR (SWI) in a mouse model of AD. We show that SWI best shows areas of increased iron accumulation when compared to standard sequences.

  12. Resonant X-ray magnetic scattering studies of the TmNi 2B 2C spin density wave

    NASA Astrophysics Data System (ADS)

    Mannix, Danny; Thompson, Paul; Brown, Simon; Bouchenoire, Laurence; Canfield, Paul

    2004-11-01

    We report on polarisation resolved, resonant X-ray magnetic scattering (RXMS) studies of the spin density wave (SDW) formed in the TmNi 2B 2C superconductor. From this high wave-vector resolution investigation, we find the incommensurate magnetic SDW propagation vector to be ( 0±τ0±τ0) with τ=0.096 rlu, slightly larger than the value previously deduced from magnetic neutron studies ( τ=0.093 rlu). The widths of the SDW peaks at 1 K are consistent with long-range magnetic order and we have deduced a magnetic correlation length of ∼1200 Å. When the incident photons are tuned to the Tm L 3 absorption edge, the RXMS energy response consists of a double peak feature, arising from both dipole (E1) transitions, probing the 5d conduction band polarisation, and quadrupole (E2) transitions, probing the Tm 4f magnetic moments. The RXMS wave-vector dependences of the (0± τ 0± τ L) SDW satellites are consistent with the transverse spin-density wave structure, with moments orientated along the crystallographic c-axis, originally proposed from neutron-scattering measurements. Our RXMS data are also in good agreement with the magnetic neutron-scattering response for the thermal evolution of the magnetic moments down to 1 K and in deducing a Nèel temperature of T=1.5 K. However, the RXMS probe reveals a small shift of the magnetic propagation vector of the order 3×10 -3 rlu along the (1 1 0) direction, on decreasing temperature below TN. Using very high-resolution X-ray studies with a conventional Si(1 1 1) analyser, no change in width or position is found below TN or Tc. We have also not observed any charge modulation peaks at 2τ, indicating that the SDW does not couple to the lattice.

  13. Interaction between x-ray and magnetic vortices

    NASA Astrophysics Data System (ADS)

    van Veenendaal, Michel

    2015-12-01

    The interaction between two topological objects, an x-ray beam carrying orbital angular momentum (OAM) and a magnetic vortex, is studied theoretically. The resonant x-ray scattering intensity is calculated as a function of the relative position of the magnetic and x-ray vortices. For a homogeneous system, the charge scattering is zero. For magnetic scattering, the intensity profile strongly depends on the relative topological indices of the x-ray and magnetic singularities. A strong enhancement in the intensity profile is observed for equal winding factors. Additionally, the profile displays edge effects, which depend on the scattering conditions, the radial dependence of the magnetic vortex, and the Laguerre-Gaussian mode of the OAM x-ray beam. The potential of resonant OAM x-ray scattering from magnetic vortices opens the door to study the dynamics and switching of magnetic vortices.

  14. Magnetic order of multiferroic ErMn2O5 studied by resonant soft x-ray Bragg diffraction

    NASA Astrophysics Data System (ADS)

    Staub, U.; Bodenthin, Y.; García-Fernández, M.; de Souza, R. A.; Garganourakis, M.; Golovenchits, E. I.; Sanina, V. A.; Lushnikov, S. G.

    2010-04-01

    Resonant magnetic soft x-ray diffraction is used to study the magnetic order of the Mn sublattices in multiferroic ErMn2O5 . Data were collected at the MnL2,3 edges as a function of temperature, incident polarization, including the analysis of scattered polarizations for selected azimuths. The energy dependence of the magnetic reflections depends on the azimuthal angle in the commensurate magnetic (CM) ferroelectric (FE) phase, indicating different contributions to the scattering. In the incommensurate magnetic [two-dimensional (2D)-ICM] phase, the two observed reflections ( 1/2±δx 0 1/4+δz ) have distinct energy dependences too. Different origins of these differences in spectral shape are discussed. The azimuthal angle dependence at the L3 edge can only be qualitatively described by a generalized magnetic model. The observed discrepancies may indicate the importance of magnetoelectric multipole scattering to these reflections. Reciprocal mesh scans show diffuse scattering along q and perpendicular to q as well as along the ( h 0 0) direction in the CM phase. Diffuse scattering is also observed along ( h 0 0) in the one-dimensional-ICM phase. At higher temperatures, in the 2D-ICM phase, the diffuse magnetic scattering is almost isotropic.

  15. Construction of hydrodynamic bead models from high-resolution X-ray crystallographic or nuclear magnetic resonance data.

    PubMed Central

    Byron, O

    1997-01-01

    Computer software such as HYDRO, based upon a comprehensive body of theoretical work, permits the hydrodynamic modeling of macromolecules in solution, which are represented to the computer interface as an assembly of spheres. The uniqueness of any satisfactory resultant model is optimized by incorporating into the modeling procedure the maximal possible number of criteria to which the bead model must conform. An algorithm (AtoB, for atoms to beads) that permits the direct construction of bead models from high resolution x-ray crystallographic or nuclear magnetic resonance data has now been formulated and tested. Models so generated then act as informed starting estimates for the subsequent iterative modeling procedure, thereby hastening the convergence to reasonable representations of solution conformation. Successful application of this algorithm to several proteins shows that predictions of hydrodynamic parameters, including those concerning solvation, can be confirmed. PMID:8994627

  16. X-ray induced demagnetization of single-molecule magnets

    SciTech Connect

    Dreiser, Jan; Westerström, Rasmus; Piamonteze, Cinthia; Nolting, Frithjof; Rusponi, Stefano; Brune, Harald; Yang, Shangfeng; Popov, Alexey; Dunsch, Lothar; Greber, Thomas

    2014-07-21

    Low-temperature x-ray magnetic circular dichroism measurements on the endohedral single-molecule magnet DySc{sub 2}N@C{sub 80} at the Dy M{sub 4,5} edges reveal a shrinking of the opening of the observed hysteresis with increasing x-ray flux. Time-dependent measurements show that the exposure of the molecules to x-rays resonant with the Dy M{sub 5} edge accelerates the relaxation of magnetization more than off-resonant x-rays. The results cannot be explained by a homogeneous temperature rise due to x-ray absorption. Moreover, the observed large demagnetization cross sections indicate that the resonant absorption of one x-ray photon induces the demagnetization of many molecules.

  17. Imaging Systems for Medical Diagnosis: Fundamentals and Technical Solutions - X-Ray Diagnostics- Computed Tomography - Nuclear Medical Diagnostics - Magnetic Resonance Imaging - Ultrasound Technology

    NASA Astrophysics Data System (ADS)

    Krestel, Erich

    1990-10-01

    Erick Krestel, Editor Imaging Systems for Medical Diagnostics This book provides physicians and clinical physicists with detailed information on todya's imaging modalities and assists them in selecting the optimal system for each clinical application. Physicists, engineers and computer specialists engaged in research and development and sales departments will also find this book to be of considerable use. It may also be employed at universities, training centers and in technical seminars. The physiological and physical fundamentals are explained in part 1. The technical solutions contained in part 2 illustrate the numerous possibilities available in x-ray diagnostics, computed tomography, nuclear medical diagnostics, magnetic resonance imaging, sonography and biomagnetic diagnostics. Overview of Contents Physiology of vision Image quality X-ray and gamma radiation X-ray diagnostics Computed tomography Nuclear medical diagnostics Magnetic resonance imaging Sonography Biomagnetic diagnostics

  18. In vivo measurement of body composition of chickens using quantitative magnetic resonance (QMR)and dual x-ray absorptiometry (DXA)

    Technology Transfer Automated Retrieval System (TEKTRAN)

    QMR is a nuclear magnetic resonance based method for measuring the fat, lean and water content of the total body of the live animal. The purpose of this study was to evaluate the use of QMR for measuring the body composition of chickens while comparing QMR results to those obtained by dual X-ray ab...

  19. Spin-flop transition on Gd5Ge4 observed by x-ray resonant magnetic scattering and first-principles calculations of magnetic anisotropy

    SciTech Connect

    Tan, L.; Kreyssig, A.; Nandi, S.; Jia, S.; Lee, Y. B.; Lang, J. C.; Islam, Z.; Lograsso, T.; Schlagel, D.; Pecharsky, V.; Gschneidner, K.; Canfield, P.; Harmon, B.; McQueeney, R.; Goldman, A.

    2008-02-21

    X-ray resonant magnetic scattering was employed to study a fully reversible spin-flop transition in orthorhombic Gd{sub 5}Ge{sub 4} and to elucidate details of the magnetic structure in the spin-flop phase. The orientation of the moments at the three Gd sites flop 90{sup o} from the c axis to the a axis when a magnetic field, H{sub sf} = 9 kOe, is applied along the c axis at T = 9 K. The magnetic space group changes from Pnm'a to Pn'm'a' for all three Gd sublattices. The magnetic anisotropy energy determined from experimental measurements is in good agreement with the calculations of the magnetic anisotropy based on the spin-orbit coupling of the conduction electrons and an estimation of the dipolar interactions anisotropy. No significant magnetostriction effects were observed at the spin-flop transition.

  20. Characterization of the phosphoserine of pepsinogen using /sup 31/P nuclear magnetic resonance: corroboration of X-ray crystallographic results

    SciTech Connect

    Williams, S.P.; Bridger, W.A.; James, M.N.G.

    1986-10-21

    The endogenous phosphoserine residue in porcine pepsinogen has been titrated with use of phosphorus-31 nuclear magnetic resonance (/sup 31/P NMR). It has an observed pK/sub a/sub 2// of 6.7 and a narrow line width (approx. =10 Hz). The phosphate can be readily removed by an acid phosphatase from potato; however, it is resistant to hydrolysis by several alkaline phosphatases. The X-ray crystal structure of porcine pepsinogen at 1.8-A resolution shows a rather weak and diffuse region of electron density in the vicinity of the phosphorylated serine residue. This suggests considerable dynamic mobility or conformational disorder of the phosphate. In order to define more fully this behavior the NMR data have been used to corroborate these crystallographic results. All these physical data are consistent with a highly mobile phosphoserine residue on the surface of the zymogen and freely exposed to solvent. In addition, certain properties of this phosphoserine moiety on pepsinogen are similar to those of one of the phosphorylated residues of ovalbumin. The possible significance of this is discussed.

  1. Single-crystal X-ray diffraction and resonant X-ray magnetic scattering at helium-3 temperatures in high magnetic fields at beamline P09 at PETRA III.

    PubMed

    Francoual, S; Strempfer, J; Warren, J; Liu, Y; Skaugen, A; Poli, S; Blume, J; Wolff-Fabris, F; Canfield, P C; Lograsso, T

    2015-09-01

    The resonant scattering and diffraction beamline P09 at PETRA III at DESY is equipped with a 14 T vertical field split-pair magnet. A helium-3 refrigerator is available that can be fitted inside the magnet's variable-temperature insert. Here the results of a series of experiments aimed at determining the beam conditions permitting operations with the He-3 insert are presented. By measuring the tetragonal-to-orthorhombic phase transition occurring at 2.1 K in the Jahn-Teller compound TmVO4, it is found that the photon flux at P09 must be attenuated down to 1.5 × 10(9) photons s(-1) for the sample to remain at temperatures below 800 mK. Despite such a reduction of the incident flux and the subsequent use of a Cu(111) analyzer, the resonant X-ray magnetic scattering signal at the Tm LIII absorption edge associated with the spin-density wave in TmNi2B2C below 1.5 K is intense enough to permit a complete study in magnetic field and at sub-Kelvin temperatures to be carried out. PMID:26289272

  2. X-Ray Diffraction Microscopy of Magnetic Structures

    SciTech Connect

    Turner, J.; Lima, E.; Huang, X.; Krupin, O.; Seu, K.; Parks, D.; Kevan, S.; Kisslinger, K.; McNulty, I.; Gambino, R.; Mangin, S.; Roy, S. and Fischer, P.

    2011-07-14

    We report the first proof-of-principle experiment of iterative phase retrieval from magnetic x-ray diffraction. By using the resonant x-ray excitation process and coherent x-ray scattering, we show that linearly polarized soft x rays can be used to image both the amplitude and the phase of magnetic domain structures. We recovered the magnetic structure of an amorphous terbium-cobalt thin film with a spatial resolution of about 75 nm at the Co L{sub 3} edge at 778 eV. In comparison with soft x-ray microscopy images recorded with Fresnel zone plate optics at better than 25 nm spatial resolution, we find qualitative agreement in the observed magnetic structure.

  3. X-ray spectroscopy of magnetic CVs

    NASA Astrophysics Data System (ADS)

    Matt, Giorgio

    I discuss two topics in X-ray spectroscopy of magnetic CVs: reflection from the white dwarf surface, and opacity effects in the post shock plasma. I also briefly mention future observational perspectives, with particular emphasis on the Constellation X-ray mission.

  4. Temperature and field dependent magnetization in a sub-μm patterned Co/FeRh film studied by resonant x-ray scattering

    NASA Astrophysics Data System (ADS)

    Lounis, Lounès; Spezzani, Carlo; Delaunay, Renaud; Fortuna, Franck; Obstbaum, Martin; Günther, Stefan; Back, Christian H.; Popescu, Horia; Vidal, Franck; Sacchi, Maurizio

    2016-05-01

    We studied the temperature and field dependence of the magnetization in a Co/FeRh/MgO(0 0 1) film patterned into a matrix of sub-μm sized rectangles, using element selective resonant scattering of polarized soft x-rays. We show that it is possible to reverse partially the magnetization of the Co layer in a thermal cycle that crosses the FeRh antiferromagnetic to ferromagnetic transition. Our results support interest in patterned Co/FeRh films and their potential for achieving temperature induced magnetization switching.

  5. Structure of nanocrystalline calcium silicate hydrates: insights from X-ray diffraction, synchrotron X-ray absorption and nuclear magnetic resonance

    PubMed Central

    Grangeon, Sylvain; Claret, Francis; Roosz, Cédric; Sato, Tsutomu; Gaboreau, Stéphane; Linard, Yannick

    2016-01-01

    The structure of nanocrystalline calcium silicate hydrates (C–S–H) having Ca/Si ratios ranging between 0.57 ± 0.05 and 1.47 ± 0.04 was studied using an electron probe micro-analyser, powder X-ray diffraction, 29Si magic angle spinning NMR, and Fourier-transform infrared and synchrotron X-ray absorption spectroscopies. All samples can be described as nanocrystalline and defective tobermorite. At low Ca/Si ratio, the Si chains are defect free and the Si Q 3 and Q 2 environments account, respectively, for up to 40.2 ± 1.5% and 55.6 ± 3.0% of the total Si, with part of the Q 3 Si being attributable to remnants of the synthesis reactant. As the Ca/Si ratio increases up to 0.87 ± 0.02, the Si Q 3 environment decreases down to 0 and is preferentially replaced by the Q 2 environment, which reaches 87.9 ± 2.0%. At higher ratios, Q 2 decreases down to 32.0 ± 7.6% for Ca/Si = 1.38 ± 0.03 and is replaced by the Q 1 environment, which peaks at 68.1 ± 3.8%. The combination of X-ray diffraction and NMR allowed capturing the depolymerization of Si chains as well as a two-step variation in the layer-to-layer distance. This latter first increases from ∼11.3 Å (for samples having a Ca/Si ratio <∼0.6) up to 12.25 Å at Ca/Si = 0.87 ± 0.02, probably as a result of a weaker layer-to-layer connectivity, and then decreases down to 11 Å when the Ca/Si ratio reaches 1.38 ± 0.03. The decrease in layer-to-layer distance results from the incorporation of interlayer Ca that may form a Ca(OH)2-like structure, nanocrystalline and intermixed with C–S–H layers, at high Ca/Si ratios. PMID:27275135

  6. X-ray resonant Raman spectroscopy

    SciTech Connect

    Cowan, P.L.; LeBrun, T.; Deslattes, R.D.

    1995-08-01

    X-ray resonant Raman scattering presents great promise as a high-resolution spectroscopic probe of the electronic structure of matter. Unlike other methods, the technique avoids the loss of energy resolution resulting from the lifetime broadening of short-lived core-excited states. In addition, measurements of polarization and angular anisotropies yield information on the symmetries of electronic states of atoms and molecules. We studied the L{sub 3} edge of xenon, where the lifetime broadening is a major feature of the spectra recorded previously. X-ray fluorescence spectra were taken of both the L{alpha}{sub l,2} and L{beta}{sub 2,15} peaks over a range of energies from 10 eV below the edge to 40 eV above. These spectra show the evolution of resonant Raman scattering into characteristic fluorescence as the photon energy is scanned across the edge, and confirm several features of these spectra such as asymmetries in resonant peak shapes due to the onset of the ionization continuum. These results constitute the most comprehensive study of X-ray resonant Raman scattering to date, and were submitted for publication. Studies of other cases are under way, and new instruments that would match the unique characteristics of the APS - and thus render a new range of experiments possible - are under consideration.

  7. Inelastic magnetic X-ray scattering

    NASA Astrophysics Data System (ADS)

    Platzman, P. M.; Tzoar, N.

    1985-04-01

    The theory of magnetic X-ray scattering is used to discuss the possibilities for employing inelastic scattering to probe the magnetic properties of condensed matter systems. In particular, it is shown how the interference between the nonmagnetic (Compton) and magnetic scattering arising from the use of circularly polarized X-rays is absolutely essential in such experiments. The very beautiful preliminary experiments by Sakai and Ono (1976) on Fe which use circularly polarized Moessbauer gamma-rays will be discussed. They already show the sensitivity of the technique to the 'magnetic form factor'. In addition, the physics of a unique quarter wave plate employed in obtaining circularly polarized X-rays is considered, and the implications of this advance for doing such experiments on existing synchrotron X-ray sources are discussed.

  8. A theoretical framework for dichroism and the resonance-enhanced scattering of x-rays by magnetic materials: II. Quadrupolar absorption events

    NASA Astrophysics Data System (ADS)

    Lovesey, Stephen W.

    1996-12-01

    Previous work with the resonant scattering length that is based on an atomic model and dipolar absorption events is extended to encompass quadrupolar absorption events. The scattering length is the common element in calculations of the attenuation coefficient, dichroism and the cross-sections for elastic and inelastic resonance-enhanced scattering of x-rays by magnetic materials. Both jj-coupling and Russell - Saunders coupling schemes for the atomic electrons are utilized; included are tables of relevant Racah unit-tensor operators for the valence shell 0953-8984/8/50/025/img1.

  9. Measurement of midfemoral shaft geometry: repeatability and accuracy using magnetic resonance imaging and dual-energy X-ray absorptiometry.

    PubMed

    Woodhead, H J; Kemp, A F; Blimkie CJR; Briody, J N; Duncan, C S; Thompson, M; Lam, A; Howman-Giles, R; Cowell, C T

    2001-12-01

    Although macroscopic geometric architecture is an important determinant of bone strength, there is limited published information relating to the validation of the techniques used in its measurement. This study describes new techniques for assessing geometry at the midfemur using magnetic resonance imaging (MRI) and dual-energy X-ray absorptiometry (DXA) and examines both the repeatability and the accuracy of these and previously described DXA methods. Contiguous transverse MRI (Philips 1.5T) scans of the middle one-third femur were made in 13 subjects, 3 subjects with osteoporosis. Midpoint values for total width (TW), cortical width (CW), total cross-sectional area (TCSA), cortical cross-sectional area (CCSA), and volumes from reconstructed three-dimensional (3D) images (total volume [TV] and cortical volume [CVol]) were derived. Midpoint TW and CW also were determined using DXA (Lunar V3.6, lumbar software) by visual and automated edge detection analysis. Repeatability was assessed on scans made on two occasions and then analyzed twice by two independent observers (blinded), with intra- and interobserver repeatability expressed as the CV (CV +/- SD). Accuracy was examined by comparing MRI and DXA measurements of venison bone (and Perspex phantom for MRI), against "gold standard" measures made by vernier caliper (width), photographic image digitization (area) and water displacement (volume). Agreement between methods was analyzed using mean differences (MD +/- SD%). MRI CVs ranged from 0.5 +/- 0.5% (TV) to 3.1 +/- 3.1% (CW) for intraobserver and 0.55 +/- 0.5% (TV) to 3.6 +/- 3.6% (CW) for interobserver repeatability. DXA results ranged from 1.6 +/- 1.5% (TW) to 4.4 +/- 4.5% (CW) for intraobserver and 3.8 +/- 3.8% (TW) to 8.3 +/- 8.1% (CW) for interobserver variation. MRI accuracy was excellent for TV (3.3 +/- 6.4%), CVol (3.5 +/- 4.0%), TCSA (1.8 +/- 2.6%), and CCSA (1.6 +/- 4.2%) but not TW (4.1 +/- 1.4%) or CW (16.4 +/14.9%). DXA results were TW (6.8 +/- 2

  10. Schumann resonance frequency increase during solar X-ray bursts

    NASA Astrophysics Data System (ADS)

    Roldugin, V. C.; Maltsev, Y. P.; Vasiljev, A. N.; Schokotov, A. Y.; Belyajev, G. G.

    2004-01-01

    Variations of the first mode Schumann resonance frequency in the Kola Peninsula and of the first and second mode frequencies in Kamchatka during seven days of March-April 2001, when the intensive solar X-ray bursts occurred, are studied with 5 min averaging. All X-ray bursts were accompanied by ˜0.2 Hz increase in the first mode frequency, at least in one of the magnetic components. Duration of the increases coincided with that of the bursts. For the second mode the increase (in average by ˜0.3 Hz) was registered in most events, when the ELF noise level was not very high.

  11. Early experience with X-ray magnetic resonance fusion for low-flow vascular malformations in the pediatric interventional radiology suite.

    PubMed

    Hwang, Tiffany J; Girard, Erin; Shellikeri, Sphoorti; Setser, Randolph; Vossough, Arastoo; Ho-Fung, Victor; Cahill, Anne Marie

    2016-03-01

    This technical innovation describes our experience using an X-ray magnetic resonance fusion (XMRF) software program to overlay 3-D MR images on real-time fluoroscopic images during sclerotherapy procedures for vascular malformations at a large pediatric institution. Five cases have been selected to illustrate the application and various clinical utilities of XMRF during sclerotherapy procedures as well as the technical limitations of this technique. The cases demonstrate how to use XMRF in the interventional suite to derive additional information to improve therapeutic confidence with regards to the extent of lesion filling and to guide clinical management in terms of intraprocedural interventional measures. PMID:26681438

  12. Spin Projection of Empty Partial Density of States by Resonant X-ray Scattering (RXS): Application to Materials with Different Magnetic Ordering

    SciTech Connect

    Draeger, Guenter; Machek, Pavel

    2003-01-24

    We report the first experimental spin projections of empty partial density of states in antiferromagnetic NiO and CuO, paramagnetic MnO and in ferrimagnetic Dy3Fe5O12 by means of resonant X-ray scattering (RXS). Resolving resonantly scattered K{alpha}1,2 , K{beta}1,3 , L{alpha}1 and L1 core line spectra into their spin-up and spin-down components the spin character of the dipole- and quadrupole-excited conduction band states can quantitatively be analyzed. Since the method employs spin conservation in the RXS process and local spin references, it needs neither circularly polarized radiation nor sample magnetization for measuring the spectra. Hence, antiferro- and paramagnetic materials can be investigated as well. In the paper, the basic idea of the novel method, its experimental realization and the data treatment are reported including the spectra decomposition into the spin-up and spin-down components by using Principal Component Analysis (PCA). New and unambiguous results will be presented providing the opportunity to verify experimentally the results of spin-dependent (LSDA+U) calculations. So we argue the new spectroscopy complements X-ray magnetic dichroism, which is silent for antiferro- and paramagnetic materials. In fact, the novel method gives insight into the spin polarization of conduction band states in correlated materials, independently on their magnetic ordering.

  13. Novel motor design for rotating anode x-ray tubes operating in the fringe field of a magnetic resonance imaging system

    SciTech Connect

    Lillaney, Prasheel; Pelc, Norbert; Shin Mihye; Hinshaw, Waldo; Fahrig, Rebecca; Bennett, N. Robert

    2013-02-15

    Purpose: Using hybrid x-ray/MR (XMR) systems for image guidance during interventional procedures could enhance the diagnosis and treatment of neurologic, oncologic, cardiovascular, and other disorders. The authors propose a close proximity hybrid system design in which a C-arm fluoroscopy unit is placed immediately adjacent to the solenoid magnet of a MR system with a minimum distance of 1.2 m between the x-ray and MR imaging fields of view. Existing rotating anode x-ray tube designs fail within MR fringe field environments because the magnetic fields alter the electron trajectories in the x-ray tube and act as a brake on the induction motor, reducing the rotation speed of the anode. In this study the authors propose a novel motor design that avoids the anode rotation speed reduction. Methods: The proposed design replaces the permanent magnet stator found in brushed dc motors with the radial component of the MR fringe field. The x-ray tube is oriented such that the radial component of the MR fringe field is orthogonal to the cathode-anode axis. Using a feedback position sensor and the support bearings as electrical slip rings, the authors use electrical commutation to eliminate the need for mechanical brushes and commutators. A vacuum compatible prototype of the proposed motor design was assembled, and its performance was evaluated at various operating conditions. The prototype consisted of a 3.1 in. diameter anode rated at 300 kHU with a ceramic rotor that was 5.6 in. in length and had a 2.9 in. diameter. The material chosen for all ceramic components was MACOR, a machineable glass ceramic developed by Corning Inc. The approximate weight of the entire assembly was 1750 g. The maximum rotation speed, angular acceleration, and acceleration time of the motor design were investigated, as well as the dependence of these parameters on rotor angular offset, magnetic field strength, and field orientation. The resonance properties of the authors' assembly were also

  14. Novel motor design for rotating anode x-ray tubes operating in the fringe field of a magnetic resonance imaging system

    PubMed Central

    Lillaney, Prasheel; Shin, Mihye; Hinshaw, Waldo; Bennett, N. Robert; Pelc, Norbert; Fahrig, Rebecca

    2013-01-01

    Purpose: Using hybrid x-ray/MR (XMR) systems for image guidance during interventional procedures could enhance the diagnosis and treatment of neurologic, oncologic, cardiovascular, and other disorders. The authors propose a close proximity hybrid system design in which a C-arm fluoroscopy unit is placed immediately adjacent to the solenoid magnet of a MR system with a minimum distance of 1.2 m between the x-ray and MR imaging fields of view. Existing rotating anode x-ray tube designs fail within MR fringe field environments because the magnetic fields alter the electron trajectories in the x-ray tube and act as a brake on the induction motor, reducing the rotation speed of the anode. In this study the authors propose a novel motor design that avoids the anode rotation speed reduction. Methods: The proposed design replaces the permanent magnet stator found in brushed dc motors with the radial component of the MR fringe field. The x-ray tube is oriented such that the radial component of the MR fringe field is orthogonal to the cathode-anode axis. Using a feedback position sensor and the support bearings as electrical slip rings, the authors use electrical commutation to eliminate the need for mechanical brushes and commutators. A vacuum compatible prototype of the proposed motor design was assembled, and its performance was evaluated at various operating conditions. The prototype consisted of a 3.1 in. diameter anode rated at 300 kHU with a ceramic rotor that was 5.6 in. in length and had a 2.9 in. diameter. The material chosen for all ceramic components was MACOR, a machineable glass ceramic developed by Corning Inc. The approximate weight of the entire assembly was 1750 g. The maximum rotation speed, angular acceleration, and acceleration time of the motor design were investigated, as well as the dependence of these parameters on rotor angular offset, magnetic field strength, and field orientation. The resonance properties of the authors’ assembly were also

  15. Wide-Angle X-Ray Scattering and Solid-State Nuclear Magnetic Resonance Data Combined to Test Models for Cellulose Microfibrils in Mung Bean Cell Walls1

    PubMed Central

    Newman, Roger H.; Hill, Stefan J.; Harris, Philip J.

    2013-01-01

    A synchrotron wide-angle x-ray scattering study of mung bean (Vigna radiata) primary cell walls was combined with published solid-state nuclear magnetic resonance data to test models for packing of (1→4)-β-glucan chains in cellulose microfibrils. Computer-simulated peak shapes, calculated for 36-chain microfibrils with perfect order or uncorrelated disorder, were sharper than those in the experimental diffractogram. Introducing correlated disorder into the models broaden the simulated peaks but only when the disorder was increased to unrealistic magnitudes. Computer-simulated diffractograms, calculated for 24- and 18-chain models, showed good fits to experimental data. Particularly good fits to both x-ray and nuclear magnetic resonance data were obtained for collections of 18-chain models with mixed cross-sectional shapes and occasional twinning. Synthesis of 18-chain microfibrils is consistent with a model for cellulose-synthesizing complexes in which three cellulose synthase polypeptides form a particle and six particles form a rosette. PMID:24154621

  16. Resonant X-ray emission with a standing wave excitation

    PubMed Central

    Ruotsalainen, Kari O.; Honkanen, Ari-Pekka; Collins, Stephen P.; Monaco, Giulio; Moretti Sala, Marco; Krisch, Michael; Hämäläinen, Keijo; Hakala, Mikko; Huotari, Simo

    2016-01-01

    The Borrmann effect is the anomalous transmission of x-rays in perfect crystals under diffraction conditions. It arises from the interference of the incident and diffracted waves, which creates a standing wave with nodes at strongly absorbing atoms. Dipolar absorption of x-rays is thus diminished, which makes the crystal nearly transparent for certain x-ray wave vectors. Indeed, a relative enhancement of electric quadrupole absorption via the Borrmann effect has been demonstrated recently. Here we show that the Borrmann effect has a significantly larger impact on resonant x-ray emission than is observable in x-ray absorption. Emission from a dipole forbidden intermediate state may even dominate the corresponding x-ray spectra. Our work extends the domain of x-ray standing wave methods to resonant x-ray emission spectroscopy and provides means for novel spectroscopic experiments in d- and f-electron systems. PMID:26935531

  17. Conformational isomerism in solid state of AMG 853--structure studies using solid-state nuclear magnetic resonance and X-ray diffraction.

    PubMed

    Kiang, Y-H; Nagapudi, Karthik; Wu, Tian; Peterson, Matthew L; Jona, Janan; Staples, Richard J; Stephens, Peter W

    2015-07-01

    Investigation of an additional resonance peak in the (19) F solid-state nuclear magnetic resonance (NMR) spectrum of AMG 853, a dual antagonist of DP and CRTH2 previously in clinical development for asthma, has led to the identification of two conformational isomers coexisting in the crystal lattice in a continuous composition range between 89.7%:10.3% and 96.5%:3.5%. These two isomers differ in the chloro-flurorophenyl moiety orientation-the aromatic ring is flipped by 180° in these two isomers. The level of the minor isomer is directly measured through integration of the two peaks in the (19) F solid-state NMR spectrum. The values obtained from the NMR data are in excellent agreement with the degree of disorder of the fluorine atom in the crystal structure, refined using both single-crystal and high-resolution powder X-ray diffraction data. PMID:25912152

  18. X-ray resonator with pear-shaped reflectors

    SciTech Connect

    Churikov, V A

    2003-11-30

    An X-ray resonator design is proposed in which peculiar pear-shaped reflectors, which are grazing-incidence X-ray mirrors, serve as optical elements. Special features of this resonator are relatively high reflector efficiencies and the axial symmetry of the output radiation. (resonators)

  19. PEGylated NaHoF4 nanoparticles as contrast agents for both X-ray computed tomography and ultra-high field magnetic resonance imaging.

    PubMed

    Ni, Dalong; Zhang, Jiawen; Bu, Wenbo; Zhang, Chen; Yao, Zhenwei; Xing, Huaiyong; Wang, Jing; Duan, Fei; Liu, Yanyan; Fan, Wenpei; Feng, Xiaoyuan; Shi, Jianlin

    2016-01-01

    It is well-known that multimodal imaging can integrate the advantages of different imaging modalities by overcoming their individual limitations. As ultra-high field magnetic resonance imaging (MRI) will be inevitably used in future MRI/X-ray computed tomography (CT) scanner, it is highly expected to develop high-performance nano-contrast agents for ultra-high field MR and CT dual-modality imaging, which has not been reported yet. Moreover, specific behavior of nano-contrast agents for ultra-high field MRI is a challenging work and still remains unknown. Herein, a novel type of NaHoF4 nanoparticles (NPs) with varied particle sizes were synthesized and explored as high-performance dual-modality contrast agents for ultra-high field MR and CT imaging. The specific X-ray absorption and MR relaxivity enhancements with varied nanoparticle diameters (3 nm, 7 nm, 13 nm and 29 nm) under different magnetic field (1.5/3.0/7.0 T) are investigated. Based on experimental results and theoretical analysis, the Curie and dipolar relaxation mechanisms of NaHoF4 NPs are firstly separated. Our results will greatly promote the future medical translational development of the NaHoF4 nano-contrast agents for ultra-high field MR/CT dual-modality imaging applications. PMID:26546914

  20. Magnetization dynamics in an exchange-coupled NiFe/CoFe bilayer studied by x-ray detected ferromagnetic resonance

    NASA Astrophysics Data System (ADS)

    Stenning, G. B. G.; Shelford, L. R.; Cavill, S. A.; Hoffmann, F.; Haertinger, M.; Hesjedal, T.; Woltersdorf, G.; Bowden, G. J.; Gregory, S. A.; Back, C. H.; de Groot, P. A. J.; van der Laan, G.

    2015-01-01

    Exchange-coupled hard and soft magnetic layers find extensive use in data storage applications, for which their dynamical response has great importance. With bulk techniques, such as ferromagnetic resonance (FMR), it is difficult to access the behaviour and precise influence of each individual layer. By contrast, the synchrotron radiation-based technique of x-ray detected ferromagnetic resonance (XFMR) allows element-specific and phase-resolved FMR measurements in the frequency range 0.5-11 GHz. Here, we report the study of the magnetization dynamics of an exchange-coupled Ni0.81Fe0.19 (43.5 nm)/Co0.5Fe0.5 (30 nm) bilayer system using magnetometry and vector network analyser FMR, combined with XFMR at the Ni and Co L2 x-ray absorption edges. The epitaxially grown bilayer exhibits two principal resonances denoted as the acoustic and optical modes. FMR experiments show that the Kittel curves of the two layers cannot be taken in isolation, but that their modelling needs to account for an interlayer exchange coupling. The angular dependence of FMR indicates a collective effect for the modes of the magnetically hard CoFe and soft NiFe layer. The XFMR precessional scans show that the acoustic mode is dominated by the Ni signal with the Co and Ni magnetization precessing in phase, whereas the optical mode is dominated by the Co signal with the Co and Ni magnetization precessing in anti-phase. The response of the Co signal at the Ni resonance, and vice versa, show induced changes in both amplitude and phase, which can be ascribed to the interface exchange coupling. An interesting aspect of phase-resolved XFMR is the ability to distinguish between static and dynamic exchange coupling. The element-specific precessional scans of the NiFe/CoFe bilayer clearly have the signature of static exchange coupling, in which the effective field in one layer is aligned along the magnetization direction of the other layer.

  1. X-ray magnetic circular dichroism imaging with hard X-rays.

    PubMed

    Sato, K; Ueji, Y; Okitsu, K; Matsushita, T; Amemiya, Y

    2001-05-01

    X-ray polarization-contrast images resulting from X-ray magnetic circular dichroism (XMCD) in the hard X-ray region have been successfully recorded for the first time. The apparatus used consisted of an X-ray polarizer, double X-ray phase retarders, and a high-spatial-resolution X-ray charge-coupled-device detector. The sample used was a hexagonal-close-packed cobalt polycrystal foil having a thickness of about 4 microns. The X-ray polarization-contrast image resulting from XMCD was observed at a photon energy of 10 eV above the cobalt K-absorption edge (7709 eV). The observed contrast in the image was reversed by inversion of the magnetic field. Furthermore, the contrast was reversed again at a photon energy of 32 eV above the cobalt K-absorption edge. PMID:11486407

  2. Non-destructive Analysis of Oil-Contaminated Soil Core Samples by X-ray Computed Tomography and Low-Field Nuclear Magnetic Resonance Relaxometry: a Case Study

    PubMed Central

    Mitsuhata, Yuji; Nishiwaki, Junko; Kawabe, Yoshishige; Utsuzawa, Shin; Jinguuji, Motoharu

    2010-01-01

    Non-destructive measurements of contaminated soil core samples are desirable prior to destructive measurements because they allow obtaining gross information from the core samples without touching harmful chemical species. Medical X-ray computed tomography (CT) and time-domain low-field nuclear magnetic resonance (NMR) relaxometry were applied to non-destructive measurements of sandy soil core samples from a real site contaminated with heavy oil. The medical CT visualized the spatial distribution of the bulk density averaged over the voxel of 0.31 × 0.31 × 2 mm3. The obtained CT images clearly showed an increase in the bulk density with increasing depth. Coupled analysis with in situ time-domain reflectometry logging suggests that this increase is derived from an increase in the water volume fraction of soils with depth (i.e., unsaturated to saturated transition). This was confirmed by supplementary analysis using high-resolution micro-focus X-ray CT at a resolution of ∼10 μm, which directly imaged the increase in pore water with depth. NMR transverse relaxation waveforms of protons were acquired non-destructively at 2.7 MHz by the Carr–Purcell–Meiboom–Gill (CPMG) pulse sequence. The nature of viscous petroleum molecules having short transverse relaxation times (T2) compared to water molecules enabled us to distinguish the water-saturated portion from the oil-contaminated portion in the core sample using an M0–T2 plot, where M0 is the initial amplitude of the CPMG signal. The present study demonstrates that non-destructive core measurements by medical X-ray CT and low-field NMR provide information on the groundwater saturation level and oil-contaminated intervals, which is useful for constructing an adequate plan for subsequent destructive laboratory measurements of cores. PMID:21258437

  3. High-energy magnetic excitations in overdoped La2 -xSrxCuO4 studied by neutron and resonant inelastic x-ray scattering

    NASA Astrophysics Data System (ADS)

    Wakimoto, S.; Ishii, K.; Kimura, H.; Fujita, M.; Dellea, G.; Kummer, K.; Braicovich, L.; Ghiringhelli, G.; Debeer-Schmitt, L. M.; Granroth, G. E.

    2015-05-01

    We have performed neutron inelastic scattering and resonant inelastic x-ray scattering (RIXS) at the Cu-L3 edge to study high-energy magnetic excitations at energy transfers of more than 100 meV for overdoped La2 -xSrxCuO4 with x =0.25 (Tc=15 K) and x =0.30 (nonsuperconducting) using identical single-crystal samples for the two techniques. From constant-energy slices of neutron-scattering cross sections, we have identified magnetic excitations up to ˜250 meV for x =0.25 . Although the width in the momentum direction is large, the peak positions along the (π ,π ) direction agree with the dispersion relation of the spin wave in the nondoped La2CuO4 (LCO), which is consistent with the previous RIXS results of cuprate superconductors. Using RIXS at the Cu-L3 edge, we have measured the dispersion relations of the so-called paramagnon mode along both (π ,π ) and (π ,0 ) directions. Although in both directions the neutron and RIXS data connect with each other and the paramagnon along (π ,0 ) agrees well with the LCO spin-wave dispersion, the paramagnon in the (π ,π ) direction probed by RIXS appears to be less dispersive and the excitation energy is lower than the spin wave of LCO near (π /2 ,π /2 ) . Thus, our results indicate consistency between neutron inelastic scattering and RIXS, and elucidate the entire magnetic excitation in the (π ,π ) direction by the complementary use of two probes. The polarization dependence of the RIXS profiles indicates that appreciable charge excitations exist in the same energy range of magnetic excitations, reflecting the itinerant character of the overdoped sample. A possible anisotropy in the charge excitation intensity might explain the apparent differences in the paramagnon dispersion in the (π ,π ) direction as detected by the x-ray scattering.

  4. Furthering the understanding of silicate-substitution in α-tricalcium phosphate: an X-ray diffraction, X-ray fluorescence and solid-state nuclear magnetic resonance study.

    PubMed

    Duncan, J; Hayakawa, S; Osaka, A; MacDonald, J F; Hanna, J V; Skakle, J M S; Gibson, I R

    2014-03-01

    High-purity (SupT) and reagent-grade (ST), stoichiometric and silicate-containing α-tricalcium phosphate (α-TCP: ST0/SupT0 and Si-TCP x=0.10: ST10/SupT10) were prepared by solid-state reaction based on the substitution mechanism Ca3(PO4)(2-x)(SiO4)x. Samples were determined to be phase pure by X-ray diffraction (XRD), and Rietveld analysis performed on the XRD data confirmed inclusion of Si in the α-TCP structure as determined by increases in unit cell parameters; particularly marked increases in the b-axis and β-angle were observed. X-ray fluorescence (XRF) confirmed the presence of expected levels of Si in Si-TCP compositions as well as significant levels of impurities (Mg, Al and Fe) present in all ST samples; SupT samples showed both expected levels of Si and a high degree of purity. Phosphorus ((31)P) magic-angle-spinning solid-state nuclear magnetic resonance (MAS NMR) measurements revealed that the high-purity reagents used in the synthesis of SupT0 can resolve the 12 expected peaks in the (31)P spectrum of α-TCP compared to the low-purity ST0 that showed significant spectral line broadening; line broadening was also observed with the inclusion of Si which is indicative of induced structural disorder. Silicon ((29)Si) MAS NMR was also performed on both Si-TCP samples which revealed Q(0) species of Si with additional Si Q(1)/Q(2) species that may indicate a potential charge-balancing mechanism involving the inclusion of disilicate groups; additional Q(4) Si species were also observed, but only for ST10. Heating and cooling rates were briefly investigated by (31)P MAS NMR which showed no significant line broadening other than that associated with the emergence of β-TCP which was only realised with the reagent-grade sample ST0. This study provides an insight into the structural effects of Si-substitution in α-TCP and could provide a basis for understanding how substitution affects the physicochemical properties of the material. PMID:24287162

  5. Magnetic Excitations in Thin Film Ba2 IrO4 and Sr2 IrO4 Probed by Resonant Inelastic X-ray Scattering

    NASA Astrophysics Data System (ADS)

    Clancy, J. P.; Lupascu, A.; Gretarsson, H.; Upton, M. H.; Kim, J.; Islam, Z.; Uchida, M.; Schlom, D. G.; Shen, K. M.; Nichols, J.; Terzic, J.; Cao, G.; Seo, S. S. A.; Katukuri, V. M.; Hozoi, L.; van den Brink, J.; Stoll, H.; Kim, Y.-J.

    2014-03-01

    We have performed resonant inelastic x-ray scattering (RIXS) measurements on epitaxial thin film samples of the layered perovskite iridates Ba2IrO4 and Sr2IrO4. These materials display a novel Jeff = 1/2 Mott insulating ground state driven by strong 5d spin-orbit coupling effects. By studying 10 to 50 nm thin film samples grown on a variety of different substrates (GSO, STO, LSAT), we have investigated the impact of applied tensile/compressive strain on the characteristic magnetic and electronic excitations of these materials. Unlike other perturbations, such as doping or applied magnetic field, we find that applied strain does not alter the magnetic structure of Ba2IrO4 or Sr2IrO4. However, strain does affect the magnetic energy scales of these systems, providing a means of tuning both the ordering temperature (Tn) and the magnetic exchange interactions (J). In addition, we show that the dispersion of the low-lying magnon and spin-orbit exciton modes is renormalized by strain-induced structural changes.

  6. Mn L{sub 2,3} edge resonant x-ray scattering in manganites: Influence of the magnetic state

    SciTech Connect

    Stojic, N.; Binggeli, N.; Altarelli, M.

    2005-09-01

    We present an analysis of the dependence of the resonant orbital-order and magnetic scattering spectra on the spin configuration. We consider an arbitrary spin direction with respect to the local crystal field axis, thus lowering significantly the local symmetry. To evaluate the atomic scattering in this case, we generalized the Hannon-Trammel formula and implemented it inside the framework of atomic multiplet calculations in a crystal field. For an illustration, we calculate the magnetic and orbital scattering in the CE phase of La{sub 0.5}Sr{sub 1.5}MnO{sub 4} in the cases when the spins are aligned with the crystal lattice vector a (or equivalently b) and when they are rotated in the ab-plane by 45 deg. with respect to this axis. Magnetic spectra differ for the two cases. For the orbital scattering, we show that for the former configuration there is a non-negligible {sigma}{yields}{sigma}{sup '} ({pi}{yields}{pi}{sup '}) scattering component, which vanishes in the 45 deg. case, while the {sigma}{yields}{pi}{sup '} ({pi}{yields}{sigma}{sup '}) components are similar in the two cases. From the consideration of two 90 deg. spin canted structures, we conclude there is a significant dependence of the orbital scattering spectra on the spin arrangement. Recent experiments detected a sudden decrease of the orbital scattering intensity upon increasing the temperature above the Neel temperature in La{sub 0.5}Sr{sub 1.5}MnO{sub 4}. We discuss this behavior considering the effect of different types of misorientations of the spins on the orbital scattering spectrum.

  7. Locking of iridium magnetic moments to the correlated rotation of oxygen octahedra in Sr₂IrO₄ revealed by x-ray resonant scattering.

    PubMed

    Boseggia, S; Walker, H C; Vale, J; Springell, R; Feng, Z; Perry, R S; Moretti Sala, M; Rønnow, H M; Collins, S P; McMorrow, D F

    2013-10-23

    Sr2IrO4 is a prototype of the class of Mott insulators in the strong spin-orbit interaction (SOI) limit described by a Jeff = 1/2 ground state. In Sr2IrO4, the strong SOI is predicted to manifest itself in the locking of the canting of the magnetic moments to the correlated rotation by 11.8(1)° of the oxygen octahedra that characterizes its distorted layered perovskite structure. Using x-ray resonant scattering at the Ir L3 edge we have measured accurately the intensities of Bragg peaks arising from different components of the magnetic structure. From a careful comparison of integrated intensities of peaks due to basal-plane antiferromagnetism, with those due to b-axis ferromagnetism, we deduce a canting of the magnetic moments of 12.2(8)°. We thus confirm that in Sr2IrO4 the magnetic moments rigidly follow the rotation of the oxygen octahedra, indicating that, even in the presence of significant non-cubic structural distortions, it is a close realization of the Jeff = 1/2 state. PMID:24067396

  8. Resonant x-ray scattering investigation of magnetic ordering in NpAs(1 - x)Se(x) (x = 0.05, 0.10).

    PubMed

    Rodrigues, V H; Paixão, J A; Costa, M M R; Mannix, D; Bombardi, A; Rebizant, J; Lander, G H

    2011-01-19

    A resonant x-ray scattering investigation of the NpAs(1 - x)Se(x) system with single crystals of 5 and 10% Se content is reported. The main features of the magnetic phase diagram previously studied by neutron scattering were confirmed. The coexistence within a single domain of ferro- and antiferro-components in the low-T ferrimagnetic phase was established, as well as the single-k character of the incommensurate phase and of the antiferromagnetic component of the ferrimagnetic phase. A tetragonal lattice distortion was found in the ferro- and ferrimagnetic phases which is not compatible with the proposed model for the ferromagnetic phase. The study of ferromagnetism was carried out using polarization analysis of the diffracted beam to separate the scattering intensities originating from magnetism and charge, which are superimposed in reciprocal space. The magnetic character of the ferromagnetic signal calculated from the measured intensities in the polarization analysis σπ and σσ channels was confirmed by analysis of the corresponding temperature dependence. PMID:21406852

  9. X-ray suppression in gamma-ray bursts through resonant Compton scattering

    NASA Technical Reports Server (NTRS)

    Brainerd, J. J.

    1992-01-01

    An X-ray that scatters with an electron in the first Landau level of a strong magnetic field is converted into a gamma ray. This process has a resonant cross section at X-ray energies and is therefore highly likely to occur even when the first Landau level is sparsely populated. Converted X-rays are cyclotron absorbed, maintaining the equilibrium between the cyclotron photon density and the population of the first Landau level. By suppressing a neutron star's black body emission, this mechanism can produce a gamma-ray burst with a low X-ray flux.

  10. Nanoscale Imaging of Buried Structures with Elemental Specificity Using Resonant X-Ray Diffraction Microscopy

    SciTech Connect

    Song, Changyong; Bergstrom, Raymond; Ramunno-Johnson, Damien; Jiang, Huaidong; Miao, Jianwei; Paterson, David; Jonge, Martin D. de; McNulty, Ian; Lee, Jooyoung; Wang, Kang L.

    2008-01-18

    We report the first demonstration of resonant x-ray diffraction microscopy for element specific imaging of buried structures with a pixel resolution of {approx}15 nm by exploiting the abrupt change in the scattering cross section near electronic resonances. We performed nondestructive and quantitative imaging of buried Bi structures inside a Si crystal by directly phasing coherent x-ray diffraction patterns acquired below and above the Bi M{sub 5} edge. We anticipate that resonant x-ray diffraction microscopy will be applied to element and chemical state specific imaging of a broad range of systems including magnetic materials, semiconductors, organic materials, biominerals, and biological specimens.

  11. Synthesis, Characterization, In Vitro Phantom Imaging, and Cytotoxicity of A Novel Graphene-Based Multimodal Magnetic Resonance Imaging - X-Ray Computed Tomography Contrast Agent.

    PubMed

    Lalwani, Gaurav; Sundararaj, Joe Livingston; Schaefer, Kenneth; Button, Terry; Sitharaman, Balaji

    2014-06-14

    Graphene nanoplatelets (GNPs), synthesized using potassium permanganate-based oxidation and exfoliation followed by reduction with hydroiodic acid (rGNP-HI), have intercalated manganese ions within the graphene sheets, and upon functionalization with iodine, show excellent potential as biomodal contrast agents for magnetic resonance imaging (MRI) and computed tomography (CT). Structural characterization of rGNP-HI nanoparticles with low- and high-resolution transmission electron microscope (TEM) showed disc-shaped nanoparticles (average diameter, 200 nm, average thickness, 3 nm). Energy dispersive X-ray spectroscopy (EDX) analysis confirmed the presence of intercalated manganese. Raman spectroscopy and X-ray diffraction (XRD) analysis of rGNP-HI confirmed the reduction of oxidized GNPs (O-GNPs), absence of molecular and physically adsorbed iodine, and the functionalization of graphene with iodine as polyiodide complexes (I3 (-) and I5 (-)). Manganese and iodine content were quantified as 5.1 ± 0.5 and 10.54 ± 0.87 wt% by inductively-coupled plasma optical emission spectroscopy and ion-selective electrode measurements, respectively. In vitro cytotoxicity analysis, using absorbance (LDH assay) and fluorescence (calcein AM) based assays, performed on NIH3T3 mouse fibroblasts and A498 human kidney epithelial cells, showed CD50 values of rGNP-HI between 179-301 µg/ml, depending on the cell line and the cytotoxicity assay. CT and MRI phantom imaging of rGNP-HI showed high CT (approximately 3200% greater than HI at equimolar iodine concentration) and MRI (approximately 59% greater than equimolar Mn(2+) solution) contrast. These results open avenues for further in vivo safety and efficacy studies towards the development of carbon nanostructure-based multimodal MRI-CT contrast agents. PMID:24999431

  12. Synthesis, Characterization, In Vitro Phantom Imaging, and Cytotoxicity of A Novel Graphene-Based Multimodal Magnetic Resonance Imaging - X-Ray Computed Tomography Contrast Agent

    PubMed Central

    Lalwani, Gaurav; Sundararaj, Joe Livingston; Schaefer, Kenneth; Button, Terry; Sitharaman, Balaji

    2014-01-01

    Graphene nanoplatelets (GNPs), synthesized using potassium permanganate-based oxidation and exfoliation followed by reduction with hydroiodic acid (rGNP-HI), have intercalated manganese ions within the graphene sheets, and upon functionalization with iodine, show excellent potential as biomodal contrast agents for magnetic resonance imaging (MRI) and computed tomography (CT). Structural characterization of rGNP-HI nanoparticles with low- and high-resolution transmission electron microscope (TEM) showed disc-shaped nanoparticles (average diameter, 200 nm, average thickness, 3 nm). Energy dispersive X-ray spectroscopy (EDX) analysis confirmed the presence of intercalated manganese. Raman spectroscopy and X-ray diffraction (XRD) analysis of rGNP-HI confirmed the reduction of oxidized GNPs (O-GNPs), absence of molecular and physically adsorbed iodine, and the functionalization of graphene with iodine as polyiodide complexes (I3− and I5−). Manganese and iodine content were quantified as 5.1 ± 0.5 and 10.54 ± 0.87 wt% by inductively-coupled plasma optical emission spectroscopy and ion-selective electrode measurements, respectively. In vitro cytotoxicity analysis, using absorbance (LDH assay) and fluorescence (calcein AM) based assays, performed on NIH3T3 mouse fibroblasts and A498 human kidney epithelial cells, showed CD50 values of rGNP-HI between 179-301 µg/ml, depending on the cell line and the cytotoxicity assay. CT and MRI phantom imaging of rGNP-HI showed high CT (approximately 3200% greater than HI at equimolar iodine concentration) and MRI (approximately 59% greater than equimolar Mn2+ solution) contrast. These results open avenues for further in vivo safety and efficacy studies towards the development of carbon nanostructure-based multimodal MRI-CT contrast agents. PMID:24999431

  13. X-ray resonant magnetic scattering investigations of hexagonal multiferroics RMnO3 (R = Dy, Ho, Er)

    SciTech Connect

    Nandi, Shibabrata

    2009-01-01

    Electricity and magnetism were unified into a common subject by James Clerk Maxwell in the nineteenth century yielding the electromagnetic theory. Four equations govern the dynamics of electric charges and magnetic fields, commonly known as Maxwell's equations. Maxwell's equations demonstrate that an accelerated charged particle can produce magnetic fields and a time varying magnetic field can induce a voltage - thereby linking the two phenomena. However, in solids, electric and magnetic ordering are most often considered separately and usually with good reason: the electric charges of electrons and ions are responsible for the charge effects, whereas the electron spin governs magnetic properties.

  14. Deconvoluting Protein (Un)folding Structural Ensembles Using X-Ray Scattering, Nuclear Magnetic Resonance Spectroscopy and Molecular Dynamics Simulation

    PubMed Central

    Nasedkin, Alexandr; Marcellini, Moreno; Religa, Tomasz L.; Freund, Stefan M.; Menzel, Andreas; Fersht, Alan R.; Jemth, Per; van der Spoel, David; Davidsson, Jan

    2015-01-01

    The folding and unfolding of protein domains is an apparently cooperative process, but transient intermediates have been detected in some cases. Such (un)folding intermediates are challenging to investigate structurally as they are typically not long-lived and their role in the (un)folding reaction has often been questioned. One of the most well studied (un)folding pathways is that of Drosophila melanogaster Engrailed homeodomain (EnHD): this 61-residue protein forms a three helix bundle in the native state and folds via a helical intermediate. Here we used molecular dynamics simulations to derive sample conformations of EnHD in the native, intermediate, and unfolded states and selected the relevant structural clusters by comparing to small/wide angle X-ray scattering data at four different temperatures. The results are corroborated using residual dipolar couplings determined by NMR spectroscopy. Our results agree well with the previously proposed (un)folding pathway. However, they also suggest that the fully unfolded state is present at a low fraction throughout the investigated temperature interval, and that the (un)folding intermediate is highly populated at the thermal midpoint in line with the view that this intermediate can be regarded to be the denatured state under physiological conditions. Further, the combination of ensemble structural techniques with MD allows for determination of structures and populations of multiple interconverting structures in solution. PMID:25946337

  15. Soft x-ray coherent diffraction imaging on magnetic nanostructures

    NASA Astrophysics Data System (ADS)

    Shi, Xiaowen; Lee, James; Mishra, Shrawan; Parks, Daniel; Tyliszczak, Tolek; Shapiro, David; Roy, Sujoy; Kevan, Steve; Stxm Team At Als Collaboration; Soft X-Ray Microscopy Group At Als Collaboration; Soft X-ray scattering at ALS, LBL Team

    2014-03-01

    Coherent soft X-rays diffraction imaging enable coherent magnetic resonance scattering at transition metal L-edge to be probed so that magnetic domains could be imaged with very high spatial resolution with phase contrast, reaching sub-10nm. One of the overwhelming advantages of using coherent X-rays is the ability to resolve phase contrast images with linearly polarized light with both phase and absorption contrast comparing to real-space imaging, which can only be studied with circularly polarized light with absorption contrast only. Here we report our first results on high-resolution of magnetic domains imaging of CoPd multilayer thin film with coherent soft X-ray ptychography method. We are aiming to resolve and understand magnetic domain wall structures with the highest obtainable resolution here at Advanced Light Source. In principle types of magnetic domain walls could be studied so that Neel or Bloch walls can be distinguished by imaging. This work at LBNL was supported by the Director, Office of Science, Office of Basic Energy Sciences, of the US Department of Energy (contract no. DE-AC02- 05CH11231).

  16. High-energy magnetic excitations in overdoped La2-xSrxCuO4 studied by neutron and resonant inelastic X-ray scattering

    DOE PAGESBeta

    Wakimoto, S.; Ishii, K.; Kimura, H.; Fujita, M.; Dellea, G.; Kummer, K.; Braicovich, L.; Ghiringhelli, G.; Debeer-Schmitt, Lisa M.; Granroth, Garrett E.

    2015-05-21

    We have performed neutron inelastic scattering and resonant inelastic x-ray scattering (RIXS) at the Cu-L3 edge to study high-energy magnetic excitations at energy transfers of more than 100 meV for overdoped La2₋xSrxCuO4 with x=0.25 (Tc=15 K) and x=0.30 (nonsuperconducting) using identical single-crystal samples for the two techniques. From constant-energy slices of neutron-scattering cross sections, we have identified magnetic excitations up to ~250 meV for x=0.25. Although the width in the momentum direction is large, the peak positions along the (π,π) direction agree with the dispersion relation of the spin wave in the nondoped La2CuO4 (LCO), which is consistent with themore » previous RIXS results of cuprate superconductors. Using RIXS at the Cu-L3 edge, we have measured the dispersion relations of the so-called paramagnon mode along both (π,π) and (π,0) directions. Although in both directions the neutron and RIXS data connect with each other and the paramagnon along (π,0) agrees well with the LCO spin-wave dispersion, the paramagnon in the (π,π) direction probed by RIXS appears to be less dispersive and the excitation energy is lower than the spin wave of LCO near (π/2,π/2). Thus, our results indicate consistency between neutron inelastic scattering and RIXS, and elucidate the entire magnetic excitation in the (π,π) direction by the complementary use of two probes. The polarization dependence of the RIXS profiles indicates that appreciable charge excitations exist in the same energy range of magnetic excitations, reflecting the itinerant character of the overdoped sample. Lastly, we find a possible anisotropy in the charge excitation intensity might explain the apparent differences in the paramagnon dispersion in the (π,π) direction as detected by the x-ray scattering.« less

  17. Tb_1-xY_xNi_2Ge_2: Investigation of the magnetic structure using x-ray resonant exchange scattering.

    NASA Astrophysics Data System (ADS)

    Wermeille, D.; Song, C.; Goldman, A. I.; Canfield, P. C.; Islam, Z.

    2001-03-01

    TbNi_2Ge2 exhibits two distinct magnetic phase transitions. One is from the high-temperature paramagnetic state to a long period antiferromagnetic phase at the Néel temperature (T_N=16.8 K) with a propagation vector τ_1=(0 0 0.758), and the other is at a lower temperature (T_t=9.3 K), where the system locks into a commensurate phase τ_1=(0 0 3/4). Additional magnetic Bragg reflections corresponding to τ_2=(1/2 1/2 0) and τ_3=(1/2 1/2 1/2) develop [1]. Recent theoretical work on Gd_1-xEu_xNi_2Ge2 [2] has suggested the connection between the band filling and the value of the ordering wave-vector of the magnetically ordered state. In this talk, we will present the results of x-ray resonant exchange scattering on the three compounds of the pseudo- ternary series Tb_1-xY_xNi_2Ge2 with x=0, 0,1 and 0.35. A comparison between the magnetic phase in the different compositions will be discussed. The magnetic ordering wave-vector, as well as the order parameter will be presented. [1] Z. Islam et al. PRB 58 8522 (1998). [2] Z. Islam et al. PRL 83 2817 (1999). The synchrotron work was performed at the Midwest Universities Collaborative Access Team (MU-CAT) sector at the Advanced Photon Source supported by U.S. DOE, BES, OS, through the Ames Laboratory under Contract No. W-31-109-Eng-38.

  18. Resonant Auger Effect at High X-Ray Intensity

    SciTech Connect

    Rohringer, N; Santra, R

    2008-03-27

    The resonant Auger effect of atomic neon exposed to high-intensity x-ray radiation in resonance with the 1s {yields} 3p transition is discussed. High intensity here means that the x-ray peak intensity is sufficient ({approx} 10{sup 18} W/cm{sup 2}) to induce Rabi oscillations between the neon ground state and the 1s{sup -1}3p ({sup 1}P) state within the relaxation lifetime of the inner-shell vacancy. For the numerical analysis presented, an effective two-level model, including a description of the resonant Auger decay process, is employed. Both coherent and chaotic x-ray pulses are treated. The latter are used to simulate radiation from x-ray free-electron lasers based on the principle of self-amplified spontaneous emission. Observing x-ray-driven atomic population dynamics in the time domain is challenging for chaotic pulse ensembles. A more practical option for experiments using x-ray free-electron lasers is to measure the line profiles in the kinetic energy distribution of the resonant Auger electron. This provides information on both atomic population dynamics and x-ray pulse properties.

  19. Resonant Soft X-ray Scattering for Soft Materials

    NASA Astrophysics Data System (ADS)

    Wang, Cheng; Young, Athony; Hexemer, Alexander; Padmore, Howard

    2015-03-01

    Over the past a few years, we have developed Resonant Soft X-ray Scattering (RSoXS) and constructed the first dedicated resonant soft x-ray scattering beamline at the Advanced Light Source, LBNL. RSoXS combines soft x-ray spectroscopy with x-ray scattering thus offers statistical information for 3D chemical morphology over a large length scale range from nanometers to micrometers. Its unique chemical sensitivity, large accessible size scale, molecular bond orientation sensitivity with polarized x-rays and high coherence have shown great potential for chemical/morphological structure characterization for many classes of materials. Some recent development of in-situ soft x-ray scattering with in-vacuum sample environment will be discussed. In order to study sciences in naturally occurring conditions, we need to overcome the sample limitations set by the low penetration depth of soft x-rays and requirement of high vacuum. Adapting to the evolving environmental cell designs utilized increasingly in the Electron Microscopy community, customized designed liquid/gas environmental cells will enable soft x-ray scattering experiments on biological, electro-chemical, self-assembly, and hierarchical functional systems in both static and dynamic fashion. Recent RSoXS results on organic electronics, block copolymer thin films, and membrane structure will be presented.

  20. Investigations of the R5(SixGe1-x)4 Intermetallic Compounds by X-Ray Resonant Magnetic Scattering

    SciTech Connect

    Lizhi Tan

    2008-08-18

    The XRMS experiment on the Gd{sub 5}Ge{sub 4} system has shown that, below the Neel temperature, T{sub N} = 127 K, the magnetic unit cells is the same as the chemical unit cell. From azimuth scans and the Q dependence of the magnetic scattering, all three Gd sites in the structure were determined to be in the same magnetic space group Pnma. The magnetic moments are aligned along the c-axis and the c-components of the magnetic moments at the three different sites are equal. The ferromagnetic slabs are stacked antiferromagnetically along the b-direction. They found an unusual order parameter curve in Gd{sub 5}Ge{sub 4}. A spin-reorientation transition is a possibility in Gd{sub 5}Ge{sub 4}, which is similar to the Tb{sub 5}Ge{sub 4} case. Tb{sub 5}Ge{sub 4} possesses the same Sm{sub 5}Ge{sub 4}-type crystallographic structure and the same magnetic space group as Gd{sub 5}Ge{sub 4} does. The difference in magnetic structure is that Tb{sub 5}Ge{sub 4} has a canted one but Gd{sub 5}Ge{sub 4} has nearly a collinear one in the low temperature antiferromagnetic phase. The competition between the magneto-crystalline anisotropy and the nearest-neighbor magnetic exchange interactions may allow a 3-dimensional canted antiferromagnetic structure in Tb{sub 5}Ge{sub 4}. The spin-reorientation transition in both Gd{sub 5}Ge{sub 4} and Tb{sub 5}Ge{sub 4} may arise from the competition between the magnetic anisotropy from the spin-orbit coupling of the conduction electrons and the dipolar interactions anisotropy.

  1. Resonant soft X-ray scattering on protein solutions

    NASA Astrophysics Data System (ADS)

    Ye, Dan; Le, Thinh; Wang, Cheng; Zwart, Peter; Gomez, Esther; Gomez, Enrique

    Protein structure is crucial for biological function, such that characterizing protein folding and packing is important for the design of therapeutics and enzymes. We propose resonant soft X-ray scattering (RSOXS) as an approach to study proteins and other biological assemblies in solution. Calculations of the scattering contrast suggest that soft X-ray scattering is more sensitive than hard X-ray scattering, because of contrast generated at the absorption edges of constituent elements such as carbon, nitrogen and oxygen. We have examined the structure of bovine serum albumin (BSA) in solution by RSOXS. We find that by varying incident X-ray energies, we are able to achieve higher scattering contrast near the absorption edge. From our RSOXS scattering result we are able to reconstruct the structure of BSA in 3D. These RSOXS results also agree with hard X-ray experiments, including crystallographic data. Our study demonstrates the potential of RSOXS for studying protein structure in solution.

  2. First Principles Calculations for X-ray Resonant Spectra and Elastic Properties

    SciTech Connect

    Yongbin Lee

    2006-05-01

    In this thesis, we discuss applications of first principles methods to x-ray resonant spectra and elastic properties calculation. We start with brief reviews about theoretical background of first principles methods, such as density functional theory, local density approximation (LDA), LDA+U, and the linear augmented plane wave (LAPW) method to solve Kohn-Sham equations. After that we discuss x-ray resonant scattering (XRMS), x-ray magnetic circular dichroism (XMCD) and the branching problem in the heavy rare earths Ledges. In the last chapter we discuss the elastic properties of the second hardest material AlMgB{sub 14}.

  3. Electron cyclotron resonance ion source plasma characterization by X-ray spectroscopy and X-ray imaging.

    PubMed

    Mascali, David; Castro, Giuseppe; Biri, Sándor; Rácz, Richárd; Pálinkás, József; Caliri, Claudia; Celona, Luigi; Neri, Lorenzo; Romano, Francesco Paolo; Torrisi, Giuseppe; Gammino, Santo

    2016-02-01

    An experimental campaign aiming to investigate electron cyclotron resonance (ECR) plasma X-ray emission has been recently carried out at the ECRISs-Electron Cyclotron Resonance Ion Sources laboratory of Atomki based on a collaboration between the Debrecen and Catania ECR teams. In a first series, the X-ray spectroscopy was performed through silicon drift detectors and high purity germanium detectors, characterizing the volumetric plasma emission. The on-purpose developed collimation system was suitable for direct plasma density evaluation, performed "on-line" during beam extraction and charge state distribution characterization. A campaign for correlating the plasma density and temperature with the output charge states and the beam intensity for different pumping wave frequencies, different magnetic field profiles, and single-gas/gas-mixing configurations was carried out. The results reveal a surprisingly very good agreement between warm-electron density fluctuations, output beam currents, and the calculated electromagnetic modal density of the plasma chamber. A charge-coupled device camera coupled to a small pin-hole allowing X-ray imaging was installed and numerous X-ray photos were taken in order to study the peculiarities of the ECRIS plasma structure. PMID:26931918

  4. Electron cyclotron resonance ion source plasma characterization by X-ray spectroscopy and X-ray imaging

    NASA Astrophysics Data System (ADS)

    Mascali, David; Castro, Giuseppe; Biri, Sándor; Rácz, Richárd; Pálinkás, József; Caliri, Claudia; Celona, Luigi; Neri, Lorenzo; Romano, Francesco Paolo; Torrisi, Giuseppe; Gammino, Santo

    2016-02-01

    An experimental campaign aiming to investigate electron cyclotron resonance (ECR) plasma X-ray emission has been recently carried out at the ECRISs—Electron Cyclotron Resonance Ion Sources laboratory of Atomki based on a collaboration between the Debrecen and Catania ECR teams. In a first series, the X-ray spectroscopy was performed through silicon drift detectors and high purity germanium detectors, characterizing the volumetric plasma emission. The on-purpose developed collimation system was suitable for direct plasma density evaluation, performed "on-line" during beam extraction and charge state distribution characterization. A campaign for correlating the plasma density and temperature with the output charge states and the beam intensity for different pumping wave frequencies, different magnetic field profiles, and single-gas/gas-mixing configurations was carried out. The results reveal a surprisingly very good agreement between warm-electron density fluctuations, output beam currents, and the calculated electromagnetic modal density of the plasma chamber. A charge-coupled device camera coupled to a small pin-hole allowing X-ray imaging was installed and numerous X-ray photos were taken in order to study the peculiarities of the ECRIS plasma structure.

  5. Resonance transition radiation X-ray laser

    NASA Technical Reports Server (NTRS)

    Reid, Max B.; Piestrup, Melvin A.

    1991-01-01

    A free electron laser is proposed using a periodic dielectric and helical magnetic field. Periodic synchronism between the electrons and the optical wave is obtained at the period of the dielectric and not at the period of the helical magnetic field. The synchronism condition and the gain of the new device are derived. The effects on the gain from dephasing and beam expansion due to elastic scattering of the electrons in the periodic medium are included in the gain calculation. Examples of the resonance transition radiation laser and klystron are given. Operation at photon energies between 2.5 and 3.5 keV with net gain up to 12 percent is feasible using high electron-beam energies of 3 and 5 GeV. Moderate (300-MeV) beam energy allows operation between 80 to 110 eV with up to 57 percent net gain using a klystron design. In both cases, rapid foil heating may limit operation to a single electron-beam pulse.

  6. X-ray holographic imaging of magnetic order in meander domain structures

    NASA Astrophysics Data System (ADS)

    Spezzani, Carlo; Popescu, Horia; Fortuna, Franck; Delaunay, Renaud; Tortarolo, Marina; Jaouen, Nicolas; Sacchi, Maurizio

    2013-01-01

    We performed x-ray holography experiments using synchrotron radiation. By analyzing the scattering of coherent circularly polarized x-rays tuned at the Co-2p resonance, we imaged perpendicular magnetic domains in a Co/Pd multilayer. We compare results obtained for continuous and laterally confined films.

  7. Applications of soft x-ray magnetic dichroism

    NASA Astrophysics Data System (ADS)

    van der Laan, G.

    2013-04-01

    Applications of x-ray magnetic circular and linear dichroism (XMCD and XMLD) are reviewed in the soft x-ray region, covering the photon energy range 0.4-2 keV, which includes important absorption edges such as the 3d transition metal L2,3 and rare earth M4,5. These techniques enable a broad range of novel and exciting studies such as on the electronic properties and magnetic ordering of novel nanostructured systems. XMCD has a sensitivity better than 0.01 monolayer (at the surface) and due to simple detection methods, such as electron yield and fluorescence yield, it has become a workhorse technique in physics and materials science. It is the only element-specific technique able to distinguish between the spin and orbital parts of the magnetic moments. The applications are vast, e.g., in x-ray holographic imaging, XMCD gives a spatial resolution of tens of nm. While many studies in the past were centered on physics, more recently new applications have emerged in areas such as chemistry, biology and earth and environmental sciences. For instance, XMCD allows the determination of the cation occupations in spinels and other ternary oxides. In scanning transmission x-ray microscopy (STXM), XMCD enables us to map biogenic magnetite redox changes resulting in a surprising degree of variation on the nanoscale. Another recent development is ferromagnetic resonance (FMR) detected by time-resolved XMCD which opens the door to element-, site- and layer-specific dynamical measurements. By exploiting the time structure of the pulsed synchrotron radiation from the storage ring the relative phase of precession in the individual magnetic layers of a multilayer stack can be determined.

  8. Resonant inelastic x-ray scattering from molecules and atoms

    SciTech Connect

    Arp, U.; Deslattes, R.D.; Miyano, K.E.; Southworth, S.H.

    1995-12-31

    X-ray fluorescence spectroscopy is one of the most powerful methods for the understanding of the electronic structure of matter. We report here on fluorescence experiments in the 2 to 6 keV photon energy range using tunable synchrotron radiation and the resulting experimental programs on resonant inelastic scattering in atoms and on polarization measurements in resonant molecular excitations.

  9. PEGylated hybrid ytterbia nanoparticles as high-performance diagnostic probes for in vivo magnetic resonance and X-ray computed tomography imaging with low systemic toxicity

    NASA Astrophysics Data System (ADS)

    Liu, Zhen; Pu, Fang; Liu, Jianhua; Jiang, Liyan; Yuan, Qinghai; Li, Zhengqiang; Ren, Jinsong; Qu, Xiaogang

    2013-05-01

    Novel nanoparticulate contrast agents with low systemic toxicity and inexpensive character have exhibited more advantages over routinely used small molecular contrast agents for the diagnosis and prognosis of disease. Herein, we designed and synthesized PEGylated hybrid ytterbia nanoparticles as high-performance nanoprobes for X-ray computed tomography (CT) imaging and magnetic resonance (MR) imaging both in vitro and in vivo. These well-defined nanoparticles were facile to prepare and cost-effective, meeting the criteria as a biomedical material. Compared with routinely used Iobitridol in clinic, our PEG-Yb2O3:Gd nanoparticles could provide much significantly enhanced contrast upon various clinical voltages ranging from 80 kVp to 140 kVp owing to the high atomic number and well-positioned K-edge energy of ytterbium. By the doping of gadolinium, our nanoparticulate contrast agent could perform perfect MR imaging simultaneously, revealing similar organ enrichment and bio-distribution with the CT imaging results. The super improvement in imaging efficiency was mainly attributed to the high content of Yb and Gd in a single nanoparticle, thus making these nanoparticles suitable for dual-modal diagnostic imaging with a low single-injection dose. In addition, detailed toxicological study in vitro and in vivo indicated that uniformly sized PEG-Yb2O3:Gd nanoparticles possessed excellent biocompatibility and revealed overall safety.Novel nanoparticulate contrast agents with low systemic toxicity and inexpensive character have exhibited more advantages over routinely used small molecular contrast agents for the diagnosis and prognosis of disease. Herein, we designed and synthesized PEGylated hybrid ytterbia nanoparticles as high-performance nanoprobes for X-ray computed tomography (CT) imaging and magnetic resonance (MR) imaging both in vitro and in vivo. These well-defined nanoparticles were facile to prepare and cost-effective, meeting the criteria as a biomedical material

  10. High resolution magnetic resonance imaging of the calcaneus: age-related changes in trabecular structure and comparison with dual X-ray absorptiometry measurements

    NASA Technical Reports Server (NTRS)

    Ouyang, X.; Selby, K.; Lang, P.; Engelke, K.; Klifa, C.; Fan, B.; Zucconi, F.; Hottya, G.; Chen, M.; Majumdar, S.; Genant, H. K.

    1997-01-01

    A high-resolution magnetic resonance imaging (MRI) protocol, together with specialized image processing techniques, was applied to the quantitative measurement of age-related changes in calcaneal trabecular structure. The reproducibility of the technique was assessed and the annual rates of change for several trabecular structure parameters were measured. The MR-derived trabecular parameters were compared with calcaneal bone mineral density (BMD), measured by dual X-ray absorptiometry (DXA) in the same subjects. Sagittal MR images were acquired at 1.5 T in 23 healthy women (mean age: 49.3 +/- 16.6 [SD]), using a three-dimensional gradient echo sequence. Image analysis procedures included internal gray-scale calibration, bone and marrow segmentation, and run-length methods. Three trabecular structure parameters, apparent bone volume (ABV/TV), intercept thickness (I.Th), and intercept separation (I.Sp) were calculated from the MR images. The short- and long-term precision errors (mean %CV) of these measured parameters were in the ranges 1-2% and 3-6%, respectively. Linear regression of the trabecular structure parameters vs. age showed significant correlation: ABV/TV (r2 = 33.7%, P < 0.0037), I.Th (r2 = 26.6%, P < 0.0118), I.Sp (r2 = 28.9%, P < 0.0081). These trends with age were also expressed as annual rates of change: ABV/TV (-0.52%/year), I.Th (-0.33%/year), and I.Sp (0.59%/year). Linear regression analysis also showed significant correlation between the MR-derived trabecular structure parameters and calcaneal BMD values. Although a larger group of subjects is needed to better define the age-related changes in trabecular structure parameters and their relation to BMD, these preliminary results demonstrate that high-resolution MRI may potentially be useful for the quantitative assessment of trabecular structure.

  11. Comparison of Combined X-Ray Radiography and Magnetic Resonance (XMR) Imaging-Versus Computed Tomography-Based Dosimetry for the Evaluation of Permanent Prostate Brachytherapy Implants

    SciTech Connect

    Acher, Peter Rhode, Kawal; Morris, Stephen; Gaya, Andrew; Miquel, Marc; Popert, Rick; Tham, Ivan; Nichol, Janette; McLeish, Kate; Deehan, Charles; Dasgupta, Prokar; Beaney, Ronald; Keevil, Stephen F.

    2008-08-01

    Purpose: To present a method for the dosimetric analysis of permanent prostate brachytherapy implants using a combination of stereoscopic X-ray radiography and magnetic resonance (MR) imaging (XMR) in an XMR facility, and to compare the clinical results between XMR- and computed tomography (CT)-based dosimetry. Methods and Materials: Patients who had received nonstranded iodine-125 permanent prostate brachytherapy implants underwent XMR and CT imaging 4 weeks later. Four observers outlined the prostate gland on both sets of images. Dose-volume histograms (DVHs) were derived, and agreement was compared among the observers and between the modalities. Results: A total of 30 patients were evaluated. Inherent XMR registration based on prior calibration and optical tracking required a further automatic seed registration step that revealed a median root mean square registration error of 4.2 mm (range, 1.6-11.4). The observers agreed significantly more closely on prostate base and apex positions as well as outlining contours on the MR images than on those from CT. Coefficients of variation were significantly higher for observed prostate volumes, D90, and V100 parameters on CT-based dosimetry as opposed to XMR. The XMR-based dosimetry showed little agreement with that from CT for all observers, with D90 95% limits of agreement ranges of 65, 118, 79, and 73 Gy for Observers 1, 2, 3, and 4, respectively. Conclusions: The study results showed that XMR-based dosimetry offers an alternative to other imaging modalities and registration methods with the advantages of MR-based prostate delineation and confident three-dimensional reconstruction of the implant. The XMR-derived dose-volume histograms differ from the CT-derived values and demonstrate less interobserver variability.

  12. Magnetic resonance imaging of the calcaneus: preliminary assessment of trabecular bone-dependent regional variations in marrow relaxation time compared with dual X-ray absorptiometry

    NASA Technical Reports Server (NTRS)

    Guglielmi, G.; Selby, K.; Blunt, B. A.; Jergas, M.; Newitt, D. C.; Genant, H. K.; Majumdar, S.

    1996-01-01

    RATIONALE AND OBJECTIVES: Marrow transverse relaxation time (T2*) in magnetic resonance (MR) imaging may be related to the density and structure of the surrounding trabecular network. We investigated regional variations of T2* in the human calcaneus and compared the findings with bone mineral density (BMD), as measured by dual X-ray absorpiometry (DXA). Short- and long-term precisions were evaluated first to determine whether MR imaging would be useful for the clinical assessment of disease status and progression in osteoporosis. METHODS: Gradient-recalled echo MR images of the calcaneus were acquired at 1.5 T from six volunteers. Measurements of T2* were compared with BMD and (for one volunteer) conventional radiography. RESULTS: T2* values showed significant regional variation; they typically were shortest in the superior region of the calcaneus. There was a linear correlation between MR and DXA measurements (r = .66 for 1/T2* versus BMD). Differences in T2* attributable to variations in analysis region-of-interest placement were not significant for five of the six volunteers. Sagittal MR images had short- and long-term precision errors of 4.2% and 3.3%, respectively. For DXA, the precision was 1.3% (coefficient of variation). CONCLUSION: MR imaging may be useful for trabecular bone assessment in the calcaneus. However, given the large regional variations in bone density and structure, the choice of an ROI is likely to play a major role in the accuracy, precision, and overall clinical efficacy of T2* measurements.

  13. Correlation of X-Ray Computed Tomography with Quantitative Nuclear Magnetic Resonance Methods for Pre-Clinical Measurement of Adipose and Lean Tissues in Living Mice

    PubMed Central

    Metzinger, Matthew N.; Miramontes, Bernadette; Zhou, Peng; Liu, Yueying; Chapman, Sarah; Sun, Lucy; Sasser, Todd A.; Duffield, Giles E.; Stack, M. Sharon; Leevy, W. Matthew

    2014-01-01

    Numerous obesity studies have coupled murine models with non-invasive methods to quantify body composition in longitudinal experiments, including X-ray computed tomography (CT) or quantitative nuclear magnetic resonance (QMR). Both microCT and QMR have been separately validated with invasive techniques of adipose tissue quantification, like post-mortem fat extraction and measurement. Here we report a head-to-head study of both protocols using oil phantoms and mouse populations to determine the parameters that best align CT data with that from QMR. First, an in vitro analysis of oil/water mixtures was used to calibrate and assess the overall accuracy of microCT vs. QMR data. Next, experiments were conducted with two cohorts of living mice (either homogenous or heterogeneous by sex, age and genetic backgrounds) to assess the microCT imaging technique for adipose tissue segmentation and quantification relative to QMR. Adipose mass values were obtained from microCT data with three different resolutions, after which the data were analyzed with different filter and segmentation settings. Strong linearity was noted between the adipose mass values obtained with microCT and QMR, with optimal parameters and scan conditions reported herein. Lean tissue (muscle, internal organs) was also segmented and quantified using the microCT method relative to the analogous QMR values. Overall, the rigorous calibration and validation of the microCT method for murine body composition, relative to QMR, ensures its validity for segmentation, quantification and visualization of both adipose and lean tissues. PMID:25299952

  14. Comparison of visceral fat mass measurement by dual-X-ray absorptiometry and magnetic resonance imaging in a multiethnic cohort: the Dallas Heart Study

    PubMed Central

    Neeland, I J; Grundy, S M; Li, X; Adams-Huet, B; Vega, G L

    2016-01-01

    Background/Objectives: Visceral adipose tissue (VAT) mass, a risk factor for cardiometabolic complications of obesity, is usually measured by magnetic resonance imaging (MRI) but this method is not practical in a clinical setting. In contrast, measurement of VAT by dual-x-ray absorptiometry (DXA) appears to circumvent the limitations of MRI. In this study, we compared measurements of VAT mass by MRI and DXA in the large, multiethnic cohort of the Dallas Heart Study (DHS). Subjects/Methods: About 2689 DHS participants underwent paired measurement of VAT by MRI and DXA. Sex-stratified analyses were performed to evaluate the correlation and agreement between DXA and MRI. Model validation was performed using bootstrapping and inter-reader variability was assessed. Results: Mean age of the cohort was 44 years, with 55% female, 48% Black and 75% overweight/obese participants. Regression analysis showed a linear relationship between DXA and MRI with R2=0.82 (95% confidence interval (CI) 0.81–0.84) for females and R2=0.86 (95% CI 0.85–0.88) for males. Mean difference between methods was 0.01 kg for females and 0.09 kg for males. Bland–Altman analysis showed that DXA tended to modestly underestimate VAT compared with MRI at lower VAT levels and overestimate it compared with MRI at higher VAT levels. Results were consistent in analyses stratified by race, body mass index status, waist girth and body fat. Inter-individual reader correlation among 50 randomly selected scans was excellent (inter-class correlation coefficient=0.997). Conclusions: VAT mass quantification by DXA was both accurate and valid among a large, multiethnic cohort within a wide range of body fatness. Further studies including repeat assessments over time will help determine its long-term applicability. PMID:27428873

  15. Femtosecond X-ray magnetic circular dichroism absorption spectroscopy at an X-ray free electron laser.

    PubMed

    Higley, Daniel J; Hirsch, Konstantin; Dakovski, Georgi L; Jal, Emmanuelle; Yuan, Edwin; Liu, Tianmin; Lutman, Alberto A; MacArthur, James P; Arenholz, Elke; Chen, Zhao; Coslovich, Giacomo; Denes, Peter; Granitzka, Patrick W; Hart, Philip; Hoffmann, Matthias C; Joseph, John; Le Guyader, Loïc; Mitra, Ankush; Moeller, Stefan; Ohldag, Hendrik; Seaberg, Matthew; Shafer, Padraic; Stöhr, Joachim; Tsukamoto, Arata; Nuhn, Heinz-Dieter; Reid, Alex H; Dürr, Hermann A; Schlotter, William F

    2016-03-01

    X-ray magnetic circular dichroism spectroscopy using an X-ray free electron laser is demonstrated with spectra over the Fe L(3,2)-edges. The high brightness of the X-ray free electron laser combined with high accuracy detection of incident and transmitted X-rays enables ultrafast X-ray magnetic circular dichroism studies of unprecedented sensitivity. This new capability is applied to a study of all-optical magnetic switching dynamics of Fe and Gd magnetic sublattices in a GdFeCo thin film above its magnetization compensation temperature. PMID:27036761

  16. Femtosecond X-ray magnetic circular dichroism absorption spectroscopy at an X-ray free electron laser

    NASA Astrophysics Data System (ADS)

    Higley, Daniel J.; Hirsch, Konstantin; Dakovski, Georgi L.; Jal, Emmanuelle; Yuan, Edwin; Liu, Tianmin; Lutman, Alberto A.; MacArthur, James P.; Arenholz, Elke; Chen, Zhao; Coslovich, Giacomo; Denes, Peter; Granitzka, Patrick W.; Hart, Philip; Hoffmann, Matthias C.; Joseph, John; Le Guyader, Loïc; Mitra, Ankush; Moeller, Stefan; Ohldag, Hendrik; Seaberg, Matthew; Shafer, Padraic; Stöhr, Joachim; Tsukamoto, Arata; Nuhn, Heinz-Dieter; Reid, Alex H.; Dürr, Hermann A.; Schlotter, William F.

    2016-03-01

    X-ray magnetic circular dichroism spectroscopy using an X-ray free electron laser is demonstrated with spectra over the Fe L3,2-edges. The high brightness of the X-ray free electron laser combined with high accuracy detection of incident and transmitted X-rays enables ultrafast X-ray magnetic circular dichroism studies of unprecedented sensitivity. This new capability is applied to a study of all-optical magnetic switching dynamics of Fe and Gd magnetic sublattices in a GdFeCo thin film above its magnetization compensation temperature.

  17. Ultrafast magnetization dynamics studies using an x-ray streakcamera

    SciTech Connect

    Bartelt, A.F.; Comin, A.; Feng, J.; Nasiatka, J.; Padmore, H.A.; Scholl, A.; Young, A.

    2005-07-13

    The spin dynamics of ferromagnetic thin films following an excitation by ultrashort 100-fs near-infrared laser pulses has recently received much attention. Here, a new approach is described using x-ray magnetic circular dichroism to investigated emagnetization and magnetization switching processes. In contrast to magneto-optical measurements, x-ray dichroism has the advantage of determining separately the spin and orbital components of the magnetic moment. The relatively low time resolution of the synchrotron x-ray probe pulses (80 ps FWHM) is overcome by employing an ultrafast x-ray streak camera with a time resolution of <1 ps. A description of the experimental setup including the x-ray/IR laser pulse synchronization and the streak camera is given.

  18. Positioning X-Ray Film With String And Magnets

    NASA Technical Reports Server (NTRS)

    Larosa, William D.; Anders, Jeffrey E.

    1990-01-01

    Technique devised to position x-ray film in normally inaccessible places for inspection of welded joints. Lead/magnet markers and string attached to ends of strips of x-ray film to facilitate positioning. Fewer shots required than in random trial-and-error sequence, and resulting images more accurate.

  19. Magnetic circular dichroism in the hard X-ray range

    NASA Astrophysics Data System (ADS)

    Rogalev, A.; Wilhelm, F.

    2015-12-01

    An overview of X-ray magnetic circular dichroism (XMCD) spectroscopy in the hard X-ray range is presented. A short historical overview shows how this technique has evolved from the early days of X-ray physics to become a workhorse technique in the modern magnetism research As with all X-ray spectroscopies, XMCD has the advantage of being element specific. Interpretation of the spectra based on magneto-optical sum rules can provide unique information about spin and orbital moment carried by absorbing atom in both amplitude and direction, can infer magnetic interactions from element selective magnetization curves, can allow separation of magnetic and non-magnetic components in heterogeneous systems. The review details the technology currently available for XMCD measurements in the hard X-ray range referring to the ESRF beamline ID12 as an example. The strengths of hard X-ray magnetic circular dichroism technique are illustrated with a wide variety of representative examples, such as actinide based ferromagnets, paramagnetism in metals, pure metallic nanoparticles, exchange spring magnets, half metallic ferromagnets, magnetism at interfaces, and dilute magnetic semiconductors. In this way, we aim to encourage researchers from various scientific communities to consider XMCD as a tool to understanding the electronic and magnetic properties of their samples.

  20. X-ray Polarisation in highly-magnetized neutron stars

    NASA Astrophysics Data System (ADS)

    Turolla, Roberto

    2016-07-01

    Radiation emitted in the vicinity of an isolated neutron star is expected to be intrinsically polarized because the high magnetic field (B˜10^{12}-10^{15} G) strongly affects the plasma opacity. The polarization fraction and polarization angle measured by an instrument, however, do not necessary coincide with the intrinsic ones, due to the effects of both quantum electrodynamics in the highly magnetized vacuum around the star (the vacuum polarization) and rotation of the Stokes parameters in the plane perpendicular to the line of sight induced by the non-uniform magnetic field. I'll review theoretical estimates for the polarization observables in the case of thermal surface emission from neutron stars and of the (soft) X-ray emission from magnetars, where magnetospheric reprocessing of radiation by resonant cyclotron scattering is important. The potentials of X-ray polarimetry to probe the physical conditions in neutron star sources and to test, for the first time, vacuum polarization are discussed in connection with the recently proposed polarimetric missions, like XIPE.

  1. X-ray tube with magnetic electron steering

    DOEpatents

    Reed, Kim W.; Turman, Bobby N.; Kaye, Ronald J.; Schneider, Larry X.

    2000-01-01

    An X-ray tube uses a magnetic field to steer electrons. The magnetic field urges electrons toward the anode, increasing the proportion of electrons emitted from the cathode that reach desired portions of the anode and consequently contribute to X-ray production. The magnetic field also urges electrons reflected from the anode back to the anode, further increasing the efficiency of the tube.

  2. Imprinting Magnetic Information in Manganites with X Rays

    NASA Astrophysics Data System (ADS)

    Garganourakis, M.; Scagnoli, V.; Huang, S. W.; Staub, U.; Wadati, H.; Nakamura, M.; Guzenko, V. A.; Kawasaki, M.; Tokura, Y.

    2012-10-01

    The effect of x rays on an orbital and charge ordered epitaxial film of a Pr0.5Ca0.5MnO3 is presented. As the film is exposed to x rays, the antiferromagnetic response increases and concomitantly the conductivity of the film improve. These results are discussed in terms of a persistent x-ray induced doping, leading to a modification of the magnetic structure. This effect allows writing electronic and magnetic information in the film and represents a novel way of manipulating magnetism.

  3. Imprinting magnetic information in manganites with x rays.

    PubMed

    Garganourakis, M; Scagnoli, V; Huang, S W; Staub, U; Wadati, H; Nakamura, M; Guzenko, V A; Kawasaki, M; Tokura, Y

    2012-10-12

    The effect of x rays on an orbital and charge ordered epitaxial film of a Pr0.5Ca0.5MnO3 is presented. As the film is exposed to x rays, the antiferromagnetic response increases and concomitantly the conductivity of the film improve. These results are discussed in terms of a persistent x-ray induced doping, leading to a modification of the magnetic structure. This effect allows writing electronic and magnetic information in the film and represents a novel way of manipulating magnetism. PMID:23102361

  4. Neonatal body composition: dual-energy X-ray absorptiometry, magnetic resonance imaging, and three-dimensional chemical shift imaging versus chemical analysis in piglets.

    PubMed

    Fusch, C; Slotboom, J; Fuehrer, U; Schumacher, R; Keisker, A; Zimmermann, W; Moessinger, A; Boesch, C; Blum, J

    1999-10-01

    An animal study to evaluate dual-energy x-ray absorptiometry (DXA) and magnetic resonance (MR) imaging and spectroscopy for measurement of neonatal body composition was performed. Twenty-three piglets with body weights ranging from 848 to 7550 g were used. After measuring total body water, animals were killed and body composition was assessed using DXA and MR (1.5 T; MR imaging, T1-weighted sagittal spin-echo sequence; MR spectroscopy, three-dimensional chemical shift imaging) as well as chemical carcass analysis (standard methods) after homogenization. Body composition by chemical analysis (percent of body weight, mean +/- SD) was as follows: body water, 75.3 +/- 3.9%; total protein, 13.9 +/- 8.8%; and total fat, 6.5 +/- 3.7%. Absolute content of fat and total ash was 7-674 and 35-237 g, respectively. Mean hydration of fat-free mass was 0.804 +/- 0.011 g/kg and decreased with increasing body weight (r2 = 0.419) independent of age. Using DXA, bone mineral content was highly correlated with calcium content (r2 = 0.992), and calcium per bone mineral content was 44.1 +/- 4.2%. DXA fat mass correlated with total fat (r2 = 0.961). Using MR, spectroscopy and chemical analysis were highly correlated with fat-to-water ratio (r2 = 0.984) and absolute fat content (r2 = 0.988). Total fat by MR imaging volumetry showed a lower correlation (r2 = 0.913) and overestimated total fat by a factor of 2.46. Conversion equations for DXA were developed (total fat = 1.31 x fat mass measured by DXA--68.8; calcium = 0.402 x bone mineral content + 1.7), which improved precision and accuracy of DXA measurements. In conclusion, both DXA and MR spectroscopy give accurate and precise estimates of neonatal body composition and may become valuable tools for the noninvasive assessment of neonatal growth and nutritional status. PMID:10509370

  5. Simultaneous surface plasmon resonance and x-ray absorption spectroscopy.

    PubMed

    Serrano, A; Rodríguez de la Fuente, O; Collado, V; Rubio-Zuazo, J; Monton, C; Castro, G R; García, M A

    2012-08-01

    We present an experimental setup for the simultaneous measurement of surface plasmon resonance (SPR) and x-ray absorption spectroscopy (XAS) on metallic thin films at a synchrotron beamline. The system allows measuring in situ and in real time the effect of x-ray irradiation on the SPR curves to explore the interaction of x-rays with matter. It is also possible to record XAS spectra while exciting SPR in order to study changes in the films induced by the excitation of surface plasmons. Combined experiments recording simultaneously SPR and XAS curves while scanning different parameters can be also carried out. The relative variations in the SPR and XAS spectra that can be detected with this setup range from 10(-3) to 10(-5), depending on the particular experiment. PMID:22938268

  6. Simultaneous surface plasmon resonance and x-ray absorption spectroscopy

    SciTech Connect

    Serrano, A.; Rodriguez de la Fuente, O.; Collado, V.; Rubio-Zuazo, J.; Castro, G. R.; Monton, C.; Garcia, M. A.

    2012-08-15

    We present an experimental setup for the simultaneous measurement of surface plasmon resonance (SPR) and x-ray absorption spectroscopy (XAS) on metallic thin films at a synchrotron beamline. The system allows measuring in situ and in real time the effect of x-ray irradiation on the SPR curves to explore the interaction of x-rays with matter. It is also possible to record XAS spectra while exciting SPR in order to study changes in the films induced by the excitation of surface plasmons. Combined experiments recording simultaneously SPR and XAS curves while scanning different parameters can be also carried out. The relative variations in the SPR and XAS spectra that can be detected with this setup range from 10{sup -3} to 10{sup -5}, depending on the particular experiment.

  7. X-ray radiation from accreting, magnetized neutron stars

    SciTech Connect

    Pavlov, G.G.

    1984-01-01

    A review is given of recent developments in the theory of emission from a magnetized plasma for accreting neutron star conditions. Some observational data on X-ray pulsars are discussed, and present problems are indicated. 26 references.

  8. Magnetically confined wind shocks in X-rays - A review

    NASA Astrophysics Data System (ADS)

    ud-Doula, Asif; Nazé, Yaël

    2016-09-01

    A subset (∼ 10%) of massive stars present strong, globally ordered (mostly dipolar) magnetic fields. The trapping and channeling of their stellar winds in closed magnetic loops leads to magnetically confined wind shocks (MCWS), with pre-shock flow speeds that are some fraction of the wind terminal speed. These shocks generate hot plasma, a source of X-rays. In the last decade, several developments took place, notably the determination of the hot plasma properties for a large sample of objects using XMM and Chandra, as well as fully self-consistent MHD modeling and the identification of shock retreat effects in weak winds. Despite a few exceptions, the combination of magnetic confinement, shock retreat and rotation effects seems to be able to account for X-ray emission in massive OB stars. Here we review these new observational and theoretical aspects of this X-ray emission and envisage some perspectives for the next generation of X-ray observatories.

  9. Bright circularly polarized soft X-ray high harmonics for X-ray magnetic circular dichroism

    PubMed Central

    Fan, Tingting; Grychtol, Patrik; Knut, Ronny; Hernández-García, Carlos; Hickstein, Daniel D.; Zusin, Dmitriy; Gentry, Christian; Dollar, Franklin J.; Mancuso, Christopher A.; Hogle, Craig W.; Kfir, Ofer; Legut, Dominik; Carva, Karel; Ellis, Jennifer L.; Dorney, Kevin M.; Chen, Cong; Shpyrko, Oleg G.; Fullerton, Eric E.; Cohen, Oren; Oppeneer, Peter M.; Milošević, Dejan B.; Becker, Andreas; Jaroń-Becker, Agnieszka A.; Popmintchev, Tenio; Murnane, Margaret M.; Kapteyn, Henry C.

    2015-01-01

    We demonstrate, to our knowledge, the first bright circularly polarized high-harmonic beams in the soft X-ray region of the electromagnetic spectrum, and use them to implement X-ray magnetic circular dichroism measurements in a tabletop-scale setup. Using counterrotating circularly polarized laser fields at 1.3 and 0.79 µm, we generate circularly polarized harmonics with photon energies exceeding 160 eV. The harmonic spectra emerge as a sequence of closely spaced pairs of left and right circularly polarized peaks, with energies determined by conservation of energy and spin angular momentum. We explain the single-atom and macroscopic physics by identifying the dominant electron quantum trajectories and optimal phase-matching conditions. The first advanced phase-matched propagation simulations for circularly polarized harmonics reveal the influence of the finite phase-matching temporal window on the spectrum, as well as the unique polarization-shaped attosecond pulse train. Finally, we use, to our knowledge, the first tabletop X-ray magnetic circular dichroism measurements at the N4,5 absorption edges of Gd to validate the high degree of circularity, brightness, and stability of this light source. These results demonstrate the feasibility of manipulating the polarization, spectrum, and temporal shape of high harmonics in the soft X-ray region by manipulating the driving laser waveform. PMID:26534992

  10. Bright circularly polarized soft X-ray high harmonics for X-ray magnetic circular dichroism.

    PubMed

    Fan, Tingting; Grychtol, Patrik; Knut, Ronny; Hernández-García, Carlos; Hickstein, Daniel D; Zusin, Dmitriy; Gentry, Christian; Dollar, Franklin J; Mancuso, Christopher A; Hogle, Craig W; Kfir, Ofer; Legut, Dominik; Carva, Karel; Ellis, Jennifer L; Dorney, Kevin M; Chen, Cong; Shpyrko, Oleg G; Fullerton, Eric E; Cohen, Oren; Oppeneer, Peter M; Milošević, Dejan B; Becker, Andreas; Jaroń-Becker, Agnieszka A; Popmintchev, Tenio; Murnane, Margaret M; Kapteyn, Henry C

    2015-11-17

    We demonstrate, to our knowledge, the first bright circularly polarized high-harmonic beams in the soft X-ray region of the electromagnetic spectrum, and use them to implement X-ray magnetic circular dichroism measurements in a tabletop-scale setup. Using counterrotating circularly polarized laser fields at 1.3 and 0.79 µm, we generate circularly polarized harmonics with photon energies exceeding 160 eV. The harmonic spectra emerge as a sequence of closely spaced pairs of left and right circularly polarized peaks, with energies determined by conservation of energy and spin angular momentum. We explain the single-atom and macroscopic physics by identifying the dominant electron quantum trajectories and optimal phase-matching conditions. The first advanced phase-matched propagation simulations for circularly polarized harmonics reveal the influence of the finite phase-matching temporal window on the spectrum, as well as the unique polarization-shaped attosecond pulse train. Finally, we use, to our knowledge, the first tabletop X-ray magnetic circular dichroism measurements at the N4,5 absorption edges of Gd to validate the high degree of circularity, brightness, and stability of this light source. These results demonstrate the feasibility of manipulating the polarization, spectrum, and temporal shape of high harmonics in the soft X-ray region by manipulating the driving laser waveform. PMID:26534992

  11. Frontiers in imaging magnetism with polarized x-rays

    SciTech Connect

    Fischer, Peter

    2015-01-08

    Although magnetic imaging with polarized x-rays is a rather young scientific discipline, the various types of established x-ray microscopes have already taken an important role in state-of-the-art characterization of the properties and behavior of spin textures in advanced materials. The opportunities ahead will be to obtain in a unique way indispensable multidimensional information of the structure, dynamics and composition of scientifically interesting and technologically relevant magnetic materials.

  12. Longitudinal detection of ferromagnetic resonance using x-ray transmission measurements

    SciTech Connect

    Boero, G.; Rusponi, S.; Kavich, J.; Rizzini, A. Lodi; Piamonteze, C.; Nolting, F.; Tieg, C.; Thiele, J.-U.; Gambardella, P.

    2009-12-15

    We describe a setup for the x-ray detection of ferromagnetic resonance in the longitudinal geometry using element-specific transmission measurements. Thin magnetic film samples are placed in a static magnetic field collinear with the propagation direction of a polarized soft x-ray beam and driven to ferromagnetic resonance by a continuous wave microwave magnetic field perpendicular to it. The transmitted photon flux is measured both as a function of the x-ray photon energy and as a function of the applied static magnetic field. We report experiments performed on a 15 nm film of doped Permalloy (Ni{sub 73}Fe{sub 18}Gd{sub 7}Co{sub 2}) at the L{sub 3}/L{sub 2}-edges of Fe, Co, and Ni. The achieved ferromagnetic resonance sensitivity is about 0.1 monolayers/{radical}(Hz). The obtained results are interpreted in the framework of a conductivity tensor based formalism. The factors limiting the sensitivity as well as different approaches for the x-ray detection of ferromagnetic resonance are discussed.

  13. Imaging magnetic structures with a transmission X-ray microscope

    NASA Astrophysics Data System (ADS)

    Fischer, P.; Eimüller, T.; Schütz, G.; Guttmann, P.; Schmahl, G.; Bayreuther, G.

    2000-05-01

    The X-ray magnetic circular dichroism (X-MCD), i.e., the dependence of the absorption of circularly polarized X-rays on the magnetization of the absorber exhibits at L-edges of transition metals values up to 25%. This can serve as a huge magnetic contrast mechanism in combination with a transmission X-ray microscope (TXM) to image magnetic domains providing a lateral resolution down to about 30 nm. The inherent element-specificity, the possibility to record images in varying external fields within a complete hysteresis loop, the relation of the contrast to local magnetic spin and orbital moments, etc. demonstrate the unique applicability to study the magnetic domain structure in current technical relevant systems like magneto-optics for high density storage media, multilayers for GMR applications or nanostructures for MRAM technology.

  14. Magnetic Untwisting in Most Solar X-Ray Jets

    NASA Technical Reports Server (NTRS)

    Moore, Ronald; Sterling, Alphonse; Falconer, David; Robe, Dominic

    2013-01-01

    From 54 X-ray jets observed in the polar coronal holes by Hinode's X-Ray Telescope (XRT) during coverage in movies from Solar Dynamic Observatory's Atmospheric Imaging Assembly (AIA) taken in its He II 304 Å band at a cadence of 12 s, we have established a basic characteristic of solar X-ray jets: untwisting motion in the spire. In this presentation, we show the progression of few of these X-ray jets in XRT images and track their untwisting in AIA He II images. From their structure displayed in their XRT movies, 19 jets were evidently standard jets made by interchange reconnection of the magnetic-arcade base with ambient open field, 32 were evidently blowout jets made by blowout eruption of the base arcade, and 3 were of ambiguous form. As was anticipated from the >10,000 km span of the base arcade in most polar X-ray jets and from the disparity of standard jets and blowout jets in their magnetic production, few of the standard X-ray jets (3 of 19) but nearly all of the blowout X-ray jets (29 of 32) carried enough cool (T is approximately 105 K) plasma to be seen in their He II movies. In the 32 X-ray jets that showed a cool component, the He II movies show 10-100 km/s untwisting motions about the axis of the spire in all 3 standard jets and in 26 of the 29 blowout jets. Evidently, the open magnetic field in nearly all blowout X-ray jets and probably in most standard X-ray jets carries transient twist. This twist apparently relaxes by propagating out along the open field as a torsional wave. High-resolution spectrograms and Dopplergrams have shown that most Type-II spicules have torsional motions of 10-30 km/s. Our observation of similar torsional motion in X-ray jets strengthens the case for Type-II spicules being made in the same way as X-ray jets, by blowout eruption of a twisted magnetic arcade in the spicule base and/or by interchange reconnection of the twisted base arcade with the ambient open field. This work was funded by NASA's Heliophysics Division

  15. X-ray holographic imaging of magnetic order in patterned Co/Pd multilayers

    NASA Astrophysics Data System (ADS)

    Spezzani, Carlo; Fortuna, Franck; Delaunay, Renaud; Popescu, Horia; Sacchi, Maurizio

    2013-12-01

    We address the role of lateral confinement in determining the micromagnetic structure of small objects featuring perpendicular magnetic anisotropy. We have imaged the spatial distribution of magnetic domains in Co/Pd multilayered objects by x-ray holography in transmission mode, a technique based on resonant coherent scattering of polarized x rays. In addition to high spatial resolution and magnetic sensitivity, x-ray holography features chemical selectivity and probes the entire bulk of the magnetic sample. By analyzing and comparing images of several magnetic objects (squares and rectangles with 0.4-3-μm lateral sizes) that underwent the same preparation procedure and magnetic history, we highlight the influence of the object shape and of its orientation with respect to an external field in determining the remanent magnetic microstructure. The discussion of our results is backed by micromagnetic calculations.

  16. Magnetic x-ray dichroism in ultrathin epitaxial films

    SciTech Connect

    Tobin, J.G.; Goodman, K.W.; Cummins, T.R.

    1997-04-01

    The authors have used Magnetic X-ray Linear Dichroism (MXLD) and Magnetic X-ray Circular Dichroism (MXCD) to study the magnetic properties of epitaxial overlayers in an elementally specific fashion. Both MXLD and MXCD Photoelectron Spectroscopy were performed in a high resolution mode at the Spectromicroscopy Facility of the ALS. Circular Polarization was obtained via the utilization of a novel phase retarder (soft x-ray quarter wave plate) based upon transmission through a multilayer film. The samples were low temperature Fe overlayers, magnetic alloy films of NiFe and CoNi, and Gd grown on Y. The authors results include a direct comparison of high resolution angle resolved Photoelectron Spectroscopy performed in MXLD and MXCD modes as well as structural studies with photoelectron diffraction.

  17. The relationship between partial pressure of oxygen and perfusion in two murine tumors after X-ray irradiation: a combined gadopentetate dimeglumine dynamic magnetic resonance imaging and in vivo electron paramagnetic resonance oximetry study.

    PubMed

    Goda, F; Bacic, G; O'Hara, J A; Gallez, B; Swartz, H M; Dunn, J F

    1996-07-15

    Changes of partial pressure of oxygen (pO2) and blood perfusion were studied in MTG-B and RIF-1 tumors (n = 5 each) before and after a single 20-Gy dose of X-ray irradiation. Using electron paramagnetic resonance oximetry, we have observed an initial fast decrease of pO2 after irradiation, followed by a slow increase. The time course of these changes was faster in the MTG-B tumors than in the RIF-1 tumors. Gadopentetate dimeglumine (Gd-DTPA) dynamic magnetic resonance imaging studies showed a reduction in uptake of Gd-DTPA at the time of minimum pO2 and a recovery at the time of maximum pO2 in each tumor. Previous work indicates that there is microscopic heterogeneity in tumors, with well-vascularized "capillary regions" being closer to capillaries than poorly vascularized "noncapillary regions." We propose a two-component (slow and fast) model of Gd-DTPA uptake that is designed to quantify the kinetics of these two compartments by analyzing the total tumor uptake kinetics without having to identify specific regions of interest. Total perfusion in the tumors was greatly reduced at the time of minimum oxygenation, and the volume of the slow component increased after irradiation. We conclude that a decrease in blood perfusion is one of the main causes of the decline in pO2 observed after irradiation. PMID:8764132

  18. Stellar X-ray Emission From Magnetically Funneled Shocks

    NASA Astrophysics Data System (ADS)

    Guenther, Hans

    Stars and planets form in giant molecular clouds, so they are deeply embedded in their early stages. When they become optically visible, the young stars are still surrounded by a proto-planetary disk, where planets evolve. These stars are called classical T Tauri stars (CTTS). A key, yet poorly constrained, parameter for the disk evolution is the stellar high-energy emission. It can ionize the outer layers of the disk, change its chemistry and even drive photoevaporation of the disk. Thus the spectral shape and the temporal variability of the stellar X-ray and UV emission shapes the gas and dust properties in some regions of the disk. It sets the photoevaporation timescale which provides an upper limit for planet formation. CTTS still actively accrete mass from their disk. The infalling matter is funneled by the stellar magnetic field and impacts on the star close to free fall velocity. A hot accretion shock develops, which emits X-rays which are distinct from any coronal X-rays. Eventually the disk disperses and bulk planet formation comes to an end. X-ray emitting shocks can still occur at a later stage in stellar evolution, if e.g. the magnetic field is strong enough to funnel the stellar wind to collide in the disk midplane. This so-called magnetically confined wind shock model was originally developed for the A0p star IQ Aur. The magnetically funneled accretion model has been successfully tested for CTTS in a small mass range only; the magnetically confined wind shock model lacks a comparison for high-resolution X-ray grating spectra for all but the most massive stars. In this proposal we request funding to analyze three XMM-Newton observations, which will probe X-ray emitting shocks in stars with magnetic fields: DN Tau (observed as category C target in cycle 8), a CTTS with much lower mass than previous CTTS with X- ray grating spectroscopy; MN Lup (to be observed in cycle 9), a prime candidate for simultaneous X-ray/Doppler-imaging studies; and IQ Aur (to

  19. Interference between magnetism and surface roughness in coherent soft X-ray scattering

    SciTech Connect

    Rahmim, A.; Tixier, S.; Tiedje, T.; Eisebitt, S.; Lorgen, M.; Scherer, R.; Eberhardt, W.; Luning, J.; Scholl, A.

    2002-06-15

    In coherent soft x-ray scattering from magnetically ordered surfaces there are contributions to the scattering from the magnetic domains, from the surface roughness, and from the diffraction associated with the pinhole aperture used as a coherence filter. In the present work, we explore the interplay between these contributions by analyzing speckle patterns in diffusely scattered x rays from the surface of magnetic thin films. Magnetic contrast from the surface of anti ferro magnetically ordered LaFeO3 films is caused by magnetic linear dichroism in resonant x-ray scattering. The samples studied possess two types of domains with their magnetic orientations perpendicular to each other. By tuning the x-ray energy from one of the two Fe-L3 resonant absorption peaks to the other, the relative amplitudes of the x-ray scattering from the two domains is inverted which results in speckle pattern changes. A theoretical expression is derived for the intensity correlation between the speckle patterns with the magnetic contrast inverted and not inverted. The model is found to be in good agreement with the x-ray-scattering observations and independent measurements of the surface roughness. An analytical expression for the correlation function gives an explicit relation between the change in the speckle pattern and the roughness, and magnetic and aperture scattering. Changes in the speckle pattern are shown to arise from beating of magnetic scattering with the roughness scattering and diffraction from the aperture. The largest effect is found when the surface roughness scatter is comparable in intensity to the magnetic scatter.

  20. Synthesis, X-ray structure, magnetic resonance, and DFT analysis of a soluble copper(II) phthalocyanine lacking C-H bonds.

    PubMed

    Moons, Hans; Łapok, Łukasz; Loas, Andrei; Van Doorslaer, Sabine; Gorun, Sergiu M

    2010-10-01

    The synthesis, crystal structure, and electronic properties of perfluoro-isopropyl-substituted perfluorophthalocyanine bearing a copper atom in the central cavity (F(64)PcCu) are reported. While most halogenated phthalocyanines do not exhibit long-term order sufficient to form large single crystals, this is not the case for F(64)PcCu. Its crystal structure was determined by X-ray analysis and linked to the electronic properties determined by electron paramagnetic resonance (EPR). The findings are corroborated by density functional theory (DFT) computations, which agree well with the experiment. X-band continuous-wave EPR spectra of undiluted F(64)PcCu powder, indicate the existence of isolated metal centers. The electron-withdrawing effect of the perfluoroalkyl (R(f)) groups significantly enhances the complexes solubility in organic solvents like alcohols, including via their axial coordination. This coordination is confirmed by X-band (1)H HYSCORE experiments and is also seen in the solid state via the X-ray structure. Detailed X-band CW-EPR, X-band Davies and Mims ENDOR, and W-band electron spin-echo-detected EPR studies of F(64)PcCu in ethanol allow the determination of the principal g values and the hyperfine couplings of the metal, nitrogen, and fluorine nuclei. Comparison of the g and metal hyperfine values of F(64)PcCu and other PcCu complexes in different matrices reveals a dominant effect of the matrix on these EPR parameters, while variations in the ring substituents have only a secondary effect. The relatively strong axial coordination occurs despite the diminished covalency of the C-N bonds and potentially weakening Jahn-Teller effects. Surprisingly, natural abundance (13)C HYSCORE signals could be observed for a frozen ethanol solution of F(64)PcCu. The (13)C nuclei contributing to the HYSCORE spectra could be identified as the pyrrole carbons by means of DFT. Finally, (19)F ENDOR and easily observable paramagnetic NMR were found to relate well to the

  1. X-RAY EMISSION FROM MAGNETIC MASSIVE STARS

    SciTech Connect

    Nazé, Yaël; Petit, Véronique; Rinbrand, Melanie; Owocki, Stan; Cohen, David; Ud-Doula, Asif; Wade, Gregg A.

    2014-11-01

    Magnetically confined winds of early-type stars are expected to be sources of bright and hard X-rays. To clarify the systematics of the observed X-ray properties, we have analyzed a large series of Chandra and XMM-Newton observations, corresponding to all available exposures of known massive magnetic stars (over 100 exposures covering ∼60% of stars compiled in the catalog of Petit et al.). We show that the X-ray luminosity is strongly correlated with the stellar wind mass-loss rate, with a power-law form that is slightly steeper than linear for the majority of the less luminous, lower- M-dot B stars and flattens for the more luminous, higher- M-dot O stars. As the winds are radiatively driven, these scalings can be equivalently written as relations with the bolometric luminosity. The observed X-ray luminosities, and their trend with mass-loss rates, are well reproduced by new MHD models, although a few overluminous stars (mostly rapidly rotating objects) exist. No relation is found between other X-ray properties (plasma temperature, absorption) and stellar or magnetic parameters, contrary to expectations (e.g., higher temperature for stronger mass-loss rate). This suggests that the main driver for the plasma properties is different from the main determinant of the X-ray luminosity. Finally, variations of the X-ray hardnesses and luminosities, in phase with the stellar rotation period, are detected for some objects and they suggest that some temperature stratification exists in massive stars' magnetospheres.

  2. Resonant soft x-ray scattering investigation of orbital and magnetic ordering in La{sub 0.5}Sr{sub 1.5}MnO{sub 4}

    SciTech Connect

    Wilkins, S.B.; Stojic, N.; Binggeli, N.; Beale, T.A.W.; Hatton, P.D.; Castleton, C.W.M.; Prabhakaran, D.; Boothroyd, A.T.; Altarelli, M.

    2005-06-15

    We report resonant x-ray scattering data of the orbital and magnetic ordering at low temperatures at the Mn L{sub 2,3} edges in La{sub 0.5}Sr{sub 1.5}MnO{sub 4}. The orderings display complex energy features close to the Mn absorption edges. Systematic modeling with atomic multiplet crystal field calculations was used to extract meaningful information regarding the interplay of spin, orbital, and Jahn-Teller order. These calculations provide a good general agreement with the observed energy dependence of the scattered intensity for a dominant orbital ordering of the d{sub x{sup 2}}{sub -z{sup 2}}/d{sub y{sup 2}}{sub -z{sup 2}} type. In addition, the origins of various spectral features are identified. The temperature dependence of the orbital and magnetic ordering was measured and suggests a strong interplay between the magnetic and orbital order parameters.

  3. Imaging of magnetic domains by transmission x-ray microscopy

    NASA Astrophysics Data System (ADS)

    Fischer, P.; Eimüller, T.; Schütz, G.; Guttmann, P.; Schmahl, G.; Pruegl, K.; Bayreuther, G.

    1998-03-01

    The combination of the high-resolution transmission x-ray microscope (TXM) based on the zone plate technique with the x-ray magnetic circular dichroism (X-MCD) providing a huge magnetic contrast is a new technique to image magnetic domain structures. It is inherently element specific and contains information on the local spin and orbital moments of the absorbing species that can be obtained by applying magneto-optical sum rules. A lateral spatial resolution depending on the quality of the zone plates down to 30 nm can be achieved. We report on first results at the Fe 0022-3727/31/6/012/img9 edges of Fe both in amorphous and in multilayered Gd-Fe systems. With a TXM set-up at BESSY I adapted to record magnetic images in varying magnetic fields the evolution of magnetic domains within a complete hysteresis loop and magnetic aftereffects have been studied.

  4. Robust x-ray tubes for use within magnetic fields of MR scanners.

    PubMed

    Wen, Zhifei; Fahrig, Rebecca; Pelc, Norbert J

    2005-07-01

    A hybrid system that combines an x-ray fluoroscopic system and a magnetic resonance (MR) system can provide physicians with the synergy of exquisite soft tissue contrast (from MR) and high temporal and spatial resolutions (from x ray), which may significantly benefit a number of image-guided interventional procedures. However, the system configuration may require the x-ray tube to be placed in a magnetic field, which can hinder the proper functioning of the x-ray tube by deflecting its electron beam. From knowledge of how the magnetic field affects the electron trajectories, we propose creating another magnetic field along the cathode-anode axis using either solenoids or permanent magnets to reduce the deflection of the electron beam for two cases: a strong and slightly misaligned field or a weak field that is arbitrary in direction. Theoretical analysis is presented and the electron beam is simulated in various external magnetic fields with a finite element modeling program. Results show that both correction schemes enhance the robustness of the x-ray tube operation in an externally applied magnetic field. PMID:16121589

  5. X-rays and magnetism: a review of program in magnetic studies with polarized soft x-rays

    NASA Astrophysics Data System (ADS)

    Fischer, Peter; Ohldag, Hendrik

    2015-09-01

    Magnetism is among the most active and attractive areas in modern solid state physics because of intriguing phenomena interesting to fundamental research and a manifold of technological applications. State-of-the-art synthesis of advanced magnetic materials, e.g. in hybrid structures paves the way to new functionalities. To characterize modern magnetic materials and the associated magnetic phenomena, polarized x-rays have emerged as unique probes due to their specific interaction with magnetic materials. A large variety of spectroscopic and microscopic techniques have been developed to quantify in an element, valence and site-sensitive way properties of ferro-, ferri-, and antiferromagnetic systems, such as spin and orbital moments, and to image nanoscale spin textures and their dynamics with sub-ns time and almost 10 nm spatial resolution. The enormous intensity of x-rays and their degree of coherence at next generation x-ray facilities will open the fsec time window to magnetic studies addressing fundamental time scales in magnetism with nanometer spatial resolution. This review will give an introduction into contemporary topics of nanoscale magnetic materials and provide an overview of analytical spectroscopy and microscopy tools based on x-ray dichroism effects. Selected examples of current research will demonstrate the potential and future directions of these techniques.

  6. Orbital and magnetic ordering in Pr1-xCaxMnO3 and Nd1-xSrxMnO3 manganites near half doping studied by resonant soft x-ray powder diffraction

    NASA Astrophysics Data System (ADS)

    Staub, U.; García-Fernández, M.; Bodenthin, Y.; Scagnoli, V.; de Souza, R. A.; Garganourakis, M.; Pomjakushina, E.; Conder, K.

    2009-06-01

    Here we present resonant soft x-ray diffraction data in the vicinity of the MnL2,3 edges on R1-xTxMnO3 manganites ( R=Pr , Nd and T=Ca , Sr) close to half doping. For Pr0.6Ca0.4MnO3 (PCMO), the energy dependence of the superimposed orbital and magnetic reflections are studied using various incident x-ray polarizations. For Nd0.5Sr0.5MnO3 (NSMO), the energy dependence of the orbital ordering reflection is found to be very similar to that found in other manganites systems. These two results are compared to those presented in the literature on single-crystal samples. Whereas our results are in good agreement with the spectral shape of a superposition of magnetic and orbital signals in PCMO, the magnetic signals are only moderately larger than the orbital signals. The results on NSMO do not agree with previously presented data on single crystals and cast doubt on the proposed occurrence of a double-stripe orbital order.

  7. Detecting magnetic flux distributions in superconductors with polarized x rays

    NASA Astrophysics Data System (ADS)

    Stahl, Claudia; Audehm, Patrick; Gräfe, Joachim; Ruoß, Stephen; Weigand, Markus; Schmidt, Mathias; Treiber, Sebastian; Bechtel, Michael; Goering, Eberhard; Schütz, Gisela; Albrecht, Joachim

    2014-09-01

    The magnetic flux distribution arising from a high-Tc superconductor is detected and visualized using polarized x rays. Therefore, we introduce a sensor layer, namely, an amorphous, soft-magnetic Co40Fe40B20 cover layer, providing a large x-ray magnetic circular dichroism (XMCD). Temperature-dependent XMCD spectroscopy on the magnetic layer has been performed. Exploiting the temperature dependence of the critical current density of the superconductor we find a quantitative correlation between the XMCD signal and the in-plane stray field of the superconductor. Magneto-optical Kerr effect experiments on the sensor layer can simulate the stray field of the superconductor and hence verify the correlation. We show that the XMCD contrast in the sensor layer corresponds to the in-plane magnetic flux distribution of the superconductor and can hence be used to image magnetic structures in superconductors.

  8. In situ small-angle x-ray and nuclear resonant scattering study of the evolution of structural and magnetic properties of an Fe thin film on MgO (001)

    NASA Astrophysics Data System (ADS)

    Sharma, Gagan; Gupta, Ajay; Gupta, Mukul; Schlage, Kai; Wille, H.-C.

    2015-12-01

    Growth of magnetron sputtered Fe films on clean single crystalline MgO (001) substrate has been studied using in situ grazing incidence small angle x-ray scattering (GISAXS) and grazing incidence nuclear resonant scattering (GINRS) measurements. While GISAXS provides information about morphological changes, GINRS provides information about structural and magnetic properties, thus making it possible to correlate the evolution of magnetic properties with that of morphology and structure of the film. The film exhibits a Volmer-Weber type growth, with percolation transition occurring around 2 nm film thickness. Presence of a finite quadrupole splitting, as seen in GINRS measurements, suggests a significant distortion from cubic symmetry up to a film thickness of 3.5 nm, which can be attributed to hybridization between Fe 3 d and O 2 p orbitals at the interface as well as in-plane tensile strain induced as a result of coalescence of islands. Initially Fe islands exhibit superparamagnetic relaxation, while finite magnetic moment appears upon formation of macroscopic percolation islands. The film exhibits a weak perpendicular magnetic anisotropy (PMA), which vanishes concurrently with disappearance of structural distortion, suggesting that the observed PMA at least partly originates from inherent strain in the film. No presence of any known oxide of Fe was detected at the interface. More precise information about topological and magnetic structure of the interfaces between Fe and MgO layers is obtained using combined x-ray reflectivity and nuclear resonance reflectivity measurements on a 57Fe/MgO multilayer. Measurements show that about two monolayers of Fe at the interface have a reduced hyperfine field, providing evidence for hybridization with O atoms, as predicted by theory.

  9. Microfabrication of High Resolution X-ray Magnetic Calorimeters

    SciTech Connect

    Hsieh, W.-T.; Stevenson, Thomas R.; Bandler, Simon R.; Kelly, Daniel P.; Porst, Jan P.; Rotzinger, Hannes; Seidel, George M.

    2009-12-16

    Metallic magnetic calorimeter (MMC) is one of the most promising x-ray detector technologies for providing the very high energy resolution needed for future astronomical x-ray imaging spectroscopy. For this purpose, we have developed micro-fabricated 5x5 arrays of MMC of which each individual pixel has excellent energy resolution as good as 3.4 eV at 6 keV x-ray. Here we report on the fabrication techniques developed to achieve good resolution and high efficiency. These include: processing of a thin insulation layer for strong magnetic coupling between the AuEr sensor film and the niobium pick-up coil; production of overhanging absorbers for enhanced efficiency of x-ray absorption; fabrication on SiN membranes to minimize the effects on energy resolution from athermal phonon loss. We have also improved the deposition of the magnetic sensor film such that the film magnetization is nearly completely that is expected from the AuEr sputter target bulk material. In addition, we have included a study of a positional sensitive design, the Hydra design, which allows thermal coupling of four absorbers to a common MMC sensor and circuit.

  10. Microfabrication of High Resolution X-ray Magnetic Calorimeters

    NASA Astrophysics Data System (ADS)

    Hsieh, Wen-Ting; Bandler, Simon R.; Kelly, Daniel P.; Porst, Jan P.; Rotzinger, Hannes; Seidel, George M.; Stevenson, Thomas R.

    2009-12-01

    Metallic magnetic calorimeter (MMC) is one of the most promising x-ray detector technologies for providing the very high energy resolution needed for future astronomical x-ray imaging spectroscopy. For this purpose, we have developed micro-fabricated 5×5 arrays of MMC of which each individual pixel has excellent energy resolution as good as 3.4 eV at 6 keV x-ray. Here we report on the fabrication techniques developed to achieve good resolution and high efficiency. These include: processing of a thin insulation layer for strong magnetic coupling between the AuEr sensor film and the niobium pick-up coil; production of overhanging absorbers for enhanced efficiency of x-ray absorption; fabrication on SiN membranes to minimize the effects on energy resolution from athermal phonon loss. We have also improved the deposition of the magnetic sensor film such that the film magnetization is nearly completely that is expected from the AuEr sputter target bulk material. In addition, we have included a study of a positional sensitive design, the Hydra design, which allows thermal coupling of four absorbers to a common MMC sensor and circuit.

  11. Suzaku observations of cyclotron resonances in binary X-ray pulsars

    NASA Astrophysics Data System (ADS)

    Terada, Y.; Mihara, T.; Nagase, F.; Angelini, L.; Dotani, T.; Enoto, T.; Kitamoto, S.; Kohmura, T.; Kokubun, M.; Kotani, T.; Makishima, K.; Naik, S.; Nakajima, M.; Sugita, S.; Sudoh, K.; Suzuki, M.; Takahashi, H.; Yonetoku, D.; Yoshida, A.

    Since the typical magnetic field strengths of neutron stars reach 10 12 Gauss, the cyclotron resonance produced by a transition between Landau levels appears in the X-ray band. Systematic measurements of cyclotron absorption features in bright sources have been carried out extensively with Ginga, RXTE, BeppoSAX, and INTEGRAL. The cyclotron resonance phenomena can now be studied with a higher sensitivity over a wider hard X-ray band than before, thanks to the Hard X-ray Detector onboard the fifth Japanese X-ray satellite, Suzaku, launched in July, 2005. Suzaku observed Hercules X-1 mainly for calibration purposes, and successfully confirmed its well-known cyclotron absorption feature. Furthermore, the transient pulsar A0535+262 was observed with Suzaku on 14 September, 2005, in the decay phase of its minor outburst (Finger, M.F. Renewed Activity from A0535+26. The Astronomer's Telegram, vol. 595, 2005). The cyclotron resonance of A0535+262 was successfully detected in absorption at about 45 keV (Inoue, H., Kunieda, H., White, N., Kelley, R., Mihara, T., Terada, Y., Takahashi, H., Kokubun, M., Makishima, K. Suzaku detection of cyclotron line near 50 keV for A0535+26. The Astronomer's Telegram vol. 595, 2005; Terada, Y., Mihara, T., Nakajima, M., et al. Cyclotron resonance energies at a low X-ray luminosity: A0535+262 observed with Suzaku. ApJL 648, L139-L142, 2006), even though the object was as dim as 30 mCrab at 20 keV. Compared with previous measurements of the same feature achieved at much brighter phases (e.g., Kretschmar, P., Kreykenbohm, I., Pottschmidt, et al. Integral observes possible cyclotron line at 47 keV for 1A0535+262. The Astronomer's Telegram, vol. 601, 2005; Wilson, C.A., Finger, M.H. RXTE confirms cyclotron line near 50 keV for A0535+26. The Astronomer's Telegram 605, 2005), the Suzaku results give a new constraint to luminosity-related changes in the resonance energy that are observed in other binary pulsars (Nakajima, M., Mihara, T., Makishima

  12. Implications of stimulated resonant X-ray scattering for spectroscopy, imaging, and diffraction in the regime from soft to hard X-rays

    NASA Astrophysics Data System (ADS)

    Schreck, Simon; Beye, Martin; Föhlisch, Alexander

    2015-12-01

    The ultrahigh peak brilliance available at X-ray free-electron lasers opens the possibility to transfer nonlinear spectroscopic techniques from the optical and infrared into the X-ray regime. Here, we present a conceptual treatment of nonlinear X-ray processes with an emphasis on stimulated resonant X-ray scattering as well as a quantitative estimate for the scaling of stimulated X-ray scattering cross sections. These considerations provide the order of magnitude for the required X-ray intensities to experimentally observe stimulated resonant X-ray scattering for photon energies ranging from the extreme ultraviolet to the soft and hard X-ray regimes. At the same time, the regime where stimulated processes can safely be ignored is identified. With this basis, we discuss prospects and implications for spectroscopy, scattering, and imaging experiments at X-ray free-electron lasers.

  13. Logical operations with single x-ray photons via dynamically-controlled nuclear resonances

    PubMed Central

    Gunst, Jonas; Keitel, Christoph H.; Pálffy, Adriana

    2016-01-01

    Photonic qubits lie at the heart of quantum information technology, often encoding information in their polarization state. So far, only low-frequency optical and infrared photons have been employed as flying qubits, as the resources that are at present easiest to control. With their essentially different way of interacting with matter, x-ray qubits would bear however relevant advantages: they are extremely robust, penetrate deep through materials, and can be focused down to few-nm waveguides, allowing unprecedented miniaturization. Also, x-rays are resonant to nuclear transitions, which are very well isolated from the environment and present long coherence times. Here, we show theoretically that x-ray polarization qubits can be dynamically controlled by nuclear Mössbauer resonances. The control knob is played by nuclear hyperfine magnetic fields, that allow via fast rotations precise processing of single x-ray quanta polarization. With such rotations, single-qubit and binary logical operations such as a destructive C-NOT gate can be implemented. PMID:27118340

  14. Logical operations with single x-ray photons via dynamically-controlled nuclear resonances

    NASA Astrophysics Data System (ADS)

    Gunst, Jonas; Keitel, Christoph H.; Pálffy, Adriana

    2016-04-01

    Photonic qubits lie at the heart of quantum information technology, often encoding information in their polarization state. So far, only low-frequency optical and infrared photons have been employed as flying qubits, as the resources that are at present easiest to control. With their essentially different way of interacting with matter, x-ray qubits would bear however relevant advantages: they are extremely robust, penetrate deep through materials, and can be focused down to few-nm waveguides, allowing unprecedented miniaturization. Also, x-rays are resonant to nuclear transitions, which are very well isolated from the environment and present long coherence times. Here, we show theoretically that x-ray polarization qubits can be dynamically controlled by nuclear Mössbauer resonances. The control knob is played by nuclear hyperfine magnetic fields, that allow via fast rotations precise processing of single x-ray quanta polarization. With such rotations, single-qubit and binary logical operations such as a destructive C-NOT gate can be implemented.

  15. Logical operations with single x-ray photons via dynamically-controlled nuclear resonances.

    PubMed

    Gunst, Jonas; Keitel, Christoph H; Pálffy, Adriana

    2016-01-01

    Photonic qubits lie at the heart of quantum information technology, often encoding information in their polarization state. So far, only low-frequency optical and infrared photons have been employed as flying qubits, as the resources that are at present easiest to control. With their essentially different way of interacting with matter, x-ray qubits would bear however relevant advantages: they are extremely robust, penetrate deep through materials, and can be focused down to few-nm waveguides, allowing unprecedented miniaturization. Also, x-rays are resonant to nuclear transitions, which are very well isolated from the environment and present long coherence times. Here, we show theoretically that x-ray polarization qubits can be dynamically controlled by nuclear Mössbauer resonances. The control knob is played by nuclear hyperfine magnetic fields, that allow via fast rotations precise processing of single x-ray quanta polarization. With such rotations, single-qubit and binary logical operations such as a destructive C-NOT gate can be implemented. PMID:27118340

  16. Magnetic properties of X-ray bright points. [in sun

    NASA Technical Reports Server (NTRS)

    Golub, L.; Krieger, A. S.; Harvey, J. W.; Vaiana, G. S.

    1977-01-01

    Using high-resolution Kitt Peak National Observatory magnetograms and sequences of simultaneous S-054 soft X-ray solar images, the properties of X-ray bright points (XBP) and ephemeral active regions (ER) are compared. All XBP appear on the magnetograms as bipolar features, except for very recently emerged or old and decayed XBP. The separation of the magnetic bipoles is found to increase with the age of the XBP, with an average emergence growth rate of 2.2 plus or minus 0.4 km per sec. The total magnetic flux in a typical XBP living about 8 hr is found to be about two times ten to the nineteenth power Mx. A proportionality is found between XBP lifetime and total magnetic flux, equivalent to about ten to the twentieth power Mx per day of lifetime.

  17. Evidence for hidden quadrupolar fluctuations behind the octupole order in Ce0.7La0.3B6 from resonant x-ray diffraction in magnetic fields

    NASA Astrophysics Data System (ADS)

    Matsumura, Takeshi; Michimura, Shinji; Inami, Toshiya; Otsubo, Toru; Tanida, Hiroshi; Iga, Fumitoshi; Sera, Masafumi

    2014-01-01

    The multipole ordered phase in Ce0.7La0.3B6, emerging below 1.5 K and named phase IV, has been studied by resonant x-ray diffraction in magnetic fields. By utilizing diamond x-ray phase plates to rotate the incident linear polarization and a conventional crystal analyzer system, full linear polarization analysis has been performed to identify the order parameters. The analysis shows that the Γ5g(Oyz, Ozx, Oxy) quadrupoles are more induced by the field than the Γ3g (O20 and O22) quadrupoles on the Γ5u (Tx+y +zβ) antiferro-octupole order in phase IV. The problem is that this result is contradictory to a mean-field calculation, which inevitably gives the Γ3g quadrupole as the main induced moment. This result indicates that the Γ5g quadrupole order is close in energy. We consider that a large fluctuation of the Γ5g quadrupole is hidden behind the primary ordering of the Γ5u octupole and that the multipolar fluctuation significantly affects the ordering phenomenon.

  18. Miniature pulsed magnet system for synchrotron x-ray measurements

    SciTech Connect

    Linden, Peter J. E. M. van der; Mathon, Olivier; Strohm, Cornelius; Sikora, Marcin

    2008-07-15

    We have developed a versatile experimental apparatus for synchrotron x-ray measurements in pulsed high magnetic fields. The apparatus consists of a double cryostat incorporating a liquid nitrogen bath to cool the miniature pulsed coil and an independent helium flow cryostat allowing sample temperatures from 4 up to 250 K. The high duty cycle miniature pulsed coils can generate up to 38 T. During experiments at 30 T a repetition rate of 6 pulses/min was routinely reached. Using a 4 kJ power supply, the pulse duration was between 500 {mu}s and 1 ms. The setup was used for nuclear forward scattering measurements on {sup 57}Fe up to 25 T on the ESRF beamline ID18. In another experiment, x-ray magnetic circular dichroism was measured up to 30 T on the ESRF energy dispersive beamline ID24.

  19. Investigation of electron trajectories of an x-ray tube in magnetic fields of MR scanners

    SciTech Connect

    Wen Zhifei; Fahrig, Rebecca; Conolly, Steven; Pelc, Norbert J.

    2007-06-15

    A hybrid x-ray/MR system combining an x-ray fluoroscopic system and an open-bore magnetic resonance (MR) system offers advantages from both powerful imaging modalities and thus can benefit numerous image-guided interventional procedures. In our hybrid system configurations, the x-ray tube and detector are placed in the MR magnet and therefore experience a strong magnetic field. The electron beam inside the x-ray tube can be deflected by a misaligned magnetic field, which may damage the tube. Understanding the deflection process is crucial to predicting the electron beam deflection and avoiding potential damage to the x-ray tube. For this purpose, the motion of an electron in combined electric (E) and magnetic (B) fields was analyzed theoretically to provide general solutions that can be applied to different geometries. For two specific cases, a slightly misaligned strong field and a perpendicular weak field, computer simulations were performed with a finite-element method program. In addition, experiments were conducted using an open MRI magnet and an inserted electromagnet to quantitatively verify the relationship between the deflections and the field misalignment. In a strong (B>>E/c; c: speed of light) and slightly misaligned magnetic field, the deflection in the plane of E and B caused by electrons following the magnetic field lines is the dominant component compared to the deflection in the ExB direction due to the drift of electrons. In a weak magnetic field (B{<=}E/c), the main deflection is in the ExB direction and is caused by the perpendicular component of the magnetic field.

  20. Magnetic excitations and phonons simultaneously studied by resonant inelastic x-ray scattering in optimally doped Bi1.5Pb0.55Sr1.6La0.4CuO6 +δ

    NASA Astrophysics Data System (ADS)

    Peng, Y. Y.; Hashimoto, M.; Sala, M. Moretti; Amorese, A.; Brookes, N. B.; Dellea, G.; Lee, W.-S.; Minola, M.; Schmitt, T.; Yoshida, Y.; Zhou, K.-J.; Eisaki, H.; Devereaux, T. P.; Shen, Z.-X.; Braicovich, L.; Ghiringhelli, G.

    2015-08-01

    Magnetic excitations in the optimally doped high-Tc superconductor Bi1.5Pb0.55Sr1.6La0.4CuO6 +δ (OP-Bi2201, Tc≃34 K) are investigated by Cu L3 edge resonant inelastic x-ray scattering (RIXS), below and above the pseudogap opening temperature. At both temperatures the broad spectral distribution disperses along the (1,0) direction up to ˜350 meV at zone boundary, similar to other hole-doped cuprates. However, above ˜0.22 reciprocal lattice units, we observe a concurrent intensity decrease for magnetic excitations and quasielastic signals with weak temperature dependence. This anomaly seems to indicate a coupling between magnetic, lattice, and charge modes in this compound. We also compare the magnetic excitation spectra near the antinodal zone boundary in the single layer OP-Bi2201 and in the bilayer optimally doped Bi1.5Pb0.6Sr1.54CaCu2O8 +δ (OP-Bi2212, Tc≃96 K). The strong similarities in the paramagnon dispersion and in their energy at zone boundary indicate that the strength of the superexchange interaction and the short-range magnetic correlation cannot be directly related to Tc, not even within the same family of cuprates.

  1. Toward broad-band x-ray detected ferromagnetic resonance in longitudinal geometry

    SciTech Connect

    Ollefs, K.; Meckenstock, R.; Spoddig, D.; Römer, F. M.; Hassel, Ch.; Schöppner, Ch.; Farle, M.; Ney, V.; Ney, A.

    2015-06-14

    An ultrahigh-vacuum-compatible setup for broad-band X-ray detected ferromagnetic resonance (XFMR) in longitudinal geometry is introduced which relies on a low-power, continuous-wave excitation of the ferromagnetic sample. A simultaneous detection of the conventional ferromagnetic resonance via measuring the reflected microwave power and the XFMR signal of the X-ray absorption is possible. First experiments on the Fe and Co L{sub 3}-edges of a permalloy film covered with Co nanostripes as well as the Fe and Ni K-edges of a permalloy film are presented and discussed. Two different XFMR signals are found, one of which is independent of the photon energy and therefore does not provide element-selective information. The other much weaker signal is element-selective, and the dynamic magnetic properties could be detected for Fe and Co separately. The dependence of the latter XFMR signal on the photon helicity of the synchrotron light is found to be distinct from the usual x-ray magnetic circular dichroism effect.

  2. Method and apparatus for molecular imaging using x-rays at resonance wavelengths

    DOEpatents

    Chapline, G.F. Jr.

    Holographic x-ray images are produced representing the molecular structure of a microscopic object, such as a living cell, by directing a beam of coherent x-rays upon the object to produce scattering of the x-rays by the object, producing interference on a recording medium between the scattered x-rays from the object and unscattered coherent x-rays and thereby producing holograms on the recording surface, and establishing the wavelength of the coherent x-rays to correspond with a molecular resonance of a constituent of such object and thereby greatly improving the contrast, sensitivity and resolution of the holograms as representations of molecular structures involving such constituent. For example, the coherent x-rays may be adjusted to the molecular resonant absorption line of nitrogen at about 401.3 eV to produce holographic images featuring molecular structures involving nitrogen.

  3. Method and apparatus for molecular imaging using X-rays at resonance wavelengths

    DOEpatents

    Chapline, Jr., George F.

    1985-01-01

    Holographic X-ray images are produced representing the molecular structure of a microscopic object, such as a living cell, by directing a beam of coherent X-rays upon the object to produce scattering of the X-rays by the object, producing interference on a recording medium between the scattered X-rays from the object and unscattered coherent X-rays and thereby producing holograms on the recording surface, and establishing the wavelength of the coherent X-rays to correspond with a molecular resonance of a constituent of such object and thereby greatly improving the contrast, sensitivity and resolution of the holograms as representations of molecular structures involving such constituent. For example, the coherent X-rays may be adjusted to the molecular resonant absorption line of nitrogen at about 401.3 eV to produce holographic images featuring molecular structures involving nitrogen.

  4. Fabrication of Metallic Magnetic Calorimeter X-ray Detector Arrays

    NASA Astrophysics Data System (ADS)

    Hsieh, W.-T.; Adams, J. A.; Bandler, S. R.; Beyer, J.; Denis, K. L.; Eguchi, H.; Figueroa-Feliciano, E.; Rotzinger, H.; Schneider, G. H.; Seidel, G. M.; Stevenson, T. R.; Travers, D. E.

    2008-04-01

    Microcalorimeters with metallic magnetic sensors show great promise for use in astronomical X-ray spectroscopy. We describe the design and fabrication of a lithographically patterned magnetic microcalorimeter. A paramagnetic AuEr film is sputter-deposited as the sensor, which is coupled to a low noise SQUID via a meander superconducting pickup loop used as an inductor. This inductor also provides the magnetic field bias to the sensor. The AuEr film is deposited over this meander such that the field created by a large current flowing in the loop magnetizes the sensor material. The use of thin film techniques in the fabrication of these magnetic sensors not only allows strong magnetic coupling between the sensor and the inductor, it also is scalable for array fabrication.

  5. Phase-resolved x-ray ferromagnetic resonance measurements in fluorescence yield

    SciTech Connect

    Marcham, M. K.; Keatley, P. S.; Neudert, A.; Hicken, R. J.; Cavill, S. A.; Shelford, L. R.; van der Laan, G.; Telling, N. D.; Childress, J. R.; Katine, J. A.; Shafer, P.; Arenholz, E.

    2010-10-14

    Phase-resolved x-ray ferromagnetic resonance (XFMR) has been measured in fluorescence yield, extending the application of XFMR to opaque samples on opaque substrates. Magnetization dynamics were excited in a Co{sub 50}Fe{sub 50}(0.7)/Ni{sub 90}Fe{sub 10}(5) bilayer by means of a continuous wave microwave excitation, while x-ray magnetic circular dichroism (XMCD) spectra were measured stroboscopically at different points in the precession cycle. By tuning the x-ray energy to the L{sub 3} edges of Ni and Fe, the dependence of the real and imaginary components of the element specific magnetic susceptibility on the strength of an externally applied static bias field was determined. First results from measurements on a Co{sub 50}Fe{sub 50}(0.7)/Ni{sub 90}Fe{sub 10}(5)/Dy(1) sample confirm that enhanced damping results from the addition of the Dy cap.

  6. Registration of planar bioluminescence to magnetic resonance and x-ray computed tomography images as a platform for the development of bioluminescence tomography reconstruction algorithms

    NASA Astrophysics Data System (ADS)

    Beattie, Bradley J.; Klose, Alexander D.; Le, Carl H.; Longo, Valerie A.; Dobrenkov, Konstantine; Vider, Jelena; Koutcher, Jason A.; Blasberg, Ronald G.

    2009-03-01

    The procedures we propose make possible the mapping of two-dimensional (2-D) bioluminescence image (BLI) data onto a skin surface derived from a three-dimensional (3-D) anatomical modality [magnetic resonance (MR) or computed tomography (CT)] dataset. This mapping allows anatomical information to be incorporated into bioluminescence tomography (BLT) reconstruction procedures and, when applied using sources visible to both optical and anatomical modalities, can be used to evaluate the accuracy of those reconstructions. Our procedures, based on immobilization of the animal and a priori determined fixed projective transforms, should be more robust and accurate than previously described efforts, which rely on a poorly constrained retrospectively determined warping of the 3-D anatomical information. Experiments conducted to measure the accuracy of the proposed registration procedure found it to have a mean error of 0.36+/-0.23 mm. Additional experiments highlight some of the confounds that are often overlooked in the BLT reconstruction process, and for two of these confounds, simple corrections are proposed.

  7. Registration of planar bioluminescence to magnetic resonance and x-ray computed tomography images as a platform for the development of bioluminescence tomography reconstruction algorithms

    PubMed Central

    Beattie, Bradley J.; Klose, Alexander D.; Le, Carl H.; Longo, Valerie A.; Dobrenkov, Konstantine; Vider, Jelena; Koutcher, Jason A.; Blasberg, Ronald G.

    2009-01-01

    The procedures we propose make possible the mapping of two-dimensional (2-D) bioluminescence image (BLI) data onto a skin surface derived from a three-dimensional (3-D) anatomical modality [magnetic resonance (MR) or computed tomography (CT)] dataset. This mapping allows anatomical information to be incorporated into bioluminescence tomography (BLT) reconstruction procedures and, when applied using sources visible to both optical and anatomical modalities, can be used to evaluate the accuracy of those reconstructions. Our procedures, based on immobilization of the animal and a priori determined fixed projective transforms, should be more robust and accurate than previously described efforts, which rely on a poorly constrained retrospectively determined warping of the 3-D anatomical information. Experiments conducted to measure the accuracy of the proposed registration procedure found it to have a mean error of 0.36±0.23 mm. Additional experiments highlight some of the confounds that are often overlooked in the BLT reconstruction process, and for two of these confounds, simple corrections are proposed. PMID:19405773

  8. Cation Ordering in Li[NixMnxCo(1-2x)]O2-Layered Cathode Materials: A Nuclear Magnetic Resonance (NMR), Pair Distribution Function, X-ray Absorption Spectroscopy, and Electrochemical Study

    SciTech Connect

    Zeng,D.; Cabana, J.; Breger, J.; Yoon, W.; Grey, C.

    2007-01-01

    Several members of the compositional series Li[NixMnxCo(1-2x)]O2 (0.01 = x = 1/3) were synthesized and characterized. X-ray diffraction results confirm the presence of the layered a-NaFeO2-type structure, while X-ray absorption near-edge spectroscopy experiments verify the presence of Ni2+, Mn4+, and Co3+. Their local environment and short-range ordering were investigated by using a combination of 6Li magic angle spinning (MAS) nuclear magnetic resonance (NMR) spectroscopy and neutron pair distribution function (PDF) analysis, associated with reverse Monte Carlo (RMC) calculations. The 6Li MAS NMR spectra of compounds with low Ni/Mn contents (x = 0.10) show several well-resolved resonances, which start to merge when the amount of Ni and Mn increases, finally forming a broad resonance at high Ni/Mn contents. Analysis of the 6Li MAS NMR 6Li[Ni0.02Mn0.02Co0.96]O2 spectrum, is consistent with the formation of Ni2+ and Mn4+ clusters within the transition-metal layers, even at these low-doping levels. The oxidation state of Ni in this high Co content sample strongly depends upon the Li/transition metal ratio of the starting materials. Neutron PDF analysis of the highest Ni/Mn content sample Li[Ni1/3Mn1/3Co1/3]O2 shows a tendency for Ni cations to be close to Mn cations in the first coordination shell; however, the Co3+ ions are randomly distributed. Analysis of the intensity of the 'LiCoO2' resonance, arising from Li surrounded by Co3+ in its first two cation coordination shells, for the whole series provides further evidence for a nonrandom distribution of the transition-metal cations. The presence of the insulator-to-metal transition seen in the electrochemical profiles of these materials upon charging correlates strongly with the concentration of the 'LiCoO2' resonance.

  9. Resonant and non-resonant X-ray scattering from C 70

    NASA Astrophysics Data System (ADS)

    Guo, Jinghua; Skytt, Per; Wassdahl, Nial; Nordgren, Joseph; Luo, Yi; Vahtras, Olav; Ågren, Hans

    1995-03-01

    Resonant and non-resonant X-ray scattering spectra of the C 70 molecule are presented and analyzed by ab initio Hartree-Fock calculations using a newly developed formalism for symmetry selective inelastic X-ray scattering. Compared to C 60, a weak excitation energy dependence of the spectra features is observed. The change from 'soccer-ball' (I h) to 'rugby-ball' (D 5h) shapes leads to less symmetry selectivity but larrger polarization selectivity. In contrast to C 60, the RIXS spectrum of C 70 molecule is dense even for narrow-band excitation.

  10. Electron Paramagnetic Resonance studies of x-ray irradiated Nafion

    NASA Astrophysics Data System (ADS)

    Fragoso, Juan; Usher, Timothy

    2007-03-01

    Fuel cells promise a bright future as power sources for a variety of electronic equipment as well as more power demanding elements. Nafion (DuPont's trademark of a sulfonated tetrafluorethylene polymer modified from Teflon) is the heart of Proton Exchange Membrane Fuel Cells (PEMFCs) as well as Direct Methanol Fuel Cells (DMFCs). Fuel cells are used to power electronic equipment on spacecraft, satellites and unpiloted high altitude aircraft, where ionizing radiation can be a concern. Electron Paramagnetic Resonance (EPR) is a spectroscopic technique that is very sensitive to free radicals such as those produced by ionizing radiation therefore EPR can give us a window into the degradation of the Nafion membranes due to the ionizing radiation. Nafion samples were irradiated using a x-ray diffractometer with a copper target operating at 40kV and 55mA for at least 3hrs. X-Band EPR spectroscopy of the irradiated nafion reveals a peak at 3400G with a width of 10G, which decays over time, completely diminishing in a couple of weeks. Preliminary results from the polarization studies on the effects of ionizing radiation will also be presented.

  11. Soft X-ray measurements in magnetic fusion plasma physics

    NASA Astrophysics Data System (ADS)

    Botrugno, A.; Gabellieri, L.; Mazon, D.; Pacella, D.; Romano, A.

    2010-11-01

    Soft X-ray diagnostic systems and their successful application in the field of magnetic fusion plasma physics are discussed. Radiation with wavelength in the region of Soft X-Ray (1-30 keV) is largely produced by high temperature plasmas, carrying important information on many processes during a plasma discharge. Soft X-ray diagnostics are largely used in various fusion devices all over the world. These diagnostic systems are able to obtain information on electron temperature, electron density, impurity transport, Magneto Hydro Dynamic instabilities. We will discuss the SXR diagnostic installed on FTU in Frascati (Italy) and on Tore Supra in Cadarache (France), with special emphasis on diagnostic performances. Moreover, we will discuss the two different inversion methods for tomographic reconstruction used in Frascati and in Cadarache, the first one is relied on a guessed topology of iso-emissivity surfaces, the second one on regularization techniques, like minimum Fisher or maximum entropy. Finally, a new and very fast 2D imaging system with energy discrimination and high time resolution will be summarized as an alternative approach of SXR detection system.

  12. Periodic X-ray Emission in Flare Stars: Resonant MHD Absorption?

    NASA Astrophysics Data System (ADS)

    Mullan, D. J.; Johnson, M.

    1993-12-01

    Magnetic fields play a role in the heating of coronae in the Sun and cool dwarfs, but the physical processes at work are not yet clear. Several magnetic models have been proposed for coronal heating. In one class of models, resonant absorption of MHD waves in closed loops is believed to be at work. In a very general sense, resonance implies the existence of a preferred frequency. Thus, resonant absorption models would be subject to a decisive test if periodicities could be identified in the coronal emission. We have searched for periodicities in the EINSTEIN X-ray fluxes of 15 cool dwarfs. Statistically significant periodicities have been detected in several stars, including EQ Vir, AD Leo, and Prox Cen. The period detected in Prox Cen is consistent with MHD resonance in the loop for which parameters were derived by Haisch in his study of X-ray light curves in Einstein data. For AD Leo, ROSAT/HRI and EXOSAT data also suggest the presence of periodicity at the same period as in the EINSTEIN data. For EQ Vir, EXOSAT data suggest the presence of the same period as in the EINSTEIN data. However, the statistical significance of the ROSAT and EXOSAT periods is not as good as those for EINSTEIN. This work has been supported by NASA Grant NAGW-2456, by the NASA Space Grant College program, and by the NASA Astrophysical Data Program.

  13. Magnetically-coupled microcalorimeter arrays for x-ray astrophysics

    NASA Astrophysics Data System (ADS)

    Bandler, Simon

    The "X-ray Surveyor" has been listed by NASA as one of the four major large mission concepts to be studied in the next Astrophysics Decadal Review in its preliminary list of large concepts. One of the key instruments on such a mission would be a very large format X-ray microcalorimeter array, with an array size of greater than 100 thousand pixels. Magnetically-coupled microcalorimeters (MCC) are one of the technologies with the greatest potential to meet the requirements of this mission, and this proposal is one to carry out research specifically to reach the goals of this vision. The "X-ray Surveyor" is a concept for a future mission that will make X-ray observations that are instrumental to understanding the quickly emerging population of galaxies and supermassive black holes at z ~10. The observations will trace the formation of galaxies and their assembly into large-scale structures starting from the earliest possible epochs. This mission would be observing baryons and large-scale physical processes outside of the very densest regions in the local Universe. This can be achieved with an X-ray observatory with similar angular resolution as Chandra but with significantly improved optic area and detector sensitivity. Chandra-scale angular resolution (1" or better) is essential in building more powerful, higher throughput observatories to avoid source confusion and remain photon-limited rather than background-limited. A prime consideration for the microcalorimeter camera on this type of mission is maintaining ~ 1 arcsec spatial resolution over the largest possible field of view, even if this means a slight trade-off against the spectral resolution. A uniform array of 1" pixels covering at least 5'x5' field of view is desired. To reduce the number of sensors read out, in geometries where extremely fine pitch (~50 microns) is desired, the most promising technologies are those in which a thermal sensor such an MCC can read out a sub-array of 20-25 individual 1'

  14. Non-invasive methods for the determination of body and carcass composition in livestock: dual-energy X-ray absorptiometry, computed tomography, magnetic resonance imaging and ultrasound: invited review.

    PubMed

    Scholz, A M; Bünger, L; Kongsro, J; Baulain, U; Mitchell, A D

    2015-07-01

    The ability to accurately measure body or carcass composition is important for performance testing, grading and finally selection or payment of meat-producing animals. Advances especially in non-invasive techniques are mainly based on the development of electronic and computer-driven methods in order to provide objective phenotypic data. The preference for a specific technique depends on the target animal species or carcass, combined with technical and practical aspects such as accuracy, reliability, cost, portability, speed, ease of use, safety and for in vivo measurements the need for fixation or sedation. The techniques rely on specific device-driven signals, which interact with tissues in the body or carcass at the atomic or molecular level, resulting in secondary or attenuated signals detected by the instruments and analyzed quantitatively. The electromagnetic signal produced by the instrument may originate from mechanical energy such as sound waves (ultrasound - US), 'photon' radiation (X-ray-computed tomography - CT, dual-energy X-ray absorptiometry - DXA) or radio frequency waves (magnetic resonance imaging - MRI). The signals detected by the corresponding instruments are processed to measure, for example, tissue depths, areas, volumes or distributions of fat, muscle (water, protein) and partly bone or bone mineral. Among the above techniques, CT is the most accurate one followed by MRI and DXA, whereas US can be used for all sizes of farm animal species even under field conditions. CT, MRI and US can provide volume data, whereas only DXA delivers immediate whole-body composition results without (2D) image manipulation. A combination of simple US and more expensive CT, MRI or DXA might be applied for farm animal selection programs in a stepwise approach. PMID:25743562

  15. Real-time high-resolution X-ray imaging and nuclear magnetic resonance study of the hydration of pure and Na-doped C3A in the presence of sulfates

    SciTech Connect

    Kirchheim,, A. P.; Dal Molin, D.C.; Emwas, Abdul-Hamid; Provis, J.L.; Fischer, P.; Monteiro, P.J.M.

    2010-12-01

    This study details the differences in real-time hydration between pure tricalcium aluminate (cubic C{sub 3}A or 3CaO {center_dot} Al{sub 2}O{sub 3}) and Na-doped tricalcium aluminate (orthorhombic C{sub 3}A or Na{sub 2}Ca{sub 8}Al{sub 6}O{sub 18}), in aqueous solutions containing sulfate ions. Pure phases were synthesized in the laboratory to develop an independent benchmark for the reactions, meaning that their reactions during hydration in a simulated early age cement pore solution (saturated with respect to gypsum and lime) were able to be isolated. Because the rate of this reaction is extremely rapid, most microscopy methods are not adequate to study the early phases of the reactions in the early stages. Here, a high-resolution full-field soft X-ray imaging technique operating in the X-ray water window, combined with solution analysis by {sup 27}Al nuclear magnetic resonance (NMR) spectroscopy, was used to capture information regarding the mechanism of C{sub 3}A hydration during the early stages. There are differences in the hydration mechanism between the two types of C{sub 3}A, which are also dependent on the concentration of sulfate ions in the solution. The reactions with cubic C{sub 3}A (pure) seem to be more influenced by higher concentrations of sulfate ions, forming smaller ettringite needles at a slower pace than the orthorhombic C{sub 3}A (Na-doped) sample. The rate of release of aluminate species into the solution phase is also accelerated by Na doping.

  16. Magnetic smart material application to adaptive x-ray optics

    NASA Astrophysics Data System (ADS)

    Ulmer, M. P.; Graham, Michael E.; Vaynman, Semyon; Cao, J.; Takacs, Peter Z.

    2010-09-01

    We discuss a technique of shape modification that can be applied to thin walled ({100-400 micron thickness) electroformed replicated optics or slumped glass optics to improve the near net shape of the mirror as well as the midfrequency ripple. The process involves sputter deposition of a magnetic smart material (MSM) film onto a permanently magnetic material. The MSM material exhibits strains about 400 times stronger than ordinary ferromagnetic materials. The deformation process involves a magnetic write head which traverses the surface, and under the guidance of active metrology feedback, locally magnetizes the surface to impart strain where needed. Designs and basic concepts as applied to space borne X-ray optics will be described.

  17. Resonant Soft X-ray Scattering Studies of Multiferroic YMn2O5

    SciTech Connect

    Partzsch, S.; Wilkins, S.B.; Schierle, E.; Soltwisch, V.; Hill, J.P.; Weschke, E.; Souptel, D.; Buchner, B.; Geck, J.

    2011-06-17

    We performed soft x-ray resonant scattering at the MnL{sub 2,3}- and OK edges of YMn{sub 2}O{sub 5}. While the resonant intensity at the MnL{sub 2,3} edges represent the magnetic order parameter, the resonant scattering at the OK edge is found to be directly related to the macroscopic ferroelectric polarization. The latter observation reveals the important role of the spin-dependent Mn-O hybridization for the multiferroicity of YMn{sub 2}O{sub 5}. We present details about how to obtain correct energy dependent lineshapes and discuss the origin of the resonant intensity at the OK edge.

  18. X-ray resonant exchange scattering of rare-earth nickel borocarbides

    SciTech Connect

    Detlefs, C.

    1997-10-08

    The purpose of this thesis is to investigate the systematics of the microscopic magnetic order within a series of isostructural compounds and, at the same, to develop the relatively young experimental method of x-ray resonant exchange scattering (XRES). In this thesis, the author presents XRES studies of several rare-earth nickel borocarbides, RNi{sub 2}B{sub 2}C. He shows that XRES, similar to the neutron techniques, allows the determination of the orientation of the magnetic moment by measuring the Q-dependence of the scattered intensity of magnetic Bragg reflections. As samples in this study, he chose the recently discovered family of rare-earth nickel borocarbides, RNi{sub 2}B{sub 2}C, which display a wide variety of magnetic structures. Furthermore, in several of these materials, long range magnetic order coexists with superconductivity over some temperature range.

  19. Revealing the electronic ground state of ReNiO3 combining Ni-L3 x-ray absorption and resonant inelastic x-ray scattering

    NASA Astrophysics Data System (ADS)

    Bisogni, Valentina; Catalano, Sara; Green, Robert; Gibert, Marta; Scherwitzl, Raoul; Huang, Yaobo; Balandesh, Shadi; Strocov, Vladimir N.; Zubko, Pavlo; Sawatzky, George; Triscone, Jean-Marc; Schmitt, Thorsten

    Rare-earth nickelates ReNiO3 attract a lot of interest thanks to their intriguing physical properties like sharp metal to insulator transition, unusual magnetic order and expected superconductivity in nickelate-based heterostructures. Full understanding of these materials, however, is hampered by the difficulties in describing their electronic ground state (GS). Taking a NdNiO3 thin film as a representative example, we reveal with x-ray absorption and resonant inelastic x-ray scattering unusual coexistence of bound and continuum excitations, providing strong evidence for abundant O 2p holes in the GS of these materials. Using an Anderson impurity model interpretation, we show that these distinct spectral signatures arise from a Ni 3d8 configuration along with holes in the O 2p valence band, confirming suggestions that these materials exhibit a negative charge-transfer energy, with O 2p states extending across the Fermi level.

  20. X-ray absorption near-edge structure and nuclear magnetic resonance study of the lithium-sulfur battery and its components.

    PubMed

    Patel, Manu U M; Arčon, Iztok; Aquilanti, Giuliana; Stievano, Lorenzo; Mali, Gregor; Dominko, Robert

    2014-04-01

    Understanding the mechanism(s) of polysulfide formation and knowledge about the interactions of sulfur and polysulfides with a host matrix and electrolyte are essential for the development of long-cycle-life lithium-sulfur (Li-S) batteries. To achieve this goal, new analytical tools need to be developed. Herein, sulfur K-edge X-ray absorption near-edge structure (XANES) and (6,7) Li magic-angle spinning (MAS) NMR studies on a Li-S battery and its sulfur components are reported. The characterization of different stoichiometric mixtures of sulfur and lithium compounds (polysulfides), synthesized through a chemical route with all-sulfur-based components in the Li-S battery (sulfur and electrolyte), enables the understanding of changes in the batteries measured in postmortem mode and in operando mode. A detailed XANES analysis is performed on different battery components (cathode composite and separator). The relative amounts of each sulfur compound in the cathode and separator are determined precisely, according to the linear combination fit of the XANES spectra, by using reference compounds. Complementary information about the lithium species within the cathode are obtained by using (7) Li MAS NMR spectroscopy. The setup for the in operando XANES measurements can be viewed as a valuable analytical tool that can aid the understanding of the sulfur environment in Li-S batteries. PMID:24497200

  1. Reproducibility and accuracy of body composition assessments in mice by dual energy x-ray absorptiometry and time domain nuclear magnetic resonance

    PubMed Central

    Halldorsdottir, Solveig; Carmody, Jill; Boozer, Carol N.; Leduc, Charles A.; Leibel, Rudolph L.

    2011-01-01

    Objective To assess the accuracy and reproducibility of dual-energy absorptiometry (DXA; PIXImus™) and time domain nuclear magnetic resonance (TD-NMR; Bruker Optics) for the measurement of body composition of lean and obese mice. Subjects and measurements Thirty lean and obese mice (body weight range 19–67 g) were studied. Coefficients of variation for repeated (x 4) DXA and NMR scans of mice were calculated to assess reproducibility. Accuracy was assessed by comparing DXA and NMR results of ten mice to chemical carcass analyses. Accuracy of the respective techniques was also assessed by comparing DXA and NMR results obtained with ground meat samples to chemical analyses. Repeated scans of 10–25 gram samples were performed to test the sensitivity of the DXA and NMR methods to variation in sample mass. Results In mice, DXA and NMR reproducibility measures were similar for fat tissue mass (FTM) (DXA coefficient of variation [CV]=2.3%; and NMR CV=2.8%) (P=0.47), while reproducibility of lean tissue mass (LTM) estimates were better for DXA (1.0%) than NMR (2.2%) (

  2. Quantitative x-ray magnetic circular dichroism mapping with high spatial resolution full-field magnetic transmission soft x-ray spectro-microscopy

    SciTech Connect

    Robertson, MacCallum J.; Agostino, Christopher J.; N'Diaye, Alpha T.; Chen, Gong; Im, Mi-Young; Fischer, Peter

    2015-05-07

    The spectroscopic analysis of X-ray magnetic circular dichroism (XMCD), which serves as strong and element-specific magnetic contrast in full-field magnetic transmission soft x-ray microscopy, is shown to provide information on the local distribution of spin (S) and orbital (L) magnetic moments down to a spatial resolution of 25 nm limited by the x-ray optics used in the x-ray microscope. The spatially resolved L/S ratio observed in a multilayered (Co 0.3 nm/Pt 0.5 nm) × 30 thin film exhibiting a strong perpendicular magnetic anisotropy decreases significantly in the vicinity of domain walls, indicating a non-uniform spin configuration in the vertical profile of a domain wall across the thin film. Quantitative XMCD mapping with x-ray spectro-microscopy will become an important characterization tool for systems with topological or engineered magnetization inhomogeneities.

  3. Quantitative x-ray magnetic circular dichroism mapping with high spatial resolution full-field magnetic transmission soft x-ray spectro-microscopy

    NASA Astrophysics Data System (ADS)

    Robertson, MacCallum J.; Agostino, Christopher J.; N'Diaye, Alpha T.; Chen, Gong; Im, Mi-Young; Fischer, Peter

    2015-05-01

    The spectroscopic analysis of X-ray magnetic circular dichroism (XMCD), which serves as strong and element-specific magnetic contrast in full-field magnetic transmission soft x-ray microscopy, is shown to provide information on the local distribution of spin (S) and orbital (L) magnetic moments down to a spatial resolution of 25 nm limited by the x-ray optics used in the x-ray microscope. The spatially resolved L/S ratio observed in a multilayered (Co 0.3 nm/Pt 0.5 nm) × 30 thin film exhibiting a strong perpendicular magnetic anisotropy decreases significantly in the vicinity of domain walls, indicating a non-uniform spin configuration in the vertical profile of a domain wall across the thin film. Quantitative XMCD mapping with x-ray spectro-microscopy will become an important characterization tool for systems with topological or engineered magnetization inhomogeneities.

  4. High-energy magnetic excitations in overdoped La2-xSrxCuO4 studied by neutron and resonant inelastic X-ray scattering

    SciTech Connect

    Wakimoto, S.; Ishii, K.; Kimura, H.; Fujita, M.; Dellea, G.; Kummer, K.; Braicovich, L.; Ghiringhelli, G.; Debeer-Schmitt, Lisa M.; Granroth, Garrett E.

    2015-05-21

    We have performed neutron inelastic scattering and resonant inelastic x-ray scattering (RIXS) at the Cu-L3 edge to study high-energy magnetic excitations at energy transfers of more than 100 meV for overdoped La2₋xSrxCuO4 with x=0.25 (Tc=15 K) and x=0.30 (nonsuperconducting) using identical single-crystal samples for the two techniques. From constant-energy slices of neutron-scattering cross sections, we have identified magnetic excitations up to ~250 meV for x=0.25. Although the width in the momentum direction is large, the peak positions along the (π,π) direction agree with the dispersion relation of the spin wave in the nondoped La2CuO4 (LCO), which is consistent with the previous RIXS results of cuprate superconductors. Using RIXS at the Cu-L3 edge, we have measured the dispersion relations of the so-called paramagnon mode along both (π,π) and (π,0) directions. Although in both directions the neutron and RIXS data connect with each other and the paramagnon along (π,0) agrees well with the LCO spin-wave dispersion, the paramagnon in the (π,π) direction probed by RIXS appears to be less dispersive and the excitation energy is lower than the spin wave of LCO near (π/2,π/2). Thus, our results indicate consistency between neutron inelastic scattering and RIXS, and elucidate the entire magnetic excitation in the (π,π) direction by the complementary use of two probes. The polarization dependence of the RIXS profiles indicates that appreciable charge excitations exist in the same energy range of magnetic excitations, reflecting the itinerant character of the overdoped sample. Lastly, we find a possible anisotropy in the charge excitation intensity might explain the apparent differences in the paramagnon dispersion in the (π,π) direction as detected by the x-ray scattering.

  5. Electronic Structure of In2O3 from Resonant X-ray Emission Spectroscopy

    SciTech Connect

    Piper, L.; DeMasi, A; Cho, S; Smith, K; Fuchs, F; Bechstedt, F; Korber, C; Klein, A; Payne, D; Egdell, R

    2009-01-01

    The valence and conduction band structures of In2O3 have been measured using a combination of valence band x-ray photoemission spectroscopy, O K-edge resonant x-ray emission spectroscopy, and O K-edge x-ray absorption spectroscopy. Excellent agreement is noted between the experimental spectra and O 2p partial density of states calculated within hybrid density functional theory. Our data are consistent with a direct band gap for In2O3.

  6. Magnetic soft x-ray microscopy-imaging fast spin dynamics inmagnetic nanostructures

    SciTech Connect

    Fischer, Peter; Kim, Dong-Hyun; Mesler, Brooke L.; Chao, Weilun; Sakdinawat, Anne E.; Anderson, Erik H.

    2007-06-01

    Magnetic soft X-ray microscopy combines 15nm spatial resolution with 70ps time resolution and elemental sensitivity. Fresnel zone plates are used as X-ray optics and X-ray magnetic circular dichroism serves as magnetic contrast mechanism. Thus scientifically interesting and technologically relevant low dimensional nanomagnetic systems can be imaged at fundamental length and ultrafast time scales in a unique way. Studies include magnetization reversal in magnetic multilayers, nanopatterned systems, vortex dynamics in nanoelements and spin current induced phenomena.

  7. Direct surface magnetometry with photoemission magnetic x-ray dichroism

    SciTech Connect

    Tobin, J.G.; Goodman, K.W.; Schumann, F.O.

    1997-04-01

    Element specific surface magnetometry remains a central goal of synchrotron radiation based studies of nanomagnetic structures. One appealing possibility is the combination of x-ray absorption dichroism measurements and the theoretical framework provided by the {open_quotes}sum rules.{close_quotes} Unfortunately, sum rule analysis are hampered by several limitations including delocalization of the final state, multi-electronic phenomena and the presence of surface dipoles. An alternative experiment, Magnetic X-Ray Dichroism in Photoelectron Spectroscopy, holds out promise based upon its elemental specificity, surface sensitivity and high resolution. Computational simulations by Tamura et al. demonstrated the relationship between exchange and spin orbit splittings and experimental data of linear and circular dichroisms. Now the authors have developed an analytical framework which allows for the direct extraction of core level exchange splittings from circular and linear dichroic photoemission data. By extending a model initially proposed by Venus, it is possible to show a linear relation between normalized dichroism peaks in the experimental data and the underlying exchange splitting. Since it is reasonable to expect that exchange splittings and magnetic moments track together, this measurement thus becomes a powerful new tool for direct surface magnetometry, without recourse to time consuming and difficult spectral simulations. The theoretical derivation will be supported by high resolution linear and circular dichroism data collected at the Spectromicroscopy Facility of the Advanced Light Source.

  8. Towards magnetic 3D x-ray imaging

    NASA Astrophysics Data System (ADS)

    Fischer, Peter; Streubel, R.; Im, M.-Y.; Parkinson, D.; Hong, J.-I.; Schmidt, O. G.; Makarov, D.

    2014-03-01

    Mesoscale phenomena in magnetism will add essential parameters to improve speed, size and energy efficiency of spin driven devices. Multidimensional visualization techniques will be crucial to achieve mesoscience goals. Magnetic tomography is of large interest to understand e.g. interfaces in magnetic multilayers, the inner structure of magnetic nanocrystals, nanowires or the functionality of artificial 3D magnetic nanostructures. We have developed tomographic capabilities with magnetic full-field soft X-ray microscopy combining X-MCD as element specific magnetic contrast mechanism, high spatial and temporal resolution due to the Fresnel zone plate optics. At beamline 6.1.2 at the ALS (Berkeley CA) a new rotation stage allows recording an angular series (up to 360 deg) of high precision 2D projection images. Applying state-of-the-art reconstruction algorithms it is possible to retrieve the full 3D structure. We will present results on prototypic rolled-up Ni and Co/Pt tubes and glass capillaries coated with magnetic films and compare to other 3D imaging approaches e.g. in electron microscopy. Supported by BES MSD DOE Contract No. DE-AC02-05-CH11231 and ERC under the EU FP7 program (grant agreement No. 306277).

  9. Nuclear resonant inelastic X-ray scattering at high pressure and low temperature

    PubMed Central

    Bi, Wenli; Zhao, Jiyong; Lin, Jung-Fu; Jia, Quanjie; Hu, Michael Y.; Jin, Changqing; Ferry, Richard; Yang, Wenge; Struzhkin, Viktor; Alp, E. Ercan

    2015-01-01

    A new synchrotron radiation experimental capability of coupling nuclear resonant inelastic X-ray scattering with the cryogenically cooled high-pressure diamond anvil cell technique is presented. The new technique permits measurements of phonon density of states at low temperature and high pressure simultaneously, and can be applied to studies of phonon contribution to pressure- and temperature-induced magnetic, superconducting and metal–insulator transitions in resonant isotope-bearing materials. In this report, a pnictide sample, EuFe2As2, is used as an example to demonstrate this new capability at beamline 3-ID of the Advanced Photon Source, Argonne National Laboratory. A detailed description of the technical development is given. The Fe-specific phonon density of states and magnetism from the Fe sublattice in Eu57Fe2As2 at high pressure and low temperature were derived by using this new capability. PMID:25931094

  10. Nuclear resonant inelastic X-ray scattering at high pressure and low temperature

    DOE PAGESBeta

    Bi, Wenli; Zhao, Jiyong; Lin, Jung -Fu; Jia, Quanjie; Hu, Michael Y.; Jin, Changqing; Ferry, Richard; Yang, Wenge; Struzhkin, Viktor; Alp, E. Ercan

    2015-01-01

    In this study, a new synchrotron radiation experimental capability of coupling nuclear resonant inelastic X-ray scattering with the cryogenically cooled high-pressure diamond anvil cell technique is presented. The new technique permits measurements of phonon density of states at low temperature and high pressure simultaneously, and can be applied to studies of phonon contribution to pressure- and temperature-induced magnetic, superconducting and metal–insulator transitions in resonant isotope-bearing materials. In this report, a pnictide sample, EuFe2As2, is used as an example to demonstrate this new capability at beamline 3-ID of the Advanced Photon Source, Argonne National Laboratory. A detailed description of the technicalmore » development is given. The Fe-specific phonon density of states and magnetism from the Fe sublattice in Eu57Fe2As2 at high pressure and low temperature were derived by using this new capability.« less

  11. X-ray laser resonator for the kilo-electron-volt range

    SciTech Connect

    Chen, Jie; Tomov, Ivan V.; Er, Ali O.; Rentzepis, Peter M.

    2013-04-29

    We have designed, constructed, and tested an x-ray laser resonator operating in the hard x-ray, keV energy region. This ring x-ray laser cavity is formed by four highly oriented pyrolytic graphite crystals. The crystals are set at the Bragg angles that allow for the complete 360 Degree-Sign round trip of the 2.37 A, 5.23 keV L{sub {alpha}} line of neodymium. In addition, we also present experimental data of a similar ring laser resonator that utilizes the Cr K{sub {alpha}}, 5.41 keV, x-ray line to propagate through the four mirrors of the cavity. The specific properties of these x-ray laser resonator mirrors, including reflection losses and cavity arrangement, are presented.

  12. Performance of Magnetic Penetration Thermometers for X-Ray Astronomy

    NASA Technical Reports Server (NTRS)

    Nagler, P. C.; Adams, J. S.; Balvin, M. A.; Bandler, S. R.; Denis, K. L.; Hsieh, W. T.; Kelly, D. P.; Porst, J. P.; Sadleir, J. E.; Seidel, G. M.; Smith, S. J.; Stevenson, T. R.

    2012-01-01

    The ideal X-ray camera for astrophysics would have more than a million pixels and provide an energy resolution of better than leV FWHM for energies up to 10 keY. We have microfabricated and characterized thin-film magnetic penetration thermometers (MPTs) that show great promise towards meeting these capabilities. MPTs operate in similar fashion to metallic magnetic calorimeters (MMCs), except that a superconducting sensor takes the place of a paramagnetic sensor and it is the temperature dependence of the superconductor's diamagnetic response that provides the temperature sensitivity. We present a description of the design and performance of our prototype thin-film MPTs with MoAu bilayer sensors, which have demonstrated an energy resolution of approx 2 eV FWHM at 1.5 keY and 4.3 eV FWHM at 5.9 keY.

  13. X-ray Spectroscopy and Magnetism in Mineralogy

    NASA Astrophysics Data System (ADS)

    Sainctavit, Philippe; Brice-Profeta, Sandrine; Gaudry, Emilie; Letard, Isabelle; Arrio, Marie-Anne

    The objective of this paper is to present the kind of information that can be gained in the field of mineralogy from the use of x-ray magnetic spectroscopies. We review some of the questions that are unsettled and that could benefit from an interdisciplinary approach where magnetism, spectroscopy and mineralogy could be mixed. Most of the attention is focused on iron and some other 3d transition elements. The mineralogy of planetary cores and its relation with known meteorites are exemplified. The various oxide phases in the mantle and the nature of iron in these phases is also underlined. The presence of transition elements in insulating minerals and its relation with macroscopic properties such as the color of gemstones are reviewed. Finally an introduction to paleomagnetism is given with a special attention to nanomaghemites.

  14. Magnetic Nature of the 500 meV peak in La2−xSrxCuO4 Observed with Resonant Inelastic X-ray Scattering at the Cu K-edge

    SciTech Connect

    Hill, J.P.; Ellis, D.S.; Kim, J.; Wakimoto, S.; Birgeneau, R.J.; Shvyd’ko, Y.; Casa, D.; Gog, T.; Ishii, K.; Ikeuchi, K.; Paramekanti, A.; Kim, Y.-J.

    2010-02-15

    We present a comprehensive study of the temperature and doping dependence of the 500 meV peak observed at q = ({pi},0) in resonant inelastic x-ray scattering (RIXS) experiments on La{sub 2}CuO{sub 4}. The intensity of this peak persists above the Neel temperature (T{sub N} = 320 K), but decreases gradually with increasing temperature, reaching zero at around T = 500 K. The peak energy decreases with temperature in close quantitative accord with the behavior of the two-magnon B{sub 1g} Raman peak in La{sub 2}CuO{sub 4} and, with suitable rescaling, agrees with the Raman peak shifts in EuBa{sub 2}Cu{sub 3}O{sub 6} and K{sub 2}NiF{sub 4}. The overall dispersion of this excitation in the Brillouin zone is found to be in agreement with theoretical calculations for a two-magnon excitation. Upon doping, the peak intensity decreases analogous to the Raman mode intensity and appears to track the doping dependence of the spin-correlation length. Taken together, these observations strongly suggest that the 500 meV mode is magnetic in character and is likely a two-magnon excitation.

  15. Gd3+ complex-modified NaLuF4-based upconversion nanophosphors for trimodality imaging of NIR-to-NIR upconversion luminescence, X-Ray computed tomography and magnetic resonance.

    PubMed

    Xia, Ao; Chen, Min; Gao, Yuan; Wu, Dongmei; Feng, Wei; Li, Fuyou

    2012-07-01

    Multimodality molecular imaging has recently attracted much attention, because it can take advantage of individual imaging modalities by fusing together information from several molecular imaging techniques. Herein, we report a multifunctional lanthanide-based nanoparticle for near-infrared to near-infrared (NIR-to-NIR) upconversion luminescence (UCL), X-ray computed tomography (CT) and T(1)-enhanced magnetic resonance (MR) trimodality in-vivo imaging. By careful selection of the lanthanide elements, core-shell structured lanthanide-based nanoparticles, NaLuF(4):Yb(3+),Tm(3+)@SiO(2)-GdDTPA nanoparticles (UCNP@SiO(2)-GdDTPA) have been designed and synthesized. We also prove that the application of UCNP@SiO(2)-GdDTPA for NIR-to-NIR UCL, CT and MRI multi-modality in-vivo imaging can be established successfully. In addition, the biological toxicity of UCNP@SiO(2)-GdDTPA is evaluated by the methyl thiazolyl tetrazolium (MTT) assay and histological analysis of viscera sections. PMID:22560666

  16. An integrative approach combining ion mobility mass spectrometry, X-ray crystallography, and nuclear magnetic resonance spectroscopy to study the conformational dynamics of α1-antitrypsin upon ligand binding

    PubMed Central

    Nyon, Mun Peak; Prentice, Tanya; Day, Jemma; Kirkpatrick, John; Sivalingam, Ganesh N; Levy, Geraldine; Haq, Imran; Irving, James A; Lomas, David A; Christodoulou, John; Gooptu, Bibek; Thalassinos, Konstantinos

    2015-01-01

    Native mass spectrometry (MS) methods permit the study of multiple protein species within solution equilibria, whereas ion mobility (IM)-MS can report on conformational behavior of specific states. We used IM-MS to study a conformationally labile protein (α1-antitrypsin) that undergoes pathological polymerization in the context of point mutations. The folded, native state of the Z-variant remains highly polymerogenic in physiological conditions despite only minor thermodynamic destabilization relative to the wild-type variant. Various data implicate kinetic instability (conformational lability within a native state ensemble) as the basis of Z α1-antitrypsin polymerogenicity. We show the ability of IM-MS to track such disease-relevant conformational behavior in detail by studying the effects of peptide binding on α1-antitrypsin conformation and dynamics. IM-MS is, therefore, an ideal platform for the screening of compounds that result in therapeutically beneficial kinetic stabilization of native α1-antitrypsin. Our findings are confirmed with high-resolution X-ray crystallographic and nuclear magnetic resonance spectroscopic studies of the same event, which together dissect structural changes from dynamic effects caused by peptide binding at a residue-specific level. IM-MS methods, therefore, have great potential for further study of biologically relevant thermodynamic and kinetic instability of proteins and provide rapid and multidimensional characterization of ligand interactions of therapeutic interest. PDB Code(s): 4PYW PMID:26011795

  17. Resonant x-ray scattering in 3d-transition-metal oxides: Anisotropy and charge orderings

    NASA Astrophysics Data System (ADS)

    Subías, G.; García, J.; Blasco, J.; Herrero-Martín, J.; Sánchez, M. C.

    2009-11-01

    The structural, magnetic and electronic properties of transition metal oxides reflect in atomic charge, spin and orbital degrees of freedom. Resonant x-ray scattering (RXS) allows us to perform an accurate investigation of all these electronic degrees. RXS combines high-Q resolution x-ray diffraction with the properties of the resonance providing information similar to that obtained by atomic spectroscopy (element selectivity and a large enhancement of scattering amplitude for this particular element and sensitivity to the symmetry of the electronic levels through the multipole electric transitions). Since electronic states are coupled to the local symmetry, RXS reveals the occurrence of symmetry breaking effects such as lattice distortions, onset of electronic orbital ordering or ordering of electronic charge distributions. We shall discuss the strength of RXS at the K absorption edge of 3d transition-metal oxides by describing various applications in the observation of local anisotropy and charge disproportionation. Examples of these resonant effects are (I) charge ordering transitions in manganites, Fe3O4 and ferrites and (II) forbidden reflections and anisotropy in Mn3+ perovskites, spinel ferrites and cobalt oxides. In all the studied cases, the electronic (charge and/or anisotropy) orderings are determined by the structural distortions.

  18. Hard-X-ray magnetic microscopy and local magnetization analysis using synchrotron radiation.

    PubMed

    Suzuki, Motohiro

    2014-11-01

    X-ray measurement offers several useful features that are unavailable from other microscopic means including electron-based techniques. By using X-rays, one can observe the internal parts of a thick sample. This technique basically requires no high vacuum environment such that measurements are feasible for wet specimens as well as under strong electric and magnetic fields and even at a high pressure. X-ray spectroscopy using core excitation provides element-selectivity with significant sensitivities to the chemical states and atomic magnetic moments in the matter. Synchrotron radiation sources produce a small and low-divergent X-ray beam, which can be converged to a spot with the size of a micrometer or less using X-ray focusing optics. The recent development in the focusing optics has been driving X-ray microscopy, which has already gone into the era of X-ray nanoscopy. With the use of the most sophisticated focusing devices, an X-ray beam of 7-nm size has successfully been achieved [1]. X-ray microscopy maintains above-mentioned unique features of X-ray technique, being a perfect complement to electron microscopy.In this paper, we present recent studies on magnetic microscopy and local magnetic analysis using hard X-rays. The relevant instrumentation developments are also described. The X-ray nanospectroscopy station of BL39XU at SPring-8 is equipped with a focusing optics consisting of two elliptic mirrors, and a focused X-ray beam with the size of 100 × 100 nm(2) is available [2]. Researchers can perform X-ray absorption spectroscopy: nano-XAFS (X-ray absorption fine structure) using the X-ray beam as small as 100 nm. The available X-ray energy is from 5 to 16 keV, which allows nano-XAFS study at the K edges of 3d transition metals, L edges of rare-earth elements and 5d noble metals. Another useful capability of the nanoprobe is X-ray polarization tunability, enabling magnetic circular dichroism (XMCD) spectroscopy with a sub-micrometer resolution. Scanning

  19. Electrostatic focal spot correction for x-ray tubes operating in strong magnetic fields

    SciTech Connect

    Lillaney, Prasheel; Shin, Mihye; Hinshaw, Waldo; Fahrig, Rebecca

    2014-11-01

    Purpose: A close proximity hybrid x-ray/magnetic resonance (XMR) imaging system offers several critical advantages over current XMR system installations that have large separation distances (∼5 m) between the imaging fields of view. The two imaging systems can be placed in close proximity to each other if an x-ray tube can be designed to be immune to the magnetic fringe fields outside of the MR bore. One of the major obstacles to robust x-ray tube design is correcting for the effects of the MR fringe field on the x-ray tube focal spot. Any fringe field component orthogonal to the x-ray tube electric field leads to electron drift altering the path of the electron trajectories. Methods: The method proposed in this study to correct for the electron drift utilizes an external electric field in the direction of the drift. The electric field is created using two electrodes that are positioned adjacent to the cathode. These electrodes are biased with positive and negative potential differences relative to the cathode. The design of the focusing cup assembly is constrained primarily by the strength of the MR fringe field and high voltage standoff distances between the anode, cathode, and the bias electrodes. From these constraints, a focusing cup design suitable for the close proximity XMR system geometry is derived, and a finite element model of this focusing cup geometry is simulated to demonstrate efficacy. A Monte Carlo simulation is performed to determine any effects of the modified focusing cup design on the output x-ray energy spectrum. Results: An orthogonal fringe field magnitude of 65 mT can be compensated for using bias voltages of +15 and −20 kV. These bias voltages are not sufficient to completely correct for larger orthogonal field magnitudes. Using active shielding coils in combination with the bias electrodes provides complete correction at an orthogonal field magnitude of 88.1 mT. Introducing small fields (<10 mT) parallel to the x-ray tube electric

  20. Electrostatic focal spot correction for x-ray tubes operating in strong magnetic fields

    PubMed Central

    Lillaney, Prasheel; Shin, Mihye; Hinshaw, Waldo; Fahrig, Rebecca

    2014-01-01

    Purpose: A close proximity hybrid x-ray/magnetic resonance (XMR) imaging system offers several critical advantages over current XMR system installations that have large separation distances (∼5 m) between the imaging fields of view. The two imaging systems can be placed in close proximity to each other if an x-ray tube can be designed to be immune to the magnetic fringe fields outside of the MR bore. One of the major obstacles to robust x-ray tube design is correcting for the effects of the MR fringe field on the x-ray tube focal spot. Any fringe field component orthogonal to the x-ray tube electric field leads to electron drift altering the path of the electron trajectories. Methods: The method proposed in this study to correct for the electron drift utilizes an external electric field in the direction of the drift. The electric field is created using two electrodes that are positioned adjacent to the cathode. These electrodes are biased with positive and negative potential differences relative to the cathode. The design of the focusing cup assembly is constrained primarily by the strength of the MR fringe field and high voltage standoff distances between the anode, cathode, and the bias electrodes. From these constraints, a focusing cup design suitable for the close proximity XMR system geometry is derived, and a finite element model of this focusing cup geometry is simulated to demonstrate efficacy. A Monte Carlo simulation is performed to determine any effects of the modified focusing cup design on the output x-ray energy spectrum. Results: An orthogonal fringe field magnitude of 65 mT can be compensated for using bias voltages of +15 and −20 kV. These bias voltages are not sufficient to completely correct for larger orthogonal field magnitudes. Using active shielding coils in combination with the bias electrodes provides complete correction at an orthogonal field magnitude of 88.1 mT. Introducing small fields (<10 mT) parallel to the x-ray tube electric

  1. Sapphire hard X-ray Fabry-Perot resonators for synchrotron experiments.

    PubMed

    Tsai, Yi Wei; Wu, Yu Hsin; Chang, Ying Yi; Liu, Wen Chung; Liu, Hong Lin; Chu, Chia Hong; Chen, Pei Chi; Lin, Pao Te; Fu, Chien Chung; Chang, Shih Lin

    2016-05-01

    Hard X-ray Fabry-Perot resonators (FPRs) made from sapphire crystals were constructed and characterized. The FPRs consisted of two crystal plates, part of a monolithic crystal structure of Al2O3, acting as a pair of mirrors, for the backward reflection (0 0 0 30) of hard X-rays at 14.3147 keV. The dimensional accuracy during manufacturing and the defect density in the crystal in relation to the resonance efficiency of sapphire FPRs were analyzed from a theoretical standpoint based on X-ray cavity resonance and measurements using scanning electron microscopic and X-ray topographic techniques for crystal defects. Well defined resonance spectra of sapphire FPRs were successfully obtained, and were comparable with the theoretical predictions. PMID:27140144

  2. Use of electron cyclotron resonance x-ray source for nondestructive testing application

    NASA Astrophysics Data System (ADS)

    Baskaran, R.; Selvakumaran, T. S.

    2006-03-01

    Electron cyclotron resonance (ECR) technique is being used for generating x rays in the low-energy region (<150keV). Recently, the source is used for the calibration of thermoluminescent dosimetry (TLD) badges. In order to qualify the ECR x-ray source for imaging application, the source should give uniform flux over the area under study. Lead collimation arrangement is made to get uniform flux. The flux profile is measured using a teletector at different distance from the port and uniform field region of 10×10cm2 has been marked at 20cm from the x-ray exit port. A digital-to-analog converter (DAC) circuit pack is used for examining the source performance. The required dose for nondestructive testing examination has been estimated using a hospital x-ray machine and it is found to be 0.05mSv. Our source experimental parameters are tuned and the DAC circuit pack was exposed for nearly 7min to get the required dose value. The ECR x-ray source operating parameters are argon pressure: 10-5Torr, microwave power: 350W, and coil current: 0A. The effective energy of the x-ray spectrum is nearly 40keV. The x-ray images obtained from ECR x-ray source and hospital medical radiography machine are compared. It is found that the image obtained from ECR x-ray source is suitable for NDT application.

  3. Use of electron cyclotron resonance x-ray source for nondestructive testing application

    SciTech Connect

    Baskaran, R.; Selvakumaran, T.S.

    2006-03-15

    Electron cyclotron resonance (ECR) technique is being used for generating x rays in the low-energy region (<150 keV). Recently, the source is used for the calibration of thermoluminescent dosimetry (TLD) badges. In order to qualify the ECR x-ray source for imaging application, the source should give uniform flux over the area under study. Lead collimation arrangement is made to get uniform flux. The flux profile is measured using a teletector at different distance from the port and uniform field region of 10x10 cm{sup 2} has been marked at 20 cm from the x-ray exit port. A digital-to-analog converter (DAC) circuit pack is used for examining the source performance. The required dose for nondestructive testing examination has been estimated using a hospital x-ray machine and it is found to be 0.05 mSv. Our source experimental parameters are tuned and the DAC circuit pack was exposed for nearly 7 min to get the required dose value. The ECR x-ray source operating parameters are argon pressure: 10{sup -5} Torr, microwave power: 350 W, and coil current: 0 A. The effective energy of the x-ray spectrum is nearly 40 keV. The x-ray images obtained from ECR x-ray source and hospital medical radiography machine are compared. It is found that the image obtained from ECR x-ray source is suitable for NDT application.

  4. Collective nature of spin excitations in superconducting cuprates probed by resonant inelastic X-ray scattering.

    PubMed

    Minola, M; Dellea, G; Gretarsson, H; Peng, Y Y; Lu, Y; Porras, J; Loew, T; Yakhou, F; Brookes, N B; Huang, Y B; Pelliciari, J; Schmitt, T; Ghiringhelli, G; Keimer, B; Braicovich, L; Le Tacon, M

    2015-05-29

    We used resonant inelastic x-ray scattering (RIXS) with and without analysis of the scattered photon polarization, to study dispersive spin excitations in the high temperature superconductor YBa_{2}Cu_{3}O_{6+x} over a wide range of doping levels (0.1≤x≤1). The excitation profiles were carefully monitored as the incident photon energy was detuned from the resonant condition, and the spin excitation energy was found to be independent of detuning for all x. These findings demonstrate that the largest fraction of the spin-flip RIXS profiles in doped cuprates arises from magnetic collective modes, rather than from incoherent particle-hole excitations as recently suggested theoretically [Benjamin et al. Phys. Rev. Lett. 112, 247002 (2014)]. Implications for the theoretical description of the electron system in the cuprates are discussed. PMID:26066453

  5. Full Polarization Analysis of Resonant Superlattice and Forbidden x-ray Reflections in Magnetite

    SciTech Connect

    Wilkins, S.B.; Bland, S.R.; Detlefs, B.; Beale, T.A.W.; Mazzoli, C.; Joly, Y.; Hatton, P.D.; Lorenzo, J.E.; Brabers, V.A.M.

    2009-12-02

    Despite being one of the oldest known magnetic materials, and the classic mixed valence compound, thought to be charge ordered, the structure of magnetite below the Verwey transition is complex and the presence and role of charge order is still being debated. Here, we present resonant x-ray diffraction data at the iron K-edge on forbidden (0, 0, 2n+1){sub C} and superlattice (0, 0, 2n+1/2)C reflections. Full linear polarization analysis of the incident and scattered light was conducted in order to explore the origins of the reflections. Through simulation of the resonant spectra we have confirmed that a degree of charge ordering takes place, while the anisotropic tensor of susceptibility scattering is responsible for the superlattice reflections below the Verwey transition. We also report the surprising result of the conversion of a significant proportion of the scattered light from linear to nonlinear polarization.

  6. Soft X-Ray Magnetic Imaging of Focused Ion Beam Lithographically Patterned Fe Thin Films

    SciTech Connect

    Cook, Paul J.; Shen, Tichan H.; Grundy, PhilJ.; Im, Mi Young; Fischer, Peter; Morton, Simon A.; Kilcoyne, Arthur D.L.

    2008-11-09

    We illustrate the potential of modifying the magnetic behavior and structural properties of ferromagnetic thin films using focused ion beam 'direct-write' lithography. Patterns inspired by the split-ring resonators often used as components in meta-materials were defined upon 15 nm Fe films using a 30 keV Ga{sup +} focused ion beam at a dose of 2 x 10{sup 16} ions cm{sup -2}. Structural, chemical and magnetic changes to the Fe were studied using transmission soft X-ray microscopy at the ALS, Berkeley CA. X-ray absorption spectra showed a 23% reduction in the thickness of the film in the Ga irradiated areas, but no change to the chemical environment of Fe was evident. X-ray images of the magnetic reversal process show domain wall pinning around the implanted areas, resulting in an overall increase in the coercivity of the film. Transmission electron microscopy showed significant grain growth in the implanted regions.

  7. Soft x-ray ptychography studies of nanoscale magnetic and structural correlations in thin SmCo5 films

    NASA Astrophysics Data System (ADS)

    Shi, X.; Fischer, P.; Neu, V.; Elefant, D.; Lee, J. C. T.; Shapiro, D. A.; Farmand, M.; Tyliszczak, T.; Shiu, H.-W.; Marchesini, S.; Roy, S.; Kevan, S. D.

    2016-02-01

    High spatial resolution magnetic x-ray spectromicroscopy at x-ray photon energies near the cobalt L3 resonance was applied to probe an amorphous 50 nm thin SmCo5 film prepared by off-axis pulsed laser deposition onto an x-ray transparent 200 nm thin Si3N4 membrane. Alternating gradient magnetometry shows a strong in-plane anisotropy and an only weak perpendicular magnetic anisotropy, which is confirmed by magnetic transmission soft x-ray microscopy images showing over a field of view of 10 μm a primarily stripe-like domain pattern but with local labyrinth-like domains. Soft x-ray ptychography in amplitude and phase contrast was used to identify and characterize local magnetic and structural features over a field of view of 1 μm with a spatial resolution of about 10 nm. There, the magnetic labyrinth domain patterns are accompanied by nanoscale structural inclusions that are primarily located in close proximity to the magnetic domain walls. Our analysis suggests that these inclusions are nanocrystalline Sm2Co17 phases with nominally in-plane magnetic anisotropy.

  8. X-ray studies of neutron stars and their magnetic fields

    NASA Astrophysics Data System (ADS)

    Makishima, K.

    2016-05-01

    Utilizing results obtained over the past quarter century mainly with Japanese X-ray astronomy satellites, a review is given to some aspects of neutron stars (NSs), with a particular emphasis on the magnetic fields (MFs) of mass-accreting NSs and magnetars. Measurements of electron cyclotron resonance features in binary X-ray pulsars, using the Ginga and Suzaku observatories, clarified that their surface MFs are concentrated in a narrow range of (1?7) × 10^8 T. Extensive studies of magnetars with Suzaku reinforced their nature as neutron stars with truly strong MFs, and revealed several important clues to their formation, evolution, and physical states. Taking all these results into account, a discussion is made on the origin and evolution of these strong MFs. One possible scenario is that the MF of NSs is a manifestation of some fundamental physics, e.g., neutron spin alignment or chirality violation, and the MF makes transitions from strong to weak states.

  9. Unraveling skyrmion spin texture using resonant soft x-ray scattering

    NASA Astrophysics Data System (ADS)

    Roy, Sujoy

    2015-03-01

    The recent discovery of skyrmions, that were originally predicted in context of high energy physics, in magnetic materials has sparked tremendous interest in the research community due to its rich physics and potential in spintronics applications. Skyrmions have an unusual spin texture that manifests as magnetic knot and can be easily moved around. Understanding the fundamental physics and mechanisms for controlling their dynamical properties presents important scientific challenges. So far experimental verifications of the skyrmions in magnetic systems have come from neutron scattering and Lorentz transmission electron microscopy (TEM) measurements. In this talk we report the first observation of the skyrmions using resonant soft x-ray scattering. We have used soft x-rays tuned to the Cu L3 edge to diffract off the skyrmion lattice in a multiferroic Cu2OSeO3 compound. We show that in Cu2OSeO3 there exist two skyrmion lattices arising due to the two inequivalent Cu-O sublattices that have two different magnetically active d-orbitals. The two skyrmion sublattices are mutually rotated with respect to each other. The angle of rotation could be changed by an external magnetic field, thereby indicating possible existence of a new phase. We have also studied skyrmion spin texture in an ultra-thin Fe/Gd multilayer that shows perpendicular anisotropy. The Fe/Gd sample exhibits a near perfect aligned stripe phase. Within a small range of temperature and magnetic field we observe a hexagonal scattering pattern due to skyrmion bubbles. Analysis of the scattering pattern suggests that the skyrmion lattice unit cell contains two skyrmions. The biskyrmion state is also revealed by Lorentz TEM images. The near room temperature discovery of skyrmion in a technology relevant material is a significant step towards using skyrmions in magnetic devices. Work at LBNL was supported by the Office of Basic Energy Sciences of the U.S. Department of Energy (Contract No. DE-AC02-05CH11231).

  10. Octupole Magnet For Soft X Ray Magnetic Dichroism Experiments: Design and Performance

    SciTech Connect

    Arenholz, Elke; Prestemon, Soren O.

    2004-05-12

    An octupole magnet endstation for soft x ray magnetic dichroism measurements has been developed at the Advanced Light Source. The system consists of an eight pole electromagnet that surrounds a small vacuum chamber. The magnet provides fields up to 0.9 T that can be applied in any direction relative to the incoming x ray beam. High precision magnetic circular and linear dichroism spectra can be obtained reversing the magnetic field for each photon energy in an energy scan. Moreover, the field dependence of all components of the magnetization vector can be studied in detail by choosing various angles of x ray incidence while keeping the relative orientation of magnetic field and sample fixed.

  11. Octupole magnet for soft X ray magnetic dichroism experiments: Design and performance

    SciTech Connect

    Arenholz, Elke; Prestemon, Soren O.

    2003-08-24

    An octupole magnet endstation for soft x-ray magnetic dichroism measurements has been developed at the Advanced Light Source. The system consists of an eight pole electromagnet that surrounds a small vacuum chamber. The magnet provides fields up to 0.9 T that can be applied in any direction relative to the incoming x-ray beam. High precision magnetic circular and linear dichroism spectra can be obtained reversing the magnetic field for each photon energy in an energy scan. Moreover, the field dependence of all components of the magnetization vector can be studied in detail by choosing various angles of x-ray incidence while keeping the relative orientation of magnetic field and sample fixed.

  12. A 23Na magic angle spinning nuclear magnetic resonance, XANES, and high-temperature X-ray diffraction study of NaUO3, Na4UO5, and Na2U2O7.

    PubMed

    Smith, A L; Raison, P E; Martel, L; Charpentier, T; Farnan, I; Prieur, D; Hennig, C; Scheinost, A C; Konings, R J M; Cheetham, A K

    2014-01-01

    The valence state of uranium has been confirmed for the three sodium uranates NaU(V)O3/[Rn](5f(1)), Na4U(VI)O5/[Rn](5f(0)), and Na2U(VI)2O7/[Rn](5f(0)), using X-ray absorption near-edge structure (XANES) spectroscopy. Solid-state (23)Na magic angle spinning nuclear magnetic resonance (MAS NMR) measurements have been performed for the first time, yielding chemical shifts at -29.1 (NaUO3), 15.1 (Na4UO5), and -14.1 and -19 ppm (Na1 8-fold coordinated and Na2 7-fold coordinated in Na2U2O7), respectively. The [Rn]5f(1) electronic structure of uranium in NaUO3 causes a paramagnetic shift in comparison to Na4UO5 and Na2U2O7, where the electronic structure is [Rn]5f(0). A (23)Na multi quantum magic angle spinning (MQMAS) study on Na2U2O7 has confirmed a monoclinic rather than rhombohedral structure with evidence for two distinct Na sites. DFT calculations of the NMR parameters on the nonmagnetic compounds Na4UO5 and Na2U2O7 have permitted the differentiation between the two Na sites of the Na2U2O7 structure. The linear thermal expansion coefficients of all three compounds have been determined using high-temperature X-ray diffraction: αa = 22.7 × 10(-6) K(-1), αb = 12.9 × 10(-6) K(-1), αc = 16.2 × 10(-6) K(-1), and αvol = 52.8 × 10(-6) K(-1) for NaUO3 in the range 298-1273 K; αa = 37.1 × 10(-6) K(-1), αc = 6.2 × 10(-6) K(-1), and αvol = 81.8 × 10(-6) K(-1) for Na4UO5 in the range 298-1073 K; αa = 6.7 × 10(-6) K(-1), αb = 14.4 × 10(-6) K(-1), αc = 26.8 × 10(-6) K(-1), αβ = -7.8 × 10(-6) K(-1), and αvol = -217.6 × 10(-6) K(-1) for Na2U2O7 in the range 298-573 K. The α to β phase transition reported for the last compound above about 600 K was not observed in the present studies, either by high-temperature X-ray diffraction or by differential scanning calorimetry. PMID:24350659

  13. X-ray magneto-optic KERR effect studies of spring magnet heterostructures.

    SciTech Connect

    Kortright, J. B.; Kim, S.-K.; Fullerton, E. E.; Jiang, J. S.; Bader, S. D.

    2000-11-01

    The complex 3-dimensional magnetization reversal behavior of Sin-Co/Fe exchange spring films is used to test the sensitivity of different resonant soft x-ray magneto-optical Kerr effect (MOKE) measurements to changes in longitudinal and transverse moments within the SOIIFe layer and to changes in these moments in depth within the Fe layer. As in the visible MOKE, changes in longitudinal and net transverse moments are resolved by measuring both Kerr rotation and intensity loops in the near the Fe 2p core resonance. These x-ray MOKE signals measured using linear incident polarization are more directly interpreted in terms of longitudinal and transverse moments than are the same signals measured using elliptical polarization. Varying photon energy near the Fe L3line is shown to be an effective means of resolving distinctly different reversal behavior at the top and bottom of the 20 nm thick Fe layer resulting from the strong exchange coupling at the Sin-Co/Fe interface. Measured x-ray MOKE spectra and signals are in qualitative agreement with those calculated using standard magneto-optical formalisms incorporating interference between different layers and measured helicity-dependent magneto-optical constants for Fe.

  14. X-ray magneto-optic Kerr effect studies of spring magnet heterostructures

    SciTech Connect

    Kortright, J.B.; Kim, Sang-Koog; Fullerton, E.E.; Jiang, J.S.; Bader, S.D.

    2000-11-02

    The complex 3-dimensional magnetization reversal behavior of Sm-Co/Fe exchange spring films is used to test the sensitivity of different resonant soft x-ray magneto-optical Kerr effect (MOKE) measurements to changes in longitudinal and transverse moments within the soft Fe layer and to changes in these moments in depth within the Fe layer. As in the visible MOKE, changes in longitudinal and net transverse moments are resolved by measuring both Kerr rotation and intensity loops, respectively, near the Fe 2p core resonance. These x-ray MOKE signals measured using linear incident polarization are more directly interpreted in terms of longitudinal and transverse moments than are the same signals measured using elliptical polarization. Varying photon energy near the Fe L{sub 3} line is shown to be an effective means of resolving distinctly different reversal behavior at the top and bottom of the 20 nm thick Fe layer resulting from the strong exchange coupling at the Sm-Co/Fe interface. Measured x-ray MOKE spectra and signals are in qualitative agreement with those calculated using standard magneto-optical formalisms incorporating interference between different layers and measured helicity-dependent magneto-optical constants for Fe.

  15. The high-field magnet endstation for X-ray magnetic dichroism experiments at ESRF soft X-ray beamline ID32.

    PubMed

    Kummer, K; Fondacaro, A; Jimenez, E; Velez-Fort, E; Amorese, A; Aspbury, M; Yakhou-Harris, F; van der Linden, P; Brookes, N B

    2016-03-01

    A new high-field magnet endstation for X-ray magnetic dichroism experiments has been installed and commissioned at the ESRF soft X-ray beamline ID32. The magnet consists of two split-pairs of superconducting coils which can generate up to 9 T along the beam and up to 4 T orthogonal to the beam. It is connected to a cluster of ultra-high-vacuum chambers that offer a comprehensive set of surface preparation and characterization techniques. The endstation and the beam properties have been designed to provide optimum experimental conditions for X-ray magnetic linear and circular dichroism experiments in the soft X-ray range between 400 and 1600 eV photon energy. User operation started in November 2014. PMID:26917134

  16. Comparison of nuclear magnetic resonance spectroscopy with dual-photon absorptiometry and dual-energy X-ray absorptiometry in the measurement of thoracic vertebral bone mineral density: compressive force versus bone mineral.

    PubMed

    Myers, T J; Battocletti, J H; Mahesh, M; Gulati, M; Wilson, C R; Pintar, F; Reinartz, J

    1994-05-01

    31P nuclear magnetic resonance spectroscopy (NMRS) measurements were made on human T2 and T3 vertebral bodies. The bone mineral content (BMC) of isolated vertebral bodies minus the posterior elements and disks was measured using (1) NMRS on a 3.5 T, 85 mm bore GE Medical Systems NT-150 superconducting spectrometer, (2) a Lunar Corporation DPX-L dual-energy X-ray absorptiometry (DXA) scanner in an anterior-posterior (AP) orientation, (3) a Norland Corporation XR26 DXA scanner, also in an AP direction, and (4) a Norland Corporation model 2600 dual-photon absorptiometry (DPA) densitometer in both the AP and superior-inferior (SI) directions. Vertebral body volumes were measured using a water displacement technique to determine volume bone mineral densities (VBMD). They were then compressed to failure using an electrohydraulic testing device, followed by ashing in a muffle furnace at 700 degrees C for 18 h. Correlations of BMC between NMRS and DPA, DXA and ashing were excellent (0.96 < or = r < or = 0.99); in a one-way analysis of variance (ANOVA) test, means were not statistically different at a p level of 0.757. The correlations of VBMD between NMRS and the other methods were not as good (0.83 < or = r < or = 0.95); in a one-way ANOVA test, means were not statistically different at a p level of 0.089. BMC was a better predictor of ultimate compressive failure than VBMD for all six methods. For NMRS, the regression coefficient for BMC was r2 = 0.806, compared with r2 = 0.505 for VBMD. NMRS may prove an alternative to present methods of determining bone mineral. PMID:8069051

  17. A simulation of X-ray shielding for a superconducting electron cyclotron resonance ion source

    SciTech Connect

    Park, Jin Yong; Won, Mi-Sook; Lee, Byoung-Seob; Yoon, Jang-Hee; Choi, Seyong; Ok, Jung-Woo; Choi, Jeong-Sik; Kim, Byoung-Chul

    2014-02-15

    It is generally assumed that large amounts of x-rays are emitted from the ion source of an Electron Cyclotron Resonance (ECR) instrument. The total amount of x-rays should be strictly limited to avoid the extra heat load to the cryostat of the superconducting ECR ion source, since they are partly absorbed by the cold mass into the cryostat. A simulation of x-ray shielding was carried out to determine the effective thickness of the x-ray shield needed via the use of Geant4. X-ray spectra of the 10 GHz Nanogan ECR ion source were measured as a function of the thickness variation in the x-ray shield. The experimental results were compared with Geant4 results to verify the effectiveness of the x-ray shield. Based on the validity in the case of the 10 GHz ECR ion source, the x-ray shielding results are presented by assuming the spectral temperature of the 28 GHz ECR ion source.

  18. On the maximum accretion luminosity of magnetized neutron stars: connecting X-ray pulsars and ultraluminous X-ray sources

    NASA Astrophysics Data System (ADS)

    Mushtukov, Alexander A.; Suleimanov, Valery F.; Tsygankov, Sergey S.; Poutanen, Juri

    2015-12-01

    We study properties of luminous X-ray pulsars using a simplified model of the accretion column. The maximal possible luminosity is calculated as a function of the neutron star (NS) magnetic field and spin period. It is shown that the luminosity can reach values of the order of 1040 erg s-1 for the magnetar-like magnetic field (B ≳ 1014 G) and long spin periods (P ≳ 1.5 s). The relative narrowness of an area of feasible NS parameters which are able to provide higher luminosities leads to the conclusion that L ≃ 1040 erg s-1 is a good estimate for the limiting accretion luminosity of an NS. Because this luminosity coincides with the cut-off observed in the high-mass X-ray binaries luminosity function which otherwise does not show any features at lower luminosities, we can conclude that a substantial part of ultraluminous X-ray sources are accreting neutron stars in binary systems.

  19. X-ray magnetic circular dichroism and x-ray absorption spectroscopy of novel magnetic thin films

    SciTech Connect

    Brewer, M.A.; Ju, H.L.; Krishnan, K.M.

    1997-04-01

    The optimization of the magnetic properties of materials for a wide range of applications requires a dynamic iteration between synthesis, property measurements and characterization at appropriate length scales. The authors interest arises both from the increased appreciation of the degree to which magnetic properties can be influenced by tailored microstructures and the ability to characterize them by x-ray scattering/dichroism techniques. Preliminary results of this work at the ALS on `giant` moment in {alpha}{double_prime}-Fe{sub 16}N{sub 2} and `colossal` magnetoresistance in manganite perovskites is presented here. It has recently been claimed that {alpha}{double_prime}-Fe{sub 16}N{sub 2} possesses a giant magnetization of 2.9 T ({approximately}2300 emu/cc) when grown on lattice-matched In{sub 0.2}Ga{sub 0.8}As(001) and Fe/GaAs(001). However, attempts at growth on simpler substrates have resulted in only a modest enhancement in moment and often in multiphase mixtures. Theoretical calculations based on the band structure of Fe{sub 16}N{sub 2} predict values for the magnetization around 2.3 T ({approximately}1780 emu/cc), well below Sugita`s claims, but consistent with the magnetization reported by several other workers. Using appropriate sum rules applied to the integrated MCD spectrum, they hope to determine the magnetic moment of the iron species in the {alpha}{double_prime}-Fe{sub 16}N{sub 2} films and other phases and resolve the orbital and spin contributions to the moment. There is also rapidly growing interest in the `colossal magnetoresistance` effect observed in manganese oxides for both fundamental and commercial applications. To address some of these issues the authors have measured the electron energy loss spectra (EELS) of manganese perovskites at room temperature.

  20. X-ray scattering study of pyrochlore iridates: Crystal structure, electronic, and magnetic excitations

    NASA Astrophysics Data System (ADS)

    Clancy, J. P.; Gretarsson, H.; Lee, E. K. H.; Tian, Di; Kim, J.; Upton, M. H.; Casa, D.; Gog, T.; Islam, Z.; Jeon, Byung-Gu; Kim, Kee Hoon; Desgreniers, S.; Kim, Yong Baek; Julian, S. J.; Kim, Young-June

    2016-07-01

    We have investigated the structural, electronic, and magnetic properties of the pyrochlore iridates Eu2Ir2O7 and Pr2Ir2O7 using a combination of resonant elastic x-ray scattering, x-ray powder diffraction, and resonant inelastic x-ray scattering (RIXS). The structural parameters of Eu2Ir2O7 have been examined as a function of temperature and applied pressure, with a particular emphasis on regions of the phase diagram where electronic and magnetic phase transitions have been reported. We find no evidence of crystal symmetry change over the range of temperatures (˜6 to 300 K) and pressures (˜0.1 to 17 GPa) studied. We have also investigated the electronic and magnetic excitations in single-crystal samples of Eu2Ir2O7 and Pr2Ir2O7 using high-resolution Ir L3-edge RIXS. In spite of very different ground state properties, we find that these materials exhibit qualitatively similar excitation spectra, with crystal field excitations at ˜3 -5 eV, spin-orbit excitations at ˜0.5 -1 eV, and broad low-lying excitations below ˜0.15 eV. In single-crystal samples of "Eu-rich" Eu2Ir2O7 (found to possess an actual stoichiometry of Eu2.18Ir1.82O7.06 ) we observe highly damped magnetic excitations at ˜45 meV, which display significant momentum dependence. We compare these results with recent dynamical structure factor calculations.

  1. Imaging nanoscale magnetic structures with polarized soft x-ray photons

    SciTech Connect

    Fischer, P.; Im, M.-Y.

    2010-01-18

    Imaging nanoscale magnetic structures and their fast dynamics is scientifically interesting and technologically of highest relevance. The combination of circularly polarized soft X-ray photons which provide a strong X-ray magnetic circular dichroism effect at characteristic X-ray absorption edges, with a high resolution soft X-ray microscope utilizing Fresnel zone plate optics allows to study in a unique way the stochastical behavior in the magnetization reversal process of thin films and the ultrafast dynamics of magnetic vortices and domain walls in confined ferromagnetic structures. Future sources of fsec short and high intense soft X-ray photon pulses hold the promise of magnetic imaging down to fundamental magnetic length and time scales.

  2. Measurement of the high energy component of the x-ray spectra in the VENUS electron cyclotron resonance ion source

    SciTech Connect

    Leitner, D.; Benitez, J. Y.; Lyneis, C. M.; Todd, D. S.; Ropponen, T.; Ropponen, J.; Koivisto, H.; Gammino, S.

    2008-03-15

    High performance electron cyclotron resonance (ECR) ion sources, such as VENUS (Versatile ECR for NUclear Science), produce large amounts of x-rays. By studying their energy spectra, conclusions can be drawn about the electron heating process and the electron confinement. In addition, the bremsstrahlung from the plasma chamber is partly absorbed by the cold mass of the superconducting magnet, adding an extra heat load to the cryostat. Germanium or NaI detectors are generally used for x-ray measurements. Due to the high x-ray flux from the source, the experimental setup to measure bremsstrahlung spectra from ECR ion sources is somewhat different from that for the traditional nuclear physics measurements these detectors are generally used for. In particular, the collimation and background shielding can be problematic. In this paper, we will discuss the experimental setup for such a measurement, the energy calibration and background reduction, the shielding of the detector, and collimation of the x-ray flux. We will present x-ray energy spectra and cryostat heating rates depending on various ion source parameters, such as confinement fields, minimum B-field, rf power, and heating frequency.

  3. Extracting paramagnon excitations from resonant inelastic x-ray scattering experiments

    NASA Astrophysics Data System (ADS)

    Lamsal, Jagat; Montfrooij, Wouter

    2016-06-01

    Resonant x-ray scattering experiments on high-temperature superconductors and related cuprates have revealed the presence of intense paramagnon scattering at high excitation energies, of the order of several hundred meV. The excitation energies appear to show very similar behavior across all compounds, ranging from magnetically ordered, via superconductors, to heavy fermion systems. However, we argue that this apparent behavior has been inferred from the data through model fitting which implicitly imposes such similarities. Using model fitting that is free from such restrictions, we show that the paramagnons are not nearly as well defined as has been asserted previously, and that some paramagnons might not represent propagating excitations at all. Our work indicates that the data published previously in the literature will need to be reanalyzed with proper models.

  4. Innovative uses of X-ray FEL and the pulsed magnets: High magnetic field X-ray scattering studies on quantum materials

    NASA Astrophysics Data System (ADS)

    Jang, H.; Nojiri, H.; Gerber, S.; Lee, W.-S.; Zhu, D.; Lee, J.-S.; Kao, C.-C.

    X-ray scattering under high magnetic fields provides unique opportunities for solving many scientific puzzles in quantum materials, such as strongly correlated electron systems. Incorporating high magnetic field capability presents serious challenges at an x-ray facility, including the limitation on the maximum magnetic field even with a DC magnet (up to ~20 Tesla), expensive cost in development, radiation damage, and limited flexibility in the experimental configuration. These challenges are especially important when studying the symmetry broken state induced by the high magnetic field are necessary, for example, exploring intertwined orders between charge density wave (CDW) and high Tc superconductivity. Moreover, a gap in magnetic field strengths has led to many discrepancies and puzzling issues for understanding strongly correlated systems - is a CDW competing or more intimately intertwined with high-temperature superconductivity. To bridge this gap and resolve these experimental discrepancies, one needs an innovative experimental approach. Here, we will present a new approach to x-ray scattering under high magnetic field up to 28 Teals by taking advantage of brilliant x-ray free electron laser (FEL). The FEL generates sufficiently high photon flux for single shot x-ray scattering experiment. In this talk, we will also present the first demonstration about the field induced CDW order in YBCO Ortho-VIII with 28 Tesla, which show the totally unexpected three-dimensional behavior.

  5. Magnetic fields in X-ray emitting A-type stars

    NASA Astrophysics Data System (ADS)

    Schröder, C.; Hubrig, S.; Schmitt, J. H. M. M.

    2008-04-01

    A common explanation for the observed X-ray emission of A-type stars is the presence of a hidden late-type companion. While this hypothesis can be shown to be correct in some cases, there is also evidence suggesting that low-mass companions cannot be the proper cause for the observed X-ray activity in all cases. Babel and Montmerle (1997) presented a theoretical framework to explain the X-ray emission from magnetic Ap/Bp stars, focusing on the A0p star IQ Aur. We test whether this theoretical model is capable of explaining the observed X-ray emissions. We present observations of 13 A-type stars that have been associated with X-ray emission detected by ROSAT. To determine the mean longitudinal magnetic field strength we measured the circular polarization in the wings of the Balmer lines using FORS 1. Although the emission of those objects with magnetic fields does fit the prediction of the Babel & Montmerle model, not all X-ray detections are related to the presence of a magnetic field. Additionally, the strengths of magnetic fields do not correlate with the X-ray luminosity and thus the magnetically-confined wind shock model cannot explain the X-ray emission from all investigated stars.

  6. Topological X-Rays Revisited

    ERIC Educational Resources Information Center

    Lynch, Mark

    2012-01-01

    We continue our study of topological X-rays begun in Lynch ["Topological X-rays and MRI's," iJMEST 33(3) (2002), pp. 389-392]. We modify our definition of a topological magnetic resonance imaging and give an affirmative answer to the question posed there: Can we identify a closed set in a box by defining X-rays to probe the interior and without…

  7. Neutron and X-Ray Diffraction Studies of Magnetic Order in Uranium-Based Heavy Fermion Superconductors

    NASA Astrophysics Data System (ADS)

    Lussier, Jean-Guy

    UPt_3, URu_2 Si_2, UNi_2 Al_3 and UPd_2 Al_3 form a special group among the uranium alloys because they exhibit heavy fermion character, magnetic order and superconductivity. This main interest in the study of this group of compounds resides in the simultaneous occurrence of magnetism and superconductivity at low temperature. Such a state could potentially involve an unconventional superconducting pairing mechanism, different from that contained in standard BCS theory. In this thesis, the magnetic states of three of these materials (URu_2Si _2, UNi_2Al _3 and UPd_2Al _3) is investigated with neutron and the relatively new resonant magnetic X-ray scattering techniques. The work presented here on URu_2Si _2 follows an earlier effort that demonstrated the applicabililty of the resonant X-ray technique to this weak magnetic system. Access to reciprocal space was extended in order to confirm the multipolar form of the resonant X-ray cross-section and to explore the limits of the technique compared to neutron scattering. The situation with the newly discovered UNi_2Al _3 and UPd_2Al _3 was different since their magnetic structure and phases needed first to be established. This task was achieved using two magnetic probes (neutron and X-ray scattering). Several magnetic order parameters in the normal and in the superconducting phase were also measured. The incommensurate magnetic order found in UNi_2Al_3 by neutron scattering constitutes the first observation of long range order in this compound. Other measurements on this compound provided some clues about the evolution of the magnetic structure in high magnetic fields.

  8. Magnetic ordering and transitions of EuSe studied by x-ray diffraction

    NASA Astrophysics Data System (ADS)

    Díaz, B.; Granado, E.; Abramof, E.; Torres, L.; Lechner, R. T.; Springholz, G.; Bauer, G.

    2010-05-01

    The magnetic phase diagram and thermal expansion of EuSe is revisited using a high-quality 3200-Å -thick epitaxial film grown over a (111)BaF2 substrate. Resonant magnetic x-ray diffraction experiments reveal a highly hysteretic magnetic phase diagram between 1.8 and TN˜4.7K , in which two antiferromagnetic phases with propagation vectors k⃗I=[(1)/(4),(1)/(4),-(1)/(4)] (represented by ↑↑↓↓ ) and k⃗II=[(1)/(2),(1)/(2),-(1)/(2)](↑↓↑↓) are observed. In addition, a defective phase with k⃗III=[h,h,-h]((1)/(4)x-ray diffraction experiments show unit-cell hysteretic distortions that correlate with the transitions to the different magnetic phases existing below TN .

  9. Probing symmetry and symmetry breaking in resonant soft-x-ray fluorescence spectra of molecules

    SciTech Connect

    Glans, P.; Gunnelin, K.; Guo, J.

    1997-04-01

    Conventional non-resonant soft X-ray emission brings about information about electronic structure through its symmetry and polarization selectivity, the character of which is governed by simple dipole rules. For centro-symmetric molecules with the emitting atom at the inversion center these rules lead to selective emission through the required parity change. For the more common classes of molecules which have lower symmetry or for systems with degenerate core orbitals (delocalized over identical sites), it is merely the local symmetry selectivity that provides a probe of the local atomic orbital contribution to the molecular orbital. For instance, in X-ray spectra of first row species the intensities essentially map the p-density at each particular atomic site, and, in a molecular orbital picture, the contribution of the local p-type atomic orbitals in the LCAO description of the molecular orbitals. The situation is different for resonant X-ray fluorescence spectra. Here strict parity and symmetry selectivity gives rise to a strong frequency dependence for all molecules with an element of symmetry. In addition to symmetry selectivity the strong frequency dependence of resonant X-ray emission is caused by the interplay between the shape of a narrow X-ray excitation energy function and the lifetime and vibrational broadenings of the resonantly excited core states. This interplay leads to various observable effects, such as linear dispersion, resonance narrowing and emission line (Stokes) doubling. Also from the point of view of polarization selectivity, the resonantly excited X-ray spectra are much more informative than the corresponding non-resonant spectra. Examples are presented for nitrogen, oxygen, and carbon dioxide molecules.

  10. Resonant X-Ray Scattering Studies of Charge Order in Cuprates

    NASA Astrophysics Data System (ADS)

    Comin, Riccardo; Damascelli, Andrea

    2016-03-01

    X-ray techniques have been used for more than a century to study the atomic and electronic structure in practically any type of material. The advent of correlated electron systems, in particular complex oxides, brought about new scientific challenges and opportunities for the advancement of conventional X-ray methods. In this context, the need for new approaches capable of selectively sensing new forms of orders involving all degrees of freedom -- charge, orbital, spin, and lattice -- paved the way for the emergence and success of resonant X-ray scattering, which has become an increasingly popular and powerful tool for the study of electronic ordering phenomena in solids. We review the recent resonant X-ray scattering breakthroughs in the copper oxide high-temperature superconductors, in particular regarding the phenomenon of charge order, a broken-symmetry state occurring when valence electrons self-organize into periodic structures. After a brief historical perspective on charge order, we outline the milestones in the development of resonant X-ray scattering as well as the basic theoretical formalism underlying its unique capabilities. The rest of the review focuses on the recent contributions of resonant scattering to the advancements in our description and understanding of charge order. To conclude, we propose a series of present and upcoming challenges and discuss the future outlook for this technique.

  11. Molecular orientation in soft matter thin films studied by resonant soft X-ray reflectivity

    SciTech Connect

    Mezger, Markus; Jerome, Blandine; Kortright, Jeffrey B.; Valvidares, Manuel; Gullikson, Eric; Giglia, Angelo; Mahne, Nicola; Nannarone, Stefano

    2011-01-12

    We present a technique to study depth profiles of molecular orientation in soft matter thin films with nanometer resolution. The method is based on dichroism in resonant soft X-ray reflectivity using linear s- and p-polarization. It combines the chemical sensitivity of Near-Edge X-ray Absorption Fine Structure spectroscopy to specific molecular bonds and their orientation relative to the polarization of the incident beam with the precise depth profiling capability of X-ray reflectivity. We demonstrate these capabilities on side chain liquid crystalline polymer thin films with soft X-ray reflectivity data at the carbon K edge. Optical constants of the anisotropic refractive index ellipsoid were obtained from a quantitative analysis using the Berreman formalism. For films up to 50 nm thickness we find that the degree of orientation of the long axis exhibits no depth variation and isindependent of the film thickness.

  12. Lifetime-vibrational interference effects in resonantly excited x-ray emission spectra of CO

    SciTech Connect

    Skytt, P.; Glans, P.; Gunnelin, K.

    1997-04-01

    The parity selection rule for resonant X-ray emission as demonstrated for O{sub 2} and N{sub 2} can be seen as an effect of interference between coherently excited degenerate localized core states. One system where the core state degeneracy is not exact but somewhat lifted was previously studied at ALS, namely the resonant X-ray emission of amino-substituted benzene (aniline). It was shown that the X-ray fluorescence spectrum resulting from excitation of the C1s at the site of the {open_quotes}aminocarbon{close_quotes} could be described in a picture separating the excitation and the emission processes, whereas the spectrum corresponding to the quasi-degenerate carbons could not. Thus, in this case it was necessary to take interference effects between the quasi-degenerate intermediate core excited states into account in order to obtain agreement between calculations and experiment. The different vibrational levels of core excited states in molecules have energy splittings which are of the same order of magnitude as the natural lifetime broadening of core excitations in the soft X-ray range. Therefore, lifetime-vibrational interference effects are likely to appear and influence the band shapes in resonant X-ray emission spectra. Lifetime-vibrational interference has been studied in non-resonant X-ray emission, and in Auger spectra. In this report the authors discuss results of selectively excited soft X-ray fluorescence spectra of molecules, where they focus on lifetime-interference effects appearing in the band shapes.

  13. Critical Reexamination of Resonant Soft X-Ray Bragg Forbidden Reflections in Magnetite

    SciTech Connect

    Wilkins, S.B.; Di Matteo, S.; Beale, T.A.W.; Joly, Y.; Mazzoli, C.; Hatton, P.D.; Bencok, P.; Yakhou, F.; Brabers, V.A.M.

    2009-05-01

    Magnetite, Fe{sub 3}O{sub 4}, displays a highly complex low-temperature crystal structure that may be charge and orbitally ordered. Many of the recent experimental claims of such ordering rely on resonant soft x-ray diffraction at the oxygen K and iron L edges. We have reexamined this system and undertaken soft x-ray diffraction experiments on a high-quality single crystal. Contrary to previous claims in the literature, we show that the intensity observed at the Bragg forbidden (001/2){sub c} reflection can be explained purely in terms of the low-temperature structural displacements around the resonant atoms. This does not necessarily mean that magnetite is not charge or orbitally ordered but rather that the present sensitivity of resonant soft x-ray experiments does not allow conclusive demonstration of such ordering.

  14. Studying Nanoscale Magnetism and its Dynamics with Soft X-ray Microscopy

    SciTech Connect

    Mccall, Monnikue M; Fischer, Peter

    2008-05-01

    Magnetic soft X-ray microscopy allows for imaging magnetic structures at a spatial resolution down to 15nm and a time resolution in the sub-100ps regime. Inherent elemental specificity can be used to image the magnetic response of individual components such as layers in multilayered systems. This review highlights current achievements and discusses the future potential of magnetic soft X-ray microscopy at fsec X-ray sources where snapshot images of ultrafast spin dynamics with a spatial resolution below 10nm will become feasible.

  15. X-ray effects in charge-ordered manganites: A magnetic mechanism of persistent photoconductivity

    SciTech Connect

    Keimer, B.; Casa, D.; Kiryukhin, V.; Saleh, O.A.; Hill, J.P.; Tomioka, Y.; Tokura, Y. |

    1998-12-31

    Charge-ordered manganites of composite Pr{sub 1{minus}x}(Ca{sub 1{minus}y}Sr{sub y}){sub x}MnO{sub 3} exhibit persistent photoconductivity when illuminated by x-rays. The authors review transport and x-ray diffraction data as functions of x-ray exposure, magnetic field, and temperature which shed light on the origin of this unusual behavior. The experimental evidence suggests that the mechanism primarily involves a ferromagnetic polarization of local spins by hot electrons generated by the x-rays.

  16. Time-Resolved X-Ray Magnetic Circular Dichroism - A Selective Probe of Magnetization Dynamics on Nanosecond Timescales

    NASA Astrophysics Data System (ADS)

    Pizzini, Stefania; Vogel, Jan; Bonfim, Marlio; Fontaine, Alain

    Many synchrotron radiation techniques have been developed in the last 15 years for studying the magnetic properties of thin-film materials. The most attractive properties of synchrotron radiation are its energy tunability and its time structure. The first property allows measurements in resonant conditions at an absorption edge of each of the magnetic elements constituting the probed sample, and the latter allows time-resolved measurements on subnanosecond timescales. In this review, we introduce some of the synchrotron-based techniques used for magnetic investigations. We then describe in detail X-ray magnetic circular dichroism (XMCD) and how time-resolved XMCD studies can be carried out in the pump-probe mode. Finally, we illustrate some applications to magnetization reversal dynamics in spin valves and tunnel junctions, using fast magnetic field pulses applied along the easy magnetization axis of the samples. Thanks to the element-selectivity of X-ray absorption spectroscopy, the magnetization dynamics of the soft (Permalloy) and the hard (cobalt) layers can be studied independently. In the case of spin valves, this allowed us to show that two magnetic layers that are strongly coupled in a static regime can become uncoupled on nanosecond timescales.Present address: Universidade Federal do Paraná, Centro Politécnico CP 19011, Curitiba - PR CEP 81531-990, Brazil

  17. Neptunium multipoles and resonant x-ray Bragg diffraction by neptunium dioxide (NpO2)

    NASA Astrophysics Data System (ADS)

    Lovesey, S. W.; Detlefs, C.; Rodríguez-Fernández, A.

    2012-06-01

    The low-temperature ordered state of neptunium dioxide (NpO2) remains enigmatic. After decades of experimental and theoretical efforts, long-range order of a time-odd (magnetic) high-order atomic multipole moment is now generally considered to be the fundamental order parameter, the most likely candidate being a magnetic triakontadipole (rank 5). To date, however, direct experimental observation of the primary order parameter remains outstanding. In the light of new experimental findings, we re-examine the effect of crystal symmetry on the atomic multipoles and the resulting x-ray resonant scattering signature. Our simulations use the crystallographic point group \\bar {3}m (D3d), because corresponding magnetic groups \\bar {3}{m}^{\\prime}, {\\bar {3}}^{\\prime}{m}^{\\prime} and {\\bar {3}}^{\\prime}m are shown by us to be at odds with a wealth of experimental results. In addition to the previously observed (secondary) quadrupole order, we derive expressions for higher-order multipoles that might be observed in future experiments. In particular, magnetic octupole moments are predicted to contribute to Np M2,3 and L2,3 resonant scattering via E2-E2 events. The Lorentzian-squared lineshape observed at the M4 resonance is shown to be the result of the anisotropy of the 3p3/2 core levels. Quantitative comparison of our calculations to the measured data yields a core-hole width Γ = 2.60(7) eV and a core-state exchange energy \\vert \\varepsilon (\\frac{1}{2})\\vert =0.7 6(2) eV.

  18. Neptunium multipoles and resonant x-ray Bragg diffraction by neptunium dioxide (NpO2).

    PubMed

    Lovesey, S W; Detlefs, C; Rodríguez-Fernández, A

    2012-06-27

    The low-temperature ordered state of neptunium dioxide (NpO(2)) remains enigmatic. After decades of experimental and theoretical efforts, long-range order of a time-odd (magnetic) high-order atomic multipole moment is now generally considered to be the fundamental order parameter, the most likely candidate being a magnetic triakontadipole (rank 5). To date, however, direct experimental observation of the primary order parameter remains outstanding. In the light of new experimental findings, we re-examine the effect of crystal symmetry on the atomic multipoles and the resulting x-ray resonant scattering signature. Our simulations use the crystallographic point group ̅3m (D(3d)), because corresponding magnetic groups ̅3m', ̅3'm', and ̅3'm are shown by us to be at odds with a wealth of experimental results. In addition to the previously observed (secondary) quadrupole order, we derive expressions for higher-order multipoles that might be observed in future experiments. In particular, magnetic octupole moments are predicted to contribute to Np M(2,3) and L(2,3) resonant scattering via E2–E2 events. The Lorentzian-squared lineshape observed at the M(4) resonance is shown to be the result of the anisotropy of the 3p(3/2) core levels. Quantitative comparison of our calculations to the measured data yields a core–hole width Γ = 2.60(7) eV and a core-state exchange energy [absolute value]ε(1/2)[absolute value] = 0.76(2) eV. PMID:22652978

  19. Nuclear resonant inelastic X-ray scattering at high pressure and low temperature

    SciTech Connect

    Bi, Wenli; Zhao, Jiyong; Lin, Jung -Fu; Jia, Quanjie; Hu, Michael Y.; Jin, Changqing; Ferry, Richard; Yang, Wenge; Struzhkin, Viktor; Alp, E. Ercan

    2015-01-01

    In this study, a new synchrotron radiation experimental capability of coupling nuclear resonant inelastic X-ray scattering with the cryogenically cooled high-pressure diamond anvil cell technique is presented. The new technique permits measurements of phonon density of states at low temperature and high pressure simultaneously, and can be applied to studies of phonon contribution to pressure- and temperature-induced magnetic, superconducting and metal–insulator transitions in resonant isotope-bearing materials. In this report, a pnictide sample, EuFe2As2, is used as an example to demonstrate this new capability at beamline 3-ID of the Advanced Photon Source, Argonne National Laboratory. A detailed description of the technical development is given. The Fe-specific phonon density of states and magnetism from the Fe sublattice in Eu57Fe2As2 at high pressure and low temperature were derived by using this new capability.

  20. Resonant x-ray scattering study of SmNi_2Ge_2

    NASA Astrophysics Data System (ADS)

    Islam, Zahirul; Lang, J.; Vasiliu-Doloc, L.; Srajer, G.; Canfield, P.

    2001-03-01

    Recently it was established that a strong Fermi-surface nesting is responsible for the magnetic ordering vector in the rare-earth nickel germanide (RNi_2Ge_2) compounds [Z. Islam et al. Phys. Rev. Lett. 83, 2817 (1999)]. In this work, using the x-ray resonant exchange scattering technique, we confirm that the magnetic structures of SmNi_2Ge2 are also in accordance with nesting. This material orders in an incommensurate antiferromagnetic (AF) structure characterized by a single propagation vector, q=(0 0 q_z). The value of qz is temperature dependent and approaches ~0.775 r.l.u. near TN = 17.8 K. Below Tt = 11.8 K, the AF structure is characterized by qz = 0.79±0.002, indicating a long-period ordered phase. Both ordered phases are consistent with a basal-plane helical structure. The temperature dependence of the helical structures is consistent with the theory of `superzone' gap. In addition, a strong quadrupolar resonance below the Sm L_III-edge was observed and compared to recent theoretical work. (The work at APS was supported by the U.S. DOE under contract no. W-31-109-Eng-38 and, in part, by the State of Illinois under HECA.)

  1. Resonant photo-pumping x-ray-laser scheme using intense characteristic x rays for water-window radiation generation

    SciTech Connect

    Kawachi, Tetsuya; Kato, Yoshiaki

    2011-12-15

    A line pair for a resonant photo-pumping x-ray-laser scheme is proposed in which the wavelength matching between the aluminum K{alpha}{sub 2} line ({lambda}= 0.833 95 nm) and the 2p{sup 6}-(2p{sub 1/2},4d{sub 3/2}){sub 1} transition of the neonlike zinc ions ({lambda}= 0.834 00 nm) is used. The population kinetics code of the neonlike zinc ions in plasma under irradiation of the aluminum K{alpha} line shows that substantial amplification gain can be generated in the transition of (2p{sub 1/2},3p{sub 1/2}){sub 0}-(2p{sub 1/2},4d{sub 3/2}){sub 1} at a wavelength of 3.5 nm. We also investigate the experimental arrangement of this scheme, which implies that this scheme is feasible with the present ultra-short-pulse-laser technology.

  2. X-Ray Comb Generation from Nuclear-Resonance-Stabilized X-Ray Free-Electron Laser Oscillator for Fundamental Physics and Precision Metrology

    SciTech Connect

    Adams, B. W.; Kim, K. -J.

    2015-03-31

    An x-ray free-electron laser oscillator (XFELO) is a next-generation x-ray source, similar to free-electron laser oscillators at VUV and longer wavelengths but using crystals as high-reflectivity x-ray mirrors. Each output pulse from an XFELO is fully coherent with high spectral purity. The temporal coherence length can further be increased drastically, from picoseconds to microseconds or even longer, by phase-locking successive XFELO output pulses, using the narrow nuclear resonance lines of nuclei such as Fe-57 as a reference. We show that the phase fluctuation due to the seismic activities is controllable and that due to spontaneous emission is small. The fluctuation of electron-bunch spacing contributes mainly to the envelope fluctuation but not to the phase fluctuation. By counting the number of standing-wave maxima formed by the output of the nuclear-resonance-stabilized (NRS) XFELO over an optically known length, the wavelength of the nuclear resonance can be accurately measured, possibly leading to a new length or frequency standard at x-ray wavelengths. A NRS-XFELO will be an ideal source for experimental x-ray quantum optics as well as other fundamental physics. The technique can be refined for other, narrower resonances such as Ta-181 or Sc-45.

  3. Magnetic fields in A-type stars associated with X-ray emission

    NASA Astrophysics Data System (ADS)

    Schröder, C.; Hubrig, S.; Schmitt, J. H. M. M.

    2008-06-01

    A common explanation for the observed X-ray emission of A-type stars is the presence of a hidden late-type companion. While this assumption can be shown to be correct in some cases, a number of lines of evidence suggests that low-mass companions cannot be the correct cause for the observed activity in all cases. A model explains the X-ray emission for magnetic Ap/Bp stars, focusing on the A0p star IQ Aur. In this paper we test whether this theoretical model is able to explain the observed X-ray emission. We present the observations of 13 A-type stars that have been associated with X-ray emission detected by ROSAT. To determine the mean longitudinal magnetic field strength we measured the circular polarization in the wings of the Balmer lines using FORS1. Although the emission of those objects that possess magnetic fields fits the prediction of the Babel and Montmerle model, not all X-ray detections are connected to the presence of a magnetic field. Additionally, the measured magnetic fields do not correlate with the X-ray luminosity. Accordingly, the magnetically confined wind shock model cannot explain the X-ray emission from all the presented stars.

  4. A long-lived coronal X-ray arcade. [force-free magnetic field analysis

    NASA Technical Reports Server (NTRS)

    Mcguire, J. P.; Tandberg-Hanssen, E.; Krall, K. R.; Wu, S. T.; Smith, J. B., Jr.; Speich, D. M.

    1977-01-01

    A large, long-lived, soft X-ray emitting arch system observed during a Skylab mission is analyzed. The supposition is that these arches owe their stability to the stable coronal magnetic-field configuration. A global constant alpha force-free magnetic field analysis, is used to describe the arches which stayed in the same approximate position for several solar rotations. A marked resemblance is noted between the theoretical magnetic field configuration and the observed X-ray emmitting feature.

  5. K{beta} resonant x-ray emission spectra in MnF{sub 2}

    SciTech Connect

    Taguchi, M.; Parlebas, J. C.; Uozumi, T.; Kotani, A.; Kao, C.-C.

    2000-01-15

    We report experimental and theoretical results on Mn K{beta} resonant x-ray emission spectra (K{beta} RXES) at the pre-edge region of K-edge x-ray absorption spectroscopy in a powdered MnF{sub 2} sample. The experimental results are studied theoretically in terms of coherent second-order optical process, using a MnF{sub 6}{sup -4} cluster model with the effects of intra-atomic multiplet coupling and interatomic hybridization in the space of three configurations and taking into account both the Mn 1s-3d quadrupole excitation and the Mn 1s-4p dipole excitation. The agreement between theory and experiment is good. Moreover, we show that if the sample is a single crystal the resonant x-ray emission spectroscopy caused by the quadrupole excitation has a strong sensitivity to the angle of the incident photon. (c) 2000 The American Physical Society.

  6. X-rays from magnetic intermediate mass Ap/Bp stars

    NASA Astrophysics Data System (ADS)

    Robrade, Jan

    2016-09-01

    The X-ray emission of magnetic intermediate mass Ap/Bp stars is reviewed and put into context of intrinsic as well as extrinsic hypotheses for its origin. New X-ray observations of Ap/Bp stars are presented and combined with an updated analysis of the available datasets, providing the largest sample of its type that is currently available. In the studied stars the X-ray detections are found predominantly among the more massive, hotter and more luminous targets. Their X-ray properties are quite diverse and beside strong soft X-ray emission significant magnetic activity is frequently present. While a connection between more powerful winds and brighter X-ray emission is expected in intrinsic models, the scatter in X-ray luminosity at given bolometric luminosity is so far unexplained and several observational features like X-ray light curves and flaring, luminosity distributions and spectral properties are often similar to those of low-mass stars. It remains to be seen if these features can be fully reproduced by magnetospheres of intermediate mass stars. The article discusses implications for magnetically confined wind-shock models (MCWS) and stellar magnetospheres under the assumption that the intrinsic model is applicable, but also examines the role of possible companions. Further, related magnetospheric phenomena are presented and an outlook on future perspectives is given.

  7. Uranium Hydridoborates: Synthesis, Magnetism, and X-ray/Neutron Diffraction Structures.

    PubMed

    Braunschweig, H; Gackstatter, A; Kupfer, T; Radacki, K; Franke, S; Meyer, K; Fucke, K; Lemée-Cailleau, M-H

    2015-08-17

    While uranium hydridoborate complexes containing the [BH4](-) moiety have been well-known in the literature for many years, species with functionalized borate centers remained considerably rare. We were now able to prepare several uranium hydridoborates (1-4) with amino-substituted borate moieties with high selectivity by smooth reaction of [Cp*2UMe2] (Cp* = C5Me5) and [Cp'2UMe2] (Cp' = 1,2,4-tBu3C5H2) with the aminoborane H2BN(SiMe3)2. A combination of nuclear magnetic resonance spectroscopy, deuteration experiments, magnetic SQUID measurements, and X-ray/neutron diffraction studies was used to verify the anticipated molecular structures and oxidation states of 1-4 and helped to establish a linear tridentate coordination mode of the borate anions. PMID:26247295

  8. Evidence for Resonance Scattering in the X-ray Spectrum of Zeta Puppis

    NASA Technical Reports Server (NTRS)

    Leutenegger, Maurice

    2008-01-01

    We present XMM-Newton Reflection Grating Spectrometer observations of pairs of X-ray emission line profiles from the 0 star Zeta Pup that originate from the same He-like ion. The two profiles in each pair have different shapes and cannot both be consistently fit by models assuming the same wind parameters. We show that the differences in profile shape can be accounted for in a model including the effects of resonance scattering, which affects the resonance line in the pair but not the intercombination line. This implies that resonance scattering is also important in single resonance lines, where its effect is difficult to distinguish from a low effective continuum optical depth in the wind. Thus, resonance scattering may help reconcile X-ray line profile shapes with literature mass-loss rates.

  9. Using Resonant Soft X-rays to Reveal Internal Organic Thin Film Structure

    NASA Astrophysics Data System (ADS)

    Gann, Eliot

    This dissertation details the establishment and expansion of resonant soft X-ray scattering techniques to reveal the internal structure of organic thin films. These films are increasingly important in numerous electronic systems, including organic thin film transistors, organic photovoltaics, and organic light emitting diodes. These devices use the electrical properties of polymers to respectively turn on and off conduction, turn light into electricity, and create light. The performance of each of these systems depends critically on their physical structure but unfortunately, traditional techniques fail to adequately characterize that structure. This dissertation will explore the use of soft X-ray scattering to reveal the mesoscale structure or organic electronic devices. This begins with an overview of the field to make the case for soft X-rays being an appropriate and novel tool. Next, to explain how to collect accurate soft X-ray scattering, the development of a new and unique soft X-ray scattering facility will be presented. Having the tools, the next step is to develop scattering theories and models for understanding and correctly analyzing scattering from these complicated devices. This includes development and comparison of analysis techniques and theory to simulate scattering. This simulation system is then used in the development of a theory to understand the novel phenomenon of anisotropic X-ray scattering from isotropic organic samples. Finally, I will describe the development and first use of a method able to simultaneously measure size scales and chemical structure with depth sensitivity in thin films: Grazing Resonant Soft X-ray Scattering. This work provides valuable understanding and tools to the field of materials characterization, opening up new opportunities for principled design of organic electronics.

  10. Electronic Structure in Thin Film Organic Semiconductors Studied using Soft X-ray Emission and Resonant Inelastic X-ray Scattering

    SciTech Connect

    Zhang,Y.; Downes, J.; Wang, S.; Learmonth, T.; Plucinski, L.; Matsuura, A.; McGuinness, C.; Glans, P.; Bernardis, S.; et al.

    2006-01-01

    The electronic structure of thin films of the organic semiconductors copper and vanadyl (VO) phthalocyanine (Pc) has been measured using resonant soft X-ray emission spectroscopy and resonant inelastic X-ray scattering. For Cu-Pc we report the observation of two discrete states near E{sub F}. This differs from published photoemission results, but is in excellent agreement with density functional calculations. For VO-Pc, the vanadyl species is shown to be highly localized. Both dipole forbidden V 3d to V 3d*, and O 2p to V 3d* charge transfer transitions are observed, and explained in a local molecular orbital model.

  11. X-ray magnetic circular dichroism measurements using an X-ray phase retarder on the BM25 A-SpLine beamline at the ESRF

    PubMed Central

    Boada, Roberto; Laguna-Marco, María Ángeles; Gallastegui, Jon Ander; Castro, Germán R.; Chaboy, Jesús

    2010-01-01

    Circularly polarized X-rays produced by a diamond X-ray phase retarder of thickness 0.5 mm in the Laue transmission configuration have been used for recording X-ray magnetic circular dichroism (XMCD) on the bending-magnet beamline BM25A (SpLine) at the ESRF. Field reversal and helicity reversal techniques have been used to carry out the measurements. The performance of the experimental set-up has been demonstrated by recording XMCD in the energy range from 7 to 11 keV. PMID:20400827

  12. Multidimensional Attosecond Resonant X-Ray Spectroscopy of Molecules: Lessons from the Optical Regime

    PubMed Central

    Mukamel, Shaul; Healion, Daniel; Zhang, Yu; Biggs, Jason D.

    2013-01-01

    New free-electron laser and high-harmonic generation X-ray light sources are capable of supplying pulses short and intense enough to perform resonant nonlinear time-resolved experiments in molecules. Valence-electron motions can be triggered impulsively by core excitations and monitored with high temporal and spatial resolution. We discuss possible experiments that employ attosecond X-ray pulses to probe the quantum coherence and correlations of valence electrons and holes, rather than the charge density alone, building on the analogy with existing studies of vibrational motions using femtosecond techniques in the visible regime. PMID:23245522

  13. Resonant inelastic x-ray scattering at the limit of subfemtosecond natural lifetime

    SciTech Connect

    Marchenko, T.; Journel, L.; Marin, T.; Guillemin, R.; Carniato, S.; Simon, M.; Zitnik, M.; Kavcic, M.; Bucar, K.; Mihelic, A.; Hoszowska, J.; Cao, W.

    2011-04-14

    We present measurements of the resonant inelastic x-ray scattering (RIXS) spectra of the CH{sub 3}I molecule in the hard-x-ray region near the iodine L{sub 2} and L{sub 3} absorption edges. We show that dispersive RIXS spectral features that were recognized as a fingerprint of dissociative molecular states can be interpreted in terms of ultrashort natural lifetime of {approx}200 attoseconds in the case of the iodine L-shell core-hole. Our results demonstrate the capacity of the RIXS technique to reveal subtle dynamical effects in molecules with sensitivity to nuclear rearrangement on a subfemtosecond time scale.

  14. Strong higher-order resonant contributions to x-ray line polarization in hot plasmas

    NASA Astrophysics Data System (ADS)

    Shah, Chintan; Amaro, Pedro; Steinbrügge, Rene; Beilmann, Christian; Bernitt, Sven; Fritzsche, Stephan; Surzhykov, Andrey; Crespo López-Urrutia, José R.; Tashenov, Stanislav

    2016-06-01

    We studied angular distributions of x rays emitted in resonant recombination of highly charged iron and krypton ions, resolving dielectronic, trielectronic, and quadruelectronic channels. A tunable electron beam drove these processes, inducing x rays registered by two detectors mounted along and perpendicular to the beam axis. The measured emission asymmetries comprehensively benchmarked full-order atomic calculations. We conclude that accurate polarization diagnostics of hot plasmas can only be obtained under the premise of inclusion of higher-order processes that were neglected in earlier work.

  15. Strong higher-order resonant contributions to x-ray line polarization in hot plasmas.

    PubMed

    Shah, Chintan; Amaro, Pedro; Steinbrügge, Rene; Beilmann, Christian; Bernitt, Sven; Fritzsche, Stephan; Surzhykov, Andrey; Crespo López-Urrutia, José R; Tashenov, Stanislav

    2016-06-01

    We studied angular distributions of x rays emitted in resonant recombination of highly charged iron and krypton ions, resolving dielectronic, trielectronic, and quadruelectronic channels. A tunable electron beam drove these processes, inducing x rays registered by two detectors mounted along and perpendicular to the beam axis. The measured emission asymmetries comprehensively benchmarked full-order atomic calculations. We conclude that accurate polarization diagnostics of hot plasmas can only be obtained under the premise of inclusion of higher-order processes that were neglected in earlier work. PMID:27415199

  16. X-ray-spectroscopy analysis of electron-cyclotron-resonance ion-source plasmas

    SciTech Connect

    Santos, J. P.; Martins, M. C.; Parente, F.; Costa, A. M.; Marques, J. P.; Indelicato, P.

    2010-12-15

    Analysis of x-ray spectra emitted by highly charged ions in an electron-cyclotron-resonance ion source (ECRIS) may be used as a tool to estimate the charge-state distribution (CSD) in the source plasma. For that purpose, knowledge of the electron energy distribution in the plasma, as well as the most important processes leading to the creation and de-excitation of ionic excited states are needed. In this work we present a method to estimate the ion CSD in an ECRIS through the analysis of the x-ray spectra emitted by the plasma. The method is applied to the analysis of a sulfur ECRIS plasma.

  17. Toroidal silicon polarization analyzer for resonant inelastic x-ray scattering.

    PubMed

    Gao, Xuan; Casa, Diego; Kim, Jungho; Gog, Thomas; Li, Chengyang; Burns, Clement

    2016-08-01

    Resonant Inelastic X-ray Scattering (RIXS) is a powerful probe for studying electronic excitations in materials. Standard high energy RIXS measurements do not measure the polarization of the scattered x-rays, which is unfortunate since it carries information about the nature and symmetry of the excitations involved in the scattering process. Here we report the fabrication of thin Si-based polarization analyzers with a double-concave toroidal surface, useful for L-edge RIXS studies in heavier atoms such as the 5-d transition metals. PMID:27587100

  18. Magnetic properties of GdT2Zn20 (T = Fe, Co) investigated by x-ray diffraction and spectroscopy

    DOE PAGESBeta

    J. R. L. Mardegan; Fabbris, G.; Francoual, S.; Veiga, L. S. I.; Strempfer, J.; Haskel, D.; Ribeiro, R. A.; Avila, M. A.; Giles, C.

    2016-01-26

    In this study, we investigate the magnetic and electronic properties of the GdT2Zn20 (T=Fe and Co) compounds using x-ray resonant magnetic scattering (XRMS), x-ray absorption near-edge structure (XANES), and x-ray magnetic circular dichroism (XMCD). The XRMS measurements reveal that GdCo2Zn20 has a commensurate antiferromagnetic spin structure with a magnetic propagation vector →/τ = (12,12,12) below the Néel temperature (TN ~ 5.7 K). Only the Gd ions carry a magnetic moment forming an antiferromagnetic structure with magnetic representation Γ6. For the ferromagnetic GdFe2Zn20 compound, an extensive investigation was performed at low temperature and under magnetic field using XANES and XMCD. Amore » strong XMCD signal of about 12.5% and 9.7% is observed below the Curie temperature (TC ~ 85K) at the Gd L2 and L3 edges, respectively. In addition, a small magnetic signal of about 0.06% of the jump is recorded at the Zn K edge, suggesting that the Zn 4p states are spin polarized by the Gd 5d extended orbitals.« less

  19. Spin pumping through a topological insulator probed by x-ray detected ferromagnetic resonance

    NASA Astrophysics Data System (ADS)

    Figueroa, A. I.; Baker, A. A.; Collins-McIntyre, L. J.; Hesjedal, T.; van der Laan, G.

    2016-02-01

    In the field of spintronics, the generation of a pure spin current (without macroscopic charge flow) through spin pumping of a ferromagnetic (FM) layer opens up the perspective of a new generation of dissipation-less devices. Microwave driven ferromagnetic resonance (FMR) can generate a pure spin current that enters adjacent layers, allowing for both magnetization reversal (through spin-transfer torque) and to probe spin coherence in non-magnetic materials. However, standard FMR is unable to probe multilayer dynamics directly, since the measurement averages over the contributions from the whole system. The synchrotron radiation-based technique of x-ray detected FMR (XFMR) offers an elegant solution to this drawback, giving access to element-, site-, and layer-specific dynamical measurements in heterostructures. In this work, we show how XFMR has provided unique information to understand spin pumping and spin transfer torque effects through a topological insulator (TI) layer in a pseudo-spin valve heterostructure. We demonstrate that TIs function as efficient spin sinks, while also allowing a limited dynamic coupling between ferromagnetic layers. These results shed new light on the spin dynamics of this novel class of materials, and suggest future directions for the development of room temperature TI-based spintronics.

  20. Resonantly photo-pumped nickel-like erbium X-ray laser

    DOEpatents

    Nilsen, Joseph

    1990-01-01

    A resonantly photo-pumped X-ray laser (10) that enhances the gain of seve laser lines that also lase because of collisional excitations and recombination processes, is described. The laser comprises an aluminum (12) and erbium (14) foil combination (16) that is driven by two beams (18, 20) of intense line focused (22, 24) optical laser radiation. Ground state nickel-like erbium ions (34) are resonantly photo-pumped by line emission from hydrogen-like aluminum ions (32).

  1. Probing single magnon excitations in Sr₂IrO₄ using O K-edge resonant inelastic x-ray scattering

    SciTech Connect

    Liu, X.; Dean, M. P. M.; Liu, J.; Chiuzbaian, S. G.; Jaouen, N.; Nicolaou, A.; Yin, W. G.; Rayan Serrao, C.; Ramesh, R.; Ding, H.; Hill, J. P.

    2015-04-28

    Resonant inelastic X-ray scattering (RIXS) at the L-edge of transition metal elements is now commonly used to probe single magnon excitations. Here we show that single magnon excitations can also be measured with RIXS at the K-edge of the surrounding ligand atoms when the center heavy metal elements have strong spin-orbit coupling. This is demonstrated with oxygen K-edge RIXS experiments on the perovskite Sr₂IrO₄, where low energy peaks from single magnon excitations were observed. This new application of RIXS has excellent potential to be applied to a wide range of magnetic systems based on heavy elements, for which the L-edge RIXS energy resolutions in the hard X-ray region is usually poor.

  2. Probing single magnon excitations in Sr₂IrO₄ using O K-edge resonant inelastic x-ray scattering

    DOE PAGESBeta

    Liu, X.; Dean, M. P. M.; Liu, J.; Chiuzbaian, S. G.; Jaouen, N.; Nicolaou, A.; Yin, W. G.; Rayan Serrao, C.; Ramesh, R.; Ding, H.; et al

    2015-04-28

    Resonant inelastic X-ray scattering (RIXS) at the L-edge of transition metal elements is now commonly used to probe single magnon excitations. Here we show that single magnon excitations can also be measured with RIXS at the K-edge of the surrounding ligand atoms when the center heavy metal elements have strong spin-orbit coupling. This is demonstrated with oxygen K-edge RIXS experiments on the perovskite Sr₂IrO₄, where low energy peaks from single magnon excitations were observed. This new application of RIXS has excellent potential to be applied to a wide range of magnetic systems based on heavy elements, for which the L-edgemore » RIXS energy resolutions in the hard X-ray region is usually poor.« less

  3. Resonant elastic X-ray scattering in chemistry and materials science

    NASA Astrophysics Data System (ADS)

    Helliwell, J. R.; Helliwell, M.; Kaucic, V.; Logar, N. Z.

    2012-06-01

    The applications of anomalous scattering for locating metal atoms and discriminating between different elements has increased when optimised with synchrotron X-radiation.The on-resonance effect enhances the targeted elemental signal and allows small occupancies to be determined, including in situations of a mixed metal population at a single atomic site. Thus the applications of resonant elastic X-ray scattering in biological, inorganic and materials chemistry is being widely applied to single crystals, which is our emphasis, but also powders, fibres, solutions, amorphous and thin film states of matter. Recent developments have included the use of high photon energies (upto 100 keV) as well as softer X-rays (2 keV). The various instrument and technical capabilities have improved in the last 15 years. This ease of measurement of the resonant scattering signals along with absorption edge shifts indicates an expansion to the measurement of multiple data sets, to allow monitoring of redox changes. Whilst crystal structure determination in biological crystallography has been revolutionised by the MAD method, it is not a requirement for chemical or materials crystallography, as other phasing techniques are routine. Synchrotron source upgrades will allow nano-sized X-ray beams to be more widely available. The new X-ray lasers suggest new capabilities too.

  4. Investigation of self-filtering unstable resonator for soft x-ray lasers

    NASA Astrophysics Data System (ADS)

    Ghani-Moghadam, G.; Farahbod, A. H.

    2016-07-01

    In this paper, it is proposed that the self-filtering unstable resonator (SFUR) is suitable for soft x-ray lasers which have active medium with a short-gain-lifetime. In order to evaluate the idea, we have analyzed the self-filtering unstable resonator in two dimensions with Ne-like Fe soft x-ray active medium for transitions 2p5 3 p → 2p5 3 s and 3d9 4 d → 3d9 4 p at 25.5 nm. The role of field-limiting aperture in mode propagation has been shown. Moreover, beam quality factor M2 has been calculated and output mode behavior studied and compared with a plane-parallel (PP) resonator of equal length. The calculations indicate that the M2 factor in SFUR resonator is smaller than PP resonator and therefore output beam divergence is lower and the mode quality is much better. It is expected that a high quality beam of soft x-ray laser with brightness of the order 1013 W / cm2 sr and energy more than 10 nJ may be achievable with a properly designed diffraction-filtered unstable resonator.

  5. Double-confocal resonator for X-ray generation via intracavity Thomson scattering

    SciTech Connect

    Xie, M.

    1995-12-31

    There has been a growing interest in developing compact X-ray sources through Thomson scattering of a laser beam by a relativistic electron beam. For higher X-ray flux it is desirable to have the scattering to occur inside an optical resonator where the laser power is higher. In this paper I propose a double-confocal resonator design optimized for head-on Thomson scattering inside an FEL oscillator and analyze its performance taking into account the diffraction and FEL gain. A double confocal resonator is equivalent to two confocal resonators in series. Such a resonator has several advantages: it couples electron beam through and X-ray out of the cavity with holes on cavity mirrors, thus allowing the system to be compact; it supports the FEL mode with minimal diffraction loss through the holes; it provides a laser focus in the forward direction for a better mode overlap with the electron beam; and it provides a focus at the same location in the backward direction for higher Thomson scattering efficiency; in addition, the mode size at the focal point and hence the Rayleigh range can be adjusted simply through intracavity apertures; furthermore, it gives a large mode size at the mirrors to reduce power loading. Simulations as well as analytical results will be presented. Also other configurations of intracavity Thomson scattering where the double-confocal resonator could be useful will be discussed.

  6. Role of screening and angular distributions in resonant soft-x-ray emission of CO

    SciTech Connect

    Skytt, P.; Glans, P.; Gunnelin, K.

    1997-04-01

    In the present work the authors focus on two particular properties of resonant X-ray emission, namely core hole screening of the excited electron, and anisotropy caused by the polarization of the exciting synchrotron radiation. The screening of the core hole by the excited electron causes energy shifts and intensity variations in resonant spectra compared to the non-resonant case. The linear polarization of the synchrotron radiation and the dipole nature of the absorption process create a preferential alignment selection of the randomly oriented molecules in the case of resonant excitation, producing an anisotropy in the angular distribution of the emitted X-rays. The authors have chosen CO for this study because this molecule has previously served as a showcase for non-resonant X-ray emission, mapping the valence electronic structure differently according to the local selection rules. With the present work they take interest in how this characteristic feature of the spectroscopy is represented in the resonant case.

  7. Resonant soft X-ray scattering study of twist bend nematic phase

    NASA Astrophysics Data System (ADS)

    Zhu, Chenhui; Young, Anthony; Wang, Cheng; Hexemer, Alexander; Li, Quan; Lavrentovich, Oleg; Walba, David; Tuchband, Michael; Shuai, Min; Clark, Noel

    Liquid crystals (LCs) form many interesting nano-scale structures, many of which can be probed with X-ray scattering techniques, typically hard X-rays due to its high penetrating power. However, in the hard X-ray regime, the scattering contrast of some LC nanostructures can be extremely low due to their weak electron density modulation. Here we show it is possible to use resonant soft x-rays to probe the helical pitch of the newly discovered twist bend nematic phase, which is purely a twist bend structure with no electron density modulation. The in-situ temperature dependent measurement will be presented and discussed. This work together with our previous study on the helical nanofilament B4 phase shows the great potential of soft x-ray scattering in liquid crystals. Supported by the Director of the Office of Science, Office of Basic Energy Sciences, of the U.S. Department of Energy under Contract No. DE-AC02-05CH11231.

  8. High-resolution soft X-ray beamline ADRESS at the Swiss Light Source for resonant inelastic X-ray scattering and angle-resolved photoelectron spectroscopies

    PubMed Central

    Strocov, V. N.; Schmitt, T.; Flechsig, U.; Schmidt, T.; Imhof, A.; Chen, Q.; Raabe, J.; Betemps, R.; Zimoch, D.; Krempasky, J.; Wang, X.; Grioni, M.; Piazzalunga, A.; Patthey, L.

    2010-01-01

    The concepts and technical realisation of the high-resolution soft X-ray beamline ADRESS operating in the energy range from 300 to 1600 eV and intended for resonant inelastic X-ray scattering (RIXS) and angle-resolved photoelectron spectroscopy (ARPES) are described. The photon source is an undulator of novel fixed-gap design where longitudinal movement of permanent magnetic arrays controls not only the light polarization (including circular and 0–180° rotatable linear polarizations) but also the energy without changing the gap. The beamline optics is based on the well established scheme of plane-grating monochromator operating in collimated light. The ultimate resolving power E/ΔE is above 33000 at 1 keV photon energy. The choice of blazed versus lamellar gratings and optimization of their profile parameters is described. Owing to glancing angles on the mirrors as well as optimized groove densities and profiles of the gratings, the beamline is capable of delivering high photon flux up to 1 × 1013 photons s−1 (0.01% BW)−1 at 1 keV. Ellipsoidal refocusing optics used for the RIXS endstation demagnifies the vertical spot size down to 4 µm, which allows slitless operation and thus maximal transmission of the high-resolution RIXS spectrometer delivering E/ΔE > 11000 at 1 keV photon energy. Apart from the beamline optics, an overview of the control system is given, the diagnostics and software tools are described, and strategies used for the optical alignment are discussed. An introduction to the concepts and instrumental realisation of the ARPES and RIXS endstations is given. PMID:20724785

  9. High-resolution soft X-ray beamline ADRESS at the Swiss Light Source for resonant inelastic X-ray scattering and angle-resolved photoelectron spectroscopies.

    PubMed

    Strocov, V N; Schmitt, T; Flechsig, U; Schmidt, T; Imhof, A; Chen, Q; Raabe, J; Betemps, R; Zimoch, D; Krempasky, J; Wang, X; Grioni, M; Piazzalunga, A; Patthey, L

    2010-09-01

    The concepts and technical realisation of the high-resolution soft X-ray beamline ADRESS operating in the energy range from 300 to 1600 eV and intended for resonant inelastic X-ray scattering (RIXS) and angle-resolved photoelectron spectroscopy (ARPES) are described. The photon source is an undulator of novel fixed-gap design where longitudinal movement of permanent magnetic arrays controls not only the light polarization (including circular and 0-180 degrees rotatable linear polarizations) but also the energy without changing the gap. The beamline optics is based on the well established scheme of plane-grating monochromator operating in collimated light. The ultimate resolving power E/DeltaE is above 33000 at 1 keV photon energy. The choice of blazed versus lamellar gratings and optimization of their profile parameters is described. Owing to glancing angles on the mirrors as well as optimized groove densities and profiles of the gratings, the beamline is capable of delivering high photon flux up to 1 x 10(13) photons s(-1) (0.01% BW)(-1) at 1 keV. Ellipsoidal refocusing optics used for the RIXS endstation demagnifies the vertical spot size down to 4 microm, which allows slitless operation and thus maximal transmission of the high-resolution RIXS spectrometer delivering E/DeltaE > 11000 at 1 keV photon energy. Apart from the beamline optics, an overview of the control system is given, the diagnostics and software tools are described, and strategies used for the optical alignment are discussed. An introduction to the concepts and instrumental realisation of the ARPES and RIXS endstations is given. PMID:20724785

  10. Soft x-ray ptychography studies of nanoscale magnetic and structural correlations in thin SmCo5 films

    NASA Astrophysics Data System (ADS)

    Fischer, P.; Shi, X.; Neu, V.; Elefant, D.; Lee, J. C. T.; Shapiro, D. A.; Farmand, M.; Tyliszczak, T.; Shiu, W.; Marchesini, S.; Roy, S.; Kevan, S. D.

    Soft x-ray ptychographic imaging was applied to probe an amorphous 50 nm thin SmCo5 film prepared by off-axis pulsed laser deposition and exhibiting a strong perpendicular magnetic anisotropy. Amplitude and phase contrast images, retrieved at photon energies near the cobalt L3 resonance, were used to identify and characterize magnetic and structural features with a spatial resolution of about10 nm. Aside from the common magnetic labyrinth domain pattern, nanoscale structural inclusions were identified that are primarily located in close proximity to the magnetic domain walls. X-ray absorption spectroscopy suggests that these inclusions are nanocrystalline Sm2Co17 phases with nominally in-plane magnetic anisotropy. Our results indicate that x-ray ptychographic imaging enables fruitful studies of magnetic and structural correlations at length scales relevant to emerging magnetic and spintronic devices. Supported by the Director of the Office of Science, Office of Basic Energy Sciences, of the U.S. Department of Energy under Contract No. DEAC02-05CH11231.

  11. Irreversible transformation of ferromagnetic ordered stripe domains in single-shot infrared-pump/resonant-x-ray-scattering-probe experiments

    NASA Astrophysics Data System (ADS)

    Bergeard, Nicolas; Schaffert, Stefan; López-Flores, Víctor; Jaouen, Nicolas; Geilhufe, Jan; Günther, Christian M.; Schneider, Michael; Graves, Catherine; Wang, Tianhan; Wu, Benny; Scherz, Andreas; Baumier, Cédric; Delaunay, Renaud; Fortuna, Franck; Tortarolo, Marina; Tudu, Bharati; Krupin, Oleg; Minitti, Michael P.; Robinson, Joe; Schlotter, William F.; Turner, Joshua J.; Lüning, Jan; Eisebitt, Stefan; Boeglin, Christine

    2015-02-01

    The evolution of a magnetic domain structure upon excitation by an intense, femtosecond infrared (IR) laser pulse has been investigated using single-shot based time-resolved resonant x-ray scattering at the x-ray free electron laser LCLS. A well-ordered stripe domain pattern as present in a thin CoPd alloy film has been used as a prototype magnetic domain structure for this study. The fluence of the IR laser pump pulse was sufficient to lead to an almost complete quenching of the magnetization within the ultrafast demagnetization process taking place within the first few hundreds of femtoseconds following the IR laser pump pulse excitation. On longer time scales this excitation gave rise to subsequent irreversible transformations of the magnetic domain structure. Under our specific experimental conditions, it took about 2 ns before the magnetization started to recover. After about 5 ns the previously ordered stripe domain structure had evolved into a disordered labyrinth domain structure. Surprisingly, we observe after about 7 ns the occurrence of a partially ordered stripe domain structure reoriented into a novel direction. It is this domain structure in which the sample's magnetization stabilizes as revealed by scattering patterns recorded long after the initial pump-probe cycle. Using micromagnetic simulations we can explain this observation based on changes of the magnetic anisotropy going along with heat dissipation in the film.

  12. Prospects for x-ray polarimetry measurements of magnetic fields in magnetized liner inertial fusion plasmas

    SciTech Connect

    Lynn, Alan G. Gilmore, Mark

    2014-11-15

    Magnetized Liner Inertial Fusion (MagLIF) experiments, where a metal liner is imploded to compress a magnetized seed plasma may generate peak magnetic fields ∼10{sup 4} T (100 Megagauss) over small volumes (∼10{sup −10}m{sup 3}) at high plasma densities (∼10{sup 28}m{sup −3}) on 100 ns time scales. Such conditions are extremely challenging to diagnose. We discuss the possibility of, and issues involved in, using polarimetry techniques at x-ray wavelengths to measure magnetic fields under these extreme conditions.

  13. X-ray studies of neutron stars and their magnetic fields.

    PubMed

    Makishima, Kazuo

    2016-01-01

    Utilizing results obtained over the past quarter century mainly with Japanese X-ray astronomy satellites, a review is given to some aspects of neutron stars (NSs), with a particular emphasis on the magnetic fields (MFs) of mass-accreting NSs and magnetars. Measurements of electron cyclotron resonance features in binary X-ray pulsars, using the Ginga and Suzaku observatories, clarified that their surface MFs are concentrated in a narrow range of (1-7) × 10(8) T. Extensive studies of magnetars with Suzaku reinforced their nature as neutron stars with truly strong MFs, and revealed several important clues to their formation, evolution, and physical states. Taking all these results into account, a discussion is made on the origin and evolution of these strong MFs. One possible scenario is that the MF of NSs is a manifestation of some fundamental physics, e.g., neutron spin alignment or chirality violation, and the MF makes transitions from strong to weak states. PMID:27169348

  14. New possibilities in nanoscale surface structure diagnostics using X-ray standing waves under conditions of continuous resonant X-ray Raman scattering

    NASA Astrophysics Data System (ADS)

    Zel'Tser, I. A.; Kukushkin, S. A.; Moos, E. N.

    2008-07-01

    The main principles, new possibilities, and instrumental implementations of a structure-sensitive spectroscopy of the surface of condensed media probed by X-ray standing waves (XSWs) are considered in the case of electron emission under the action of continuous resonant X-ray Raman scattering. It is shown that prospects for the development and use of the new possibilities offered by the XSW method for surface investigations are related to the creation of a set of specific experimental equipment and special sources of synchrotron radiation.

  15. 4 f excitations in Ce Kondo lattices studied by resonant inelastic x-ray scattering

    NASA Astrophysics Data System (ADS)

    Amorese, A.; Dellea, G.; Fanciulli, M.; Seiro, S.; Geibel, C.; Krellner, C.; Makarova, I. P.; Braicovich, L.; Ghiringhelli, G.; Vyalikh, D. V.; Brookes, N. B.; Kummer, K.

    2016-04-01

    The potential of resonant inelastic soft x-ray scattering to measure 4 f crystal electric-field excitation spectra in Ce Kondo lattices has been examined. Spectra have been obtained for several Ce systems and show a well-defined structure determined by crystal-field, spin-orbit, and charge-transfer excitations only. The spectral shapes of the excitation spectra can be well understood in the framework of atomic multiplet calculations. For CeCu2Si2 we found notable disagreement between the inelastic x-ray-scattering spectra and theoretical calculations when using the crystal-field scheme proposed from inelastic neutron scattering. Modified sets of crystal-field parameters yield better agreement. Our results also show that, with the very recent improvements of soft x-ray spectrometers in resolution to below 30 meV at the Ce M4 ,5 edges, resonant inelastic x-ray scattering could be an ideal tool to determine the crystal-field scheme in Ce Kondo lattices and other rare-earth compounds.

  16. The X-ray Light Curves of Magnetic Cataclysmic Variables with Non-zero Shock Heights

    NASA Astrophysics Data System (ADS)

    Mukai, Koji

    The hard X-ray emitting shocks in magnetic CVs are probably 0.01-0.1 Rwd tall. Self occultation of X-ray emitting regions under such shocks must be calculated using a full, three-dimensional geometry: The difference between the top and the bottom of the shock is substantial in this regard. In this paper, I present the results of crude simulations showing that the non-zero shock height probably is an important factor in the hard X-ray spin modulations of IPs, with applications to XY Ari and EX Hya.

  17. Computer solutions for studying correlations between solar magnetic fields and Skylab X-ray observations

    NASA Technical Reports Server (NTRS)

    Teuber, D.; Tandberg-Hanssen, E.; Hagyard, M. J.

    1977-01-01

    A method is described which correlates the NASA-Marshall Space Flight Center (MSFC) Image Data Processing System (IDAPS) and MSFC magnetograph data to X-ray and H-alpha observations from the Skylab mission. Solutions of Laplace's equation in three dimensions, based on the magnetograph data, are convolved with observed X-ray and H-alpha regions. Matched filtering (template matching) provides a best fit of the observed X-ray regions to the computed total magnetic vector magnitude between 10,000 and 15,000 km above the photosphere.

  18. Effects of dispersion and absorption in resonant Bragg diffraction of x-rays.

    PubMed

    Lovesey, S W; Scagnoli, V; Dobrynin, A N; Joly, Y; Collins, S P

    2014-03-26

    Resonant diffraction of x-rays by crystals with anisotropic optical properties is investigated theoretically, to assess how the intensity of a Bragg spot is influenced by effects related to dispersion (birefringence) and absorption (dichroism). Starting from an exact but opaque expression, simple analytic results are found to expose how intensity depends on dispersion and absorption in the primary and secondary beams and, also, the azimuthal angle (rotation of the crystal about the Bragg wavevector). If not the full story for a given application, our results are more than adequate to explore consequences of dispersion and absorption in the intensity of a Bragg spot. Results are evaluated for antiferromagnetic copper oxide, and low quartz. For CuO, one of our results reproduces all salient features of a previously published simulation of the azimuthal-angle dependence of a magnetic Bragg peak. It is transparent in our analytic result that dispersion and absorption effects alone cannot reproduce published experimental data. Available data for the azimuthal-angle dependence of space-group forbidden reflections (0,0, l), with l ≠ 3n, of low quartz depart from symmetry imposed by the triad axis of rotation symmetry. The observed asymmetry can be induced by dispersion and absorption even though absorption coefficients are constant, independent of the azimuthal angle, in this class of reflections. PMID:24599265

  19. Analysis of Order Formation in Block Copolymer Thin Films Using Resonant Soft X-Ray Scattering

    SciTech Connect

    Virgili, J.M.; Tao, Y.; Kortright, J.B.; Balsara, N.P.; Segalman, R.A.; /UC, Berkeley /LBL, Berkeley

    2007-07-13

    The lateral order of poly(styrene-block-isoprene) copolymer (PS-b-PI) thin films is characterized by the emerging technique of resonant soft X-ray scattering (RSOXS) at the carbon {pi}* resonance and compared to ordering in bulk samples of the same materials measured using conventional small-angle X-ray scattering. We show resonance using theory and experiment that the loss of scattering intensity expected with a decrease in sample volume in the case of thin films can be overcome by tuning X-rays to the {pi}* resonance of PS or PI. Using RSOXS, we study the microphase ordering of cylinder- and sphere-forming PS-b-PI thin films and compare these results to position space data obtained by atomic force microscopy. Our ability to examine large sample areas ({approx}9000 {micro}m{sup 2}) by RSOXS enables unambiguous identification of the lateral lattice structure in the thin films. In the case of the sphere-forming copolymer thin film, where the spheres are hexagonally arranged, the average sphere-to-sphere spacing is between the bulk (body-centered cubic) nearest neighbor and bulk unit cell spacings. In the case of the cylinder-forming copolymer thin film, the cylinder-to-cylinder spacing is within experimental error of that obtained in the bulk.

  20. Resonant x-ray reflectivity study of partial decomposed boron nitride thin films using Indus-1 synchrotron

    SciTech Connect

    Nayak, Maheswar Lodha, Gyanendra S.

    2014-04-24

    We determined the microstructural parameters and chemical composition profile of partial decomposed boron nitride thin films using x-ray reflectivity near the respective absorption edges. The elemental specificity and optical contrast variation properties of the resonant effect are utilized to combine chemical analysis with physical microstructure of thin films from x-ray scattered intensities. We demonstrated these aspects through calculations and experiments in the soft x-ray region near the boron K-absorption edge.

  1. 1,3-Alternate calix[4]arene nitronyl nitroxide tetraradical and diradical: synthesis, X-ray crystallography, paramagnetic NMR spectroscopy, EPR spectroscopy, and magnetic studies

    SciTech Connect

    Rajca, Andrzej; Pink, Maren; Mukherjee, Sumit; Rajca, Suchada; Das, Kausik

    2008-04-02

    Calix[4]arenes constrained to 1,3-alternate conformation and functionalized at the upper rim with four and two nitronyl nitroxides have been synthesized, and characterized by X-ray crystallography, magnetic resonance (EPR and {sup 1}H NMR) spectroscopy, and magnetic studies. Such calix[4]arene tetraradicals and diradicals provide scaffolds for through-bond and through-space intramolecular exchange couplings.

  2. Atomic motion of resonantly vibrating quartz crystal visualized by time-resolved X-ray diffraction

    NASA Astrophysics Data System (ADS)

    Aoyagi, Shinobu; Osawa, Hitoshi; Sugimoto, Kunihisa; Fujiwara, Akihiko; Takeda, Shoichi; Moriyoshi, Chikako; Kuroiwa, Yoshihiro

    2015-11-01

    Transient atomic displacements during a resonant thickness-shear vibration of AT-cut α-quartz are revealed by time-resolved X-ray diffraction under an alternating electric field. The lattice strain resonantly amplified by the alternating electric field is ˜104 times larger than that induced by a static electric field. The resonantly amplified lattice strain is achieved by fast displacements of oxygen anions and collateral resilient deformation of Si-O-Si angles bridging rigid SiO4 tetrahedra, which efficiently transduce electric energy into elastic energy.

  3. Atomic motion of resonantly vibrating quartz crystal visualized by time-resolved X-ray diffraction

    SciTech Connect

    Aoyagi, Shinobu; Osawa, Hitoshi; Sugimoto, Kunihisa; Fujiwara, Akihiko

    2015-11-16

    Transient atomic displacements during a resonant thickness-shear vibration of AT-cut α-quartz are revealed by time-resolved X-ray diffraction under an alternating electric field. The lattice strain resonantly amplified by the alternating electric field is ∼10{sup 4} times larger than that induced by a static electric field. The resonantly amplified lattice strain is achieved by fast displacements of oxygen anions and collateral resilient deformation of Si−O−Si angles bridging rigid SiO{sub 4} tetrahedra, which efficiently transduce electric energy into elastic energy.

  4. Magnetic and structural properties of Fe/Pd multilayers studied by magnetic x-ray dichroism and x-ray absorption spectroscopy

    SciTech Connect

    Mini, S.M. |; Fullerton, E.E.; Sowers, C.H.; Fontaine, A.; Pizzini, S.; Bommannavar, A.S.; Traverse, A.; Baudelet, F.

    1994-12-01

    The results of magnetic circular x-ray dichroism (MCXD) measurements and extended x-ray absorption fine structure measurements (EXAFS) of the Fe K-edges of textured Fe(110)/Pd(111) multilayers are reported. The EXAFS results indicates that the iron in the system goes from bcc to a more densely packed system as the thickness of the iron layer is decreased. The magnetic properties were measured by SQUID magnetometry from 5-350 K. For all the samples, the saturation magnetization was significantly enhanced over the bulk values indicating the interface Pd atoms are polarized by the Fe layer. The enhancement corresponds to a moment of {approx}2.5{mu}{sub B} per interface Pd atom.

  5. Calibration standard of body tissue with magnetic nanocomposites for MRI and X-ray imaging

    NASA Astrophysics Data System (ADS)

    Rahn, Helene; Woodward, Robert; House, Michael; Engineer, Diana; Feindel, Kirk; Dutz, Silvio; Odenbach, Stefan; StPierre, Tim

    2016-05-01

    We present a first study of a long-term phantom for Magnetic Resonance Imaging (MRI) and X-ray imaging of biological tissues with magnetic nanocomposites (MNC) suitable for 3-dimensional and quantitative imaging of tissues after, e.g. magnetically assisted cancer treatments. We performed a cross-calibration of X-ray microcomputed tomography (XμCT) and MRI with a joint calibration standard for both imaging techniques. For this, we have designed a phantom for MRI and X-ray computed tomography which represents biological tissue enriched with MNC. The developed phantoms consist of an elastomer with different concentrations of multi-core MNC. The matrix material is a synthetic thermoplastic gel, PermaGel (PG). The developed phantoms have been analyzed with Nuclear Magnetic Resonance (NMR) Relaxometry (Bruker minispec mq 60) at 1.4 T to obtain R2 transverse relaxation rates, with SQUID (Superconducting QUantum Interference Device) magnetometry and Inductively Coupled Plasma Mass Spectrometry (ICP-MS) to verify the magnetite concentration, and with XμCT and 9.4 T MRI to visualize the phantoms 3-dimensionally and also to obtain T2 relaxation times. A specification of a sensitivity range is determined for standard imaging techniques X-ray computed tomography (XCT) and MRI as well as with NMR. These novel phantoms show a long-term stability over several months up to years. It was possible to suspend a particular MNC within the PG reaching a concentration range from 0 mg/ml to 6.914 mg/ml. The R2 relaxation rates from 1.4 T NMR-relaxometry show a clear connection (R2=0.994) with MNC concentrations between 0 mg/ml and 4.5 mg/ml. The MRI experiments have shown a linear correlation of R2 relaxation and MNC concentrations as well but in a range between MNC concentrations of 0 mg/ml and 1.435 mg/ml. It could be shown that XμCT displays best moderate and high MNC concentrations. The sensitivity range for this particular XμCT apparatus yields from 0.569 mg/ml to 6.914 mg/ml. The

  6. IQ Aur: A new mode of X-ray generation in magnetic stars ?

    NASA Astrophysics Data System (ADS)

    Schmitt, Jurgen

    2007-10-01

    We propose to obtain the first high-resolution X-ray spectrum of the peculiar magnetic A-type star IQ Aur. From previous X-ray observations IQ Aur is known as a strong (LX ~ 4 10**29 erg/s), but very soft (TX ~ 0.29 keV) X-ray source. An attribution of IQ~Aur's X-ray emission to a low-mass companion would imply totally unusual properties of such an hypothesized object, thus IQ Aur is a good candidate for an A-type star with intrinsic X-ray emission.The XMM-Newton RGS spectrum will constrain the location of the X-ray emission site from a measurement or upper limit to the strength of the OVII f line, the overall RGS spectrum will determine the elemental abundances, which may be far away from solar,and the phase coverage will allow a search for rotational modulation of IQ Aur's X-ray flux.

  7. Resonant X-ray diffraction in incommensurately modulated crystals. Symmetry consideration of anisotropic anomalous scattering.

    PubMed

    Ovchinnikova; Dmitrienko

    1999-01-01

    Symmetry restrictions on the intensities and polarization properties of main reflections and their satellites are found for incommensurately modulated crystals in the case of anisotropic anomalous X-ray diffraction near absorption edges. It is shown that the modulation becomes a source of additional anisotropy for each resonant scatterer and induces a modulated behaviour of the susceptibility tensor. The four-dimensional approach is used to calculate the set of possible reflections. It is found that additional ('forbidden') reflections may appear both in the system of main reflections and in the system of satellites. The anisotropy also results in complex azimuthal and polarization properties of each reflection. The displacive modulation is discussed in detail. The ATS reflections corresponding to the resonant X-ray diffraction near the K-edge of iron in pyrrhotite-5.5C are considered. PMID:10927227

  8. Magnetic Dynamos and X-ray Activity in Ultracool Dwarfs (UCDs): Constraining the Role of Rotation

    NASA Astrophysics Data System (ADS)

    Cook, Benjamin A.; Williams, P. K.; Berger, E.

    2014-01-01

    Although many fully-convective stars are magnetically active, the mechanisms by which they generate, sustain, and dissipate their magnetic fields are not well-understood. Observations suggest that empirical relations between X-ray activity, rotation, and radio emission evolve dramatically between the solar and ultracool dwarf (UCD; spectral types later than ~M6) regimes. The limited number of X-ray detections has prevented the drawing of firm conclusions, however. We combine new Chandra observations of seven late-M dwarfs with three previously-unpublished measurements from the Chandra archive and data from the literature to construct a database of 38 ultracool dwarfs with both X-ray and rotation measurements, the largest such catalog yet presented. We identify a substantial number of rapidly-rotating UCDs with X-ray activity as far as two orders of magnitude below the standard "saturation" level and find a significant anticorrelation between rotation and X-ray activity. We discuss several proposed "supersaturation" mechanisms that suggest a direct connection between faster rotation and suppression of X-ray activity and find many of them to be inconsistent with the data. We instead suggest the observed effect may be indirectly driven by a separate parameter correlated with both X-ray activity and rotation. The strength and topology of large-scale stellar magnetic fields have been found to vary widely within UCDs of similar stellar parameters. We speculate varying field topologies could explain the observed trends. This work is supported in part by the NSF REU and DOD ASSURE programs under NSF grant no. 1262851 and by the Smithsonian Institution. We also acknowledge support from the NSF through Grant AST-1008361 and from NASA through Chandra Award Number G02-13007A issued by the Chandra X-ray Observatory Center, operated by the Smithsonian Astrophysical Observatory and NASA under contract NAS8-03060.

  9. Resonantly Enhanced Betatron Hard X-rays from Ionization Injected Electrons in a Laser Plasma Accelerator

    PubMed Central

    Huang, K.; Li, Y. F.; Li, D. Z.; Chen, L. M.; Tao, M. Z.; Ma, Y.; Zhao, J. R.; Li, M. H.; Chen, M.; Mirzaie, M.; Hafz, N.; Sokollik, T.; Sheng, Z. M.; Zhang, J.

    2016-01-01

    Ultrafast betatron x-ray emission from electron oscillations in laser wakefield acceleration (LWFA) has been widely investigated as a promising source. Betatron x-rays are usually produced via self-injected electron beams, which are not controllable and are not optimized for x-ray yields. Here, we present a new method for bright hard x-ray emission via ionization injection from the K-shell electrons of nitrogen into the accelerating bucket. A total photon yield of 8 × 108/shot and 108 photons with energy greater than 110 keV is obtained. The yield is 10 times higher than that achieved with self-injection mode in helium under similar laser parameters. The simulation suggests that ionization-injected electrons are quickly accelerated to the driving laser region and are subsequently driven into betatron resonance. The present scheme enables the single-stage betatron radiation from LWFA to be extended to bright γ-ray radiation, which is beyond the capability of 3rd generation synchrotrons. PMID:27273170

  10. Resonantly Enhanced Betatron Hard X-rays from Ionization Injected Electrons in a Laser Plasma Accelerator.

    PubMed

    Huang, K; Li, Y F; Li, D Z; Chen, L M; Tao, M Z; Ma, Y; Zhao, J R; Li, M H; Chen, M; Mirzaie, M; Hafz, N; Sokollik, T; Sheng, Z M; Zhang, J

    2016-01-01

    Ultrafast betatron x-ray emission from electron oscillations in laser wakefield acceleration (LWFA) has been widely investigated as a promising source. Betatron x-rays are usually produced via self-injected electron beams, which are not controllable and are not optimized for x-ray yields. Here, we present a new method for bright hard x-ray emission via ionization injection from the K-shell electrons of nitrogen into the accelerating bucket. A total photon yield of 8 × 10(8)/shot and 10(8 )photons with energy greater than 110 keV is obtained. The yield is 10 times higher than that achieved with self-injection mode in helium under similar laser parameters. The simulation suggests that ionization-injected electrons are quickly accelerated to the driving laser region and are subsequently driven into betatron resonance. The present scheme enables the single-stage betatron radiation from LWFA to be extended to bright γ-ray radiation, which is beyond the capability of 3(rd) generation synchrotrons. PMID:27273170

  11. Resonantly Enhanced Betatron Hard X-rays from Ionization Injected Electrons in a Laser Plasma Accelerator

    NASA Astrophysics Data System (ADS)

    Huang, K.; Li, Y. F.; Li, D. Z.; Chen, L. M.; Tao, M. Z.; Ma, Y.; Zhao, J. R.; Li, M. H.; Chen, M.; Mirzaie, M.; Hafz, N.; Sokollik, T.; Sheng, Z. M.; Zhang, J.

    2016-06-01

    Ultrafast betatron x-ray emission from electron oscillations in laser wakefield acceleration (LWFA) has been widely investigated as a promising source. Betatron x-rays are usually produced via self-injected electron beams, which are not controllable and are not optimized for x-ray yields. Here, we present a new method for bright hard x-ray emission via ionization injection from the K-shell electrons of nitrogen into the accelerating bucket. A total photon yield of 8 × 108/shot and 108 photons with energy greater than 110 keV is obtained. The yield is 10 times higher than that achieved with self-injection mode in helium under similar laser parameters. The simulation suggests that ionization-injected electrons are quickly accelerated to the driving laser region and are subsequently driven into betatron resonance. The present scheme enables the single-stage betatron radiation from LWFA to be extended to bright γ-ray radiation, which is beyond the capability of 3rd generation synchrotrons.

  12. SIGNS OF MAGNETIC ACCRETION IN THE X-RAY PULSAR BINARY GX 301-2

    SciTech Connect

    Ikhsanov, Nazar R.; Finger, Mark H.

    2012-07-01

    Observations of the cyclotron resonance scattering feature in the X-ray spectrum of GX 301-2 suggest that the surface field of the neutron star is B{sub CRSF} {approx} 4 Multiplication-Sign 10{sup 12} G. The same value has been derived in modeling the rapid spin-up episodes in terms of the Keplerian disk accretion scenario. However, the spin-down rate observed during the spin-down trends significantly exceeds the value expected in currently used spin-evolution scenarios. This indicates that either the surface field of the star exceeds 50 B{sub CRSF} or a currently used accretion scenario is incomplete. We show that the above discrepancy can be avoided if the accreting material is magnetized. The magnetic pressure in the accretion flow increases more rapidly than its ram pressure and, under certain conditions, significantly affects the accretion picture. The spin-down torque applied to the neutron star in this case is larger than that evaluated within a non-magnetized accretion scenario. We find that the observed spin evolution of the pulsar can be explained in terms of the magnetically controlled accretion flow scenario provided the surface field of the neutron star is {approx}B{sub CRSF}.

  13. Identification of inversion domains in KTiOPO{sub 4}via resonant X-ray diffraction

    SciTech Connect

    Fabrizi, Federica; Thomas, Pamela A.; Nisbet, Gareth; Collins, Stephen P.

    2015-05-14

    The identification and high-resolution mapping of the absolute crystallographic structure in multi-domain ferroelectric KTiOPO{sub 4} is achieved through a novel synchrotron X-ray diffraction method. On a single Bragg reflection, the intensity ratio in resonant diffraction below and above the Ti absorption K edge demonstrates a domain contrast up to a factor of ∼270, thus implementing a non-contact, non-destructive imaging technique with micrometre spatial resolution, applicable to samples of arbitrarily large dimensions. A novel method is presented for the identification of the absolute crystallographic structure in multi-domain polar materials such as ferroelectric KTiOPO{sub 4}. Resonant (or ‘anomalous’) X-ray diffraction spectra collected across the absorption K edge of Ti (4.966 keV) on a single Bragg reflection demonstrate a huge intensity ratio above and below the edge, providing a polar domain contrast of ∼270. This allows one to map the spatial domain distribution in a periodically inverted sample, with a resolution of ∼1 µm achieved with a microfocused beam. This non-contact, non-destructive technique is well suited for samples of large dimensions (in contrast with traditional resonant X-ray methods based on diffraction from Friedel pairs), and its potential is particularly relevant in the context of physical phenomena connected with an absence of inversion symmetry, which require characterization of the underlying absolute atomic structure (such as in the case of magnetoelectric coupling and multiferroics)

  14. Development of an x-ray diffraction camera used in magnetic fields up to 10 T

    SciTech Connect

    Mitsui, Yoshifuru; Takahashi, Kohki; Watanabe, Kazuo; Koyama, Keiichi

    2011-12-15

    A high-field x-ray diffraction (HF-XRD) camera was developed to observe structural changes of magnetic materials in magnetic fields up to 10 T. The instrument mainly consists of a Debye-Scherrer-type camera with a diameter of 80.1 mm, a 10-T cryocooled superconducting magnet with a 100-mm room-temperature bore, an x-ray source, a power supply, and a chiller for the x-ray source. An x-ray detector (image plate) in the HF-XRD camera can be taken out and inserted into the magnet without changing the sample position. The performance of the instrument was tested by measuring the HF-XRD for silicon and ferromagnetic MnBi powders. A change of x-ray diffraction pattern was observed due to the magnetic orientation of MnBi, showing that the instrument is useful for studying field-induced orientation processes and structural properties of field-controlled materials.

  15. Development of an x-ray diffraction camera used in magnetic fields up to 10 T.

    PubMed

    Mitsui, Yoshifuru; Koyama, Keiichi; Takahashi, Kohki; Watanabe, Kazuo

    2011-12-01

    A high-field x-ray diffraction (HF-XRD) camera was developed to observe structural changes of magnetic materials in magnetic fields up to 10 T. The instrument mainly consists of a Debye-Scherrer-type camera with a diameter of 80.1 mm, a 10-T cryocooled superconducting magnet with a 100-mm room-temperature bore, an x-ray source, a power supply, and a chiller for the x-ray source. An x-ray detector (image plate) in the HF-XRD camera can be taken out and inserted into the magnet without changing the sample position. The performance of the instrument was tested by measuring the HF-XRD for silicon and ferromagnetic MnBi powders. A change of x-ray diffraction pattern was observed due to the magnetic orientation of MnBi, showing that the instrument is useful for studying field-induced orientation processes and structural properties of field-controlled materials. PMID:22225246

  16. Minimalist coupled evolution model for stellar X-ray activity, rotation, mass loss, and magnetic field

    NASA Astrophysics Data System (ADS)

    Blackman, Eric G.; Owen, James E.

    2016-05-01

    Late-type main-sequence stars exhibit an X-ray to bolometric flux ratio that depends on {tilde{R}o}, the ratio of rotation period to convective turnover time, as {tilde{R}o}^{-ζ } with 2 ≤ ζ ≤ 3 for {tilde{R}o} > 0.13, but saturates with |ζ| < 0.2 for {tilde{R}o} < 0.13. Saturated stars are younger than unsaturated stars and show a broader spread of rotation rates and X-ray activity. The unsaturated stars have magnetic fields and rotation speeds that scale roughly with the square root of their age, though possibly flattening for stars older than the Sun. The connection between faster rotators, stronger fields, and higher activity has been established observationally, but a theory for the unified time-evolution of X-ray luminosity, rotation, magnetic field and mass loss that captures the above trends has been lacking. Here we derive a minimalist holistic framework for the time evolution of these quantities built from combining a Parker wind with new ingredients: (1) explicit sourcing of both the thermal energy launching the wind and the X-ray luminosity via dynamo produced magnetic fields; (2) explicit coupling of X-ray activity and mass-loss saturation to dynamo saturation (via magnetic helicity build-up and convection eddy shredding); (3) use of coronal equilibrium to determine how magnetic energy is divided into wind and X-ray contributions. For solar-type stars younger than the Sun, we infer conduction to be a subdominant power loss compared to X-rays and wind. For older stars, conduction is more important, possibly quenching the wind and reducing angular momentum loss. We focus on the time evolution for stars younger than the Sun, highlighting what is possible for further generalizations. Overall, the approach shows promise towards a unified explanation of all of the aforementioned observational trends.

  17. X-ray resonant scattering of (004n+2) forbidden reflections in spinel ferrites

    NASA Astrophysics Data System (ADS)

    Subías, G.; Garcia, J.; Proietti, M. G.; Blasco, J.; Renevier, H.; Hodeau, J. L.; Sánchez, M. C.

    2004-10-01

    The origin of the x-ray resonant scattering of (002) and (006) forbidden reflections in the spinel ferrites has been investigated. Resonant features were previously observed in Fe3O4 at the pre-edge and main-edge energies of the FeK -absorption edge. They were ascribed to dipole-quadrupole and dipole transitions at the tetrahedral and pseudo-octahedral Fe ions, respectively. To corroborate this origin and to differentiate between effects at the different metal sites, we have studied the energy and azimuthal dependencies of these reflections at the Fe, Co, and MnK edges in MnFe2O4 and CoFe2O4 spinels. Mn2+ mainly replaces Fe in the tetrahedral site whereas Co2+ occupies the octahedral site. No pre-edge peak is observed either at the FeK -edge in MnFe2O4 or at the CoK edge in CoFe2O4 . On the other hand, the peak at the absorption edge and the oscillations at energies beyond the edge are observed at the FeK edge in MnFe2O4 and CoFe2O4 and at the CoK edge in CoFe2O4 . Therefore, the pre-edge peak comes from the metal ions at the tetrahedral site while the main-edge peak arises from the metal ions at the pseudo-octahedral site of the spinel structure. The azimuthal dependence and the energy line shape confirm the dipole-quadrupole and dipole characters of these pre-edge and main-edge resonances, respectively. The energy-dependence spectra of Fe3O4 above and below the Néel temperature are alike, discarding any magnetic effect on the resonant spectra. Finally, the fine structure at energies beyond the absorption edge has been theoretically simulated considering only the local anisotropy of the dipolar atomic scattering factor of the pseudo-octahedral metal atom. These results demonstrate that (004n+2) resonant reflections arise from the anisotropy of the local structure around the transition-metal atom without contributions of charge or d -orbital ordering.

  18. Probing the spin polarization of current by soft x-ray imaging of current-induced magnetic vortex dynamics

    SciTech Connect

    Kasai, Shinya; Fischer, Peter; Im, Mi-Young; Yamada, Keisuke; Nakatani, Yoshinobu; Kobayashi, Kensuke; Kohno, Hiroshi; Ono, Teruo

    2008-12-09

    Time-resolved soft X-ray transmission microscopy is applied to image the current-induced resonant dynamics of the magnetic vortex core realized in a micron-sized Permalloy disk. The high spatial resolution better than 25 nm enables us to observe the resonant motion of the vortex core. The result also provides the spin polarization of the current to be 0.67 {+-} 0.16 for Permalloy by fitting the experimental results with an analytical model in the framework of the spin-transfer torque.

  19. High Spectral Resolution X-ray Observation of Magnetic CVs: EX Hya

    SciTech Connect

    Luna, G; Brickhouse, N S; Mauche, C W

    2008-04-07

    In magnetic cataclysmic variables (CVs) the primary is a highly magnetized white dwarf (WD) whose field controls the accretion flow close to the WD, leading to a shock and accretion column that radiate chiefly in X-rays. We present preliminary results from a 500 ks Chandra HETG observation of the brightest magnetic CV EX Hya. From the observational dataset we are able to measure the temperature and density at different points of the cooling accretion column using sensitive line ratios. We also construct line-based light curves to search for rotational modulation of the X-ray emission.

  20. Local structure analysis of magnetic transparent conducting films by x-ray spectroscopy

    NASA Astrophysics Data System (ADS)

    Nakamura, Toshihiro

    2016-02-01

    We prepared Mn-doped indium-tin oxide (ITO) films on glass substrates by radio-frequency magnetron sputtering and investigated local structures surrounding Mn ions in the films by x-ray absorption spectroscopy. The Fourier transform of the extended x-ray absorption fine structure (EXAFS) spectrum indicated that the Mn ions preferably substitute the In ions at the b sites of the In2O3 lattice. According to the threshold energy obtained from the inflection point of the edge in the x-ray absorption near edge structure (XANES) spectrum, the valence of the Mn ions was evaluated to range from  +2 to  +3. These x-ray absorption spectroscopic data are useful for revealing the origin of the magnetism of the Mn-doped ITO films.

  1. Incommensurate charge density fluctuations in underdoped YBCO detected by resonant x-ray scattering

    NASA Astrophysics Data System (ADS)

    Ghiringhelli, Giacomo

    2013-03-01

    A key issue in high Tc superconductivity is the short and mid range ordering of spin and charge degrees of freedom when doping disrupts the long range antiferromagnetic order of parent compounds. Cu sites are the main, although not the only, actors in the play. Inelastic and elastic scattering of x rays, when performed at the Cu L3 absorption resonance, can be used to map the spin and charge excitation spectra and, simultaneously, to unveil the presence of spatial modulations in the charge or spin densities. We have used angle-resolved resonant inelastic soft x-ray scattering (RIXS) and resonant elastic soft x-ray scattering (REXS) to identify two-dimensional charge fluctuations with an incommensurate periodicity of ~ 3 . 2 lattice units in the copper oxide planes of the superconductors (Y,Nd)Ba2Cu3O6+x with hole concentrations 0 . 09 < p < 0 . 13 per planar Cu ion [G. Ghiringhelli et al, Science 337, 821 (2012)]. The intensity and correlation length of the fluctuation signal increase strongly upon cooling down to the superconducting transition temperature, Tc; further cooling below Tc abruptly reverses the divergence of the charge correlations. In combination with prior observations of a large gap in the spin excitation spectrum, these data indicate an incipient charge-density-wave instability that competes with superconductivity. Further measurements on an Ortho III sample have confirmed that the charge fluctuations are independent of the chain ordering [A. J. Achkar et al, Phys. Rev. Lett. 109, 167001 (2012)]. Put into perspective, these results show that often elastic and inelastic x-ray scattering experiments should be ideally performed jointly, to explore with the greatest sensitivity charge and spin fluctuations [L. Braicovich et al, Phys. Rev. Lett. 104, 077002, (2010)].

  2. Dissociation of chloromethanes upon resonant σ{sup *} excitation studied by x-ray scattering

    SciTech Connect

    Bohinc, R.; Bučar, K.; Kavčič, M.; Žitnik, M.; Journel, L.; Guillemin, R.; Marchenko, T.; Simon, M.; Cao, W.

    2013-10-07

    The dissociation process following the Cl K-shell excitation to σ{sup *} resonances is studied by high resolution spectroscopy of resonant elastic and inelastic x-ray scattering on CH{sub 3}Cl, CH{sub 2}Cl{sub 2}, CHCl{sub 3}, and CCl{sub 4} molecules. Calculations employing the transition potential and Delta-Kohn-Sham DFT approach are in good agreement with the measured total fluorescence yield and show the presence of a second quasidegenerate group of states with σ{sup *} character above the lowest σ{sup *} unoccupied molecular orbital for molecules with more than one Cl atom. A bandwidth narrowing and a nonlinear dispersion behavior is extracted from the Kα spectral maps for both σ{sup *} resonances. The fitted data indicate that the widths of the Franck-Condon distributions for the first and second σ{sup *} resonances are comparable for all the molecules under study. In addition, an asymmetric broadening of the emission peaks is observed for resonant elastic x-ray scattering with zero detuning on both σ{sup *} resonances. This is attributed to the fast dissociation, transferring about 0.15 of the scattering probability into higher vibrational modes.

  3. Dissociation of chloromethanes upon resonant σ* excitation studied by x-ray scattering

    NASA Astrophysics Data System (ADS)

    Bohinc, R.; Žitnik, M.; Bučar, K.; Kavčič, M.; Journel, L.; Guillemin, R.; Marchenko, T.; Simon, M.; Cao, W.

    2013-10-01

    The dissociation process following the Cl K-shell excitation to σ* resonances is studied by high resolution spectroscopy of resonant elastic and inelastic x-ray scattering on CH3Cl, CH2Cl2, CHCl3, and CCl4 molecules. Calculations employing the transition potential and Delta-Kohn-Sham DFT approach are in good agreement with the measured total fluorescence yield and show the presence of a second quasidegenerate group of states with σ* character above the lowest σ* unoccupied molecular orbital for molecules with more than one Cl atom. A bandwidth narrowing and a nonlinear dispersion behavior is extracted from the Kα spectral maps for both σ* resonances. The fitted data indicate that the widths of the Franck-Condon distributions for the first and second σ* resonances are comparable for all the molecules under study. In addition, an asymmetric broadening of the emission peaks is observed for resonant elastic x-ray scattering with zero detuning on both σ* resonances. This is attributed to the fast dissociation, transferring about 0.15 of the scattering probability into higher vibrational modes.

  4. Monochromatic X-ray propagation in multi-Z media for imaging and diagnostics including Kα Resonance Fluorescence

    NASA Astrophysics Data System (ADS)

    Westphal, Maximillian; Lim, Sara; Nahar, Sultana; Pradhan, Anil

    2016-05-01

    Aimed at monochromatic X-ray imaging and therapy, broadband, monochromatic, and quasi-monochromatic X-ray sources and propagation through low and high-Z (HZ) media were studied with numerically and experimentally. Monte Carlo simulations were performed using the software package Geant4, and a new code Photx, to simulate X-ray image contrast, depth of penetration, and total attenuation. The data show that monochromatic and quasi-monochromatic X-rays achieve improved contrast at lower absorbed radiation doses compared to conventional broadband 120 kV or CT scans. Experimental quasi-monochromatic high-intensity laser-produced plasma sources and monochromatic synchrotron beam data are compared. Physical processes responsible for X-ray photoexcitation and absorption are numerically modelled, including a novel mechanism for accelerating Kα resonance fluorescence via twin monochromatic X-ray beam. Potential applications are medical diagnostics and high-Z material detection. Acknowledgement: Ohio Supercomputer Center, Columbus, OH.

  5. A Novel X-ray Diffractometer for the Florida Split Coil 25 Tesla Magnet

    NASA Astrophysics Data System (ADS)

    Wang, Shengyu; Kovalev, Alexey; Suslov, Alexey; Siegrist, Theo

    2014-03-01

    At National High Magnetic Field Laboratory (NHMFL), we are developing a unique X-ray diffractometer for the 25 Tesla Florida Split Coil Magnet for scattering experiments under extremely high static magnetic fields. The X-ray source is a sealed tube (copper or molybdenum anode), connected to the magnet by an evacuated beam tunnel. The detectors are either an image plate or a silicon drift detector, with the data acquisition system based on LabVIEW. Our preliminary experimental results showed that the performance of the detector electronics and the X-ray generator is reliable in the fringe magnetic fields produced at the highest field of 25 T. Using this diffractometer, we will make measurements on standard samples, such as LaB6, Al2O3 and Si, to calibrate the diffraction system. Magnetic samples, such as single crystal HoMnO3 and stainless steel 301 alloys will be measured subsequently. The addition of X-ray diffraction to the unique split coil magnet will significantly expand the NHMFL experimental capabilities. Therefore, external users will be able to probe spin - lattice interactions at static magnetic fields up to 25T. This project is supported by NSF-DMR Award No.1257649. NHMFL is supported by NSF Cooperative Agreement No. DMR-1157490, the State of Florida, and the U.S. DoE.

  6. Resonant inelastic x-ray scattering studies of the organic semiconductor copper phthalocyanine

    SciTech Connect

    Kodituwakku, C. N.; Burns, C. A.; Said, A. H.; Sinn, H.; Wang, X.; Gog, T.; Casa, D. M.; Tuel, M.; Western Michigan Univ.; DESY, Hasylab

    2008-01-01

    We report resonant inelastic x-ray scattering (RIXS) measurements on polycrystalline and single crystal samples of the organic semiconductor {beta}-copper phthalocyanine (CuPc) as well as time dependent density functional theory calculations of the electronic properties of the CuPc molecule. Resonant and nonresonant excitations were measured along the three crystal axes with 120 meV resolution. We observe molecular excitations as well as charge-transfer excitons along certain crystal directions and compare our data with the calculations. Our results demonstrate that RIXS is a powerful tool for studying excitons and other electronic excitations in organic semiconductors.

  7. Low energy excitations in iridates studied with Resonant Inelastic X-ray Scattering

    NASA Astrophysics Data System (ADS)

    Liu, Xuerong

    2013-03-01

    In the iridium oxides, the strong spin-orbit coupling (SOC) of the 5d iridium electrons entangles the orbital and spin degrees of freedom, providing opportunities for exotic magnetic states with highly anisotropic exchange interactions. At the same time, the spatially extended 5d electrons are expected to have much stronger hybridization with the oxygen 2p orbitals, comparing with that in 3d transition element compounds. Both factors make crystal symmetry and local environment crucial in determining the electronic and magnetic properties of the iridates. We present here our resonant inelastic X-ray scattering (RIXS) studies of a number of octahedrally coordinated iridates with special structures, exploring these effects. In particular, for the 1-D spin 1/2 chain compound, Sr3CuIrO6, the wavefunction of the hole in the t2g manifold was reconstructed based on the RIXS spectra. Our results show that it is significantly modified from the isotropic shape expected for Jeff = 1 / 2 states in the strong SOC limit, due to the distortion of the oxygen octahedral cage. This distortion is comparable to, or smaller than, that present in most iridates and thus this work emphasizes the importance of local symmetry for the iridate families. Further, the magnetic excitations of this material were also measured. A large gap of ~30 meV, was found, comparable to the magnetic dispersion bandwidth. This is in contrast to the gapless dispersion expected for linear chain with isotropic Heisenberg exchange interaction. We also studied Na4Ir3O8 which has a hyperkagome lattice, and is a candidate quantum spin liquid. Here, a low energy continuum is observed below the d-d excitations. Optical conductivity measurements performed on the same sample and polarization dependence of the RIXS signal suggest that these excitations are magnetic in origin, agreeing with the spin-liquid state prediction. The work at Brookhaven was supported by the U.S. Department of Energy, Division of Materials Science

  8. Resonant x-ray emission from gas-phase TiCl{sub 4}

    SciTech Connect

    Hague, C.F.; Tronc, M.; De Groot, F.

    1997-04-01

    Resonant x-ray emission spectroscopy (RXES) has proved to be a powerful tool for studying the electronic structure of condensed matter. Over the past few years it has been used mainly for studying the valence bands of solids and condensed molecules. Very recently the advent of high brightness photon beams provided by third generation synchrotron radiation source undulators, associated with efficient x-ray emission spectrometers has made it possible to perform experiments on free diatomic molecular systems. RXE spectra of free molecules are of prime importance to gain insight into their electronic structure and bonding as they reflect the symmetry of orbitals engaged in the two-electron, two-step process with the l = 0, {+-}2 parity-conserving selection rule, and are free from solid state effects which can introduce difficulties in the interpretation. They provide information (more so than XAS) on the core excited states, and, when performed at fixed incident photon energy as a function of the emitted photon energy, on the electronic excitation (charge transfer, multiplet states). Moreover the anisotropy of the angular distribution of resonant x-ray emission affects the relative intensity of the emission peaks and provides information concerning the symmetries of final states. This is a preliminary report on what are the first RXE spectra of a 3d transition metal complex in the gas phase. The experiment concerns the Ti 3d {yields}2p emission spectrum of TiCl{sub 4} over the 450 to 470 eV region.

  9. Basics of magnetic resonance imaging

    SciTech Connect

    Oldendorf, W.; Oldendorf, W. Jr.

    1988-01-01

    Beginning with the behavior of a compass needle in a magnetic field, this text uses analogies from everyday experience to explain the phenomenon of nuclear magnetic resonance and how it is used for imaging. Using a minimum of scientific abbreviations and symbols, the basics of tissue visualization and characterization are presented. A description of the various types of magnets and scanners is followed by the practical advantages and limitations of MRI relative to x-ray CT scanning.

  10. Resonant Inelastic X-ray Scattering Study of the Electronic Structure of Cu2O

    SciTech Connect

    Hill, J.P.; Kim, Y.-J.; Yamaguchi, H.; Gog, T.; Casa, D.

    2010-05-15

    A resonant inelastic x-ray scattering study of the electronic structure of the semiconductor cuprous oxide, Cu{sub 2}O, is reported. When the incident x-ray energy is tuned to the CuK-absorption edge, large enhancements of the spectral features corresponding to the electronic transitions between the valence band and the conduction band are observed. A feature at 6.5 eV can be well described by an interband transition from occupied states of mostly Cu3d character to unoccupied states with mixed 3d, 4s, and O2p character. In addition, an insulating band gap is observed, and the momentum dependence of the lower bound is measured along the {Gamma}-R direction. This is found to be in good agreement with the valence-band dispersion measured with angle-resolved photoemission spectroscopy.

  11. Magnetic X-Ray Scattering Study of GdCo2Ge2 and NdCo2Ge2

    SciTech Connect

    William Good

    2002-08-27

    The results of magnetic x-ray resonant exchange scattering (XRES) experiments are important to the development of an understanding of magnetic interactions in materials. The advantages of high Q resolution, polarization analysis, and the ability to study many different types of materials make it a vital tool in the field of condensed matter physics. Though the concept of XRES was put forth by Platzman and Tzoar in 1970, the technique did not gain much attention until the work of Gibbs and McWhan et al. in 1988. Since then, the technique of XRES has grown immensely in use and applicability. Researchers continue to improve upon the procedure and detection capabilities in order to study magnetic materials of all kinds. The XRES technique is particularly well suited to studying the rare earth metals because of the energy range involved. The resonant L edges of these elements fall between 5-10 KeV. Resonant and nonresonant x-ray scattering experiments were performed in order to develop an understanding of the magnetic ordering in GdCo{sub 2}Ge{sub 2} and NdCo{sub 2}Ge{sub 2}.

  12. Enhancement of X-ray Production in Z-Pinch Plasmas Using Magnetic Fields

    NASA Astrophysics Data System (ADS)

    Edison, N. S.; Etlicher, B.; Attelan, S.; Rouillé, C.; Chuvatin, A. S.; Aliaga, R.

    1994-03-01

    We are investigating the effects of an axial magnetic field to stabilize an aluminum vapor z-pinch. An aluminum plasma jet is created from an exploding foil in a DC magnetic field (Bz0 ≤ 300 G). The applied field is small compared to the azimuthal field, Bz0 ≫ Bϑ, and is intended to reduce the growth of instabilities during the compression phase. The pinch is driven by a 2 Ω, 0.1 TW generator (250 kA in 80 ns). Additionally, a micron sized wire may be placed on the pinch axis leading to the plasma-on-wire (POW) configuration. Qualitatively, increasing the axial magnetic field improves the pinch with the m=1 instabilities becoming negligible for fields higher than 150 G. We find that the externally applied fields can enhance x-ray production up to a critical field. Above this critical field x-ray emission decreases even though the pulse length of the radiation may still be increasing. As the applied field increases, the period of x-ray emission increases with the harder spectrum affected the least. The x-ray yield peaks for the POW and Al jet alone configurations at 150 G and 50 G respectively. Diagnostics include filtered PIN x-ray diodes, time-resolved schlieren photography, and time-integrated multiple filtered pinholes. We will present the results comparing the POW and aluminum jet configurations described above.

  13. Period Clustering of the Anomalous X-Ray Pulsars and Magnetic Field Decay in Magnetars.

    PubMed

    Colpi; Geppert; Page

    2000-01-20

    We confront theoretical models for the rotational, magnetic, and thermal evolution of an ultramagnetized neutron star, or magnetar, with available data on the anomalous X-ray pulsars (AXPs). We argue that, if the AXPs are interpreted as magnetars, their clustering of spin periods between 6 and 12 s (observed at present in this class of objects), their period derivatives, their thermal X-ray luminosities, and the association of two of them with young supernova remnants can only be understood globally if the magnetic field in magnetars decays significantly on a timescale of the order of 104 yr. PMID:10615029

  14. Molecular Orbital Simulations of Metal 1s2p Resonant Inelastic X-ray Scattering.

    PubMed

    Guo, Meiyuan; Källman, Erik; Sørensen, Lasse Kragh; Delcey, Mickaël G; Pinjari, Rahul V; Lundberg, Marcus

    2016-07-28

    For first-row transition metals, high-resolution 3d electronic structure information can be obtained using resonant inelastic X-ray scattering (RIXS). In the hard X-ray region, a K pre-edge (1s→3d) excitation can be followed by monitoring the dipole-allowed Kα (2p→1s) or Kβ (3p→1s) emission, processes labeled 1s2p or 1s3p RIXS. Here the restricted active space (RAS) approach, which is a molecular orbital method, is used for the first time to study hard X-ray RIXS processes. This is achieved by including the two sets of core orbitals in different partitions of the active space. Transition intensities are calculated using both first- and second-order expansions of the wave vector, including, but not limited to, electric dipoles and quadrupoles. The accuracy of the approach is tested for 1s2p RIXS of iron hexacyanides [Fe(CN)6](n-) in ferrous and ferric oxidation states. RAS simulations accurately describe the multiplet structures and the role of 2p and 3d spin-orbit coupling on energies and selection rules. Compared to experiment, relative energies of the two [Fe(CN)6](3-) resonances deviate by 0.2 eV in both incident energy and energy transfer directions, and multiplet splittings in [Fe(CN)6](4-) are reproduced within 0.1 eV. These values are similar to what can be expected for valence excitations. The development opens the modeling of hard X-ray scattering processes for both solution catalysts and enzymatic systems. PMID:27398775

  15. Directionality effects in the transfer of X-rays from a magnetized atmosphere: Beam pulse shape

    NASA Technical Reports Server (NTRS)

    Meszaros, P.; Bonazzola, S.

    1981-01-01

    A formalism is presented for radiation transfer in two normal polarization modes in finite and semiinfinite plane parallel uniform atmospheres with a magnetic field perpendicular to the surface and arbitrary propagation angles. This method is based on the coupled integral equations of transfer, including emission, absorption, and scattering. Calculations are performed for atmosphere parameters typical of X-ray pulsars. The directionality of the escaping radiation is investigated for several cases, varying the input distributions. Theoretical pencil beam profiles and X-ray pulse shapes are obtained assuming the radiation is emitted from the polar caps of spinning neutron stars. Implications for realistic models of accreting magnetized X-ray sources are briefly discussed.

  16. Resonance-mediated atomic ionization dynamics induced by ultraintense x-ray pulses

    NASA Astrophysics Data System (ADS)

    Ho, Phay J.; Kanter, E. P.; Young, L.

    2015-12-01

    We describe the methodology of our recently developed Monte Carlo rate equation (MCRE) approach, which systematically incorporates bound-bound resonances to model multiphoton ionization dynamics induced by high-fluence, high-intensity x-ray free-electron laser (XFEL) pulses. These resonances are responsible for ionization far beyond that predicted by the sequential single photon absorption model and are central to a quantitative understanding of atomic ionization dynamics in XFEL pulses. We also present calculated multiphoton ionization dynamics for Kr and Xe atoms in XFEL pulses for a variety of conditions, to compare the effects of bandwidth, pulse duration, pulse fluence, and photon energy. This comprehensive computational investigation reveals areas in the photon energy-pulse fluence landscape where resonances are critically important. We also uncover a mechanism, preservation of inner-shell vacancies (PIVS), whereby radiation damage is enhanced at higher XFEL intensities and identify the sequence of core-outer-Rydberg, core-valence, and core-core resonances encountered during multiphoton x-ray ionization.

  17. An H&beta surge and X-ray jet - Magnetic properties and velocity patterns

    NASA Astrophysics Data System (ADS)

    Zhang, J.; Wang, J.; Liu, Y.

    2000-09-01

    We described simultaneous observations of a surge in H&beta and an X-ray jet in NOAA 8100 on November 1, 1997. We found that the H&beta surge was spatially coincident with the X-ray jet. They occurred at the site where the pre-existing magnetic flux was ``cancelled" by a newly emerging flux of opposite polarity. At the base of the surge we identified surge-flaring in the H&beta filtergrams, and both blueshifts and redshifts in the H&beta Dopplergrams. The X-ray jet appeared about 2 hours after the first appearance of the surge. The surge consisted of two ejecting threads. Initially, these two components were twisted together, then became untwisted before the appearance of the X-ray jet. This example presents an alternative scenario of plasma ejection. The magnetic reconnection in the lower atmosphere, which was responsible for the H&beta surge, created the twisted surge threads; the X-ray jet likely resulted from a fast reconnection in the upper atmosphere, which took place well after the H&beta surge.

  18. Modification of X-Ray Tissue Doses with Strong Magnetic Fields.

    NASA Astrophysics Data System (ADS)

    Borke, Michael Faison

    1990-01-01

    The modification of dose distributions from secondary electrons produced by accelerator-generated photon or electron beams in the presence of strong magnetic fields was studied. A need exists to predict the action of magnetic fields on X-ray tissue doses and to identify those combinations of X-ray energies, magnetic field strengths, and tissue factors where the dose might be changed significantly from an exposure without the presence of a magnetic field. Modification of X-ray produced tissue dose arises from the ability of a strong magnetic field to induce deflections on the path of secondary electrons. In order to demonstrate the existence of this deflection, measurements were made of the relative dose distributions present within a tissue -equivalent phantom produced by exposures to X-rays and in the presence of strong magnetic fields. The dose measurements were made using radiographic film detectors, sandwiched within a polystyrene target phantom irradiated in the presence of different magnetic field intensities. The fields were oriented transversely to the direction of the incident X-ray beam. Optical densities of the film exposures were converted to equivalent tissue doses for comparison to the predictions of a semi-analytical relative dose model for the process. This model was a combination of the electron Continuous Slowing Down Approximation, modified to account for multiple scattering, and a exponential photon dose model. As a result of this work, it was found that: (1) strong magnetic fields in the range of 1.2 to 5 T can induce changes in the tissue distribution of X-ray produced dose to small volumes in excess of 10%, (2) the region of maximum dose may be displaced significantly from the undeflected target volume, and (3) a reasonable estimate of the magnitude of these changes can be predicted, if the X-ray energy distribution and magnetic flux density are known. Such changes in deposited doses may be clinically significant and should be taken into

  19. Theory of X-ray absorption and resonant X-ray emission spectra by electric quadrupole excitation in light rare-earth systems

    NASA Astrophysics Data System (ADS)

    Nakazawa, M.; Fukui, K.; Kotani, A.

    2003-02-01

    We have made precise theoretical calculations for both 2 p3/2→4 f X-ray absorption spectroscopy (XAS) and 4 d→2 p3/2 resonant X-ray emission spectroscopy (RXES) by electric quadrupole excitations at the L3 edge of light rare-earth elements, by means of atomic model with full multiplet effects. The calculation is based on the second-order optical formula, and the effect of the incident photon polarization is taken into account. It is shown that the 4 d-4 f interaction plays a more important role in 4 d→2 p3/2 RXES than the 4 f-4 f interaction does. Moreover, the calculated results of 4 d→2 p3/2 RXES show the strong polarization dependence, and it is originated from the spin multiplicity, which is derived from the 4 d-4 f interaction, of the RXES final states.

  20. Testing Models of Resonant Compton Scattering in X-Ray Pulsars

    NASA Technical Reports Server (NTRS)

    Brainerd, Jerome J.

    2000-01-01

    Over the performance period covered by the grant, the principal investigator modified a Monte Carlo Compton scattering code to model the propagation of x-rays through the magnetosphere of accreting neutron stars. These modifications were made to enable the author to compare the observations of x-ray pulsars to theoretical models of the system. The original code was designed to study relativistic plasmas with one of two geometries: a plane parallel plasma with a differential relativistic bulk velocity, and a static spherically symmetric plasma.- This code did not treat gravitational bending or bulk motion in the magnetosphere of a neutron star. Under the grant, the author incorporated code to trace light paths in a Schwarzschild metric. The code was modified to keep track of the photon polarization during propagati on. The investigator also modified the code so that bulk motion in an axisymmetric system is treated properly. An approximate treatment for resonant Compton scattering was added to the code. Finally, code was added that creates model observables that can be compared to observations, such as projected x-ray emission maps and energy-dependent light curves. Comparison to observations is now commencing.

  1. DEGRADATION OF MAGNET EPOXY AT NSLS X-RAY RING.

    SciTech Connect

    HU,J.P.; ZHONG,Z.; HAAS,E.; HULBERT,S.; HUBBARD,R.

    2004-05-24

    Epoxy resin degradation was analyzed for NSLS X-ring magnets after two decades of 2.58-2.8 GeV continuous electron-beam operation, based on results obtained from thermoluminescent dosimeters irradiated along the NSLS ring and epoxy samples irradiated at the beamline target location. A Monte Carlo-based particle transport code, MCNP, was utilized to verify the dose from synchrotron radiation distributed along the axial- and transverse-direction in a ring model, which simulates the geometry of a ring quadrupole magnet and its central vacuum chamber downstream of the bending-magnet photon ports. The actual life expectancy of thoroughly vacuum baked-and-cured epoxy resin was estimated from radiation tests on similar polymeric materials using a radiation source developed for electrical insulation and mechanical structure studies.

  2. Introducing a New Capability at SSRL: Resonant Soft X-ray Scattering

    NASA Astrophysics Data System (ADS)

    Lee, Jun-Sik; Jang, Hoyoung; Lu, Donghui; Kao, Chi-Chang

    Stanford Synchrotron Radiation Lightsource (SSRL) at SLAC recently developed a setup for the resonant soft x-ray scattering (RSXS). In general, the RSXS technique uniquely probes not only structural information, but also chemical specific information. This is because this technique can explore the spatial periodicities of charge, orbital, spin, and lattice with spectroscopic aspect. Moreover, the soft x-ray range is particularly relevant for a study of soft materials as it covers the K-edge of C, N, F, and O, as well as the L-edges of transition metals and M-edges of rare-earth elements. Hence, the RSXS capability has been regarded as a very powerful technique for investigating the intrinsic properties of materials such as quantum- and energy-materials. The RSXS capability at the SSRL composes of in-vacuum 4-circle diffractometer. There are also the fully motorized sample-motion manipulations. Also, the sample can be cooled down to 25 K via the liquid helium. This capability has been installed at BL 13-3, where the photon source is from elliptically polarized undulator (EPU). Covering the photon energies is from 230 eV to 1400 eV. Furthermore, this EPU system offers more degree of freedoms for controlling x-ray polarizations (linear and circular). Using the advance of controlling x-ray polarization, we can also investigate a morphology effect of local domain/grain in materials. The detailed introduction of the RSXS end-station and several results will be touched in this poster presentation.

  3. Trends in ultracool dwarf magnetism. I. X-ray suppression and radio enhancement

    SciTech Connect

    Williams, P. K. G.; Berger, E.; Cook, B. A.

    2014-04-10

    Although ultracool dwarfs (UCDs) are now known to generate and dissipate strong magnetic fields, a clear understanding of the underlying dynamo is still lacking. We have performed X-ray and radio observations of seven UCDs in a narrow range of spectral type (M6.5-M9.5) but spanning a wide range of projected rotational velocities (vsin i ≈ 3-40 km s{sup –1}). We have also analyzed unpublished archival Chandra observations of four additional objects. All of the newly observed targets are detected in the X-ray, while only one is detected in the radio, with the remainder having sensitive upper limits. We present a database of UCDs with both radio and X-ray measurements and consider the data in light of the so-called Güdel-Benz relation (GBR) between magnetic activity in these bands. Some UCDs have very bright radio emission and faint X-ray emission compared to what would be expected for rapid rotators, while others show the opposite behavior. We show that UCDs would still be radio-overluminous relative to the GBR even if their X-ray emission were at standard rapid-rotator 'saturation' levels. Recent results from Zeeman-Doppler imaging and geodynamo simulations suggest that rapidly rotating UCDs may harbor a bistable dynamo that supports either a stronger, axisymmetric magnetic field or a weaker, non-axisymmetric field. We suggest that the data can be explained in a scenario in which strong-field objects obey the GBR while weak-field objects are radio-overluminous and X-ray-underluminous, possibly because of a population of gyrosynchrotron-emitting coronal electrons that is continuously replenished by low-energy reconnection events.

  4. Trends in Ultracool Dwarf Magnetism. I. X-Ray Suppression and Radio Enhancement

    NASA Astrophysics Data System (ADS)

    Williams, P. K. G.; Cook, B. A.; Berger, E.

    2014-04-01

    Although ultracool dwarfs (UCDs) are now known to generate and dissipate strong magnetic fields, a clear understanding of the underlying dynamo is still lacking. We have performed X-ray and radio observations of seven UCDs in a narrow range of spectral type (M6.5-M9.5) but spanning a wide range of projected rotational velocities (vsin i ≈ 3-40 km s-1). We have also analyzed unpublished archival Chandra observations of four additional objects. All of the newly observed targets are detected in the X-ray, while only one is detected in the radio, with the remainder having sensitive upper limits. We present a database of UCDs with both radio and X-ray measurements and consider the data in light of the so-called Güdel-Benz relation (GBR) between magnetic activity in these bands. Some UCDs have very bright radio emission and faint X-ray emission compared to what would be expected for rapid rotators, while others show the opposite behavior. We show that UCDs would still be radio-overluminous relative to the GBR even if their X-ray emission were at standard rapid-rotator "saturation" levels. Recent results from Zeeman-Doppler imaging and geodynamo simulations suggest that rapidly rotating UCDs may harbor a bistable dynamo that supports either a stronger, axisymmetric magnetic field or a weaker, non-axisymmetric field. We suggest that the data can be explained in a scenario in which strong-field objects obey the GBR while weak-field objects are radio-overluminous and X-ray-underluminous, possibly because of a population of gyrosynchrotron-emitting coronal electrons that is continuously replenished by low-energy reconnection events.

  5. High-resolution dichroic imaging of magnetic flux distributions in superconductors with scanning x-ray microscopy

    SciTech Connect

    Ruoß, S. Stahl, C.; Weigand, M.; Schütz, G.; Albrecht, J.

    2015-01-12

    The penetration of magnetic flux into high-temperature superconductors has been observed using a high-resolution technique based on x-ray magnetic circular dichroism. Superconductors coated with thin soft-magnetic layers are observed in a scanning x-ray microscope under the influence of external magnetic fields. Resulting electric currents in the superconductor create an inhomogeneous magnetic field distribution above the superconductor and lead to a local reorientation of the ferromagnetic layer. Measuring the local magnetization of the ferromagnet by x-ray absorption microscopy with circular-polarized radiation allows the analysis of the magnetic flux distribution in the superconductor with a spatial resolution on the nanoscale.

  6. Resonant elastic x-ray scattering from the skyrmion lattice in Cu2OSeO3

    NASA Astrophysics Data System (ADS)

    Zhang, S. L.; Bauer, A.; Berger, H.; Pfleiderer, C.; van der Laan, G.; Hesjedal, T.

    2016-06-01

    We report the study of the skyrmion state near the surface of Cu2OSeO3 using soft resonant elastic x-ray scattering (REXS) at the Cu L3 edge. Within the lateral sampling area of 200 ×200 μ m2 , we found a long-range-ordered skyrmion lattice phase as well as the formation of skyrmion domains via the multiple splitting of the diffraction spots. In a recent REXS study of the skyrmion phase of Cu2OSeO3 [M. C. Langner, S. Roy, S. Mishra, J. Lee, X. Shi, M. Hossain, Y.-D. Chuang, S. Seki, Y. Tokura, S. Kevan, and R. Schoenlein, Phys. Rev. Lett. 112, 167202 (2014), 10.1103/PhysRevLett.112.167202], the authors reported the observation of the unexpected existence of two distinct skyrmion sublattices that arise from inequivalent Cu sites, and that the rotation and superposition of the two periodic structures lead to a moiré pattern. However, we find no energy splitting of the Cu peak in x-ray-absorption measurements and, instead, discuss alternative origins of the peak splitting. In particular, we find that for magnetic field directions deviating from the major cubic axes a multidomain skyrmion lattice state is obtained, which consistently explains the splitting of the magnetic spots into two—and more—peaks.

  7. Novel rhenium gasket design for nuclear resonant inelastic x-ray scattering at high pressure

    SciTech Connect

    Tanis, Elizabeth A.; Giefers, Hubertus; Nicol, Malcolm F.

    2008-02-15

    For the first time, a highly absorbing element, rhenium, has been proven to be a strong, reliable, and safe gasket material for achieving high pressure in nuclear resonant inelastic x-ray scattering (NRIXS) experiments. Rhenium foil was cut into rectangular slices and in order to reduce absorption, the elevated imprint due to preindenting of the gasket is removed using electrical discharge machining. By utilizing this novel gasket design, transmission losses were mitigated while performing NRIXS experiments conducted on the {sup 119}Sn and {sup 57}Fe Moessbauer isotopes.

  8. Interfacial Magnetism in Complex Oxide Heterostructures Probed by Neutrons and X-rays

    DOE PAGESBeta

    Liu, Yaohua; Ke, Xianglin

    2015-09-02

    Magnetic complex-oxide heterostructures are of keen interest because a wealth of phenomena at the interface of dissimilar materials can give rise to fundamentally new physics and potentially valuable functionalities. Altered magnetization, novel magnetic coupling and emergent interfacial magnetism at the epitaxial layered-oxide interfaces have all been intensively investigated, which shapes our understanding on how to utilize those materials, particularly for spintronics. Neutron and x-ray based techniques have played a decisive role in characterizing interfacial magnetic structures and clarifying the underlying physics in this rapidly developing field. Here we review some recent experimental results, with an emphasis on those studied viamore » polarized neutron reflectometery and polarized x-ray absorption spectroscopy. We conclude with some perspectives.« less

  9. Interfacial Magnetism in Complex Oxide Heterostructures Probed by Neutrons and X-rays

    SciTech Connect

    Liu, Yaohua; Ke, Xianglin

    2015-09-02

    Magnetic complex-oxide heterostructures are of keen interest because a wealth of phenomena at the interface of dissimilar materials can give rise to fundamentally new physics and potentially valuable functionalities. Altered magnetization, novel magnetic coupling and emergent interfacial magnetism at the epitaxial layered-oxide interfaces have all been intensively investigated, which shapes our understanding on how to utilize those materials, particularly for spintronics. Neutron and x-ray based techniques have played a decisive role in characterizing interfacial magnetic structures and clarifying the underlying physics in this rapidly developing field. Here we review some recent experimental results, with an emphasis on those studied via polarized neutron reflectometery and polarized x-ray absorption spectroscopy. We conclude with some perspectives.

  10. X-ray study of aligned magnetic stripe domains in perpendicular multilayers

    SciTech Connect

    Hellwig, O.; Denbeaux, G.P.; Kortright, J.B.; Fullerton, Eric E.

    2003-03-03

    We have investigated the stripe domain structure and the magnetic reversal of perpendicular Co/Pt based multilayers at room temperature using magnetometry, magnetic imaging and magnetic x-ray scattering. In-plane field cycling aligns the stripe domains along the field direction. In magnetic x-ray scattering the parallel stripe domains act as a magnetic grating resulting in observed Bragg reflections up to 5th order. We model the scattering profile to extract and quantify the domain as well as domain wall widths. Applying fields up to {approx}1.2 kOe perpendicular to the film reversibly changes the relative width of up versus down domains while maintaining the overall stripe periodicity. Fields above 1.2 kOe introduce irreversible changes into the domain structure by contracting and finally annihilating individual stripe domains. We compare the current results with modeling and previous measurements of films with perpendicular anisotropy.

  11. Polarized Resonant Critical Dimension Small Angle X-Ray Scattering for the Characterization of Polymer Patterns

    NASA Astrophysics Data System (ADS)

    Liman, Christopher; Sunday, Daniel; Ro, Hyun Wook; Richter, Lee; Hannon, Adam; Kline, R. Joseph

    Critical dimension small angle X-ray scattering (CDSAXS) is a recently developed technique that enables the characterization of the three-dimensional shape of periodic patterns, such as directed self-assembled (DSA) block copolymer (BCP) lamellae thin films. Information about the polymer patterns is extracted by fitting simulated scattering patterns to the experimental ones using an inverse iterative algorithm. Conducting CDSAXS at resonant energies near the carbon or nitrogen edge can enhance the strength of the scattering, but also causes the scattering to be influenced by any anisotropic orientation of the polymer chains. In this work, to assess the degree to which the scattering may be influenced by orientation, we simulate polarized resonant CDSAXS patterns for BCP lamellae with varying degrees of orientation, as well as orientation as a function of location within the lamellae, for different polarizations of the incident X-rays. Also, to assess the influence of a higher degree of orientation, we use capillary force lithography to pattern nanogratings of two semiconducting homopolymers which are known to orient strongly. We characterize these nanogratings, which have similar length scales to DSA BCP lamellae, with polarized resonant CDSAXS and spectroscopic ellipsometry. Finally, we fit simulated CDSAXS and ellipsometric data to the experimental data to obtain information about the shape and the orientation of the nanogratings.

  12. Low-energy d-d excitations in MnO studied by resonant x-ray fluorescence spectroscopy

    SciTech Connect

    Butorin, S.M.; Guo, J.; Magnuson, M.

    1997-04-01

    Resonant soft X-ray emission spectroscopy has been demonstrated to possess interesting abilities for studies of electronic structure in various systems, such as symmetry probing, alignment and polarization dependence, sensitivity to channel interference, etc. In the present abstract the authors focus on the feasibility of resonant soft X-ray emission to probe low energy excitations by means of resonant electronic X-ray Raman scattering. Resonant X-ray emission can be regarded as an inelastic scattering process where a system in the ground state is transferred to a low excited state via a virtual core excitation. The energy closeness to a core excitation of the exciting radiation enhances the (generally) low probability for inelastic scattering at these wavelengths. Therefore soft X-ray emission spectroscopy (in resonant electronic Raman mode) can be used to study low energy d-d excitations in transition metal systems. The involvement of the intermediate core state allows one to use the selection rules of X-ray emission, and the appearance of the elastically scattered line in the spectra provides the reference to the ground state.

  13. Influence of resonances on spectral formation of x-ray lines in Fe XVII.

    PubMed

    Chen, Guo Xin; Pradhan, Anil K

    2002-07-01

    New theoretical results from large-scale relativistic close coupling calculations reveal the precise effect of resonances in collisional excitation of x-ray lines of Ne-like Fe XVII. By employing the Breit-Pauli R-matrix method and an 89-level eigenfunction expansion, including up to n = 4 levels, significant resonance enhancement of the collision strengths of forbidden and intercombination transitions is shown. The present results should help resolve long-standing discrepancies; in particular, the present line ratios of three benchmark diagnostic lines 3C, 3D, and 3E at 15.014, 15.265, and 15.456 A, respectively, are in excellent agreement with two independent measurements on electron-beam ion traps. Strong energy dependence in cross sections due to resonances is demonstrated. PMID:12097041

  14. Resonant Soft X-Ray Contrast Variation Methods as Composition-Specific Probes of Thin Polymer Film Structure

    SciTech Connect

    Welch, Cynthia; Welch, Cynthia F.; Hjelm, Rex P.; Mang, Joseph T.; Hawley, Marilyn E.; Wrobleski, Debra A.; Orler, E. Bruce; Kortright, Jeffrey B

    2008-04-04

    We have developed complementary soft x-ray scattering and reflectometry techniques that allow for the morphological analysis of thin polymer films without resorting to chemical modification or isotopic 2 labeling. With these techniques, we achieve significant, x-ray energy-dependent contrast between carbon atoms in different chemical environments using soft x-ray resonance at the carbon edge. Because carbon-containing samples absorb strongly in this region, the scattering length density depends on both the real and imaginary parts of the atomic scattering factors. Using a model polymer film of poly(styrene-b-methyl methacrylate), we show that the soft x-ray reflectivity data is much more sensitive to these atomic scattering factors than the soft x-ray scattering data. Nevertheless, fits to both types of data yield useful morphological details on the polymer?slamellar structure that are consistent with each other and with literature values.

  15. Standing-wave excited soft x-ray photoemission microscopy: application to Co microdot magnetic arrays

    SciTech Connect

    Gray, Alexander; Kronast, Florian; Papp, Christian; Yang, See-Hun; Cramm, Stefan; Krug, Ingo P.; Salmassi, Farhad; Gullikson, Eric M.; Hilken, Dawn L.; Anderson, Erik H.; Fischer, Peter; Durr, Hermann A.; Schneider, Claus M.; Fadley, Charles S.

    2010-10-29

    We demonstrate the addition of depth resolution to the usual two-dimensional images in photoelectron emission microscopy (PEEM), with application to a square array of circular magnetic Co microdots. The method is based on excitation with soft x-ray standing-waves generated by Bragg reflection from a multilayer mirror substrate. Standing wave is moved vertically through sample simply by varying the photon energy around the Bragg condition. Depth-resolved PEEM images were obtained for all of the observed elements. Photoemission intensities as functions of photon energy were compared to x-ray optical calculations in order to quantitatively derive the depth-resolved film structure of the sample.

  16. Instrument for x-ray magnetic circular dichroism measurements at high pressures

    SciTech Connect

    Haskel, D.; Tseng, Y. C.; Lang, J. C.; Sinogeikin, S.

    2007-08-15

    An instrument has been developed for x-ray magnetic circular dichroism (XMCD) measurements at high pressures and low temperatures. This instrument couples a nonmagnetic copper-beryllium diamond anvil cell featuring perforated diamonds with a helium flow cryostat and an electromagnet. The applied pressure can be controlled in situ using a gas membrane and calibrated using Cu K-edge x-ray absorption fine structure measurements. The performance of this instrument was tested by measuring the XMCD spectra of the Gd{sub 5}Si{sub 2}Ge{sub 2} giant magnetocaloric material.

  17. Magnetic x-ray circular dichroism in Fe Co Pt multilayers

    SciTech Connect

    Tobin, J.G.; Jankowski, A.F.; Waddill, G.D.; Sterne, P.A.

    1994-04-01

    Magnetic x-ray circular dichroism in x-ray absorption has been used to investigate the ternary multilayer system, Fe Co Pt. Samples were prepared by planar magnetron sputter deposition and carefully characterized, using a variety of techniques such as grazing-incidence and high-angle x-ray scattering, Auger depth profiling and cross-section transmission electron microscopy. As previously reported, the Fe9.5{Angstrom} Pt9.5{Angstrom} exhibits a large dichroism in the Fe 2p absorption. Interestingly while the Co9.5{Angstrom} Pt9.5{Angstrom} has no measurable dichroism, the Fe4.7{Angstrom} Co4.7{Angstrom} Pt9.5{Angstrom} sample has a dichroism at both the Fe 2p and Co 2p absorption edges. These and other results are compared to slab calculation predictions. Possible explanations are discussed.

  18. Time Resolved X-ray Magnetic Circular Dichroism at the Linac Coherent Light Source

    NASA Astrophysics Data System (ADS)

    Schlotter, W.; Higley, D.; Jal, E.; Dakovski, G.; Yuan, E.; MacArthur, J.; Lutman, A.; Hirsch, K.; Granitzka, P.; Chen, Z.; Coslovich, G.; Hoffman, M.; Mitra, A.; Reid, A.; Hart, P.; Nuhn, H.-D.; Duerr, H.; Arenholz, E.; Shafer, P.; Dennes, P.; Joseph, J.; Guyader, L.; Tsukamoto, A.

    We demonstrate ultrafast time resolved X-ray Magnetic Circular Dichroism on optically switchable GdFeCo thin film samples. This method extends the element specificity of time resolved x-ray absorption spectroscopy to characterize the evolution of electron spin and orbital angular momenta. These measurements were enabled by a recent upgrade at the Linac Coherent Light Source (LCLS) to generate circularly polarized x-rays. Additionally these measurements were enhanced by new detection systems that benefit all x-ray absorption spectroscopy experiments performed in transmission. Consequently static XMCD data are in excellent agreement with similar measurements at synchrotron light sources. The LCLS is an x-ray free electron laser user facility accessible via a peer-reviewed proposal process. Acknowledgement: The Linac Coherent Light Source (LCLS), SLAC National Accelerator Laboratory, is supported by the U.S. Department of Energy, Office of Science, Office of Basic Energy Sciences under Contract No. DE-AC02-76SF00515.

  19. Tracing the X-Ray Trail

    MedlinePlus

    What you need to know about… Tracing the X-ray Trail If you’ve just completed an x-ray, computed tomography (CT), magnetic resonance (MR) Start here! or other diagnostic imaging procedure, you probably want to know when you will ... los rayos X Si acaba de hacerse una radiografía, tomografía ¡Empezar ...

  20. X-Ray Rocking Curve and Ferromagnetic Resonance Investigations of Ion-Implanted Crystals

    NASA Astrophysics Data System (ADS)

    Speriosu, Virgil Simon

    A kinematical model for general Bragg case x-ray diffraction in nonuniform films is presented. The model incorporates depth-dependent strain and structure factor. Profiles of strain and structure factor are obtained by fitting experimental rocking curves. The method is applicable to ion-implanted, diffused and multilayer crystalline structures such as heterojunctions. A comparison is made between profiles of strain and incoherent atomic displacements obtained from rocking curves and Rutherford backscattering spectrometry in Ne('+) -implanted Gd(,3)Ga(,5)O(,12). The ranges of sensitivity of the two techniques overlap for about one decade in implantation dose up to the amorphous threshold. The two techniques are in excellent agreement on the near-surface strain, but differ significantly at depths below (TURNEQ)500A. The profiles of incoherently displaced atoms agree within a factor of two. The rocking curve method is combined with analysis of ferromagnetic resonance spectra for characterization of Gd,Tm,Ga:YIG films implanted with Ne('+), He('+), and H(,2)('+) over a wide range of doses. Profiles of normal strain, lateral strain and damage were obtained. Magnetic profiles were compared with the strain profiles. The local change in uniaxial anisotropy field (DELTA)H(,k) with increasing strain shows an initially linear rise for both He('+) and Ne('+), in agreement with the magnetostriction effect. For strain values greater than (TURNEQ)1.5%, (DELTA)H(,k) saturates and decreases to nearly zero when the material becomes paramagnetic. For H(,2)('+) implantation the total (DELTA)H(,k) consists of a magnetostrictive contribution due to strain and of a comparable excess contribution associated with the local concentration of hydrogen. With increasing annealing temperature the excess (DELTA)H(,k) diminishes and above 400(DEGREES)C the only component of (DELTA)H(,k) is magnetostrictive. For all three species the behavior of the saturation magnetization 4(pi)M, the exchange

  1. Correlation between x-ray reciprocal space maps and magnetic properties of current-induced magnetization switching pseudospin valve structures

    NASA Astrophysics Data System (ADS)

    Siffalovic, P.; Chitu, L.; Halahovets, Y.; Jergel, M.; Senderak, R.; Majkova, E.; Luby, S.

    2007-02-01

    A thorough study of x-ray diffuse scattering from the spin valve structures suitable for current induced magnetization switching is presented. We used complete reciprocal space maps of diffusely scattered x rays to show the effect of bottom Au electrode on the morphology of buried spin valve interfaces. The thickness and roughness of each layer, as well as vertical and lateral roughness correlation lengths, were obtained. The impact of interfaces morphology on the magnetic properties, especially on the increase of spin valve coercivity, was measured and simulated within the frame of Néel magnetostatic coupling model based on the parameters from the x-ray diffuse scattering data. Measurement of x-ray diffuse scattering presents a rapid and nondestructive technique for in-depth and self-contained analysis of spin valve layers and interfaces.

  2. X-ray photoemission electron microscopy, a tool for the investigation of complex magnetic structures.

    SciTech Connect

    Scholl, Andreas; Ohldag, Hendrik; Nolting, Frithjof; Stohr, Joachim; Padmore, Howard A.

    2001-08-30

    X-ray Photoemission Electron Microscopy unites the chemical specificity and magnetic sensitivity of soft x-ray absorption techniques with the high spatial resolution of electron microscopy. The discussed instrument possesses a spatial resolution of better than 50 nm and is located at a bending magnet beamline at the Advanced Light Source, providing linearly and circularly polarized radiation between 250 and 1300 eV. We will present examples which demonstrate the power of this technique applied to problems in the field of thin film magnetism. The chemical and elemental specificity is of particular importance for the study of magnetic exchange coupling because it allows separating the signal of the different layers and interfaces in complex multi-layered structures.

  3. A portable high-field pulsed magnet system for x-ray scattering studies.

    SciTech Connect

    Islam, Z.; Ruff, J.P.C.; Nojiri, H.; Matsuda, Y. H.; Ross, K. A.; Gaulin, B. D.; Qu, Z.; Lang, J. C.

    2009-01-01

    We present a portable pulsed-magnet system for x-ray studies of materials in high magnetic fields (up to 30 T). The apparatus consists of a split-pair of minicoils cooled on a closed-cycle cryostat, which is used for x-ray diffraction studies with applied field normal to the scattering plane. A second independent closed-cycle cryostat is used for cooling the sample to near liquid helium temperatures. Pulsed magnetic fields (- 1 ms in total duration) are generated by discharging a configurable capacitor bank into the magnet coils. Time-resolved scattering data are collected using a combination of a fast single-photon counting detector, a multichannel scaler, and a high-resolution digital storage oscilloscope. The capabilities of this instrument are used to study a geometrically frustrated system revealing strong magnetostrictive effects in the spin-liquid state.

  4. Magnetic x-ray microscopy at low temperatures - Visualization of flux distributions in superconductors

    NASA Astrophysics Data System (ADS)

    Stahl, Claudia; Ruoß, Stephen; Weigand, Markus; Bechtel, Michael; Schütz, Gisela; Albrecht, Joachim

    2016-01-01

    X-ray Magnetic Circular Dichroism (XMCD) microscopy at liquid nitrogen temperature has been performed on bilayers of high-Tc superconducting YBCO (YBa2Cu3O7-δ) and soft-magnetic Co40Fe40B20. This should allow us to map the magnetic flux density distribution in the current-carrying state of the superconductor with high spatial resolution. For that purpose the UHV scanning X-ray microscope MAXYMUS has been upgraded by a MMR Micro Miniature Joule-Thompson cryostat capable of temperatures between 75 K and 580 K. Resulting XMCD images of the magnetic flux density in the superconductor with a field of view ranging from millimeters to micrometers are presented. The microscope's unique combination of total electron yield (TEY) measurements together with low temperatures offers novel possibilities concerning the current transport in superconductors on small length scales.

  5. Magnetic Dynamos and X-Ray Activity in Ultracool Dwarfs (UCDs): Surprises in the Radio Band

    NASA Astrophysics Data System (ADS)

    Williams, Peter K.; Cook, B. A.; Berger, E.

    2014-01-01

    Radio observations established early on that some brown dwarfs host kilogauss magnetic fields, despite their low temperatures and the absence of the shearing tachocline that is believed to be key to the solar dynamo. The observed radio emission is often surprisingly bright, exceeding the standard magnetic radio/X-ray (Güdel-Benz) relation by as much as five orders of magnitude. This effect is still not satisfactorily explained. In an attempt to improve matters, we have constructed and analyzed a comprehensive database of ultracool dwarfs with both radio and X-ray data, including new observations of seven targets with Chandra and the upgraded VLA. While all of the newly-observed objects were detected in the X-ray, only one was detected in the radio. These new targets are thus consistent with the standard relation, in striking contrast with some previous data. Some pairs of dwarfs with outwardly similar characteristics (spectral type, v sin i) have dramatically different emission properties, with radio/X-ray ratios that differ by two orders of magnitude. These results suggest that there is dramatic variance in ultracool magnetic activity. As we also discuss in a companion poster examining the relation between rotation and activity, variation in the topology of the magnetic field may explain the data. This work is supported in part by the NSF REU and DOD ASSURE programs under NSF grant no. 1262851 and by the Smithsonian Institution. We also acknowledge support from the NSF through Grant AST-1008361 and from NASA through Chandra Award Number G02-13007A issued by the Chandra X-ray Observatory Center, operated by the Smithsonian Astrophysical Observatory and NASA under contract NAS8-03060.

  6. Effects of x-ray radiation on the magnetization of high T sub c superconductors

    SciTech Connect

    Artuso, J.; Franks, L.; Hull, K. . Energy Measurements Group); Symko, O.G. . Dept. of Physics)

    1990-01-01

    Experimental results are presented on the effects of x-ray radiation on superconducting samples of polycrystalline YBaCuO and BiSrCaCuO. The radiation effects are detected by changes of the magnetization of the sample using a SQUID magnetometer. In the presence of radiation, the changes in magnetization correspond to release of trapped flux, fluxon destruction, and to low frequency noise due to flux flow. 3 refs., 4 figs.

  7. Ground state potential energy surfaces around selected atoms from resonant inelastic x-ray scattering

    NASA Astrophysics Data System (ADS)

    Schreck, Simon; Pietzsch, Annette; Kennedy, Brian; Såthe, Conny; Miedema, Piter S.; Techert, Simone; Strocov, Vladimir N.; Schmitt, Thorsten; Hennies, Franz; Rubensson, Jan-Erik; Föhlisch, Alexander

    2016-01-01

    Thermally driven chemistry as well as materials’ functionality are determined by the potential energy surface of a systems electronic ground state. This makes the potential energy surface a central and powerful concept in physics, chemistry and materials science. However, direct experimental access to the potential energy surface locally around atomic centers and to its long-range structure are lacking. Here we demonstrate how sub-natural linewidth resonant inelastic soft x-ray scattering at vibrational resolution is utilized to determine ground state potential energy surfaces locally and detect long-range changes of the potentials that are driven by local modifications. We show how the general concept is applicable not only to small isolated molecules such as O2 but also to strongly interacting systems such as the hydrogen bond network in liquid water. The weak perturbation to the potential energy surface through hydrogen bonding is observed as a trend towards softening of the ground state potential around the coordinating atom. The instrumental developments in high resolution resonant inelastic soft x-ray scattering are currently accelerating and will enable broad application of the presented approach. With this multidimensional potential energy surfaces that characterize collective phenomena such as (bio)molecular function or high-temperature superconductivity will become accessible in near future.

  8. Ground state potential energy surfaces around selected atoms from resonant inelastic x-ray scattering.

    PubMed

    Schreck, Simon; Pietzsch, Annette; Kennedy, Brian; Såthe, Conny; Miedema, Piter S; Techert, Simone; Strocov, Vladimir N; Schmitt, Thorsten; Hennies, Franz; Rubensson, Jan-Erik; Föhlisch, Alexander

    2016-01-01

    Thermally driven chemistry as well as materials' functionality are determined by the potential energy surface of a systems electronic ground state. This makes the potential energy surface a central and powerful concept in physics, chemistry and materials science. However, direct experimental access to the potential energy surface locally around atomic centers and to its long-range structure are lacking. Here we demonstrate how sub-natural linewidth resonant inelastic soft x-ray scattering at vibrational resolution is utilized to determine ground state potential energy surfaces locally and detect long-range changes of the potentials that are driven by local modifications. We show how the general concept is applicable not only to small isolated molecules such as O2 but also to strongly interacting systems such as the hydrogen bond network in liquid water. The weak perturbation to the potential energy surface through hydrogen bonding is observed as a trend towards softening of the ground state potential around the coordinating atom. The instrumental developments in high resolution resonant inelastic soft x-ray scattering are currently accelerating and will enable broad application of the presented approach. With this multidimensional potential energy surfaces that characterize collective phenomena such as (bio)molecular function or high-temperature superconductivity will become accessible in near future. PMID:26821751

  9. Which orbital and charge ordering in transition metal oxides can resonant X-ray diffraction detect?

    NASA Astrophysics Data System (ADS)

    Di Matteo, Sergio

    2009-11-01

    The present article is a brief critical review about the possibility of detecting charge and/or orbital order in transition-metal oxides by means of resonant x-ray diffraction. Many recent models of transition-metal oxides are based on charge and/or orbitally ordered ground-states and it has been claimed in the past that resonant x-ray diffraction is able to confirm or reject them. However, in spite of the many merits of this technique, such claims are ambiguous, because the interpretative frameworks used to analyze such results in transition-metal oxides, where structural distortions are always associated to the claimed charged/orbitally ordered transition, strongly influence (not to say suggest) the answer. In order to clarify this point, I discuss the two different definitions of orbital and charge orderings which are often used in the literature without a clear distinction. My conclusion is that the answer to the question of the title depends on which definition is adopted.

  10. Ground state potential energy surfaces around selected atoms from resonant inelastic x-ray scattering

    PubMed Central

    Schreck, Simon; Pietzsch, Annette; Kennedy, Brian; Såthe, Conny; Miedema, Piter S.; Techert, Simone; Strocov, Vladimir N.; Schmitt, Thorsten; Hennies, Franz; Rubensson, Jan-Erik; Föhlisch, Alexander

    2016-01-01

    Thermally driven chemistry as well as materials’ functionality are determined by the potential energy surface of a systems electronic ground state. This makes the potential energy surface a central and powerful concept in physics, chemistry and materials science. However, direct experimental access to the potential energy surface locally around atomic centers and to its long-range structure are lacking. Here we demonstrate how sub-natural linewidth resonant inelastic soft x-ray scattering at vibrational resolution is utilized to determine ground state potential energy surfaces locally and detect long-range changes of the potentials that are driven by local modifications. We show how the general concept is applicable not only to small isolated molecules such as O2 but also to strongly interacting systems such as the hydrogen bond network in liquid water. The weak perturbation to the potential energy surface through hydrogen bonding is observed as a trend towards softening of the ground state potential around the coordinating atom. The instrumental developments in high resolution resonant inelastic soft x-ray scattering are currently accelerating and will enable broad application of the presented approach. With this multidimensional potential energy surfaces that characterize collective phenomena such as (bio)molecular function or high-temperature superconductivity will become accessible in near future. PMID:26821751

  11. Identification of inversion domains in KTiOPO4 via resonant X-ray diffraction.

    PubMed

    Fabrizi, Federica; Thomas, Pamela A; Nisbet, Gareth; Collins, Stephen P

    2015-07-01

    A novel method is presented for the identification of the absolute crystallographic structure in multi-domain polar materials such as ferroelectric KTiOPO4. Resonant (or 'anomalous') X-ray diffraction spectra collected across the absorption K edge of Ti (4.966 keV) on a single Bragg reflection demonstrate a huge intensity ratio above and below the edge, providing a polar domain contrast of ∼270. This allows one to map the spatial domain distribution in a periodically inverted sample, with a resolution of ∼1 µm achieved with a microfocused beam. This non-contact, non-destructive technique is well suited for samples of large dimensions (in contrast with traditional resonant X-ray methods based on diffraction from Friedel pairs), and its potential is particularly relevant in the context of physical phenomena connected with an absence of inversion symmetry, which require characterization of the underlying absolute atomic structure (such as in the case of magnetoelectric coupling and multiferroics). PMID:25970297

  12. Resonant inelastic contact scattering of X-ray photons on atoms and ions

    NASA Astrophysics Data System (ADS)

    Hopersky, A. N.; Nadolinsky, A. M.; Yavna, V. A.

    2006-10-01

    The existence of an extended resonance structure outside the X-ray emission regions is theoretically predicted in the total double differential cross section for the scattering of linearly polarized photons on free atoms (ions). This structure is almost entirely determined by inelastic photon scattering of the contact type. The amplitude of the inelastic contact scattering probability is described using an analytical expression for a non-relativistic transition operator, which was previously obtained by the author outside the dipole and momentum approximations. The resonant inelastic contact scattering of X-ray photons on a neon atom and neonlike ions of argon, titanium, and iron has been studied. Calculations were performed in a nonrelativistic approximation for the wave functions of the scattering states, with allowance for many-body effects of the radial relaxation of one-electron orbitals in the Hartree-Fock field of a deep 1 s vacancy and (for neon atom) the double excitation/ionization of the ground atomic state.

  13. Femtosecond Single-Shot Imaging of Nanoscale Ferromagnetic Order in Co/Pd Multilayers using Resonant X-ray Holography

    SciTech Connect

    Wang, Tianhan; Zhu, Diling; Benny Wu,; Graves, Catherine; Schaffert, Stefan; Rander, Torbjorn; Muller, leonard; Vodungbo, Boris; Baumier, Cedric; Bernstein, David P.; Brauer, Bjorn; Cros, Vincent; Jong, Sanne de; Delaunay, Renaud; Fognini, Andreas; Kukreja, Roopali; Lee, Sooheyong; Lopez-Flores, Victor; Mohanty, Jyoti; Pfau, Bastian; Popescu, 5 Horia

    2012-05-15

    We present the first single-shot images of ferromagnetic, nanoscale spin order taken with femtosecond x-ray pulses. X-ray-induced electron and spin dynamics can be outrun with pulses shorter than 80 fs in the investigated fluence regime, and no permanent aftereffects in the samples are observed below a fluence of 25 mJ/cm{sup 2}. Employing resonant spatially-muliplexed x-ray holography results in a low imaging threshold of 5 mJ/cm{sup 2}. Our results open new ways to combine ultrafast laser spectroscopy with sequential snapshot imaging on a single sample, generating a movie of excited state dynamics.

  14. Core and valence excitations in resonant X-ray spectroscopy using restricted excitation window time-dependent density functional theory

    PubMed Central

    Zhang, Yu; Biggs, Jason D.; Healion, Daniel; Govind, Niranjan; Mukamel, Shaul

    2012-01-01

    We report simulations of X-ray absorption near edge structure (XANES), resonant inelastic X-ray scattering (RIXS) and 1D stimulated X-ray Raman spectroscopy (SXRS) signals of cysteine at the oxygen, nitrogen, and sulfur K and \\documentclass[12pt]{minimal}\\begin{document}$\\textrm {L}_{2,3}$\\end{document}L2,3 edges. Comparison of the simulated XANES signals with experiment shows that the restricted window time-dependent density functional theory is more accurate and computationally less expensive than the static exchange method. Simulated RIXS and 1D SXRS signals give some insights into the correlation of different excitations in the molecule. PMID:23181305

  15. Femtosecond Single-Shot Imaging of Nanoscale Ferromagnetic Order in Co/Pd Multilayers Using Resonant X-Ray Holography

    NASA Astrophysics Data System (ADS)

    Wang, Tianhan; Zhu, Diling; Wu, Benny; Graves, Catherine; Schaffert, Stefan; Rander, Torbjörn; Müller, Leonard; Vodungbo, Boris; Baumier, Cédric; Bernstein, David P.; Bräuer, Björn; Cros, Vincent; de Jong, Sanne; Delaunay, Renaud; Fognini, Andreas; Kukreja, Roopali; Lee, Sooheyong; López-Flores, Víctor; Mohanty, Jyoti; Pfau, Bastian; Popescu, Horia; Sacchi, Maurizio; Sardinha, Anna B.; Sirotti, Fausto; Zeitoun, Philippe; Messerschmidt, Marc; Turner, Joshua J.; Schlotter, William F.; Hellwig, Olav; Mattana, Richard; Jaouen, Nicolas; Fortuna, Franck; Acremann, Yves; Gutt, Christian; Dürr, Hermann A.; Beaurepaire, Eric; Boeglin, Christine; Eisebitt, Stefan; Grübel, Gerhard; Lüning, Jan; Stöhr, Joachim; Scherz, Andreas O.

    2012-06-01

    We present the first single-shot images of ferromagnetic, nanoscale spin order taken with femtosecond x-ray pulses. X-ray-induced electron and spin dynamics can be outrun with pulses shorter than 80 fs in the investigated fluence regime, and no permanent aftereffects in the samples are observed below a fluence of 25mJ/cm2. Employing resonant spatially muliplexed x-ray holography results in a low imaging threshold of 5mJ/cm2. Our results open new ways to combine ultrafast laser spectroscopy with sequential snapshot imaging on a single sample, generating a movie of excited state dynamics.

  16. Resonant inelastic soft x-ray scattering of CdS: a two-dimensional electronic structure map approach

    SciTech Connect

    Weinhardt, L.; Fuchs, O.; Fleszar, A.; Bar, M.; Blum, M.; Weigand, M.; Denlinger, J.D.; Yang, W.; Hanke, W.; Umbach, E.; Heske, C.

    2008-09-24

    Resonant inelastic x-ray scattering (RIXS) with soft x-rays is uniquely suited to study the elec-tronic structure of a variety of materials, but is currently limited by low (fluorescence yield) count rates. This limitation is overcome with a new high-transmission spectrometer that allows to measure soft x-ray RIXS"maps." The S L2,3 RIXS map of CdS is discussed and compared with density functional calculations. The map allows the extraction of decay channel-specific"absorp-tion spectra," giving detailed insight into the wave functions of occupied and unoccupied elec-tronic states.

  17. Core and Valence Excitations in Resonant X-ray Spectroscopy using Restricted Excitation Window Time-dependent Density Functional Theory

    SciTech Connect

    Zhang, Yu; Biggs, Jason D.; Healion, Daniel; Govind, Niranjan; Mukamel, Shaul

    2012-11-21

    We report simulations of X-ray absorption near edge structure (XANES), resonant inelastic X-ray scattering (RIXS) and 1D stimulated X-ray Raman spectroscopy (SXRS) signals of cysteine at the oxygen, nitrogen and sulfur K and L2,3 edges. The simulated XANES signals from the restricted window time-dependent density functional theory (REW-TDDFT) and the static exchange (STEX) method are compared with experiments, showing that REW-TDDFT is more accurate and computationally less expensive than STEX. Simulated RIXS and 1D SXRS signals from REW-TDDFT give some insights on the correlation of different excitations in the molecule.

  18. On the magnetic fields of Be/X-ray pulsars in the Small Magellanic Cloud

    NASA Astrophysics Data System (ADS)

    Ikhsanov, N. R.; Mereghetti, S.

    2015-12-01

    We explore the possibility of explaining the properties of the Be/X-ray pulsars observed in the Small Magellanic Cloud (SMC) within the magnetic levitation accretion scenario. This implies that their X-ray emission is powered by a wind-fed accretion on to a neutron star (NS) which captures matter from a magnetized stellar wind. The NS in this case is accreting matter from a non-Keplerian magnetically levitating disc which is surrounding its magnetosphere. This allows us to explain the observed periods of the pulsars in terms of spin equilibrium without the need of invoking dipole magnetic fields outside the usual range ˜1011-1013 G inferred from cyclotron features of Galactic high-mass X-ray binaries. We find that the equilibrium period of a NS, under certain conditions, depends strongly on the magnetization of the stellar wind of its massive companion and, correspondingly, on the magnetic field of the massive companion itself. This may help to explain why similar NSs in binaries with similar properties rotate with different periods yielding a large scatter of periods of the accretion-powered pulsar observed in SMC and our galaxy.

  19. A new model for the X-ray continuum of the magnetized accreting pulsars

    NASA Astrophysics Data System (ADS)

    Farinelli, Ruben; Ferrigno, Carlo; Bozzo, Enrico; Becker, Peter A.

    2016-06-01

    Context. Accreting highly magnetized pulsars in binary systems are among the brightest X-ray emitters in our Galaxy. Although a number of high-quality broad-band (0.1-100 keV) X-ray observations are available, the spectral energy distribution of these sources is usually investigated by adopting pure phenomenological models rather than models linked to the physics of accretion. Aims: In this paper, a detailed spectral study of the X-ray emission recorded from the high-mass X-ray binary pulsars Cen X-3, 4U 0115+63, and Her X-1 is carried out by using BeppoSAX and joined Suzaku +NuStar data, together with an advanced version of the compmag model, which provides a physical description of the high-energy emission from accreting pulsars, including the thermal and bulk Comptonization of cyclotron and bremsstrahlung seed photons along the neutron star accretion column. Methods: The compmag model is based on an iterative method for solving second-order partial differential equations, whose convergence algorithm has been improved and consolidated during the preparation of this paper. Results: Our analysis shows that the broad-band X-ray continuum of all considered sources can be self-consistently described by the compmag model. The cyclotron absorption features (not included in the model) can be accounted for by using Gaussian components. From the fits of the compmag model to the data we inferred the physical properties of the accretion columns in all sources, finding values reasonably close to those theoretically expected according to our current understanding of accretion in highly magnetized neutron stars. Conclusions: The updated version of the compmag model has been tailored to the physical processes that are known to occur in the columns of highly magnetized accreting neutron stars and it can thus provide a better understanding of the high-energy radiation from these sources. The availability of broad-band high-quality X-ray data, such as those provided by BeppoSAX in

  20. X-ray resonance scattering in a spherically symmetric coronal model

    NASA Technical Reports Server (NTRS)

    Haisch, B. M.; Claflin, E. S.

    1985-01-01

    In the solar corona the opacities of some of the prominent X-ray emission lines are on the order of tau of about I over typical coronal path lengths. A particular solution of the radiative transfer problem involving an extended, spherically symmetric coronal shell radiating isotropic, homogeneous emission in which single-scattering also takes place is presented and discussed. Within the context of this simplified model, it is found that scattered radiation is an important contribution to the total emergent resonance line flux and that for the He-like family of resonance (r), intercombination (i), and forbidden (f) lines, the ratio G = (f + i)/r would decrease as a function of optical depth for disk-center emission in an extended spherically symmetric corona.

  1. Resonant Auger Decay of Molecules in Intense X-Ray Laser Fields: Light-Induced Strong Nonadiabatic Effects

    SciTech Connect

    Cederbaum, Lorenz S.; Chiang, Ying-Chih; Demekhin, Philipp V.; Moiseyev, Nimrod

    2011-03-25

    The resonant Auger process is studied in intense x-ray laser fields. It is shown that the dressing of the initial and decaying states by the field leads to coupled complex potential surfaces which, even for diatomic molecules, possess intersections at which the nonadiabatic couplings are singular. HCl is studied as an explicit showcase example. The exact results differ qualitatively from those without rotations. A wealth of nonadiabatic phenomena is expected in decay processes in intense x-ray fields.

  2. Bulk vertical micromachining of single-crystal sapphire using inductively coupled plasma etching for x-ray resonant cavities

    NASA Astrophysics Data System (ADS)

    Chen, P.-C.; Lin, P.-T.; Mikolas, D. G.; Tsai, Y.-W.; Wang, Y.-L.; Fu, C.-C.; Chang, S.-L.

    2015-01-01

    To provide coherent x-ray sources for probing the dynamic structures of solid or liquid biological substances on the picosecond timescale, a high-aspect-ratio x-ray resonator cavity etched from a single crystal substrate with a nearly vertical sidewall structure is required. Although high-aspect-ratio resonator cavities have been produced in silicon, they suffer from unwanted multiple beam effects. However, this problem can be avoided by using the reduced symmetry of single-crystal sapphire in which x-ray cavities may produce a highly monochromatic transmitted x-ray beam. In this study, we performed nominal 100 µm deep etching and vertical sidewall profiles in single crystal sapphire using inductively coupled plasma (ICP) etching. The large depth is required to intercept a useful fraction of a stopped-down x-ray beam, as well as for beam clearance. An electroplated Ni hard mask was patterned using KMPR 1050 photoresist and contact lithography. The quality and performance of the x-ray cavity depended upon the uniformity of the cavity gap and therefore verticality of the fabricated vertical sidewall. To our knowledge, this is the first report of such deep, vertical etching of single-crystal sapphire. A gas mixture of Cl2/BCl3/Ar was used to etch the sapphire with process variables including BCl3 flow ratio and bias power. By etching for 540 min under optimal conditions, we obtained an x-ray resonant cavity with a depth of 95 µm, width of ~30 µm, gap of ~115 µm and sidewall profile internal angle of 89.5°. The results show that the etching parameters affected the quality of the vertical sidewall, which is essential for good x-ray resonant cavities.

  3. Measurement of the high energy component of the x-ray spectra in the VENUS electron cyclotron resonance ion source (abstract only)

    SciTech Connect

    Leitner, D.; Benitez, J. Y.; Lyneis, C. M.; Todd, D. S.; Ropponen, T.; Ropponen, J.; Koivisto, H.; Gammino, S.

    2008-02-15

    High performance electron cyclotron resonance (ECR) ion sources, such as VENUS (versatile ECR for nuclear science), produce large amounts of x rays. By studying their energy spectra, conclusions can be drawn about the electron heating process and the electron confinement. In addition, the bremsstrahlung from the plasma chamber is partly absorbed by the cold mass of the superconducting magnet adding an extra heat load to the cryostat. Germanium or NaI detectors are generally used for x-ray measurements. Due to the high x-ray flux from the source, the experimental setup to measure bremsstrahlung spectra from ECR ion sources is somewhat different than for the traditional nuclear physics measurements these detectors are generally used for. In particular, the collimation and background shielding can be problematic. In this paper we will discuss the experimental setup for such a measurement, the energy calibration and background reduction, the shielding of the detector, and collimation of the x-ray flux. We will present x-ray energy spectra and cryostat heating rates in dependence of various ion source parameters such as confinement fields, minimum B-field, rf power, and heating frequency.

  4. The simultaneous measurement of energy and linear polarization of the scattered radiation in resonant inelastic soft x-ray scattering

    SciTech Connect

    Braicovich, L. Minola, M.; Dellea, G.; Ghiringhelli, G.; Le Tacon, M.; Moretti Sala, M.; Morawe, C.; Peffen, J.-Ch.; Yakhou, F.; Brookes, N. B.; Supruangnet, R.

    2014-11-15

    Resonant Inelastic X-ray Scattering (RIXS) in the soft x-ray range is an element-specific energy-loss spectroscopy used to probe the electronic and magnetic excitations in strongly correlated solids. In the recent years, RIXS has been progressing very quickly in terms of energy resolution and understanding of the experimental results, but the interpretation of spectra could further improve, sometimes decisively, from a full knowledge of the polarization of incident and scattered photons. Here we present the first implementation, in a high resolution soft-RIXS spectrometer used to analyze the scattered radiation, of a device allowing the measurement of the degree of linear polarization. The system, based on a graded W/B{sub 4}C multilayer mirror installed in proximity of the CCD detector, has been installed on the AXES spectrometer at the ESRF (European Synchrotron Radiation Facility); it has been fully characterized and it has been used for a demonstration experiment at the Cu L{sub 3} edge on a high-T{sub c} superconducting cuprate. The loss in efficiency suffered by the spectrometer equipped with this test facility was a factor 17.5. We propose also a more advanced version, suitable for a routine use on the next generation of RIXS spectrometers and with an overall efficiency up to 10%.

  5. The simultaneous measurement of energy and linear polarization of the scattered radiation in resonant inelastic soft x-ray scattering.

    PubMed

    Braicovich, L; Minola, M; Dellea, G; Le Tacon, M; Moretti Sala, M; Morawe, C; Peffen, J-Ch; Supruangnet, R; Yakhou, F; Ghiringhelli, G; Brookes, N B

    2014-11-01

    Resonant Inelastic X-ray Scattering (RIXS) in the soft x-ray range is an element-specific energy-loss spectroscopy used to probe the electronic and magnetic excitations in strongly correlated solids. In the recent years, RIXS has been progressing very quickly in terms of energy resolution and understanding of the experimental results, but the interpretation of spectra could further improve, sometimes decisively, from a full knowledge of the polarization of incident and scattered photons. Here we present the first implementation, in a high resolution soft-RIXS spectrometer used to analyze the scattered radiation, of a device allowing the measurement of the degree of linear polarization. The system, based on a graded W/B4C multilayer mirror installed in proximity of the CCD detector, has been installed on the AXES spectrometer at the ESRF (European Synchrotron Radiation Facility); it has been fully characterized and it has been used for a demonstration experiment at the Cu L3 edge on a high-Tc superconducting cuprate. The loss in efficiency suffered by the spectrometer equipped with this test facility was a factor 17.5. We propose also a more advanced version, suitable for a routine use on the next generation of RIXS spectrometers and with an overall efficiency up to 10%. PMID:25430146

  6. Quantitative determination of bond order and lattice distortions in nickel oxide heterostructures by resonant x-ray scattering

    NASA Astrophysics Data System (ADS)

    Lu, Y.; Frano, A.; Bluschke, M.; Hepting, M.; Macke, S.; Strempfer, J.; Wochner, P.; Cristiani, G.; Logvenov, G.; Habermeier, H.-U.; Haverkort, M. W.; Keimer, B.; Benckiser, E.

    2016-04-01

    We present a combined study of Ni K -edge resonant x-ray scattering and density functional calculations to probe and distinguish electronically driven ordering and lattice distortions in nickelate heterostructures. We demonstrate that due to the low crystal symmetry, contributions from structural distortions can contribute significantly to the energy-dependent Bragg peak intensities of a bond-ordered NdNiO3 reference film. For a LaNiO3-LaAlO3 superlattice that exhibits magnetic order, we establish a rigorous upper bound on the bond-order parameter. We thus conclusively confirm predictions of a dominant spin density wave order parameter in metallic nickelates with a quasi-two-dimensional electronic structure.

  7. X-ray detection of transient magnetic moments induced by a spin current in Cu

    SciTech Connect

    Kukreja, R.; Bonetti, S.; Chen, Z.; Backes, D.; Acremann, Y.; Katine, J.; Kent, A. D.; Durr, H. A.; Ohldag, H.; Stohr, J.

    2015-08-24

    We have used a MHz lock-in x-ray spectromicroscopy technique to directly detect changes in magnetic moment of Cu due to spin injection from an adjacent Co layer. The elemental and chemical specificity of x rays allows us to distinguish two spin current induced effects. We detect the creation of transient magnetic moments of 3×10–5μB on Cu atoms within the bulk of the 28 nm thick Cu film due to spin accumulation. The moment value is compared to predictions by Mott’s two current model. We also observe that the hybridization induced existing magnetic moments at the Cu interface atoms are transiently increased by about 10% or 4×10–3μB per atom. As a result, this reveals the dominance of spin-torque alignment over Joule heat induced disorder of the interfacial Cu moments during current flow.

  8. Characterization and Performance of Magnetic Calorimeters for Applications in X-ray Spectroscopy

    NASA Astrophysics Data System (ADS)

    Porst, J.-P.; Bandler, S. R.; Adams, J. S.; Balvin, M. A.; Busch, S. E.; Eckart, M. E.; Kelley, R. L.; Kilbourne, C. A.; Lee, S. J.; Nagler, P. C.; Porter, F. S.; Sadleir, J. E.; Seidel, G. M.; Smith, S. J.; Stevenson, T. R.

    2014-09-01

    We have developed prototype arrays of metallic magnetic calorimeters for applications in X-ray astronomy. Each pixel consists of an all-gold X-ray absorber in good thermal contact to a gold-erbium paramagnetic thin film thermometer that is operated in the temperature range of 30-100 mK. The para-magnetic response is coupled to a SQUID amplifier. We have characterized pixels in an array and observed the expected temperature dependence of the magnetization and heat capacity. We have demonstrated a full width at half maximum energy resolution of 1.7 0.1 eV at 6 keV and have also read out these devices using time-division multiplexing.

  9. X-ray Detection of Transient Magnetic Moments Induced by a Spin Current in Cu.

    PubMed

    Kukreja, R; Bonetti, S; Chen, Z; Backes, D; Acremann, Y; Katine, J A; Kent, A D; Dürr, H A; Ohldag, H; Stöhr, J

    2015-08-28

    We have used a MHz lock-in x-ray spectromicroscopy technique to directly detect changes in magnetic moment of Cu due to spin injection from an adjacent Co layer. The elemental and chemical specificity of x rays allows us to distinguish two spin current induced effects. We detect the creation of transient magnetic moments of 3×10^{-5}μ_{B} on Cu atoms within the bulk of the 28 nm thick Cu film due to spin accumulation. The moment value is compared to predictions by Mott's two current model. We also observe that the hybridization induced existing magnetic moments at the Cu interface atoms are transiently increased by about 10% or 4×10^{-3}μ_{B} per atom. This reveals the dominance of spin-torque alignment over Joule heat induced disorder of the interfacial Cu moments during current flow. PMID:26371670

  10. The correspondence between X-ray bright points and evolving magnetic features in the quiet sun

    NASA Technical Reports Server (NTRS)

    Webb, D. F.; Martin, S. F.; Moses, D.; Harvey, J. W.

    1993-01-01

    The results of a study of X-ray bright points (XBPs) and small-scale evolving magnetic structures are presented. X-ray images obtained during rocket flights, full-disk magnetograms, and time-lapse magnetograms of multiple fields make up the coordinated data set. XBPs were found to be more frequently associated with pre-existing magnetic features of opposite polarity which appeared to be cancelling than with new or emerging flux regions. Most of the XBPs appeared to correspond to opposite polarity magnetic features which were converging towards each other, and some of which had not yet begun cancelling. It is suggested that most XBPs are created when converging flow brings together oppositely directed field lines. This leads to reconnection and heating in the low corona of the newly-formed loops.

  11. X-ray Detection of Transient Magnetic Moments Induced by a Spin Current in Cu

    NASA Astrophysics Data System (ADS)

    Kukreja, R.; Bonetti, S.; Chen, Z.; Backes, D.; Acremann, Y.; Katine, J. A.; Kent, A. D.; Dürr, H. A.; Ohldag, H.; Stöhr, J.

    2015-08-01

    We have used a MHz lock-in x-ray spectromicroscopy technique to directly detect changes in magnetic moment of Cu due to spin injection from an adjacent Co layer. The elemental and chemical specificity of x rays allows us to distinguish two spin current induced effects. We detect the creation of transient magnetic moments of 3 ×10-5μB on Cu atoms within the bulk of the 28 nm thick Cu film due to spin accumulation. The moment value is compared to predictions by Mott's two current model. We also observe that the hybridization induced existing magnetic moments at the Cu interface atoms are transiently increased by about 10% or 4 ×10-3μB per atom. This reveals the dominance of spin-torque alignment over Joule heat induced disorder of the interfacial Cu moments during current flow.

  12. Determination of the magnetic particle distribution in tumour tissue by means of x-ray tomography

    NASA Astrophysics Data System (ADS)

    Brunke, O.; Odenbach, S.; Jurgons, R.; Alexiou, C.; Hilger, I.; Beckmann, F.

    2006-09-01

    In biomedical applications of ferrofluids, the resulting distribution of the magnetic nanoparticles is a crucial parameter for the effect of the therapeutic approach. In order to increase the efficacy of local cancer treatments incorporating ferrofluids like magnetic drug targeting and hyperthermia, the bio-distribution of theses fluids in the respective tissue has to be optimized. Usually, the distribution of particles is determined by histological cuts of the investigated specimen, a technique which provides only local information about the overall distribution of the magnetic material, e.g. in a tumour. Radioscopic techniques based on gamma or x-rays are well established, suitable for in vivo examination and non-destructive, but only provide two-dimensional integral information in the direction of the beam. Here we have used micro-tomography—incorporating a conventional x-ray tube as well as monochromatic synchrotron radiation—as a tool for a three-dimensional analysis of the distribution of magnetic nanoparticles in biological applications. Compared to biological matter, the iron-based magnetic nanoparticles provide sufficiently high absorption for x-rays and thus serve as an intrinsic contrast agent for the examinations. The results show the principle feasibility of the method for a quantitative determination of the agglomeration behaviour of the nanoparticles within carcinogenic tissue after intravascular or intratumoural injection.

  13. Non-linear magnetization dynamics probed with X-rays: 1. Broken cylindrical symmetry of uniform modes

    NASA Astrophysics Data System (ADS)

    Goulon, J.; Brouder, Ch.; Rogalev, A.; Goujon, G.; Wilhelm, F.

    2014-10-01

    We discuss how X-ray magnetic circular dichroism (XMCD) and X-ray magnetic linear dichroism (XMLD) may complement each other to probe the nonlinear nature of the resonant precession of either spin or orbital magnetization components in aligned ferro-, ferri- or even antiferro-magnets. The Landau-Lifshitz-Gilbert (LLG) equation is solved in a rotating frame locked to the microwave pump field, while treating as time-dependent perturbations the terms which, in the formulation of the free energy density, break down the cylindrical symmetry of precession. Concretely, we analyze the time-oscillating deviations of the magnetization from the steady-state solutions of the LLG equation hereafter called SS-modes. At any perturbation order, one may derive magnetic dipole components which oscillate at harmonic frequencies of the pump frequency and could be probed with XMCD. Under bichromatic pumping, frequency mixing arises from a time-dependent Zeeman coupling between two rotating frames locked to each individual pump field. Similarly, we expect magnetic quadrupole components to oscillate at the same frequencies. For consistency, their derivation requires a perturbation calculation up to second order. The latter time-reversal even, rank-2 magnetic tensor components can be probed only with XMLD. Beyond the (reciprocal) linear dichroism classically measured in ferri- or antiferromagnetic samples, a non-reciprocal XMLD signal is to be expected when space parity is lost. Nonlinear effects strongly depend upon the relative orientations of the external bias field and of the pump field with respect to the symmetry axes of the magnetic system. This holds true for the foldover lineshape distortions, harmonic generation, frequency mixing or multiquanta excitations.

  14. X-ray absorption and x-ray magnetic dichroism study on Ca3CoRhO6 and Ca3FeRhO6

    NASA Astrophysics Data System (ADS)

    Burnus, T.; Hu, Z.; Wu, Hua; Cezar, J. C.; Niitaka, S.; Takagi, H.; Chang, C. F.; Brookes, N. B.; Lin, H.-J.; Jang, L. Y.; Tanaka, A.; Liang, K. S.; Chen, C. T.; Tjeng, L. H.

    2008-05-01

    By using x-ray absorption spectroscopy at the RhL2,3 , CoL2,3 , and FeL2,3 edges, we find a valence state of Co2+/Rh4+ in Ca3CoRhO6 and of Fe3+/Rh3+ in Ca3FeRhO6 . X-ray magnetic circular dichroism spectroscopy at the CoL2,3 edge of Ca3CoRhO6 reveals a giant orbital moment of about 1.7μB , which can be attributed to the occupation of the minority-spin d0d2 orbital state of the high-spin Co2+ (3d7) ions in trigonal prismatic coordination. This active role of the spin-orbit coupling explains the strong magnetocrystalline anisotropy and Ising-type magnetism of Ca3CoRhO6 .

  15. The Study of Highly Magnetized Neutron Stars with X-ray Polarimetry Observations

    NASA Astrophysics Data System (ADS)

    Krawczynski, H.

    X-ray polarization observations have the prospect to give us qualitatively new insights into the structure of the magnetic field of strongly magnetized pulsars and magnetars. In this talk, I will give a review over the pulsar and magnetar properties that can be studied with X-ray polarization observations. Furthermore, I will describe the balloon borne polarimeter X-Calibur and describe which insights we expect to gain from the scheduled X-Calibur flights in Fall 2014 (from Fort Sumner, New Mexico) and in 2016/2017 (McMurdo, Antarctic). I will conclude with an overview of studies that can be performed with a space-borne version of such an experiment.

  16. Magnet power supply control of the NSLS VUV and x-ray storage rings transfer lines

    SciTech Connect

    Klein, J.D.; Ramamoorthy, S.; Singh, O.; Smith, J.D.

    1985-01-01

    The transfer lines for NSLS VUV and x-ray storage rings have been split. New power supplies have been incorporated with existing ones. The existing microprocessor system has been upgraded in order to control the additional functions. This system expands the input/output port of the microprocessor to an addressable serial/parallel link to each magnet power supply. The implementation of this system will be discussed.

  17. Magnetic control in the RAP-200K-20 x-ray equipment

    SciTech Connect

    Gusev, E.A.; Drankov, V.P.; Naboishchikov, V.D.

    1989-03-01

    A description is given of the RAP-200K-20 cable-connected x-ray equipment, where a three-phase EHT transformer with magnetic control is used in the main circuit. The apparatus is compared with the best foreign competition. The circuit has an advantage over a pulse regulator in that the overvoltage level is low; there is also no interference and the efficiency is higher. All these advantages improve the performance and reliability in TV and fluorescent monitoring.

  18. HEAO 1 hard X-ray observation of clusters of galaxies and intracluster magnetic fields

    NASA Technical Reports Server (NTRS)

    Rephaeli, Yoel; Gruber, D. E.

    1988-01-01

    The results of HEAO 1 hard X-ray measurements of three clusters of galaxies, Abell 401, Abell 2255, and Abell 2256 are reported. Nonthermal components were not detected above the level of 10 to the -5th photons/sq cm/s/keV. Comparison of the flux upper limits with theoretical predictions yields lower limits of about 10 to the -7th gauss on the mean value of the intracluster magnetic fields in the central regions of these clusters.

  19. X-ray imaging of extended magnetic domain walls in Ni80Fe20 wires

    SciTech Connect

    Basu, S.; Fry, P. W.; Allwood, D. A.; Bryan, M. T.; Gibbs, M. R. J.; Schrefl, T.; Im, M.-Y.; Fischer, P.

    2009-06-20

    We have used magnetic transmission X-ray microscopy to image magnetization configurations in 700 nm wide Ni{sub 80}Fe{sub 20} planar wires attached to 'nucleation' pads Domain walls were observed to inject only across half of the wire width but extend to several micrometers in length. Magnetostatic interactions with adjacent wires caused further unusual domain wall behavior. Micromagnetic modeling suggests the extended walls have Neel-like structure along their length and indicates weaker exchange coupling than is often assumed. These observations explain previous measurements of domain wall injection and demonstrate that magnetic domain walls in larger nanowires cannot always be considered as localized entities.

  20. UCSD High Energy X-ray Timing Experiment magnetic shield design and test results

    NASA Technical Reports Server (NTRS)

    Rothschild, Richard E.; Pelling, Michael R.; Hink, Paul L.

    1991-01-01

    Results are reported from an effort to define a passive magnetic field concept for the High Energy X-ray Timing Experiment (HEXTE), in the interest of reducing the detector-gain variations due to 0.5-1.0-sec timescale magnetic field variations. This will allow a sensitivity of the order of 1 percent of the HEXTE background. While aperture modulation and automatic gain control will minimize effects on timescales of tens of seconds and longer, passive magnetic shielding of the photomultiplier tubes will address 1-sec timescale variations due to aperture motions.

  1. Microwave soft x-ray microscopy for nanoscale magnetization dynamics in the 5–10 GHz frequency range

    SciTech Connect

    Bonetti, Stefano Chen, Zhao; Kukreja, Roopali; Spoddig, Detlef; Schöppner, Christian; Meckenstock, Ralf; Ollefs, Katharina; Ney, Andreas; Pinto, Jude; Houanche, Richard; Frisch, Josef; Stöhr, Joachim; Dürr, Hermann A.; Ohldag, Hendrik

    2015-09-15

    We present a scanning transmission x-ray microscopy setup combined with a novel microwave synchronization scheme for studying high frequency magnetization dynamics at synchrotron light sources. The sensitivity necessary to detect small changes in the magnetization on short time scales and nanometer spatial dimensions is achieved by combining the excitation mechanism with single photon counting electronics that is locked to the synchrotron operation frequency. Our instrument is capable of creating direct images of dynamical phenomena in the 5-10 GHz range, with high spatial resolution. When used together with circularly polarized x-rays, the above capabilities can be combined to study magnetic phenomena at microwave frequencies, such as ferromagnetic resonance (FMR) and spin waves. We demonstrate the capabilities of our technique by presenting phase resolved images of a ∼6 GHz nanoscale spin wave generated by a spin torque oscillator, as well as the uniform ferromagnetic precession with ∼0.1° amplitude at ∼9 GHz in a micrometer-sized cobalt strip.

  2. Microwave soft x-ray microscopy for nanoscale magnetization dynamics in the 5-10 GHz frequency range

    NASA Astrophysics Data System (ADS)

    Bonetti, Stefano; Kukreja, Roopali; Chen, Zhao; Spoddig, Detlef; Ollefs, Katharina; Schöppner, Christian; Meckenstock, Ralf; Ney, Andreas; Pinto, Jude; Houanche, Richard; Frisch, Josef; Stöhr, Joachim; Dürr, Hermann A.; Ohldag, Hendrik

    2015-09-01

    We present a scanning transmission x-ray microscopy setup combined with a novel microwave synchronization scheme for studying high frequency magnetization dynamics at synchrotron light sources. The sensitivity necessary to detect small changes in the magnetization on short time scales and nanometer spatial dimensions is achieved by combining the excitation mechanism with single photon counting electronics that is locked to the synchrotron operation frequency. Our instrument is capable of creating direct images of dynamical phenomena in the 5-10 GHz range, with high spatial resolution. When used together with circularly polarized x-rays, the above capabilities can be combined to study magnetic phenomena at microwave frequencies, such as ferromagnetic resonance (FMR) and spin waves. We demonstrate the capabilities of our technique by presenting phase resolved images of a ˜6 GHz nanoscale spin wave generated by a spin torque oscillator, as well as the uniform ferromagnetic precession with ˜0.1° amplitude at ˜9 GHz in a micrometer-sized cobalt strip.

  3. Microwave soft x-ray microscopy for nanoscale magnetization dynamics in the 5-10 GHz frequency range.

    PubMed

    Bonetti, Stefano; Kukreja, Roopali; Chen, Zhao; Spoddig, Detlef; Ollefs, Katharina; Schöppner, Christian; Meckenstock, Ralf; Ney, Andreas; Pinto, Jude; Houanche, Richard; Frisch, Josef; Stöhr, Joachim; Dürr, Hermann A; Ohldag, Hendrik

    2015-09-01

    We present a scanning transmission x-ray microscopy setup combined with a novel microwave synchronization scheme for studying high frequency magnetization dynamics at synchrotron light sources. The sensitivity necessary to detect small changes in the magnetization on short time scales and nanometer spatial dimensions is achieved by combining the excitation mechanism with single photon counting electronics that is locked to the synchrotron operation frequency. Our instrument is capable of creating direct images of dynamical phenomena in the 5-10 GHz range, with high spatial resolution. When used together with circularly polarized x-rays, the above capabilities can be combined to study magnetic phenomena at microwave frequencies, such as ferromagnetic resonance (FMR) and spin waves. We demonstrate the capabilities of our technique by presenting phase resolved images of a ∼6 GHz nanoscale spin wave generated by a spin torque oscillator, as well as the uniform ferromagnetic precession with ∼0.1° amplitude at ∼9 GHz in a micrometer-sized cobalt strip. PMID:26429444

  4. Development of a graphite polarization analyzer for resonant inelastic x-ray scattering

    SciTech Connect

    Gao Xuan; Burns, Clement; Li Chengyang; Casa, Diego; Upton, Mary; Gog, Thomas; Kim, Jungho

    2011-11-15

    Resonant inelastic x-ray scattering (RIXS) is a powerful technique for studying electronic excitations in correlated electron systems. Current RIXS spectrometers measure the changes in energy and momentum of the photons scattered by the sample. A powerful extension of the RIXS technique is the measurement of the polarization state of the scattered photons which contains information about the symmetry of the excitations. This long-desired addition has been elusive because of significant technical challenges. This paper reports the development of a new diffraction-based polarization analyzer which discriminates between linear polarization components of the scattered photons. The double concave surface of the polarization analyzer was designed as a good compromise between energy resolution and throughput. Such a device was fabricated using highly oriented pyrolytic graphite for measurements at the Cu K-edge incident energy. Preliminary measurements on a CuGeO{sub 3} sample are presented.

  5. Nematicity in stripe ordered cuprates probed via resonant x-ray scattering

    DOE PAGESBeta

    Achkar, A. J.; Zwiebler, M.; McMahon, Christopher; He, F.; Sutarto, R.; Dijianto, Isaiah; Hao, Zhihao; Gingras, Michael J.P.; Hucker, M.; Gu, G. D.; et al

    2016-02-05

    We found that in underdoped cuprate superconductors, a rich competition occurs between superconductivity and charge density wave (CDW) order. Whether rotational symmetry-breaking (nematicity) occurs intrinsically and generically or as a consequence of other orders is under debate. Here, we employ resonant x-ray scattering in stripe-ordered superconductors (La,M)2CuO4 to probe the relationship between electronic nematicity of the Cu 3d orbitals, structure of the (La,M)2O2 layers, and CDW order. We find distinct temperature dependences for the structure of the (La,M)2O2 layers and the electronic nematicity of the CuO2 planes, with only the latter being enhanced by the onset of CDW order. Ourmore » results identify electronic nematicity as an order parameter that is distinct from a purely structural order parameter in underdoped striped cuprates.« less

  6. Constraining compactness and magnetic field geometry of X-ray pulsars using pulse profile statistics

    SciTech Connect

    Annala, Marja; Poutanen, Juri

    2010-07-15

    We use the statistics of 131 X-ray pulsar light curves in order to constrain the neutron star compactness and the inclination of the magnetic dipole. The X-ray pulse profiles are classified according to the number of pulses seen during one period, dividing them into two classes, single- and double-peaked. The relative fraction of pulsars in these classes is compared with the probabilities predicted by a theoretical model for different types of pencil-beam patterns. Our results show that a statistic of pulse profiles does not constrain compactness of the neutron stars. In contrast to the previous claim, the data do not require the magnetic inclination to be confined in a narrow interval but instead the magnetic dipole can have arbitrary inclinations to the rotational axis. The observed fractions of different types of light curves can be explained by taking into account the X-ray detector sensitivity (i.e. detection threshold for weak pulses), which decreases the fraction of the observed double-peaked light curves.

  7. Theory of magnetic circular dichroism of nonresonant x-ray Raman scattering

    NASA Astrophysics Data System (ADS)

    Takahashi, Manabu; Hiraoka, Nozomu

    2015-09-01

    We develop a theory of magnetic circular dichroism (MCD) of hard x-ray Raman scattering (XRS) to analyze the MCD signal at iron L edge from pure ferromagnetic iron. The obtained formula of scattering amplitude has terms corresponding to the charge (Thomson) scattering process, and the orbital and spin scattering processes in the elastic x-ray magnetic scattering. The total scattering intensity is almost independent of incident photon helicity since it is mainly produced by the charge scattering. The weak MCD signals are caused primarily by interference between the charge scattering amplitude and each of the orbital and spin scattering amplitudes. The shape of the MCD spectra depends on angle αM between the wave vector of the incident photon and the magnetization vector. At αM=0∘ , the spin scattering is suppressed so that the MCD spectrum becomes analogous to that observed in the x-ray absorption spectroscopy. At αM=135∘ , the orbital scattering is suppressed, and the spin scattering plays central roles in producing the MCD signal. The magnitude of the MCD signal turns out to be proportional to the spin density of states projected onto the 3 d states in the unoccupied state. Consequently, the value of the integrated MCD signal is proportional to the spin moment in the 3 d states at the scattering site. The calculated MCD spectra with the help of a band structure calculation well reproduce the observed spectra.

  8. Nanoscale imaging of buried topological defects with quantitative X-ray magnetic microscopy

    PubMed Central

    Blanco-Roldán, C.; Quirós, C.; Sorrentino, A.; Hierro-Rodríguez, A.; Álvarez-Prado, L. M.; Valcárcel, R.; Duch, M.; Torras, N.; Esteve, J.; Martín, J. I.; Vélez, M.; Alameda, J. M.; Pereiro, E.; Ferrer, S.

    2015-01-01

    Advances in nanoscale magnetism increasingly require characterization tools providing detailed descriptions of magnetic configurations. Magnetic transmission X-ray microscopy produces element specific magnetic domain images with nanometric lateral resolution in films up to ∼100 nm thick. Here we present an imaging method using the angular dependence of magnetic contrast in a series of high resolution transmission X-ray microscopy images to obtain quantitative descriptions of the magnetization (canting angles relative to surface normal and sense). This method is applied to 55–120 nm thick ferromagnetic NdCo5 layers (canting angles between 65° and 22°), and to a NdCo5 film covered with permalloy. Interestingly, permalloy induces a 43° rotation of Co magnetization towards surface normal. Our method allows identifying complex topological defects (merons or ½ skyrmions) in a NdCo5 film that are only partially replicated by the permalloy overlayer. These results open possibilities for the characterization of deeply buried magnetic topological defects, nanostructures and devices. PMID:26337838

  9. Remediation of Cr(VI) by biogenic magnetic nanoparticles: An x-ray magnetic circular dichroism study

    SciTech Connect

    Telling, N. D.; Coker, V. S.; Cutting, R. S.; van der Laan, G.; Pearce, C. I.; Pattrick, R. A. D.; Arenholz, E.; Lloyd, J. R.

    2009-09-04

    Biologically synthesized magnetite (Fe{sub 3}O{sub 4}) nanoparticles are studied using x-ray absorption and x-ray magnetic circular dichroism following exposure to hexavalent Cr solution. By examining their magnetic state, Cr cations are shown to exist in trivalent form on octahedral sites within the magnetite spinel surface. The possibility of reducing toxic Cr(VI) into a stable, non-toxic form, such as a Cr{sup 3+}-spinel layer, makes biogenic magnetite nanoparticles an attractive candidate for Cr remediation.

  10. Optical and resonant X-ray diffraction studies of molecular arrangements in several liquid crystals

    NASA Astrophysics Data System (ADS)

    Wang, Suntao

    Using optical and x-ray techniques, we have studied several selected liquid crystal compounds formed by three types of molecules: rod-like; hockey-stick-shaped and bent-core-shaped molecules. This thesis describes four research projects. The first one is a study of the molecular arrangements in freestanding films of three chiral compounds showing no-layer-shrinkage behavior above their bulk SmA-SmC* transition temperatures. Upon cooling under a proper electric field, novel nonplanar-anticlinic-synclinic and nonplanar-synclinic transitions have been observed in two compounds. Increasing electric field can induce a rare transition from a synclinic to an anticlinic structure. Results from both x-ray diffraction and optical studies indicate that different molecular packing arrangements exist within the Sm A phase window. The second project is to investigate three achiral meta-substituted three-ring compounds. These compounds exhibit two different tilted smectic phases, Sm C1 and SmC2. A recent paper has reported that mirror symmetry is broken in one of these compounds. However, no mirror symmetry breaking has been observed in our studies of the same compound. Our studies of another two compounds confirmed previous results that the Sm C1 and SmC2 phases are Sm C and SmCA, respectively. Thirdly, we confirmed the SM C*FI2 -SmC* phase sequence reversal in one liquid crystal compound and specially prepared binary mixtures. This phase sequence reversal was predicted by a recent phenomenological model. Moreover, the temperature range for the SM C*FI2 phase increases significantly in the mixture suggesting that such a phase sequence may exist in other compounds. The last project is to study the B2 phase formed by bent-core molecules using polarization-analyzed resonant x-ray diffraction. The B2 phase has three possible arrangements which show a two-layer unit cell. We analyzed the polarization of the resonant peaks at different Bragg orders. By comparing a theoretical

  11. Hinode observations and 3D magnetic structure of an X-ray bright point

    NASA Astrophysics Data System (ADS)

    Alexander, C. E.; Del Zanna, G.; Maclean, R. C.

    2011-02-01

    Aims: We present complete Hinode Solar Optical Telescope (SOT), X-Ray Telescope (XRT)and EUV Imaging Spectrometer (EIS) observations of an X-ray bright point (XBP) observed on the 10, 11 of October 2007 over its entire lifetime (~12 h). We aim to show how the measured plasma parameters of the XBP change over time and also what kind of similarities the X-ray emission has to a potential magnetic field model. Methods: Information from all three instruments on-board Hinode was used to study its entire evolution. XRT data was used to investigate the structure of the bright point and to measure the X-ray emission. The EIS instrument was used to measure various plasma parameters over the entire lifetime of the XBP. Lastly, the SOT was used to measure the magnetic field strength and provide a basis for potential field extrapolations of the photospheric fields to be made. These were performed and then compared to the observed coronal features. Results: The XBP measured ~15´´ in size and was found to be formed directly above an area of merging and cancelling magnetic flux on the photosphere. A good correlation between the rate of X-ray emission and decrease in total magnetic flux was found. The magnetic fragments of the XBP were found to vary on very short timescales (minutes), however the global quasi-bipolar structure remained throughout the lifetime of the XBP. The potential field extrapolations were a good visual fit to the observed coronal loops in most cases, meaning that the magnetic field was not too far from a potential state. Electron density measurements were obtained using a line ratio of Fe XII and the average density was found to be 4.95 × 109 cm-3 with the volumetric plasma filling factor calculated to have an average value of 0.04. Emission measure loci plots were then used to infer a steady temperature of log Te [ K] ~ 6.1. The calculated Fe XII Doppler shifts show velocity changes in and around the bright point of ±15 km s-1 which are observed to change

  12. Mechanical design and analysis of an eight-pole superconducting vector magnet for soft x-ray magnetic dichroism measurements

    SciTech Connect

    Arbelaez, D.; Black, A.; Prestemon, S.O.; Wang, S.; Chen, J.; Arenholz, E.

    2010-01-13

    An eight-pole superconducting magnet is being developed for soft x-ray magnetic dichroism (XMD) experiments at the Advanced Light Source, Lawrence Berkley National Laboratory (LBNL). Eight conical Nb{sub 3}Sn coils with Holmium poles are arranged in octahedral symmetry to form four dipole pairs that provide magnetic fields of up to 5 T in any direction relative to the incoming x-ray beam. The dimensions of the magnet yoke as well as pole taper, diameter, and length were optimized for maximum peak field in the magnet center using the software package TOSCA. The structural analysis of the magnet is performed using ANSYS with the coil properties derived using a numerical homogenization scheme. It is found that the use of orthotropic material properties for the coil has an important influence in the design of the magnet.

  13. X-ray magnetic circular dichroic magnetometry on Ni/Pt multilayers

    NASA Astrophysics Data System (ADS)

    Poulopoulos, P.; Wilhelm, F.; Wende, H.; Ceballos, G.; Baberschke, K.; Benea, D.; Ebert, H.; Angelakeris, M.; Flevaris, N. K.; Rogalev, A.; Brookes, N. B.

    2001-04-01

    X-ray magnetic circular dichroism measurements have been performed on Ni/Pt multilayers at a temperature of 10 K. The element specificity and shell selectivity of the technique allows us to probe Ni and Pt magnetic moments and to separate them into their constituent spin (μS) and orbital (μL) magnetic moments. The Ni magnetic moment at the interface is found to be reduced. However, magnetically "dead" Ni layers are unambiguously ruled out. Induced Pt magnetic moments up to about 0.3 μB/atom are reported. The results are compared to ab initio calculations and to previous experiments performed on NiPt alloys. The role of intermixing in the reduction of the Ni magnetic moments is also discussed.

  14. Local X-ray magnetic circular dichroism study of Fe/Cu(111) using a tunneling smart tip.

    PubMed

    DiLullo, Andrew; Shirato, Nozomi; Cummings, Marvin; Kersell, Heath; Chang, Hao; Rosenmann, Daniel; Miller, Dean; Freeland, John W; Hla, Saw-Wai; Rose, Volker

    2016-03-01

    Localized spectroscopy with simultaneous topographic, elemental and magnetic information is presented. A synchrotron X-ray scanning tunneling microscope has been employed for the local study of the X-ray magnetic circular dichroism at the Fe L2,3-edges of a thin iron film grown on Cu(111). Polarization-dependent X-ray absorption spectra have been obtained through a tunneling smart tip that serves as a photoelectron detector. In contrast to conventional spin-polarized scanning tunneling microscopy, X-ray excitations provide magnetic contrast even with a non-magnetic tip. Intensity variations in the photoexcited tip current point to chemical variations within a single magnetic Fe domain. PMID:26917146

  15. Local X-ray magnetic circular dichroism study of Fe/Cu(111) using a tunneling smart tip

    PubMed Central

    DiLullo, Andrew; Shirato, Nozomi; Cummings, Marvin; Kersell, Heath; Chang, Hao; Rosenmann, Daniel; Miller, Dean; Freeland, John W.; Hla, Saw-Wai; Rose, Volker

    2016-01-01

    Localized spectroscopy with simultaneous topographic, elemental and magnetic information is presented. A synchrotron X-ray scanning tunneling microscope has been employed for the local study of the X-ray magnetic circular dichroism at the Fe L 2,3-edges of a thin iron film grown on Cu(111). Polarization-dependent X-ray absorption spectra have been obtained through a tunneling smart tip that serves as a photoelectron detector. In contrast to conventional spin-polarized scanning tunneling microscopy, X-ray excitations provide magnetic contrast even with a non-magnetic tip. Intensity variations in the photoexcited tip current point to chemical variations within a single magnetic Fe domain. PMID:26917146

  16. Local X-ray magnetic circular dichroism study of Fe/Cu(111) using a tunneling smart tip

    DOE PAGESBeta

    DiLullo, Andrew; Shirato, Nozomi; Cummings, Marvin; Kersell, Heath; Chang, Hao; Rosenmann, Daniel; Miller, Dean; Freeland, John W.; Hla, Saw -Wai; Rose, Volker

    2016-01-28

    Localized spectroscopy with simultaneous topographic, elemental and magnetic information is presented. A synchrotron X-ray scanning tunneling microscope has been employed for the local study of the X-ray magnetic circular dichroism at the FeL2,3-edges of a thin iron film grown on Cu(111). Polarization-dependent X-ray absorption spectra have been obtained through a tunneling smart tip that serves as a photoelectron detector. In contrast to conventional spin-polarized scanning tunneling microscopy, X-ray excitations provide magnetic contrast even with a non-magnetic tip. Intensity variations in the photoexcited tip current point to chemical variations within a single magnetic Fe domain.

  17. Thermal and magnetic anomalies of α-iron: an exploration by extended x-ray absorption fine structure spectroscopy and synchrotron x-ray diffraction

    NASA Astrophysics Data System (ADS)

    Boccato, Silvia; Sanson, Andrea; Kantor, Innokenty; Mathon, Olivier; Dyadkin, Vadim; Chernyshov, Dmitry; Carnera, Alberto; Pascarelli, Sakura

    2016-09-01

    The local structure and dynamics of α-iron have been investigated by extended x-ray absorption fine structure (EXAFS) spectroscopy and x-ray diffraction (XRD) in order to shed light on some thermal and magnetic anomalies observed in the last decades. The quantitative EXAFS analysis of the first two coordination shells reveals a peculiar local vibrational dynamics of α-iron: the second neighbor distance exhibits anharmonicity and vibrational anisotropy larger than the first neighbor distance. We search for possible distortions of the bcc structure to justify the unexplained magnetostriction anomalies of α-iron and provide a value for the maximum dislocation of the central Fe atom. No thermal anomalies have been detected from the current XRD data. On the contrary, an intriguing thermal anomaly at about 150 K, ascribed to a stiffening of the Fe–Fe bonds, was found by EXAFS.

  18. Thermal and magnetic anomalies of α-iron: an exploration by extended x-ray absorption fine structure spectroscopy and synchrotron x-ray diffraction.

    PubMed

    Boccato, Silvia; Sanson, Andrea; Kantor, Innokenty; Mathon, Olivier; Dyadkin, Vadim; Chernyshov, Dmitry; Carnera, Alberto; Pascarelli, Sakura

    2016-09-01

    The local structure and dynamics of α-iron have been investigated by extended x-ray absorption fine structure (EXAFS) spectroscopy and x-ray diffraction (XRD) in order to shed light on some thermal and magnetic anomalies observed in the last decades. The quantitative EXAFS analysis of the first two coordination shells reveals a peculiar local vibrational dynamics of α-iron: the second neighbor distance exhibits anharmonicity and vibrational anisotropy larger than the first neighbor distance. We search for possible distortions of the bcc structure to justify the unexplained magnetostriction anomalies of α-iron and provide a value for the maximum dislocation of the central Fe atom. No thermal anomalies have been detected from the current XRD data. On the contrary, an intriguing thermal anomaly at about 150 K, ascribed to a stiffening of the Fe-Fe bonds, was found by EXAFS. PMID:27385480

  19. X-ray absorption and magnetic circular dichroism studies of Co2FeAl in magnetic tunnel junctions

    SciTech Connect

    Ebke, D.; Kugler, Z.; Thomas, P.; Schebaum, O.; Schafers, M.; Nissen, D.; Schmalhorst, J.; Hutten, A.; Arenholz, E.; Thomas, A.

    2010-01-11

    The bulk magnetic moment and the element specific magnetic moment of Co{sub 2}FeAl thin films were examined as a function of annealing temperature by alternating gradient magnetometer (AGM) and X-ray absorption spectroscopy (XAS)/X-ray magnetic circular dichroism (XMCD), respectively. A high magnetic moment can be achieved for all annealing temperatures and the predicted bulk and interface magnetic moment of about 5 {tilde A}{sub B} are reached via heating. We will also present tunnel magnetoresistance (TMR) values of up to 153% at room temperature and 260% at 13 K for MgO based magnetic tunnel junctions (MTJs) with Co{sub 2}FeAl and Co-Fe electrodes.

  20. Studies of SmCo5/Fe nanocomposite magnetic bilayers with magnetic soft x-ray transmission microscopy

    SciTech Connect

    Shahzad, F.; Siddiqi, S. A.; Im, M.-Y.; Avallone, A.; Fischer, P.; Hussain, Z.; Siddiqi, I.; Hellman, F.; Zhao, J.

    2009-12-04

    A hard/soft SmCo{sub 5}/Fe nanocomposite magnetic bilayer system has been fabricated on X-ray transparent 100-200 nm thin Si{sub 3}N{sub 4} membranes by magnetron sputtering. The microscopic magnetic domain pattern and its behavior during magnetization reversal in the hard and soft magnetic phases have been individually studied by element specific magnetic soft x-ray microscopy at a spatial resolution of better than 25nm. We observe that the domain patterns for soft and hard phases switch coherently throughout the full hysteresis cycle upon applying external magnetic fields. We derived local M(H) curves from the images for Fe and SmCo5 separately and found switching for both hard and soft phases same.

  1. Design considerations for the magnetic system of a prototype x-ray free electron laser

    SciTech Connect

    Vinokurov, N.A.; Dejus, R.; Friedsam, H.; Gluskin, E.S.; Maines, J.; Milton, S.V.; Moog, E.R.; Trakhtenberg, E.M.; Vasserman, I.B.

    1997-04-01

    A number of difficult technical challenges need to be solved in the fields of accelerator and free-electron laser (FEL) technologies in order to build an X-ray FEL. One of the tasks well suited to the Advanced Photon Source Low Energy Undulator Test Line (LEUTL) is to take the intermediate step of solving some of the problems of single-pass FEL operation in the ultraviolet range. The existing Advanced Photon Source (APS) linac, in addition to its role of supply positrons for the APS storage ring, will also be used to generate the particle beam for the LEUTL. Here, the design of the magnetic system for the high gain soft x-ray free electron laser is described.

  2. Facility for combined in situ magnetron sputtering and soft x-ray magnetic circular dichroism

    SciTech Connect

    Telling, N. D.; Laan, G. van der; Georgieva, M. T.; Farley, N. R. S.

    2006-07-15

    An ultrahigh vacuum chamber that enables the in situ growth of thin films and multilayers by magnetron sputtering techniques is described. Following film preparation, x-ray absorption spectroscopy (XAS) and x-ray magnetic circular dichroism (XMCD) measurements are performed by utilizing an in vacuum electromagnet. XMCD measurements on sputtered thin films of Fe and Co yield spin and orbital moments that are consistent with those obtained previously on films measured in transmission geometry and grown in situ by evaporation methods. Thin films of FeN prepared by reactive sputtering are also examined and reveal an apparent enhancement in the orbital moment for low N content samples. The advantages of producing samples for in situ XAS and XMCD studies by magnetron sputtering are discussed.

  3. Upgrade of X-ray Magnetic Diffraction Experimental System and Its Application to Ferromagnetic Material

    SciTech Connect

    Suzuki, Kosuke; Tsuji, Naruki; Akiyama, Hiromitu; Ito, Masahisa; Kitani, Kensuke; Adachi, Hiromichi; Kawata, Hiroshi

    2007-01-19

    We have performed X-ray magnetic diffraction (XMD) experiment of ferromagnets at the Photon Factory (PF) of the High Energy Accelerator Research Organization (KEK) in Tsukuba. In this study, we have upgraded the XMD experimental system in order to apply this method to as many samples as possible. Upgrade was made for (1) the X-ray counting system and related measurement program, (2) the electromagnet, and (3) the refrigerator. The performance of the system was enhanced so that (1) the counting rate capability was improved from 104cps to 105cps, (2) the maximum magnetic field was increased from 0.85T to 2.15T, and (3) the lowest sample temperature was reduced from 15K to 5K. The new system was applied to an orbital ordering compound of YTiO3, and we obtained spin magnetic form factor for the reflection plane (010) perpendicular to the b axis. The magnetic field of 2T was needed to saturate the magnetization of YTiO3 along the b axis. These are the first data with the magnetization of YTiO3 saturated along the b axis by the XMD.

  4. An investigation of resonant photoemission in Gd with x-ray linear dichroism

    SciTech Connect

    Tobin, J G

    1998-07-01

    The constructive summing of direct and indirect channels above the absorption threshold of a core level can cause a massive increase in the emission cross section, leading to a phenomenon called "resonant photoemission". Using novel magnetic linear dichroism in angular distribution photoelectron spectroscopy experiments and theoretical simulations, we have probed the nature of the resonant photoemission process in Gd metal. It now appears that temporal matching as well as energy matching is a requirement for true resonant photoemission.

  5. Magnetic circular x-ray dichroisms of Fe-Ni alloys at K edge.

    SciTech Connect

    Freeman, A. J.; Gofron, K. J.; Kimball, C. W.; Lee, P. L.; Montano, P. A.; Rao, F.; Wang, X.

    1997-04-03

    Magnetic Circular X-ray Dichroism (MCXD) studies at K edges of Fe-Ni alloys reveal changes of the MCXD signal with composition and crystal structure. We observe that the signal at the invar composition is of comparable strength as other compositions. Moreover, the edge position is strongly dependent on lattice constant. First principles calculations demonstrate that the shape and strength of the signal strongly depends on the crystal orientation, composition, and lattice constant. We find direct relation between the MCXD signal and the p DOS. We find that the MCXD at K edge probes the magnetism due to itinerant electrons.

  6. Site-Specific Studies on X-Ray Magnetic Circular Dichroism at Fe K Edge for Transition-Metal Ferrites

    NASA Astrophysics Data System (ADS)

    Matsumoto, Kenji; Saito, Fumikazu; Toyoda, Takeshi; Ohkubo, Koichi; Yamawaki, Koji; Mori, Takeharu; Hirano, Keiichi; Tanaka, Masahiko; Sasaki, Satoshi

    2000-10-01

    Experiments on X-ray magnetic circular dichroism (XMCD) were performed with synchrotron radiation for Zn and Mn-Zn ferrites (normal-spinel structure) and Ni, Co and Cu ferrites and magnetite (inverse-spinel structure). The inverse-spinel ferrites have positive-to-negative dispersion-type XMCD signals in the pre-edge region of the Fe K edge, which originate from Fe3+ ions in the A sites. There are no such signals for normal-spinel ferrites. Two kinds of negative-to-positive dispersion-type XMCD signals were observed in 7.119-7.125 keV and 7.122-7.129 keV regions of the main edge, which are caused by a mixture of Fe3+ and Fe2+ ions of the B sites in magnetite and Fe3+ ions of the B sites in the other inverse-spinel ferrites, respectively. The B-site origin of the XMCD main-edge spectra was also confirmed by observation of X-ray resonant magnetic scattering for the 222 reflection of Ni ferrite.

  7. Electrical conductivity, differential scanning calorimetry, X-ray diffraction, and 7Li nuclear magnetic resonance studies of n-C x H(2 x+1)OSO3Li ( x = 12, 14, 16, 18, and 20)

    NASA Astrophysics Data System (ADS)

    Hirakawa, Satoru; Morimoto, Yoshiaki; Honda, Hisashi

    2015-04-01

    Electrical conductivity ( σ), differential scanning calorimetry (DSC), and X-ray diffraction (XRD) measurements of n-C x H (2 x+1) OSO 3Li ( x= 12, 14, 16, 18, and 20) crystals were performed as a function of temperature. In addition, σ, DSC, and XRD observations of n-C x H (2 x+1) OSO 3Na and n-C x H (2 x+1) OSO 3K ( x= 12, 14, 16, 18, and 20) crystals were carried out for comparison. DSC results of the salts revealed several solid-solid phase transitions with large entropy changes (Δ S). For n-C 18 H 37 OSO 3Li and n-C 20 H 41 OSO 3Li salts, each melting point produced a small Δ S mp value compared with the total entropy change in the solid phases (Δ S tr1+Δ S tr2). Additionally, Li + ion diffusion was detected in the highest temperature solid phases. For K salts, larger σ values were detected for potassium alkylsulfates compared with those reported for alkyl carboxylate. 7Li NMR spectra of n-C 18 H 37 OSO 3Li crystals recorded in the low-temperature phase showed large asymmetry parameters, suggesting the Li + ions are localized at asymmetric sites in the crystals.

  8. PREFACE: REXS 2013 - Workshop on Resonant Elastic X-ray Scattering in Condensed Matter

    NASA Astrophysics Data System (ADS)

    Beutier, G.; Mazzoli, C.; Yakhou, F.; Brown, S. D.; Bombardi, A.; Collins, S. P.

    2014-05-01

    The aim of this workshop was to bring together experts in experimental and theoretical aspects of resonant elastic x-ray scattering, along with researchers who are new to the field, to discuss important recent results and the fundamentals of the technique. The meeting was a great success, with the first day dedicated to students and new researchers in the field, who received introductory lectures and tutorials. All conference delegates were invited either to make an oral presentation or to present a poster, accompanied by a short talk. The first two papers selected for the REXS13 proceedings (Grenier & Joly and Helliwell) give a basic background to the theory of REXS and applications across a wide range of scientific areas. The remainder of the papers report on some of the latest scientific results obtained by applying the REXS technique to contemporary problems in condensed matter, materials and x-ray physics. It is hoped that these proceedings provide a snapshot of the current status of a vibrant and diverse scientific technique that will be of value not just to those who attended the workshop but also to any other reader with an interest in the subject. Local Scientific Committee REXS13 International Scientific Advisory Committee M Altarelli, European XFEL, Germany F de Bergevin, European Synchrotron Radiation Facility, France J Garcia-Ruiz, Universidad de Zaragoza, Spain A I Goldman, Iowa State University, USA M Goldmann, Institut Nanosciences, France T Schulli, European Synchrotron Radiation Facility, France C R Natoli, Laboratori Nazionali de Frascati, Italy G Materlik, Diamond Light Source, UK L Paolasini, European Synchrotron Radiation Facility, France U Staub, Paul Scherrer Institut, Switzerland K Finkelstein, Cornell University, USA Y Murakami, Photon Factory, Japan REXS13 Local Scientific Committee G Beutier, CNRS Grenoble, France C Mazzoli, Politecnico di Milano, Italy F Yakhou, European Synchrotron Radiation Facility, France S D Brown, XMaS UK CRG

  9. Retrieving spin textures on curved magnetic thin films with full-field soft X-ray microscopies

    PubMed Central

    Streubel, Robert; Kronast, Florian; Fischer, Peter; Parkinson, Dula; Schmidt, Oliver G.; Makarov, Denys

    2015-01-01

    X-ray tomography is a well-established technique to characterize 3D structures in material sciences and biology; its magnetic analogue—magnetic X-ray tomography—is yet to be developed. Here we demonstrate the visualization and reconstruction of magnetic domain structures in a 3D curved magnetic thin films with tubular shape by means of full-field soft X-ray microscopies. The 3D arrangement of the magnetization is retrieved from a set of 2D projections by analysing the evolution of the magnetic contrast with varying projection angle. Using reconstruction algorithms to analyse the angular evolution of 2D projections provides quantitative information about domain patterns and magnetic coupling phenomena between windings of azimuthally and radially magnetized tubular objects. The present approach represents a first milestone towards visualizing magnetization textures of 3D curved thin films with virtually arbitrary shape. PMID:26139445

  10. Retrieving spin textures on curved magnetic thin films with full-field soft X-ray microscopies

    DOE PAGESBeta

    Streubel, Robert; Kronast, Florian; Fischer, Peter; Parkinson, Dula; Schmidt, Oliver G.; Makarov, Denys

    2015-07-03

    X-ray tomography is a well-established technique to characterize 3D structures in material sciences and biology; its magnetic analogue—magnetic X-ray tomography—is yet to be developed. We demonstrate the visualization and reconstruction of magnetic domain structures in a 3D curved magnetic thin films with tubular shape by means of full-field soft X-ray microscopies. In the 3D arrangement of the magnetization is retrieved from a set of 2D projections by analysing the evolution of the magnetic contrast with varying projection angle. By using reconstruction algorithms to analyse the angular evolution of 2D projections provides quantitative information about domain patterns and magnetic coupling phenomenamore » between windings of azimuthally and radially magnetized tubular objects. In conclusion, the present approach represents a first milestone towards visualizing magnetization textures of 3D curved thin films with virtually arbitrary shape.« less

  11. Retrieving spin textures on curved magnetic thin films with full-field soft X-ray microscopies

    SciTech Connect

    Streubel, Robert; Kronast, Florian; Fischer, Peter; Parkinson, Dula; Schmidt, Oliver G.; Makarov, Denys

    2015-07-03

    X-ray tomography is a well-established technique to characterize 3D structures in material sciences and biology; its magnetic analogue—magnetic X-ray tomography—is yet to be developed. We demonstrate the visualization and reconstruction of magnetic domain structures in a 3D curved magnetic thin films with tubular shape by means of full-field soft X-ray microscopies. In the 3D arrangement of the magnetization is retrieved from a set of 2D projections by analysing the evolution of the magnetic contrast with varying projection angle. By using reconstruction algorithms to analyse the angular evolution of 2D projections provides quantitative information about domain patterns and magnetic coupling phenomena between windings of azimuthally and radially magnetized tubular objects. In conclusion, the present approach represents a first milestone towards visualizing magnetization textures of 3D curved thin films with virtually arbitrary shape.

  12. Retrieving spin textures on curved magnetic thin films with full-field soft X-ray microscopies.

    PubMed

    Streubel, Robert; Kronast, Florian; Fischer, Peter; Parkinson, Dula; Schmidt, Oliver G; Makarov, Denys

    2015-01-01

    X-ray tomography is a well-established technique to characterize 3D structures in material sciences and biology; its magnetic analogue--magnetic X-ray tomography--is yet to be developed. Here we demonstrate the visualization and reconstruction of magnetic domain structures in a 3D curved magnetic thin films with tubular shape by means of full-field soft X-ray microscopies. The 3D arrangement of the magnetization is retrieved from a set of 2D projections by analysing the evolution of the magnetic contrast with varying projection angle. Using reconstruction algorithms to analyse the angular evolution of 2D projections provides quantitative information about domain patterns and magnetic coupling phenomena between windings of azimuthally and radially magnetized tubular objects. The present approach represents a first milestone towards visualizing magnetization textures of 3D curved thin films with virtually arbitrary shape. PMID:26139445

  13. Retrieving spin textures on curved magnetic thin films with full-field soft X-ray microscopies

    NASA Astrophysics Data System (ADS)

    Streubel, Robert; Kronast, Florian; Fischer, Peter; Parkinson, Dula; Schmidt, Oliver G.; Makarov, Denys

    2015-07-01

    X-ray tomography is a well-established technique to characterize 3D structures in material sciences and biology; its magnetic analogue--magnetic X-ray tomography--is yet to be developed. Here we demonstrate the visualization and reconstruction of magnetic domain structures in a 3D curved magnetic thin films with tubular shape by means of full-field soft X-ray microscopies. The 3D arrangement of the magnetization is retrieved from a set of 2D projections by analysing the evolution of the magnetic contrast with varying projection angle. Using reconstruction algorithms to analyse the angular evolution of 2D projections provides quantitative information about domain patterns and magnetic coupling phenomena between windings of azimuthally and radially magnetized tubular objects. The present approach represents a first milestone towards visualizing magnetization textures of 3D curved thin films with virtually arbitrary shape.

  14. Soft x-ray microscopy: facing the mesoscale challenge in magnetism

    NASA Astrophysics Data System (ADS)

    Fischer, P.; Im, M.-Y.; Hong, J.-I.

    2013-09-01

    For more than a decade magnetism research focused on a fundamental understanding and controlling of spins on a nanoscale. The next step beyond the nanoscale will be governed by mesoscale phenomena. Those are expected to add complexity and functionality, which are essential design parameters e.g. for the realization of future spintronic devices. Advanced characterization techniques will play key roles in achieving mesoscience goals and multidimensional spectromicroscopies utilizing polarized soft x-rays offering a unique combination of spatiotemporal resolution, elemental and magnetic sensitivity, and tomographic capabilities are very promising. As an example for complex behavior we show experimental results of the stochastic character of the nucleation of magnetic vortex structures in arrays of permalloy nanodisk. We have used magnetic soft x-ray microscopy to image at 25nm spatial resolution and a field of view of about 8 μm diameter both the circularity and the polarity of the disk, which allowed us to categorize the nucleated vortex state without ambiguity. We have found a symmetry breaking effect in the final vortex state, represented by a preferred handedness. We were able to identify as the origin of the asymmetry an internal Dzyaloshinskii-Moriya interaction arising from a broken inversion symmetry at the top and bottom surface/interface of the disk. Full 3-dimensional micromagnetic simulations confirmed our experimental observation. Here we present our observations with regard to disk diameter and disk thickness. Various soft x-ray microscopy approaches are currently pursued to obtain full 3dimensional images of magnetic structures, including computed reconstruction of 2dim projection images.

  15. X-Ray Emission Spectrometer Design with Single-Shot Pump-Probe and Resonant Excitation Capabilities

    SciTech Connect

    Spoth, Katherine; /SUNY, Buffalo /SLAC

    2012-08-28

    Core-level spectroscopy in the soft X-ray regime is a powerful tool for the study of chemical bonding processes. The ultrafast, ultrabright X-ray pulses generated by the Linac Coherent Light Source (LCLS) allow these reactions to be studied in greater detail than ever before. In this study, we investigated a conceptual design of a spectrometer for the LCLS with imaging in the non-dispersive direction. This would allow single-shot collection of X-ray emission spectroscopy (XES) measurements with varying laser pump X-ray probe delay or a variation of incoming X-ray energy over the illuminated area of the sample. Ray-tracing simulations were used to demonstrate how the components of the spectrometer affect its performance, allowing a determination of the optimal final design. These simulations showed that the spectrometer's non-dispersive focusing is extremely sensitive to the size of the sample footprint; the spectrometer is not able to image a footprint width larger than one millimeter with the required resolution. This is compatible with a single shot scheme that maps out the laser pump X-ray probe delay in the non-dispersive direction as well as resonant XES applications at normal incidence. However, the current capabilities of the Soft X-Ray (SXR) beamline at the LCLS do not produce the required energy range in a small enough sample footprint, hindering the single shot resonant XES application at SXR for chemical dynamics studies at surfaces. If an upgraded or future beamline at LCLS is developed with lower monochromator energy dispersion the width can be made small enough at the required energy range to be imaged by this spectrometer design.

  16. X-Ray Resonant Irradiation and High-Z Radiosensitization in Cancer Therapy Using Platinum Nano-Reagents

    NASA Astrophysics Data System (ADS)

    Nahar, Sultana N.; Lim, S.; Montenegro, M.; Pradhan, A. K.; Barth, R.; Bell, E.; Turro, C.; Pitzer, R.

    2012-06-01

    %TEXT OF YOUR ABSTRACT We describe the atomic-molecular-bio physics of X-ray irradiation of High-Z heavy-element nanomaterials as radiosensitizing agents in cancer therapy. Our reports in past few ISMSs showed that compounds of High-Z elements, Pt and Au, embedded in tumors could provide the most efficient therapy and diagnostics (theranostics) when X-rays are targeted at their resonant energies. Harmful damages due to unnecessary broadband radiation from conventional X-ray sources can be reduced considerably by using a monochromatic X-ray source at resonant energy. We will present our recent findings from Monte Carlo simulations, using Geant4 code, for X-ray energy absorption and dose deposition in tissues where the broadband X-ray sources have three different peak voltages, 100 keV, 170 keV and 6 MeV. We use platinum as an agent for killing cancerous cells via increased linear-energy-transfer (LET) and dose enhancement. We find that X-ray energies in the range below 100 keV are most efficient in achieving both the required tissue penetrative depths and deposition of energy. This confirms the previous results for Au that it is only the low-energy component around 100 keV from the 6 MV linear accelerator (LINAC) that is most effective in dose-enhanced cell killing. Preliminary experimental results cancer cells with Pt and results on Kα radiation of Al will also be presented. Acknowledgement: Partially supported by DOE, NSF; Computational work was carried out at the Ohio Supercomputer Center

  17. Interferometric phase detection at x-ray energies via Fano resonance control.

    PubMed

    Heeg, K P; Ott, C; Schumacher, D; Wille, H-C; Röhlsberger, R; Pfeifer, T; Evers, J

    2015-05-22

    Modern x-ray light sources promise access to structure and dynamics of matter in largely unexplored spectral regions. However, the desired information is encoded in the light intensity and phase, whereas detectors register only the intensity. This phase problem is ubiquitous in crystallography and imaging and impedes the exploration of quantum effects at x-ray energies. Here, we demonstrate phase-sensitive measurements characterizing the quantum state of a nuclear two-level system at hard x-ray energies. The nuclei are initially prepared in a superposition state. Subsequently, the relative phase of this superposition is interferometrically reconstructed from the emitted x rays. Our results form a first step towards x-ray quantum state tomography and provide new avenues for structure determination and precision metrology via x-ray Fano interference. PMID:26047250

  18. Thermonuclear ignition by Z-pinch X-ray radiation produced by current of an explosive magnetic generator

    NASA Astrophysics Data System (ADS)

    Garanin, S. G.; Ivanovskiy, A. V.

    2015-12-01

    The scheme of a device based a superpower disk-type magnetic explosion generator to produce a pulse of X-ray radiation with the energy exceeding the target ignition threshold is described and validated.

  19. Thermonuclear ignition by Z-pinch X-ray radiation produced by current of an explosive magnetic generator

    SciTech Connect

    Garanin, S. G.; Ivanovskiy, A. V.

    2015-12-15

    The scheme of a device based a superpower disk-type magnetic explosion generator to produce a pulse of X-ray radiation with the energy exceeding the target ignition threshold is described and validated.

  20. Arrays of nanoscale magnetic dots: Fabrication by x-ray interference lithography and characterization

    SciTech Connect

    Heyderman, L.J.; Solak, H.H.; David, C.; Atkinson, D.; Cowburn, R.P.; Nolting, F.

    2004-11-22

    X-ray interference lithography (XIL) was employed in combination with electrodeposition to fabricate arrays of nanoscale nickel dots which are uniform over 40 {mu}m and have periods down to 71 nm. Using extreme-ultraviolet light, XIL has the potential to produce magnetic dot arrays over large areas with periods well below 50 nm, and down to a theoretical limit of 6.5 nm for a 13 nm x-ray wavelength. In the nickel dot arrays, we observed the effect of interdot magnetic stray field interactions. Measuring the hysteresis loops using the magneto-optical Kerr effect, a double switching via the vortex state was observed in the nickel dots with diameters down to 44 nm and large dot separations. As the dot separations are reduced to below around 50 nm a single switching, occurring by collective rotation of the magnetic spins, is favored due to interdot magnetic stray field interactions. This results in magnetic flux closure through several dots which could be visualized with micromagnetic simulations. Further evidence of the stray field interactions was seen in photoemission electron microscopy images, where bands of contrast corresponding to chains of coupled dots were observed.

  1. X-ray imaging of vortex cores in confined magnetic structures

    SciTech Connect

    Fischer, P; Im, M -Y; Kasai, S; Yamada, K; Ono, T; Thiaville, A

    2011-02-11

    Cores of magnetic vortices in micron-sized NiFe disk structures, with thicknesses between 150 and 50 nm, were imaged and analyzed by high-resolution magnetic soft x-ray microscopy. A decrease of the vortex-core radius was observed from approximately 38 to 18 nm with decreasing disk thickness. By comparing with full three-dimensional micromagnetic simulations showing the well-known barrel structure, we obtained excellent agreement, taking into account instrumental broadening and a small perpendicular anisotropy. The proven magnetic spatial resolution of better than 25 nm was sufficient to identify a negative dip close to the vortex core, originating from stray fields of the core. Magnetic vortex structures can serve as test objects for evaluating sensitivity and spatial resolution of advanced magnetic microscopy techniques.

  2. Structural and dynamical properties of chlorinated hydrocarbons studied with resonant inelastic x-ray scattering.

    PubMed

    Bohinc, R; Žitnik, M; Bučar, K; Kavčič, M; Carniato, S; Journel, L; Guillemin, R; Marchenko, T; Kawerk, E; Simon, M; Cao, W

    2016-04-01

    We present a theoretical and experimental study of resonant inelastic x-ray scattering on a large group of chlorinated hydrocarbons: CH3Cl, CH2Cl2, CHCl3, CCl4, CH3CH2Cl, ClCH2CH2Cl, CH3CHCl2, CH3CCl3, C2H2Cl2-iso, C2H2Cl2-cis, C2H2Cl2-trans, and C6H5Cl. Differences in structural and dynamical properties of the molecules generated by diverse chemical environments are observed in the measured Cl(Kα) spectral maps as well as in the Cl(K) total fluorescence yield spectra. The energy position, relative intensity, and the width of the Franck-Condon distribution of low-lying σ(∗) and π(∗) resonances are extracted by a fitting procedure taking into account the experimental broadening. The theoretical values obtained with the transition potential and Δ Kohn-Sham methods are in good agreement with the experimental parameters indicating subtle differences due to variations in the molecular structure. PMID:27059572

  3. Structural and dynamical properties of chlorinated hydrocarbons studied with resonant inelastic x-ray scattering

    NASA Astrophysics Data System (ADS)

    Bohinc, R.; Žitnik, M.; Bučar, K.; Kavčič, M.; Carniato, S.; Journel, L.; Guillemin, R.; Marchenko, T.; Kawerk, E.; Simon, M.; Cao, W.

    2016-04-01

    We present a theoretical and experimental study of resonant inelastic x-ray scattering on a large group of chlorinated hydrocarbons: CH3Cl, CH2Cl2, CHCl3, CCl4, CH3CH2Cl, ClCH2CH2Cl, CH3CHCl2, CH3CCl3, C2H2Cl2-iso, C2H2Cl2-cis, C2H2Cl2-trans, and C6H5Cl. Differences in structural and dynamical properties of the molecules generated by diverse chemical environments are observed in the measured Cl(Kα) spectral maps as well as in the Cl(K) total fluorescence yield spectra. The energy position, relative intensity, and the width of the Franck-Condon distribution of low-lying σ∗ and π∗ resonances are extracted by a fitting procedure taking into account the experimental broadening. The theoretical values obtained with the transition potential and Δ Kohn-Sham methods are in good agreement with the experimental parameters indicating subtle differences due to variations in the molecular structure.

  4. Performance verification of the Gravity and Extreme Magnetism Small explorer (GEMS) x-ray polarimeter

    NASA Astrophysics Data System (ADS)

    Enoto, Teruaki; Black, J. Kevin; Kitaguchi, Takao; Hayato, Asami; Hill, Joanne E.; Jahoda, Keith; Tamagawa, Toru; Kaneko, Kenta; Takeuchi, Yoko; Yoshikawa, Akifumi; Marlowe, Hannah; Griffiths, Scott; Kaaret, Philip E.; Kenward, David; Khalid, Syed

    2014-07-01

    Polarimetry is a powerful tool for astrophysical observations that has yet to be exploited in the X-ray band. For satellite-borne and sounding rocket experiments, we have developed a photoelectric gas polarimeter to measure X-ray polarization in the 2-10 keV range utilizing a time projection chamber (TPC) and advanced micro-pattern gas electron multiplier (GEM) techniques. We carried out performance verification of a flight equivalent unit (1/4 model) which was planned to be launched on the NASA Gravity and Extreme Magnetism Small Explorer (GEMS) satellite. The test was performed at Brookhaven National Laboratory, National Synchrotron Light Source (NSLS) facility in April 2013. The polarimeter was irradiated with linearly-polarized monochromatic X-rays between 2.3 and 10.0 keV and scanned with a collimated beam at 5 different detector positions. After a systematic investigation of the detector response, a modulation factor >=35% above 4 keV was obtained with the expected polarization angle. At energies below 4 keV where the photoelectron track becomes short, diffusion in the region between the GEM and readout strips leaves an asymmetric photoelectron image. A correction method retrieves an expected modulation angle, and the expected modulation factor, ~20% at 2.7 keV. Folding the measured values of modulation through an instrument model gives sensitivity, parameterized by minimum detectable polarization (MDP), nearly identical to that assumed at the preliminary design review (PDR).

  5. Design of High Resolution Soft X-Ray Microcalorimeters Using Magnetic Penetration Thermometers

    NASA Technical Reports Server (NTRS)

    Busch. Sarah; Balvin, Manuel; Bandler, Simon; Denis, Kevin; Finkbeiner, Fred; Porst, Jan-Patrick; Sadlier, Jack; Smith, Stephen; Stevenson, Thomas

    2012-01-01

    We have designed high-resolution soft x-ray microcalorimeters using magnetic penetration thermometers (MPTs) in an array of pixels covering a total of 2 square centimeters to have a resolving power of 300 at energies around 300 eV. This performance is desirable for studying the soft x-ray background from the warm hot intergalactic medium. MPT devices have small sensor heat capacity and high responsivities, which makes them excellent detector technology for attempting to attain sub-eV resolution. We are investigating the feasibility of pixels with absorbers that are 625 x 625 square micrometers, up to 1 x 1 square millimeters in area and 0.35 micrometer thick and thinner. Our tests have shown that suspended gold absorbers 0.35 micrometers thick (RRR = 6.7) are feasible to fabricate. We modeled the thermal diffusion from such thin gold over the size of a 625 x 625 square micrometer absorber, and conclude that the effect of the thermalization on the resolution of a 300 eV photon is an additional approximately 0.2 eV FWHM of broadening. We discuss the thermal effects of small absorber attachment sterns on solid substrate, as well as considerations for multiplexed readout. We will present the progress we have made towards building and testing this soft x-ray detector.

  6. Performance and Characterization of Magnetic Penetration Thermometer Devices for X-Ray Spectroscopy

    NASA Technical Reports Server (NTRS)

    Porst, J. -P.; Adams, J. S.; Bandler, S. R.; Balvin, M.; Busch, S. E.; Denis, K. L.; Kelly, D.; Nagler, P.; Sadleir, J. E.; Seidel, G. M.; Smith, S.; Stevenson, T. R.

    2012-01-01

    We are developing magnetic penetration thermometers (MPTs) for applications in X-ray astronomy. These non-dissipative devices consist of an X-ray absorber in good thermal contact to a superconducting thin film with a transition temperature around T=100mK. A microfabricated superconducting planar inductor underneath is used to store a persistent current and couple the superconductor's diamagnetic response to a readout SQUID. The strong temperature dependence of the diamagnetic response make these devices suitable for highly sensitive macroscopic thermometers that are capable of achieving very high energy resolution. We present results achieved with MPTs consisting of MoAu bilayer sensors attached to overhanging square 250 micron by 250 micron gold absorbers that have demonstrated an energy resolution of delta E_FWHM=2.3eV at an X-ray energy of 5.9keV. A similar device has shown delta E_FWHM=2.0eV at 1.5 keV. Under certain conditions and for specific device geometries, the temperature responsivity of the MPTs can vary on long timescales degrading the spectral performance. We present the characterization of different inductor geometries to optimize the design for the highest possible temperature sensitivity and compare different device designs with respect to responsivity stability.

  7. An X-ray standing wave study of the diluted magnetic semiconductor Ga(Mn)As

    NASA Astrophysics Data System (ADS)

    Nemsak, Slavomir; Kuo, Cheng-Tai; Schlueter, Christoph; Gehlmann, Mathias; Lin, Shih-Chieh; Doering, Sven; Eschbach, Markus; Mlynczak, Ewa; Plucinski, Lukasz; Borek, Stephan; Minar, Jan; Ohno, Hideo; Lee, Tien-Lin; Schneider, Claus M.; Fadley, Charles S.

    We have combined the recently developed techniques of soft x-ray standing-wave angle-resolved photoemission (SW-ARPES) [Gray et al., EPL 104, 17004 (2013)] and hard x-ray ARPES (HARPES) [Gray et al., Nature Mat. 11, 957 (2012)] so as to be able to use single-crystal Bragg reflection to create the SW [Thiess et al., Sol. St. Comm. 150, 553 (2010)], thus permitting the first measurements of momentum- and element- resolved bulk electronic structure. The strengths of the SW-HARPES method are demonstrated using the dilute magnetic semiconductor Ga(1 - x)MnxAs. A strong SW is generated by Bragg reflection of ca. 3 keV x-rays from the (111) planes of both undoped GaAs and Mn-doped thin films with x=0.05. Due to the uneven occupancy of (111) planes by either Ga(Mn) or As atoms, the element-specific band structure can be obtained with a help of the SW modulation in core levels. Apart from the site specific decomposition of the electronic structure, the SW measurements also confirmed a substitutional presence of Mn atoms at the Ga sites. This technique should be applicable to a broad range of complex materials.

  8. Performance Verification of the Gravity and Extreme Magnetism Small Explorer GEMS X-Ray Polarimeter

    NASA Technical Reports Server (NTRS)

    Enoto, Teruaki; Black, J. Kevin; Kitaguchi, Takao; Hayato, Asami; Hill, Joanne E.; Jahoda, Keith; Tamagawa, Toru; Kanako, Kenta; Takeuchi, Yoko; Yoshikawa, Akifumi; Kenward, David

    2014-01-01

    olarimetry is a powerful tool for astrophysical observations that has yet to be exploited in the X-ray band. For satellite-borne and sounding rocket experiments, we have developed a photoelectric gas polarimeter to measure X-ray polarization in the 2-10 keV range utilizing a time projection chamber (TPC) and advanced micro-pattern gas electron multiplier (GEM) techniques. We carried out performance verification of a flight equivalent unit (1/4 model) which was planned to be launched on the NASA Gravity and Extreme Magnetism Small Explorer (GEMS) satellite. The test was performed at Brookhaven National Laboratory, National Synchrotron Light Source (NSLS) facility in April 2013. The polarimeter was irradiated with linearly-polarized monochromatic X-rays between 2.3 and 10.0 keV and scanned with a collimated beam at 5 different detector positions. After a systematic investigation of the detector response, a modulation factor greater than or equal to 35% above 4 keV was obtained with the expected polarization angle. At energies below 4 keV where the photoelectron track becomes short, diffusion in the region between the GEM and readout strips leaves an asymmetric photoelectron image. A correction method retrieves an expected modulation angle, and the expected modulation factor, approximately 20% at 2.7 keV. Folding the measured values of modulation through an instrument model gives sensitivity, parameterized by minimum detectable polarization (MDP), nearly identical to that assumed at the preliminary design review (PDR).

  9. Possible detection of a cyclotron resonance scattering feature in the X-ray pulsar 4U 1909+07

    SciTech Connect

    Jaisawal, Gaurava K.; Naik, Sachindra; Paul, Biswajit

    2013-12-10

    We present timing and broad band spectral studies of the high-mass X-ray binary pulsar 4U 1909+07 using data from Suzaku observations during 2010 November 2-3. The pulse period of the pulsar is estimated to be 604.11 ± 0.14 s. Pulsations are seen in the X-ray light curve up to ∼70 keV. The pulse profile is found to be strongly energy-dependent: a complex, multi-peaked structure at low energy becomes a simple single peak at higher energy. We found that the 1-70 keV pulse-averaged continuum can be fit by the sum of a blackbody and a partial covering Negative and Positive power law with Exponential cutoff model. A weak iron fluorescence emission line at 6.4 keV was detected in the spectrum. An absorption-like feature at ∼44 keV was clearly seen in the residuals of the spectral fitting, independent of the continuum model adopted. To check the possible presence of a cyclotron resonance scattering feature (CRSF) in the spectrum, we normalized the pulsar spectrum with the spectrum of the Crab Nebula. The resulting Crab ratio also showed a clear dip centered at ∼44 keV. We performed statistical tests on the residuals of the spectral fitting and also on the Crab spectral ratio to determine the significance of the absorption-like feature and identified it as a CRSF of the pulsar. We estimated the corresponding surface magnetic field of the pulsar to be 3.8 × 10{sup 12} G.

  10. Time-resolved x-ray imaging of magnetization dynamics in spin-transfer torque devices

    SciTech Connect

    Chembrolu, V.

    2010-02-24

    Time-resolved x-ray imaging techniques have recently demonstrated the capability to probe the magnetic switching of nanoscale devices. This technique has enabled, for example, the direct observation of the nonuniform intermediate states assumed by the magnetic free layer during reversal by a spin-polarized current. These experiments have shown an interesting size-dependent behavior associated with the motion of vortices to mediate the magnetization reversal which cannot be explained by the macrospin picture of spin-torque switching. In this paper we present both experimental and analytical results which show the origin of the complex switching behavior. We use time-resolved x-ray microscopy to further study the switching behavior of samples with 45{sup o} angle between the free and polarizing magnetic layers. A model is developed in terms of a linearized Landau-Lifshitz-Gilbert equation showing that the initial dynamics is dominated by the balance between the Oersted field and thermal fluctuations. The spin torque amplifies this dynamics, leading to a strong sensitivity to sample size, angle, and temperature. The model is in good agreement with current and previous experimental observations.

  11. Magnetic soft X-ray microscopy at 10nm spatial resolution

    NASA Astrophysics Data System (ADS)

    Fischer, Peter; Chao, Weilun; Im, Mi-Young; Anderson, Erik

    2011-03-01

    Magnetic soft X-ray microscopy, which combines high spatial and temporal resolution with elemental specificity by utilizing the specific features of X-ray magnetic circular dichroism effects is a unique and powerful analytical technique to image fast spin dynamics of nanoscale magnetism. The spatial resolution is determined by Fresnel zone plate lenses used as diffractive optics. FZPs are fabricated by state-of-the-art lithography techniques and the challenge is to produce a dense, circular line pattern with a high aspect ratio to achieve high efficiency. Using an overlay technique [2-3], which requires high position accuracy of the e-beam writer, FZPs with 12nm outermost zone width could be fabricated. Implementing this optic at BL 6.1.2 at the ALS in Berkeley CA, we have demonstrated that a 10nm line and space test pattern can be clearly resolved. First magnetic images of a PtCo film with a pronounced perpendicular anisotropy will be presented. Further progress to below 10nm can be anticipated in the near future. This work was supported by the U.S. Department of Energy under Contract No. DE-AC02-05-CH11231.

  12. X-ray absorption spectroscopy on magnetic nanoscale systems for modern applications.

    PubMed

    Schmitz-Antoniak, Carolin

    2015-06-01

    X-ray absorption spectroscopy facilitated by state-of-the-art synchrotron radiation technology is presented as a powerful tool to study nanoscale systems, in particular revealing their static element-specific magnetic and electronic properties on a microscopic level. A survey is given on the properties of nanoparticles, nanocomposites and thin films covering a broad range of possible applications. It ranges from the ageing effects of iron oxide nanoparticles in dispersion for biomedical applications to the characterisation on a microscopic level of nanoscale systems for data storage devices. In this respect, new concepts for electrically addressable magnetic data storage devices are highlighted by characterising the coupling in a BaTiO(3)/CoFe(2)O(4) nanocomposite as prototypical model system. But classical magnetically addressable devices are also discussed on the basis of tailoring the magnetic properties of self-assembled ensembles of FePt nanoparticles for data storage and the high-moment material Fe/Cr/Gd for write heads. For the latter cases, the importance is emphasised of combining experimental approaches in x-ray absorption spectroscopy with density functional theory to gain a more fundamental understanding. PMID:26029938

  13. Superconducting Effects in Optimization of Magnetic Penetration Thermometers for X-ray Microcalorimeters

    NASA Technical Reports Server (NTRS)

    Stevenson, Thomas R.; Balvin, M. A.; Denis, K. L.; Hsieh, W.-T.; Sadleir, J. E.; Bandler, Simon E.; Busch, Sarah E.; Merrell, W.; Kelly, Daniel P.; Nagler, Peter C.; Porst, J.-P.; Seidel, George E.; Smith, Stephen J.

    2012-01-01

    We have made high resolution x-ray microcalorimeters using superconducting MoAu bilayers and Nb meander coils. The temperature sensor is a Magnetic Penetration Thermometer (MPT). Operation is similar to metallic magnetic calorimeters, but instead of the magnetic susceptibility of a paramagnetic alloy, we use the diamagnetic response of the superconducting MoAu to sense temperature changes in an x-ray absorber. Flux-temperature responsivtty can be large for small sensor heat capacity, with enough dynamic range for applications. We find models of observed flux-temperature curves require several effects to explain flux penetration or expulsion in the microscopic devices. The superconductor is non-local, with large coherence length and weak pinning of flux. At lowest temperatures, behavior is dominated by screening currents that vary as a result of the temperature dependence of the magnetic penetration depth, modified by the effect of the nonuniformity of the applied field occurring on a scale comparable to the coherence length. In the temperature regime where responslvity is greatest, spadal variations in the order parameter become important: both local variations as flux enters/leaves the film and an intermediate state is formed, and globally as changing stability of the electrical circuit creates a Meissner transition and flux is expelled/penetrates to minimize free energy.

  14. Development of low temperature and high magnetic field X-ray diffraction facility

    NASA Astrophysics Data System (ADS)

    Shahee, Aga; Sharma, Shivani; Singh, K.; Lalla, N. P.; Chaddah, P.

    2015-06-01

    The current progress of materials science regarding multifunctional materials (MFM) has put forward the challenges to understand the microscopic origin of their properties. Most of such MFMs have magneto-elastic correlations. To investigate the underlying mechanism it is therefore essential to investigate the structural properties in the presence of magnetic field. Keeping this in view low temperature and high magnetic field (LTHM) powder x-ray diffraction (XRD), a unique state-of-art facility in the country has been developed at CSR Indore. This setup works on symmetric Bragg Brentano geometry using a parallel incident x-ray beam from a rotating anode source working at 17 kW. Using this one can do structural studies at non-ambient conditions i.e. at low- temperatures (2-300 K) and high magnetic field (+8 to -8 T). The available scattering angle ranges from 5° to 115° 2θ with a resolution better than 0.1°. The proper functioning of the setup has been checked using Si sample. The effect of magnetic field on the structural properties has been demonstrated on Pr0.5Sr0.5MnO3 sample. Clear effect of field induced phase transition has been observed. Moreover, the effect of zero field cooled and field cooled conditions is also observed.

  15. Development of low temperature and high magnetic field X-ray diffraction facility

    SciTech Connect

    Shahee, Aga; Sharma, Shivani; Singh, K.; Lalla, N. P. Chaddah, P.

    2015-06-24

    The current progress of materials science regarding multifunctional materials (MFM) has put forward the challenges to understand the microscopic origin of their properties. Most of such MFMs have magneto-elastic correlations. To investigate the underlying mechanism it is therefore essential to investigate the structural properties in the presence of magnetic field. Keeping this in view low temperature and high magnetic field (LTHM) powder x-ray diffraction (XRD), a unique state-of-art facility in the country has been developed at CSR Indore. This setup works on symmetric Bragg Brentano geometry using a parallel incident x-ray beam from a rotating anode source working at 17 kW. Using this one can do structural studies at non-ambient conditions i.e. at low- temperatures (2-300 K) and high magnetic field (+8 to −8 T). The available scattering angle ranges from 5° to 115° 2θ with a resolution better than 0.1°. The proper functioning of the setup has been checked using Si sample. The effect of magnetic field on the structural properties has been demonstrated on Pr{sub 0.5}Sr{sub 0.5}MnO{sub 3} sample. Clear effect of field induced phase transition has been observed. Moreover, the effect of zero field cooled and field cooled conditions is also observed.

  16. X-ray absorption spectroscopy on magnetic nanoscale systems for modern applications

    NASA Astrophysics Data System (ADS)

    Schmitz-Antoniak, Carolin

    2015-06-01

    X-ray absorption spectroscopy facilitated by state-of-the-art synchrotron radiation technology is presented as a powerful tool to study nanoscale systems, in particular revealing their static element-specific magnetic and electronic properties on a microscopic level. A survey is given on the properties of nanoparticles, nanocomposites and thin films covering a broad range of possible applications. It ranges from the ageing effects of iron oxide nanoparticles in dispersion for biomedical applications to the characterisation on a microscopic level of nanoscale systems for data storage devices. In this respect, new concepts for electrically addressable magnetic data storage devices are highlighted by characterising the coupling in a BaTiO3/CoFe2O4 nanocomposite as prototypical model system. But classical magnetically addressable devices are also discussed on the basis of tailoring the magnetic properties of self-assembled ensembles of FePt nanoparticles for data storage and the high-moment material Fe/Cr/Gd for write heads. For the latter cases, the importance is emphasised of combining experimental approaches in x-ray absorption spectroscopy with density functional theory to gain a more fundamental understanding.

  17. Soft X-ray Spectroscopy of Magnetic Nanostructures: New Phenomena and Applications

    NASA Astrophysics Data System (ADS)

    Arenholz, Elke

    2011-03-01

    The delicate balance between charge, spin, orbital, and lattice degrees of freedom in transition metal oxides leads to unique phenomena such as colossal magnetoresistance, high temperature superconductivity, as well as a remarkable diversity of charge, spin, and orbital ordered phases. The rich phase diagrams are determined by the strong local interaction of electrons in transition metal d orbitals. Subtle changes in d occupancy and overlap---and thereby phase transitions---can be induced by variations in temperature, by external fields, through doping and lattice distortions. In particular, interfaces can hold surprising electronic and magnetic properties that differ remarkably from the adjacent layers. Soft x-ray based techniques are ideal tools to study these systems as they are inherently element-specific, allow characterizing the valence state and the symmetry of lattice sites and provide detailed information about the electronic and magnetic structure with nanometer spatial resolution and on ultrafast time scales. Here we show that the to-date little explored angular dependence of the x-ray magnetic dichroism provides unique insights in the correlation between atomic, magnetic and electronic structure in these systems [1-4]. Taking advantage of this approach will prove invaluable for the engineering of novel nanoarchitectures to be used in low cost and energy efficient devices with improved performance and multiple functionalities. Supported by the U.S. Department of Energy under Contract No. DE-AC02-05CH11231.

  18. X-ray Magnetic circular dichroism study of hexagonal YbFeO3 thin films

    NASA Astrophysics Data System (ADS)

    Wang, Xiao; Sinha, Kishan; Xu, Xiaoshan; Liu, Yaohua; Keavney, David; Cheng, X. M.

    Multiferroic materials exhibit multiple ferroic orders simultaneously and thus have potential applications in information technology, sensing, and actuation. Hexagonal YbFeO3 is a promising candidate for a multiferroic material with room temperature ferromagnetism because of the expected enhanced Fe moment and higher transition temperature due to the exchange interaction between magnetic Yb and Fe ions. Here we report an x-ray magnetic circular dichroism (XMCD) study of (0001) Hexagonal YbFO3 thin films deposited on (111) yttria-stabilized zirconia substrates via pulsed laser deposition. XMCD spectra for the Fe L2,3 edges and Yb M5 edge were measured with the magnetic field applied parallel to the x-ray propagation direction and 20 degree away from the film normal at beamline 4ID-C of the APS at ANL. Field dependence of the XMCD spectra show that Fe and Yb each has a ferromagnetic ordering at around 6.7 K but with opposite orientations in between. The saturation magnetic moment for Fe is determined by the sum rules to be 0.07 μB / Fe cation at around 6.7 K, about 4 times larger than that in Hexagonal LuFeO3.

  19. Photospheric Fluorescence and Resonance Scattering: Non Classical Diagnostics and the Future of X-ray Stellar Spectroscopy

    NASA Technical Reports Server (NTRS)

    Drake, Jeremy

    1998-01-01

    High resolution AXAF and XMM observations of stellar coronae will yield a wealth of X-ray plasma line diagnostics that will provide a giant leap forward in our understanding of coronal densities, abundance anomalies and emission measure distributions. Unfortunately, there is one very basic unanswered question in the physics of active stellar coronae that the usual plasma diagnostics cannot address directly: What are the spatial characteristics of stellar coronae-the scale height and filling factor? What do other stellar coronae actually look like? I will discuss two novel diagnostics of coronal geometry and their application to future X-ray spectra: photospheric fluorescence and resonance line optical depths.

  20. A setup for resonant inelastic soft x-ray scattering on liquids at free electron laser light sources

    SciTech Connect

    Kunnus, Kristjan; Schreck, Simon; Foehlisch, Alexander; Eckert, Sebastian; Beye, Martin; Suljoti, Edlira; Weniger, Christian; Wernet, Philippe; Kalus, Christian; Nordlund, Dennis; Zhang, Wenkai; Hartsock, Robert W.; Gaffney, Kelly J.; Schlotter, William F.; Turner, Joshua J.; Kennedy, Brian; and others

    2012-12-15

    We present a flexible and compact experimental setup that combines an in vacuum liquid jet with an x-ray emission spectrometer to enable static and femtosecond time-resolved resonant inelastic soft x-ray scattering (RIXS) measurements from liquids at free electron laser (FEL) light sources. We demonstrate the feasibility of this type of experiments with the measurements performed at the Linac Coherent Light Source FEL facility. At the FEL we observed changes in the RIXS spectra at high peak fluences which currently sets a limit to maximum attainable count rate at FELs. The setup presented here opens up new possibilities to study the structure and dynamics in liquids.

  1. Observation of thermomagnetically recorded domains with high-resolution magnetic soft x-ray microscopy

    NASA Astrophysics Data System (ADS)

    Tsunashima, S.; Takagi, Nayuki; Yamaguchi, Atushi; Kume, Minoru; Fischer, P.; Kumazawa, M.

    2003-04-01

    Magnetic domains were thermomagnetically recorded on TbFeCo films using laser pulsed magnetic field modulation (LP-MFM) and light intensity modulation (LIM). The domains were observed with high resolution magnetic transmission X-ray microscopy (M-TXM) before and after the heat treatment in order to clarify the recording characteristics and the thermal stability of recorded domains. From the results of M-TXM images, it was found that isolated single marks whose lengths are much smaller than 100 nm can be recorded by LP-MFM but their mark lengths become often longer than designed. It was further confirmed that the heat treatment at 120 degree C for 50 hours does not influence significantly the crescent-shaped magnetic domains of 100 nm in width recorded using LP-MFM method and circular domains of 150 nm in diameter recorded using LIM method.

  2. Quantitative X-Ray Magnetic Microscopy: from parallel stripe domains to buried topological defects

    NASA Astrophysics Data System (ADS)

    Velez, Maria; Blanco-Roldan, C.; Quiros, C.; Valdes-Bango, F.; Alvarez-Prado, L. M.; Martin, J. I.; Alameda, J. M.; Hierro-Rodriguez, A.; Duch, M.; Torras, N.; Esteve, J.; Sorrentino, A.; Valcarcel, R.; Pereiro, E.; Ferrer, S.

    Magnetic transmission X-ray microscopy (TXM) is a powerful imaging technique that can produce element specific images of magnetic domains with nanometric lateral resolution. Here we present a novel imaging method in which the angular dependence of the magnetic contrast in a series of high resolution TXM images is used to obtain quantitative descriptions of the magnetization (canting angles and sense). This has been applied first to analyze parallel stripe domains in weak perpendicular anisotropy ferromagnetic NdCo5 layers of different thickness, and in NdCo5/Permalloy bilayers. Then, our method has been used to identify complex topological defects (merons or 1/2 skyrmions) in a NdCo5 film that are only partially replicated by the Permalloy overlayer. Meron propagation in trilayers (across the thickness) and in hexagonal networks (across bifurcations) will be discussed in terms of their topological characteristics (chirality and polarity). Work supported by Spanish Grant FIS2013-45469.

  3. Prospects of high-resolution resonant X-ray inelastic scattering studies on solid materials, liquids and gases at diffraction-limited storage rings

    PubMed Central

    Schmitt, Thorsten; de Groot, Frank M. F.; Rubensson, Jan-Erik

    2014-01-01

    The spectroscopic technique of resonant inelastic X-ray scattering (RIXS) will particularly profit from immensely improved brilliance of diffraction-limited storage rings (DLSRs). In RIXS one measures the intensities of excitations as a function of energy and momentum transfer. DLSRs will allow for pushing the achievable energy resolution, signal intensity and the sampled spot size to new limits. With RIXS one nowadays probes a broad range of electronic systems reaching from simple molecules to complex materials displaying phenomena like peculiar magnetism, two-dimensional electron gases, superconductivity, photovoltaic energy conversion and heterogeneous catalysis. In this article the types of improved RIXS studies that will become possible with X-ray beams from DLSRs are envisioned. PMID:25177995

  4. Observation of x-ray resonant Raman scattering: The early days

    SciTech Connect

    Sparks, C.J.

    1995-12-31

    My early observation of Raman scattering came as a serendipitous by-product of our efforts to achieve the best possible signal for x-ray fluorescent analysis. We were also investigating the x-ray spectrum produced by a monochromatic x-ray beam striking metal targets which might contribute to the inelastic background. This background could contaminate the very weak diffusively distributed elastically scattered radiation associated with defects in the perfect periodicity of crystals. Energy analysis of the x-ray spectra created by monochromatic Cu K{sub {alpha}} and Mo K{sub {alpha}} radiation impinging on highly pure metal targets showed an inelastically scattered intensity related to the energy difference between the exciting radiation and the nearest bound state. Confirmation of these observations and availability of synchrotron radiation has led to wide application of this new x-ray spectroscopy in atomic physics including its use as a probe of the unoccupied density of states.

  5. Coronal X rays from single, magnetic white dwarfs - A search and probable detection

    NASA Technical Reports Server (NTRS)

    Arnaud, Keith A.; Zhelezniakov, Vladimir V.; Trimble, Virginia

    1992-01-01

    X-ray emission from a sample of five nearby (6-20 pc), strongly magnetic (10-200 MG), relatively cool (6000-14,000 K), single white dwarfs, two of which may possess coronae was explored. One star (GR 290) at better than 99-percent confidence is detected and upper limits from Einstein Observatory IPC data for four others are given. The detected luminosities and limits are in the range 1.4-12.5 x 10 exp 27 ergs/s.

  6. Time-resolved one-dimensional detection of x-ray scattering in pulsed magnetic fields

    NASA Astrophysics Data System (ADS)

    Islam, Zahirul; Ruff, Jacob P. C.; Ross, Kate A.; Nojiri, Hiroyuki; Gaulin, Bruce D.

    2012-01-01

    We have developed an application of a one-dimensional micro-strip detector for capturing x-ray diffraction data in pulsed magnetic fields. This detector consists of a large array of 50 μm-wide Si strips with a full-frame read out at 20 kHz. Its use substantially improves data-collection efficiency and quality as compared to point detectors, because diffraction signals are recorded along an arc in reciprocal space in a time-resolved manner. By synchronizing with pulsed fields, the entire field dependence of a two-dimensional swath of reciprocal space may be determined using a small number of field pulses.

  7. Development of Si-APD Timing Detectors for Nuclear Resonant Scattering using High-energy Synchrotron X-rays

    SciTech Connect

    Kishimoto, Shunji; Zhang Xiaowei

    2007-01-19

    A timing detector with silicon avalanche photodiodes (Si-APDs) has been developed for nuclear resonant scattering using synchrotron x-rays. The detector had four pairs of a germanium plate 0.1mm thick and a Si-APD (3 mm in dia., a depletion layer of 30-{mu}m thickness). Using synchrotron x-rays of 67.4 keV, the efficiency increased to 1.5% for the incident beam, while the efficiency was 0.76 % without the germanium converters. A measurement of SR-PAC on Ni-61 was executed by using the detector. Some other types of timing detectors are planned for x-rays of E>20 keV.

  8. Development of Position-Sensitive Magnetic Calorimeter X-ray Detectors

    NASA Astrophysics Data System (ADS)

    Porst, Jan-Patrick; Bandler, Simon R.; Adams, Joseph S.; Hsieh, Wen-Ting; Rotzinger, Hannes; Seidel, George M.; Smith, Stephen J.; Stevenson, Thomas R.

    2009-12-01

    We are developing arrays of position-sensitive magnetic calorimeter (PoSM) X-ray detectors for future astronomy missions. The PoSM consists of multiple absorbers thermally coupled to one magnetic sensor. Each absorber element has a different thermal coupling to the sensor. This results in a distribution of different pulse shapes and enables position discrimination between the absorber elements. PoSMs are motivated by the desire to achieve the largest possible focal plane area with the fewest number of readout channels without compromising on spatial sampling. Optimizing the performance of PoSMs requires careful design of key parameters such as the thermal conductances between the absorbers, magnetic sensor and the heat sink, as well as the absorber heat capacities. We report on the first experimental results from four-absorber PoSMs, each absorber consisting of a two layer composite of bismuth and gold. The measured energy resolution (FWHM) was less than 5 eV for 6 keV X-rays into all four absorbers. Straightforward position discrimination by means of rise-time is also demonstrated.

  9. X-ray magnetic circular dichroism of Pseudomonas aeruginosa nickel(II) azurin.

    PubMed

    Funk, Tobias; Kennepohl, Pierre; Di Bilio, Angel J; Wehbi, William A; Young, Anthony T; Friedrich, Stephan; Arenholz, Elke; Gray, Harry B; Cramer, Stephen P

    2004-05-12

    We show that X-ray magnetic circular dichroism (XMCD) can be employed to probe the oxidation states and other electronic structural features of nickel active sites in proteins. As a calibration standard, we have measured XMCD and X-ray absorption (XAS) spectra for the nickel(II) derivative of Pseudomonas aeruginosa azurin (NiAz). Our analysis of these spectra confirms that the electronic ground state of NiAz is high-spin (S = 1); we also find that the L(3)-centroid energy is 853.1(1) eV, the branching ratio is 0.722(4), and the magnetic moment is 1.9(4) mu(B). Density functional theory (DFT) calculations on model NiAz structures establish that orbitals 3d(x2-y2) and 3d(z2) are the two valence holes in the high-spin Ni(II) ground state, and in accord with the experimentally determined orbital magnetic moment, the DFT results also demonstrate that both holes are highly delocalized, with 3d(x2-y2) having much greater ligand character. PMID:15125678

  10. Development of Position-Sensitive Magnetic Calorimeter X-ray Detectors

    SciTech Connect

    Porst, Jan-Patrick; Bandler, Simon R.; Adams, Joseph S.; Smith, Stephen J.; Hsieh, W.-T.; Stevenson, Thomas R.; Rotzinger, Hannes; Seidel, George M.

    2009-12-16

    We are developing arrays of position-sensitive magnetic calorimeter (PoSM) X-ray detectors for future astronomy missions. The PoSM consists of multiple absorbers thermally coupled to one magnetic sensor. Each absorber element has a different thermal coupling to the sensor. This results in a distribution of different pulse shapes and enables position discrimination between the absorber elements. PoSMs are motivated by the desire to achieve the largest possible focal plane area with the fewest number of readout channels without compromising on spatial sampling. Optimizing the performance of PoSMs requires careful design of key parameters such as the thermal conductances between the absorbers, magnetic sensor and the heat sink, as well as the absorber heat capacities. We report on the first experimental results from four-absorber PoSMs, each absorber consisting of a two layer composite of bismuth and gold. The measured energy resolution (FWHM) was less than 5 eV for 6 keV X-rays into all four absorbers. Straightforward position discrimination by means of rise-time is also demonstrated.

  11. X-ray magnetic-circular-dichroism study of Ni/Fe (001) multilayers

    SciTech Connect

    Lin, T.; Schwickert, M.M.; Tomaz, M.A.; Chen, H.; Harp, G.R.

    1999-06-01

    The structure and magnetic properties of Fe/Ni(001) multilayers are studied using x-ray diffraction, magneto-optical Kerr effect magnetometry, and x-ray magnetic circular dichroism. Multilayers are deposited with constant Fe layers (12 {Angstrom}) and wedged Ni layers (0{endash}30 {Angstrom}), repeated 20 times, to explore the magnetic moment and the structure dependence upon thickness of Ni (t{sub Ni}). Up to t{sub Ni}{approx}16 {Angstrom} (11 ML), both the Fe and the Ni have a bct structure, similar to the bulk structure of bcc Fe. The magnetic moments of Ni in the bct region are nearly constant at 0.85{mu}{sub B} for a Ni thickness t{sub Ni} in the range 3 {Angstrom}{lt}t{sub Ni}{lt}16 {Angstrom}. This represents a significant enhancement over the moment in bulk fcc Ni (0.59{mu}B). The Fe/Ni multilayer undergoes a crystalline phase transition between 16 {Angstrom}{lt}t{sub Ni}{lt}23 {Angstrom}, beyond which both the Fe and Ni have an fct structure. In the fct region, the Ni magnetic moment is close to its bulk value and the Fe magnetic moment drops to 1.5{mu}{sub B}, which is {approximately}70{percent} of its bulk value. The crystalline phase transition is also accompanied by a rotation of the magnetic easy axis by 45{degree} in the plane of the film. {copyright} {ital 1999} {ital The American Physical Society}

  12. Machine learning from hard x-ray surveys: applications to magnetic cataclysmic variable studies

    NASA Astrophysics Data System (ADS)

    Scaringi, Simone

    2009-11-01

    Within this thesis are discussed two main topics of contemporary astrophysics. The first is that of machine learning algorithms for astronomy whilst the second is that of magnetic cataclysmic variables (mCVs). To begin, an overview is given of ISINA: INTEGRAL Scouce Identifiction Network Algorithm. This machine learning algorithm, using random forests, is applied to the IBIS/ISGRI data set in order to ease the production of unbiased future soft gamma-ray source catalogues. The feature extraction process on an initial candidate list is described together with feature merging. Three trainng and testing sets are created in order to deal with the diverse time-scales encountered when dealing with the gamma-ray sky: one dealing with faint persistent source recognition, one dealing with strong persistent sources and a final one dealing with transients. For the latter, a new transient detection technique is introduced and described: the transient matrix. Finally the performance of the network is assessed and discussed using the testing set and some illustrative source examples. ISINA is also compared to the more conventional approach of visual inspection. Next mCVs are discussed, and in particular the properties arising from a hard X-ray selected sample which has proven remarkably efficient in detecting intermediate polars and asynchronous polars, two of the rarest type of cataclysmic variables (CVs). This thesis focuses particularly on the link between hard X-ray properties and spin/orbital periods. To this end, a new sample of these objects is constructed by cross-corelating candidate sources detected in INTEGRAL/IBIS observations against catalogues of known CVs. Also included in the analysis are hard X-ray Observations from Swift/BAT and SUZAKU/HXD in order to make the study more complete. It is found that most hard X-ray detected mCVs have Pspin/Porb<0.1 above the period gap. In this respect, attention is given to the very low number of detected systems in any ban

  13. Raman and fluorescence characteristics of resonant inelastic X-ray scattering from doped superconducting cuprates

    DOE PAGESBeta

    Huang, H. Y.; Jia, C. J.; Chen, Z. Y.; Wohlfeld, K.; Moritz, B.; Devereaux, T. P.; Wu, W. B.; Okamoto, J.; Lee, W. S.; Hashimoto, M.; et al

    2016-01-22

    Measurements of spin excitations are essential for an understanding of spin-mediated pairing for superconductivity; and resonant inelastic X-ray scattering (RIXS) provides a considerable opportunity to probe high-energy spin excitations. However, whether RIXS correctly measures the collective spin excitations of doped superconducting cuprates remains under debate. Here we demonstrate distinct Raman- and fluorescence-like RIXS excitations of Bi1.5Pb0.6Sr1.54CaCu2O8+δ. Combining photon-energy and momentum dependent RIXS measurements with theoretical calculations using exact diagonalization provides conclusive evidence that the Raman-like RIXS excitations correspond to collective spin excitations, which are magnons in the undoped Mott insulators and evolve into paramagnons in doped superconducting compounds. In contrast,more » the fluorescence-like shifts are due primarily to the continuum of particle-hole excitations in the charge channel. Our results show that under the proper experimental conditions RIXS indeed can be used to probe paramagnons in doped high-Tc cuprate superconductors.« less

  14. A new method to derive electronegativity from resonant inelastic x-ray scattering

    SciTech Connect

    Carniato, S.; Journel, L.; Guillemin, R.; Piancastelli, M. N.; Simon, M.; Stolte, W. C.; Lindle, D. W.

    2012-10-14

    Electronegativity is a well-known property of atoms and substituent groups. Because there is no direct way to measure it, establishing a useful scale for electronegativity often entails correlating it to another chemical parameter; a wide variety of methods have been proposed over the past 80 years to do just that. This work reports a new approach that connects electronegativity to a spectroscopic parameter derived from resonant inelastic x-ray scattering. The new method is demonstrated using a series of chlorine-containing compounds, focusing on the Cl 2p{sup -1}LUMO{sup 1} electronic states reached after Cl 1s{yields} LUMO core excitation and subsequent KL radiative decay. Based on an electron-density analysis of the LUMOs, the relative weights of the Cl 2p{sub z} atomic orbital contributing to the Cl 2p{sub 3/2} molecular spin-orbit components are shown to yield a linear electronegativity scale consistent with previous approaches.

  15. Raman and fluorescence characteristics of resonant inelastic X-ray scattering from doped superconducting cuprates

    PubMed Central

    Huang, H. Y.; Jia, C. J.; Chen, Z. Y.; Wohlfeld, K.; Moritz, B.; Devereaux, T. P.; Wu, W. B.; Okamoto, J.; Lee, W. S.; Hashimoto, M.; He, Y.; Shen, Z. X.; Yoshida, Y.; Eisaki, H.; Mou, C. Y.; Chen, C. T.; Huang, D. J.

    2016-01-01

    Measurements of spin excitations are essential for an understanding of spin-mediated pairing for superconductivity; and resonant inelastic X-ray scattering (RIXS) provides a considerable opportunity to probe high-energy spin excitations. However, whether RIXS correctly measures the collective spin excitations of doped superconducting cuprates remains under debate. Here we demonstrate distinct Raman- and fluorescence-like RIXS excitations of Bi1.5Pb0.6Sr1.54CaCu2O8+δ. Combining photon-energy and momentum dependent RIXS measurements with theoretical calculations using exact diagonalization provides conclusive evidence that the Raman-like RIXS excitations correspond to collective spin excitations, which are magnons in the undoped Mott insulators and evolve into paramagnons in doped superconducting compounds. In contrast, the fluorescence-like shifts are due primarily to the continuum of particle-hole excitations in the charge channel. Our results show that under the proper experimental conditions RIXS indeed can be used to probe paramagnons in doped high-Tc cuprate superconductors. PMID:26794437

  16. Simultaneous resonant x-ray diffraction measurement of polarization inversion and lattice strain in polycrystalline ferroelectrics.

    PubMed

    Gorfman, S; Simons, H; Iamsasri, T; Prasertpalichat, S; Cann, D P; Choe, H; Pietsch, U; Watier, Y; Jones, J L

    2016-01-01

    Structure-property relationships in ferroelectrics extend over several length scales from the individual unit cell to the macroscopic device, and with dynamics spanning a broad temporal domain. Characterizing the multi-scale structural origin of electric field-induced polarization reversal and strain in ferroelectrics is an ongoing challenge that so far has obscured its fundamental behaviour. By utilizing small intensity differences between Friedel pairs due to resonant scattering, we demonstrate a time-resolved X-ray diffraction technique for directly and simultaneously measuring both lattice strain and, for the first time, polarization reversal during in-situ electrical perturbation. This technique is demonstrated for BaTiO3-BiZn0.5Ti0.5O3 (BT-BZT) polycrystalline ferroelectrics, a prototypical lead-free piezoelectric with an ambiguous switching mechanism. This combines the benefits of spectroscopic and diffraction-based measurements into a single and robust technique with time resolution down to the ns scale, opening a new door to in-situ structure-property characterization that probes the full extent of the ferroelectric behaviour. PMID:26864859

  17. Chemical reduction of actinides probed by resonant inelastic X-ray scattering.

    PubMed

    Butorin, Sergei M; Shuh, David K; Kvashnina, Kristina O; Guo, Jinghua; Werme, Lars; Nordgren, Joseph

    2013-12-01

    The study addresses the possibilities of immobilizing the mobile species of actinides in the geosphere using metallic iron. Sorption on corroding iron is well-known, but there have been uncertainties with regard to the possibilities of reducing the actinyl species to sparingly soluble oxides and, thereby, permanently immobilizing them. Resonant inelastic X-ray scattering (RIXS) measurements at the actinide 5d edges on Fe foils exposed to uranium(VI) and neptunium(V) solutions in groundwater unambigiously indicate reduction of actinides to, respectively, uranium(IV) and neptunium(IV) on iron surfaces. The reduction manifests itself in an appearance of distinct specific signatures of uranium(IV) and neptunium(IV) in the RIXS profile of 5f-5f excitations. Such signatures and RIXS intensity/cross-section behavior with varying energy of incident photons can be reproduced by model atomic-multiplet calculations of the RIXS spectra. By normalizing the RIXS signal of corresponding 5f-5f excitations to core-to-core 6p-to-5d characteristic fluorescence transitions of actinides, their reduction rates on Fe samples with different exposure to actinide solutions can be estimated. Observed reduction implies similar processes in the nuclear waste canister thus suggesting reduced probability of nuclear waste release with ground waters from the canister. PMID:24187957

  18. Simultaneous resonant x-ray diffraction measurement of polarization inversion and lattice strain in polycrystalline ferroelectrics

    PubMed Central

    Gorfman, S.; Simons, H.; Iamsasri, T.; Prasertpalichat, S.; Cann, D. P.; Choe, H.; Pietsch, U.; Watier, Y.; Jones, J. L.

    2016-01-01

    Structure-property relationships in ferroelectrics extend over several length scales from the individual unit cell to the macroscopic device, and with dynamics spanning a broad temporal domain. Characterizing the multi-scale structural origin of electric field-induced polarization reversal and strain in ferroelectrics is an ongoing challenge that so far has obscured its fundamental behaviour. By utilizing small intensity differences between Friedel pairs due to resonant scattering, we demonstrate a time-resolved X-ray diffraction technique for directly and simultaneously measuring both lattice strain and, for the first time, polarization reversal during in-situ electrical perturbation. This technique is demonstrated for BaTiO3-BiZn0.5Ti0.5O3 (BT-BZT) polycrystalline ferroelectrics, a prototypical lead-free piezoelectric with an ambiguous switching mechanism. This combines the benefits of spectroscopic and diffraction-based measurements into a single and robust technique with time resolution down to the ns scale, opening a new door to in-situ structure-property characterization that probes the full extent of the ferroelectric behaviour. PMID:26864859

  19. Nuclear resonant inelastic x-ray scattering: Methodology and extraction of vibrational properties of minerals

    NASA Astrophysics Data System (ADS)

    Hu, M. Y.; Alp, E. E.; Bi, W.; Sturhahn, W.; Toellner, T. S.; Zhao, J.

    2013-12-01

    Nuclear resonant inelastic x-ray scattering (NRIXS) is a synchrotron radiation based experimental method [1]. Since its introduction almost 20 years ago [2], NRIXS has found an expanding range of applications of studying lattice dynamics in condensed matter physics, materials science, high-pressure research, geosciences, and biophysics. After the first high pressure application in geophysics of measuring sound velocity of iron up to 153 GPa [3], it has become a widely used method to investigate deep earth compositions through sound velocity measurements [4,5]. Thermodynamic properties are also explored, in particular Grueneisen parameters [6]. Later, it was realized that isotope fractionaton factors can be derived from NRIXS measurements [7,8]. Sum rules and moments of NRIXS is a critical part of this methodology [9,10]. We will discuss this and in general the data analysis of NRIXS which enables the above mentioned applications. [1] Alp et al. Hyperfine Interactions 144/145, 3 (2002) [2] Sturhahn et al., PRL 74, 3832 (1995) [3] Mao et al., Science 292, 914 (2001) [4] Hu et al., PRB 67, 094304 (2003) [5] Sturhahn & Jackson, GSA special paper 421 (2007) [6] Murphy et al., Geophys. Res. Lett. 38, L24306 (2011) [7] Polyakov, Science 323, 912 (2009) [8] Dauphas et al., Geochimica et Cosmochimica Acta 94, 254 (2012) [9] Lipkin, PRB 52, 10073 (1995) [10] Hu et al., PRB 87, 064301 (2013)

  20. Raman and fluorescence characteristics of resonant inelastic X-ray scattering from doped superconducting cuprates

    NASA Astrophysics Data System (ADS)

    Huang, H. Y.; Jia, C. J.; Chen, Z. Y.; Wohlfeld, K.; Moritz, B.; Devereaux, T. P.; Wu, W. B.; Okamoto, J.; Lee, W. S.; Hashimoto, M.; He, Y.; Shen, Z. X.; Yoshida, Y.; Eisaki, H.; Mou, C. Y.; Chen, C. T.; Huang, D. J.

    2016-01-01

    Measurements of spin excitations are essential for an understanding of spin-mediated pairing for superconductivity; and resonant inelastic X-ray scattering (RIXS) provides a considerable opportunity to probe high-energy spin excitations. However, whether RIXS correctly measures the collective spin excitations of doped superconducting cuprates remains under debate. Here we demonstrate distinct Raman- and fluorescence-like RIXS excitations of Bi1.5Pb0.6Sr1.54CaCu2O8+δ. Combining photon-energy and momentum dependent RIXS measurements with theoretical calculations using exact diagonalization provides conclusive evidence that the Raman-like RIXS excitations correspond to collective spin excitations, which are magnons in the undoped Mott insulators and evolve into paramagnons in doped superconducting compounds. In contrast, the fluorescence-like shifts are due primarily to the continuum of particle-hole excitations in the charge channel. Our results show that under the proper experimental conditions RIXS indeed can be used to probe paramagnons in doped high-Tc cuprate superconductors.

  1. Signatures of strong correlation effects in resonant inelastic x-ray scattering studies on cuprates

    NASA Astrophysics Data System (ADS)

    Li, Wan-Ju; Lin, Cheng-Ju; Lee, Ting-Kuo

    2016-08-01

    Recently, spin excitations in doped cuprates have been measured using resonant inelastic x-ray scattering. The paramagnon dispersions show the large hardening effect in the electron-doped systems and seemingly doping independence in the hole-doped systems, with the energy scales comparable to that of the antiferromagnetic (AFM) magnons. This anomalous hardening effect and the lack of softening were partially explained by using the strong-coupling t -J model but with a three-site term [Nat. Commun. 5, 3314 (2014), 10.1038/ncomms4314], although the hardening effect is already present even without the latter. By considering the t -t'-t''-J model and using the slave-boson mean-field theory, we obtain, via the spin-spin susceptibility, the spin excitations in qualitative agreement with the experiments. The doping-dependent bandwidth due to the strong correlation physics is the origin of the hardening effect. We also show that dispersions in the AFM regime, different from those in the paramagnetic (PM) regime, hardly vary with dopant density. These excitations are mainly collective in nature instead of particle-hole-like. We further discuss the interplay and different contributions of these two kinds of excitations in the PM phase and show that the dominance of the collective excitation increases with decreasing dopant concentrations.

  2. Raman and fluorescence characteristics of resonant inelastic X-ray scattering from doped superconducting cuprates.

    PubMed

    Huang, H Y; Jia, C J; Chen, Z Y; Wohlfeld, K; Moritz, B; Devereaux, T P; Wu, W B; Okamoto, J; Lee, W S; Hashimoto, M; He, Y; Shen, Z X; Yoshida, Y; Eisaki, H; Mou, C Y; Chen, C T; Huang, D J

    2016-01-01

    Measurements of spin excitations are essential for an understanding of spin-mediated pairing for superconductivity; and resonant inelastic X-ray scattering (RIXS) provides a considerable opportunity to probe high-energy spin excitations. However, whether RIXS correctly measures the collective spin excitations of doped superconducting cuprates remains under debate. Here we demonstrate distinct Raman- and fluorescence-like RIXS excitations of Bi1.5Pb0.6Sr1.54CaCu2O(8+δ). Combining photon-energy and momentum dependent RIXS measurements with theoretical calculations using exact diagonalization provides conclusive evidence that the Raman-like RIXS excitations correspond to collective spin excitations, which are magnons in the undoped Mott insulators and evolve into paramagnons in doped superconducting compounds. In contrast, the fluorescence-like shifts are due primarily to the continuum of particle-hole excitations in the charge channel. Our results show that under the proper experimental conditions RIXS indeed can be used to probe paramagnons in doped high-Tc cuprate superconductors. PMID:26794437

  3. Magnetic studies of magnetotactic bacteria by soft x-ray STXM and ptychography

    NASA Astrophysics Data System (ADS)

    Zhu, X. H.; Tyliszczak, T.; Shiu, H.-W.; Shapiro, D.; Bazylinski, D. A.; Lins, U.; Hitchcock, A. P.

    2016-01-01

    Magnetotactic bacteria (MTB) biomineralize chains of nanoscale magnetite single crystals which align the cell with the earth's magnetic field and assist the cell to migrate to, and maintain its position at, the oxic-anoxic transition zone, their preferred habitat. Here we describe use of multi-edge scanning transmission X-ray microscopy (STXM) to investigate the chemistry and magnetism of MTB on an individual cell basis. We report measurements of the orientation of the magnetic vector of magnetosome chains relative to the location of the single flagellum in marine vibrio, Magnetovibrio blakemorei strain MV-1 cells from both the southern and northern hemisphere. We also report a major improvement in both spatial resolution and spectral quality through the use of spectro-ptychography at the Fe L3 edge.

  4. Origin of the resonant x-ray scattering in LaMnO3

    NASA Astrophysics Data System (ADS)

    Subías, G.; Herrero-Martín, J.; García, J.; Blasco, J.; Mazzoli, C.; Hatada, K.; di Matteo, S.; Natoli, C. R.

    2007-06-01

    We have performed a detailed resonant x-ray scattering (RXS) study at the MnK edge of LaMnO3 by measuring the (h,0,0) , (0,k,0) and (0,0,l) forbidden reflections (h,k,l=3,5) between 10 and 300K in the σ-π channel. For all three types of reflections we observed strong resonant peaks presenting the sin2ϕ intensity modulation as a function of the azimuth scanning angle ϕ , characteristic of dipolar transitions. Their origin was ascribed to anisotropic tensor scattering, since no change either in energy line shape or in intensity was observed when crossing the Néel temperature at ˜140K . Integrated intensities were roughly constant up to 300K , contrary to previous reports found in the literature. The energy dependence of the scattered intensity for the (h,0,0) and (0,k,0) reflections was identical but different from the (0,0,l) reflection. All reflections have been explained within multiple scattering theory in terms of long-range structural distortions around Mn atoms, without invoking any kind of 3d orbital ordering. We also studied the energy dependence of the principal axes of the anomalous-scattering tensor in a case, like the present one, where the scattering atoms do not possess any point-symmetry axes. We found that they are not constant with the photon energy, implying the absence of a direct correlation between RXS and quadrupolar charge distribution in the ground state.

  5. Probing the graphite band structure with resonant soft-x-ray fluorescence

    SciTech Connect

    Carlisle, J.A.; Shirley, E.L.; Hudson, E.A.

    1997-04-01

    Soft x-ray fluorescence (SXF) spectroscopy using synchrotron radiation offers several advantages over surface sensitive spectroscopies for probing the electronic structure of complex multi-elemental materials. Due to the long mean free path of photons in solids ({approximately}1000 {angstrom}), SXF is a bulk-sensitive probe. Also, since core levels are involved in absorption and emission, SXF is both element- and angular-momentum-selective. SXF measures the local partial density of states (DOS) projected onto each constituent element of the material. The chief limitation of SXF has been the low fluorescence yield for photon emission, particularly for light elements. However, third generation light sources, such as the Advanced Light Source (ALS), offer the high brightness that makes high-resolution SXF experiments practical. In the following the authors utilize this high brightness to demonstrate the capability of SXF to probe the band structure of a polycrystalline sample. In SXF, a valence emission spectrum results from transitions from valence band states to the core hole produced by the incident photons. In the non-resonant energy regime, the excitation energy is far above the core binding energy, and the absorption and emission events are uncoupled. The fluorescence spectrum resembles emission spectra acquired using energetic electrons, and is insensitive to the incident photon`s energy. In the resonant excitation energy regime, core electrons are excited by photons to unoccupied states just above the Fermi level (EF). The absorption and emission events are coupled, and this coupling manifests itself in several ways, depending in part on the localization of the empty electronic states in the material. Here the authors report spectral measurements from highly oriented pyrolytic graphite.

  6. Evidence for the Importance of Resonance Scattering in X-Ray Emission Line Profiles of the O Star Zeta Puppis

    SciTech Connect

    Leutenegger, M.A.; Owocki, S.P.; Kahn, S.M.; Paerels, F.B.S.; /Columbia U.

    2006-10-10

    We fit the Doppler profiles of the He-like triplet complexes of O VII and N VI in the X-ray spectrum of the O star {zeta} Pup, using XMM-Newton RGS data collected over {approx} 400 ks of exposure. We find that they cannot be well fit if the resonance and intercombination lines are constrained to have the same profile shape. However, a significantly better fit is achieved with a model incorporating the effects of resonance scattering, which causes the resonance line to become more symmetric than the intercombination line for a given characteristic continuum optical depth {tau}{sub *}. We discuss the plausibility of this hypothesis, as well as its significance for our understanding of Doppler profiles of X-ray emission lines in O stars.

  7. Elimination of X-Ray Diffraction through Stimulated X-Ray Transmission

    NASA Astrophysics Data System (ADS)

    Wu, B.; Wang, T.; Graves, C. E.; Zhu, D.; Schlotter, W. F.; Turner, J. J.; Hellwig, O.; Chen, Z.; Dürr, H. A.; Scherz, A.; Stöhr, J.

    2016-07-01

    X-ray diffractive imaging with laterally coherent x-ray free-electron laser (XFEL) pulses is increasingly utilized to obtain ultrafast snapshots of matter. Here we report the amazing disappearance of single-shot charge and magnetic diffraction patterns recorded with resonantly tuned, narrow bandwidth XFEL pulses. Our experimental results reveal the exquisite sensitivity of single-shot charge and magnetic diffraction patterns of a magnetic film to the onset of field-induced stimulated elastic x-ray forward scattering. The loss in diffraction contrast, measured over 3 orders of magnitude in intensity, is in remarkable quantitative agreement with a recent theory that is extended to include diffraction.

  8. X-ray resonant photoexcitation: linewidths and energies of Kα transitions in highly charged Fe ions.

    PubMed

    Rudolph, J K; Bernitt, S; Epp, S W; Steinbrügge, R; Beilmann, C; Brown, G V; Eberle, S; Graf, A; Harman, Z; Hell, N; Leutenegger, M; Müller, A; Schlage, K; Wille, H-C; Yavaş, H; Ullrich, J; Crespo López-Urrutia, J R

    2013-09-01

    Photoabsorption by and fluorescence of the Kα transitions in highly charged iron ions are essential mechanisms for x-ray radiation transfer in astrophysical environments. We study photoabsorption due to the main Kα transitions in highly charged iron ions from heliumlike to fluorinelike (Fe24+ to Fe17+) using monochromatic x rays around 6.6 keV at the PETRA III synchrotron photon source. Natural linewidths were determined with hitherto unattained accuracy. The observed transitions are of particular interest for the understanding of photoexcited plasmas found in x-ray binary stars and active galactic nuclei. PMID:25166661

  9. Observation of Laser Induced Magnetization Dynamics in Co/Pd Multilayers with Coherent X-ray Scattering

    SciTech Connect

    Wu, Benny

    2012-04-05

    We report on time-resolved coherent x-ray scattering experiments of laser induced magnetization dynamics in Co/Pd multilayers with a high repetition rate optical pump x-ray probe setup. Starting from a multi-domain ground state, the magnetization is uniformly reduced after excitation by an intense 50 fs laser pulse. Using the normalized time correlation, we study the magnetization recovery on a picosecond timescale. The dynamic scattering intensity is separated into an elastic portion at length scales above 65 nm which retains memory of the initial domain magnetization, and a fluctuating portion at smaller length scales corresponding to domain boundary motion during recovery.

  10. Observations of laser induced magnetization dynamics in Co/Pd multilayers with coherent x-ray scattering

    NASA Astrophysics Data System (ADS)

    Wu, B.; Zhu, D.; Acremann, Y.; Miller, T. A.; Lindenberg, A. M.; Hellwig, O.; Stöhr, J.; Scherz, A.

    2011-12-01

    We report on time-resolved coherent x-ray scattering experiments of laser induced magnetization dynamics in Co/Pd multilayers with a high repetition rate optical pump x-ray probe setup. Starting from a multi-domain ground state, the magnetization is uniformly reduced after excitation by an intense 50 fs laser pulse. Using the normalized time correlation, we study the magnetization recovery on a picosecond timescale. The dynamic scattering intensity is separated into an elastic portion at length scales above 65 nm, which retains memory of the initial domain magnetization, and a fluctuating portion at smaller length scales corresponding to domain boundary motion during recovery.

  11. X-ray emission from the giant magnetosphere of the magnetic O-type star NGC 1624-2

    NASA Astrophysics Data System (ADS)

    Petit, V.; Cohen, D. H.; Wade, G. A.; Nazé, Y.; Owocki, S. P.; Sundqvist, J. O.; ud-Doula, A.; Fullerton, A.; Leutenegger, M.; Gagné, M.

    2015-11-01

    We observed NGC 1624-2, the O-type star with the largest known magnetic field (Bp ˜ 20 kG), in X-rays with the Advanced CCD Imaging Spectrometer (ACIS-S) camera on-board the Chandra X-ray Observatory. Our two observations were obtained at the minimum and maximum of the periodic Hα emission cycle, corresponding to the rotational phases where the magnetic field is the closest to equator-on and pole-on, respectively. With these observations, we aim to characterize the star's magnetosphere via the X-ray emission produced by magnetically confined wind shocks. Our main findings are as follows. (i) The observed spectrum of NGC 1624-2 is hard, similar to the magnetic O-type star θ1 Ori C, with only a few photons detected below 0.8 keV. The emergent X-ray flux is 30 per cent lower at the Hα minimum phase. (ii) Our modelling indicated that this seemingly hard spectrum is in fact a consequence of relatively soft intrinsic emission, similar to other magnetic Of?p stars, combined with a large amount of local absorption (˜1-3× 1022 cm-2). This combination is necessary to reproduce both the prominent Mg and Si spectral features, and the lack of flux at low energies. NGC 1624-2 is intrinsically luminous in X-rays (log L^{em}_X˜ 33.4) but 70-95 per cent of the X-ray emission produced by magnetically confined wind shocks is absorbed before it escapes the magnetosphere (log L^{ISMcor}_X˜ 32.5). (iii) The high X-ray luminosity, its variation with stellar rotation, and its large attenuation are all consistent with a large dynamical magnetosphere with magnetically confined wind shocks.

  12. De-excitation X rays from Resonant Coherently Excited 390-MeV/u Hydrogen-like Ar Ions

    SciTech Connect

    Datz, S.

    1999-08-01

    Resonant coherent excitation (RCE) of 390 MeV/u hydrogen-like Ar{sup 17+} ions planar channeled in a Si crystal was investigated through measurements of the de-excitation X-rays as we11 as the charge state distribution of the transmitted ions. We observed enhancements of both the fraction of ionized Ar{sup 18+} ions and the intensity of the de-excitation X-rays under the RCE condition. The n=2 states of Ar{sup 17+} in the crystal are split into four energy levels due to spin-orbit interaction and Stark effect induced by the planar potential of the crystal. The intensities of the X-rays from the lower two levels were found to be smaller compared with those from the higher two levels, which is explained by the dominance of the 2s component not decaying via a single photon emission. The difference between the resonance profiles of the charge state and the X-ray reflects the nature of n=2 states in the crystal field.

  13. Resonant inelastic x-ray scattering study at the oxygen K-edge of corner-shared Sr2CuO3 cuprate

    NASA Astrophysics Data System (ADS)

    Kumar, Umesh; Schlappa, Justine; Zhou, Kejin; Singh, Surjeet; Strocov, Vladimir; Revcolevschi, Alexandre; Rønnow, Henrik; Johnston, Steven; Schmitt, Thorsten

    We present a resonant inelastic x-ray scattering (RIXS) study at the oxygen K-edge of the spin-chain system Sr2CuO3. We investigate this system using small cluster exact diagonalization calculations for a microscopic model that considers all the orbitals of Cu and O in CuO3-unit cell. Using a canonical parameter set, we compute the XAS and RIXS spectra in comparison to the experiment. This allows us to identify the dd- and charge transfer excitations in the observed spectrum. We also infer the presence of several low energy excitations that may be related to phononic and/or magnetic excitations.

  14. Theoretical analysis of the background intensity distribution in X-ray Birefringence Imaging using synchrotron bending-magnet radiation

    NASA Astrophysics Data System (ADS)

    Sutter, John P.; Dolbnya, Igor P.; Collins, Stephen P.; Harris, Kenneth D. M.; Edwards-Gau, Gregory R.; Palmer, Benjamin A.

    2015-04-01

    In the recently developed technique of X-ray Birefringence Imaging, molecular orientational order in anisotropic materials is studied by exploiting the birefringence of linearly polarized X-rays with energy close to an absorption edge of an element in the material. In the experimental setup, a vertically deflecting high-resolution double-crystal monochromator is used upstream from the sample to select the appropriate photon energy, and a horizontally deflecting X-ray polarization analyzer, consisting of a perfect single crystal with a Bragg reflection at Bragg angle of approximately 45°, is placed downstream from the sample to measure the resulting rotation of the X-ray polarization. However, if the experiment is performed on a synchrotron bending-magnet beamline, then the elliptical polarization of the X-rays out of the electron orbit plane affects the shape of the output beam. Also, because the monochromator introduces a correlation between vertical position and photon energy to the X-ray beam, the polarization analyzer does not select the entire beam, but instead selects a diagonal stripe, the slope of which depends on the Bragg angles of the monochromator and the polarization analyzer. In the present work, the final background intensity distribution is calculated analytically because the phase space sampling methods normally used in ray traces are too inefficient for this setup. X-ray Birefringence Imaging data measured at the Diamond Light Source beamline B16 agree well with the theory developed here.

  15. Theoretical analysis of the background intensity distribution in X-ray Birefringence Imaging using synchrotron bending-magnet radiation

    SciTech Connect

    Sutter, John P. Dolbnya, Igor P.; Collins, Stephen P.; Harris, Kenneth D. M.; Edwards-Gau, Gregory R.; Palmer, Benjamin A.

    2015-04-28

    In the recently developed technique of X-ray Birefringence Imaging, molecular orientational order in anisotropic materials is studied by exploiting the birefringence of linearly polarized X-rays with energy close to an absorption edge of an element in the material. In the experimental setup, a vertically deflecting high-resolution double-crystal monochromator is used upstream from the sample to select the appropriate photon energy, and a horizontally deflecting X-ray polarization analyzer, consisting of a perfect single crystal with a Bragg reflection at Bragg angle of approximately 45°, is placed downstream from the sample to measure the resulting rotation of the X-ray polarization. However, if the experiment is performed on a synchrotron bending-magnet beamline, then the elliptical polarization of the X-rays out of the electron orbit plane affects the shape of the output beam. Also, because the monochromator introduces a correlation between vertical position and photon energy to the X-ray beam, the polarization analyzer does not select the entire beam, but instead selects a diagonal stripe, the slope of which depends on the Bragg angles of the monochromator and the polarization analyzer. In the present work, the final background intensity distribution is calculated analytically because the phase space sampling methods normally used in ray traces are too inefficient for this setup. X-ray Birefringence Imaging data measured at the Diamond Light Source beamline B16 agree well with the theory developed here.

  16. Modeling Flare Hard X-ray Emission from Electrons in Contracting Magnetic Islands

    NASA Astrophysics Data System (ADS)

    Guidoni, Silvina E.; Allred, Joel C.; Alaoui, Meriem; Holman, Gordon D.; DeVore, C. Richard; Karpen, Judith T.

    2016-05-01

    The mechanism that accelerates particles to the energies required to produce the observed impulsive hard X-ray emission in solar flares is not well understood. It is generally accepted that this emission is produced by a non-thermal beam of electrons that collides with the ambient ions as the beam propagates from the top of a flare loop to its footpoints. Most current models that investigate this transport assume an injected beam with an initial energy spectrum inferred from observed hard X-ray spectra, usually a power law with a low-energy cutoff. In our previous work (Guidoni et al. 2016), we proposed an analytical method to estimate particle energy gain in contracting, large-scale, 2.5-dimensional magnetic islands, based on a kinetic model by Drake et al. (2010). We applied this method to sunward-moving islands formed high in the corona during fast reconnection in a simulated eruptive flare. The overarching purpose of the present work is to test this proposed acceleration model by estimating the hard X-ray flux resulting from its predicted accelerated-particle distribution functions. To do so, we have coupled our model to a unified computational framework that simulates the propagation of an injected beam as it deposits energy and momentum along its way (Allred et al. 2015). This framework includes the effects of radiative transfer and return currents, necessary to estimate flare emission that can be compared directly to observations. We will present preliminary results of the coupling between these models.

  17. Magnetic dichroism in angle-resolved hard x-ray photoemission from buried layers

    NASA Astrophysics Data System (ADS)

    Kozina, Xeniya; Fecher, Gerhard H.; Stryganyuk, Gregory; Ouardi, Siham; Balke, Benjamin; Felser, Claudia; Schönhense, Gerd; Ikenaga, Eiji; Sugiyama, Takeharu; Kawamura, Naomi; Suzuki, Motohiro; Taira, Tomoyuki; Uemura, Tetsuya; Yamamoto, Masafumi; Sukegawa, Hiroaki; Wang, Wenhong; Inomata, Koichiro; Kobayashi, Keisuke

    2011-08-01

    This work reports the measurement of magnetic dichroism in angular-resolved photoemission from in-plane magnetized buried thin films. The high bulk sensitivity of hard x-ray photoelectron spectroscopy (HAXPES) in combination with circularly polarized radiation enables the investigation of the magnetic properties of buried layers. HAXPES experiments with an excitation energy of 8 keV were performed on exchange-biased magnetic layers covered by thin oxide films. Two types of structures were investigated with the IrMn exchange-biasing layer either above or below the ferromagnetic layer: one with a CoFe layer on top and another with a Co2FeAl layer buried beneath the IrMn layer. A pronounced magnetic dichroism is found in the Co and Fe 2p states of both materials. The localization of the magnetic moments at the Fe site conditioning the peculiar characteristics of the Co2FeAl Heusler compound, predicted to be a half-metallic ferromagnet, is revealed from the magnetic dichroism detected in the Fe 2p states.

  18. Lateral spin transfer torque induced magnetic switching at room temperature demonstrated by x-ray microscopy

    NASA Astrophysics Data System (ADS)

    Buhl, M.; Erbe, A.; Grebing, J.; Wintz, S.; Raabe, J.; Fassbender, J.

    2013-10-01

    Changing and detecting the orientation of nanomagnetic structures, which can be used for durable information storage, needs to be developed towards true nanoscale dimensions for keeping up the miniaturization speed of modern nanoelectronic components. Therefore, new concepts for controlling the state of nanomagnets are currently in the focus of research in the field of nanoelectronics. Here, we demonstrate reproducible switching of a purely metallic nanopillar placed on a lead that conducts a spin-polarized current at room temperature. Spin diffusion across the metal-metal (Cu to CoFe) interface between the pillar and the lead causes spin accumulation in the pillar, which may then be used to set the magnetic orientation of the pillar. In our experiments, the detection of the magnetic state of the nanopillar is performed by direct imaging via scanning transmission x-ray microscopy (STXM).

  19. Soft gamma-ray repeaters and anomalous X-ray pulsars as highly magnetized white dwarfs

    NASA Astrophysics Data System (ADS)

    Mukhopadhyay, Banibrata; Rao, A. R.

    2016-05-01

    We explore the possibility that soft gamma-ray repeaters (SGRs) and anomalous X-ray pulsars (AXPs) are powered by highly magnetized white dwarfs (B-WDs). We take a sample of SGRs and AXPs and provide the possible parameter space in mass, radius, and surface magnetic field based on their observed properties (period and its derivative) and the assumption that these sources obey the mass-radius relation derived for the B-WDs. The radius and magnetic field of B-WDs are adequate to explain energies in SGRs/AXPs as the rotationally powered energy. In addition, B-WDs also adequately explain the perplexing radio transient GCRT J1745-3009 as a white dwarf pulsar. Note that the radius and magnetic fields of B-WDs are neither extreme (unlike of highly magnetized neutron stars) nor ordinary (unlike of magnetized white dwarfs, yet following the Chandrasekhar's mass-radius relation (C-WDs)). In order to explain SGRs/AXPs, while the highly magnetized neutron stars require an extra, observationally not well established yet, source of energy, the C-WDs predict large ultra-violet luminosity which is observationally constrained from a strict upper limit. Finally, we provide a set of basic differences between the magnetar and B-WD hypotheses for SGRs/AXPs.

  20. Unique Properties of Thermally Tailored Copper: Magnetically Active Regions and Anomalous X-ray Fluorescence Emissions

    PubMed Central

    2009-01-01

    When high-purity copper (≥99.98%wt) is melted, held in its liquid state for a few hours with iterative thermal cycling, then allowed to resolidify, the ingot surface is found to have many small regions that are magnetically active. X-ray fluorescence analysis of these regions exhibit remarkably intense lines from “sensitized elements” (SE), including in part or fully the contiguous series V, Cr, Mn, Fe, and Co. The XRF emissions from SE are far more intense than expected from known impurity levels. Comparison with blanks and standards show that the thermal “tailoring” also introduces strongly enhanced SE emissions in samples taken from the interior of the copper ingots. For some magnetic regions, the location as well as the SE emissions, although persistent, vary irregularly with time. Also, for some regions extraordinarily intense “sensitized iron” (SFe) emissions occur, accompanied by drastic attenuation of Cu emissions. PMID:20037657

  1. Development of Large Bismuth Absorbers for Magnetic Calorimeters Applied to Hard X-ray Spectrometry

    NASA Astrophysics Data System (ADS)

    Rodrigues, M.; Loidl, M.; Pies, C.; Fleischmann, A.; Enss, C.

    2014-08-01

    Bismuth is an interesting material for magnetic calorimeter absorbers applied to high energy resolution X-ray spectrometry; it has a low specific heat and high atomic number. However, past detector developments with Bi absorbers were confronted with the low thermal conductivity of bismuth that degraded the energy resolution and deformed the detector response function (non-Gaussian energy peak). In the present study, we have investigated the performances of large bulk bismuth absorbers ( mm) thermally coupled to metallic magnetic sensors. Despite a very good baseline energy resolution, detectors with monolithic bismuth absorbers have degraded FWHM energy resolutions with any type of thermal coupling between the absorber and the sensor tested. In comparison tests with BiCu and BiAg bilayer absorbers demonstrated much better performances.

  2. Fast and slow magnetic deflagration fronts in type I X-ray bursts

    NASA Astrophysics Data System (ADS)

    Cavecchi, Yuri; Levin, Yuri; Watts, Anna L.; Braithwaite, Jonathan

    2016-06-01

    Type I X-ray bursts are produced by thermonuclear runaways that develop on accreting neutron stars. Once one location ignites, the flame propagates across the surface of the star. Flame propagation is fundamental in order to understand burst properties like rise time and burst oscillations. Previous work quantified the effects of rotation on the front, showing that the flame propagates as a deflagration and that the front strongly resembles a hurricane. However, the effect of magnetic fields was not investigated, despite the fact that magnetic fields strong enough to have an effect on the propagating flame are expected to be present on many bursters. In this paper, we show how the coupling between fluid layers introduced by an initially vertical magnetic field plays a decisive role in determining the character of the fronts that are responsible for the type I bursts. In particular, on a star spinning at 450 Hz (typical among the bursters), we test seed magnetic fields of 107-1010 G and find that for the medium fields the magnetic stresses that develop during the burst can speed up the velocity of the burning front, bringing the simulated burst rise time close to the observed values. By contrast, in a magnetic slow rotator like IGR J17480-2446, spinning at 11 Hz, a seed field ≳109 G is required to allow localized ignition and the magnetic field plays an integral role in generating the burst oscillations observed during the bursts.

  3. Design and testing of planar magnetic micromotors fabricated by deep x-ray lithography and electroplating

    SciTech Connect

    Guckel, H.; Christenson, T.R.; Skrobis, K.J.; Klein, J.; Karnowsky, M.

    1993-05-01

    The successful design and testing of a three-phase planar integrated magnetic micromotor is presented. Fabrication is based on a modified deep X-ray lithography and electroplating or LIGA process. Maximum rotational speeds of 33,000 rpm are obtained in air with a rotor diameter of 285 {mu}m and do not change when operated in vacuum. Real time rotor response is obtained with an integrated shaft encoder. Long lifetime is evidenced by testing to over 5(10){sup 7} ration cycles without changes in performance. Projected speeds of the present motor configuration are in the vicinity of 100 krpm and are limited by torque ripple. Higher speeds, which are attractive for sensor applications. require constant torque characteristic excitation as is evidenced by ultracentrifuge and gyroscope design. Further understanding of electroplated magnetic material properties will drive these performance improvements.

  4. Resonance Scattering of Fe XVII X-ray and EUV Lines

    NASA Technical Reports Server (NTRS)

    Bhatia, A. K.; Saba, J. L. R.; Fisher, Richard R. (Technical Monitor)

    2001-01-01

    Over the years a number of calculations have been carried out to derive intensities of various X-ray and EUV lines in Fe XVII to compare with observed spectra. The predicted intensities have not agreed with solar observations, particularly for the line at 1.5.02 Angstroms; resonance scattering has been suggested as the source for much of the disagreement. The atomic data calculated earlier used seven configurations having n=3 orbitals and the scattering calculations were carried out only for incident energies above the threshold of the highest fine-structure level. These calculations have now been extended to thirteen configurations having n=4 orbitals and the scattering calculations are carried out below as well as above the threshold of the highest fine structure level. These improved calculations of Fe XVII change the intensity ratios compared to those obtained earlier, bringing the optically thin F(15.02)/F(16.78) ratio and several other ratios closer to the observed values. However, some disagreement with the solar observations still persists, even thought the agreement of the presently calculated optically thin F(15.02)/F(15.26) ratio with the experimental results of Brown et al. (1998) and Laming et al. (2000) has improved. Some of the remaining discrepancy is still thought to be the effect of opacity, which is consistent with expected physical conditions for solar sources. EUV intensity ratios are also calculated and compared with observations. Level populations and intensity ratios are calculated, as a function of column density of Fe XVII, in the slab and cylindrical geometries. As found previously, the predicted intensities for the resonance lines at 15.02 and 15.26 Angstroms exhibit initial increases in flux relative to the forbidden line at 17.10 Angstroms and the resonance line at 16.78 Angstroms as optical thickness increases. The same behavior is predicted for the lines at 12.262 and 12.122 Angstroms. Predicted intensities for some of the allowed

  5. Observation of field-induced domain wall propagation in magnetic nanowires by magnetic transmission X-ray microscopy

    SciTech Connect

    Bryan, M. T.; Fry, P. W.; Fischer, P.; Allwood, D. A.

    2007-12-01

    Magnetic transmission X-ray microscopy (M-TXM) is used to image domain walls in magnetic ring structures formed by a 300 nm wide, 24 nm thick Ni{sub 81}Fe{sub 19} nanowire. Both transverse and vortex type domain walls are observed after application of different field sequences. Domain walls can be observed by comparing images obtained from opposite field sequences, or else domain wall propagation observed by comparing successive images in a particular field sequence. This demonstrates the potential use of M-TXM in developing and understanding planar magnetic nanowire behavior.

  6. Observation of field-induced domain wall propagation in magnetic nanowires by magnetic transmission x-ray microscopy

    NASA Astrophysics Data System (ADS)

    Bryan, M. T.; Fry, P. W.; Fischer, P. J.; Allwood, D. A.

    2008-04-01

    Magnetic transmission x-ray microscopy (M-TXM) is used to image domain walls in magnetic ring structures formed by a 300nm wide, 24nm thick Ni81Fe19 nanowire. Both transverse- and vortex-type domain walls are observed after application of different field sequences. Domain walls can be observed by comparing images obtained from opposite field sequences or else domain wall propagation observed by comparing successive images in a particular field sequence. This demonstrates the potential use of M-TXM in developing and understanding planar magnetic nanowire behavior.

  7. Advantages of a Synchrotron Bending Magnet as the Sample Illuminator for a Wide-field X-ray Microscope

    SciTech Connect

    Feser, M.; Howells, M. R.; Kirz, J.; Rudati, J.; Yun, W.

    2012-09-01

    In our paper the choice between bending magnets and insertion devices as sample illuminators for a hard X-ray full-field microscope is investigated. An optimized bending-magnet beamline design is presented. Its imaging speed is very competitive with the performance of similar microscopes installed currently at insertion-device beamlines. The fact that imaging X-ray microscopes can accept a large phase space makes them very well suited to the output characteristics of bending magnets which are often a plentiful and paid-for resource. There exist opportunities at all synchrotron light sources to take advantage of this finding to build bending-magnet beamlines that are dedicated to transmission X-ray microscope facilities. We expect that demand for such facilities will increase as three-dimensional tomography becomes routine and advanced techniques such as mosaic tomography and XANES tomography (taking three-dimensional tomograms at different energies to highlight elemental and chemical differences) become more widespread.

  8. Further comments on the effects of vacuum birefringence on the polarization of X-rays emitted from magnetic neutron stars

    NASA Technical Reports Server (NTRS)

    Chanan, G. A.; Novick, R.; Silver, E. H.

    1979-01-01

    The birefringence of the vacuum in the presence of strong (of the order of 1 teragauss) magnetic fields will in general affect the polarization of X-rays propagating through these fields. Two of the four Stokes parameters will vary so rapidly with wavelength as to be 'washed out' and unobservable, but the remaining two parameters will be unaffected. These results show that one conclusion of an earlier work is incorrect: Polarized X-ray emission from the surface of a magnetic neutron star will not in general be completely depolarized by the effects of vacuum birefringence. In particular, this birefringence has no effect on the linear polarization of cyclotron emission from the poles of magnetic neutron stars, and a similar result holds for synchrotron emission. More general cases of the propagation of polarized X-rays in magnetic fields are also discussed.

  9. An Investigation of Luminous X-Ray Pulsars: Exploring Accretion Onto the Magnetized Neutron Star LMC X-4

    NASA Astrophysics Data System (ADS)

    Brumback, McKinley

    2016-04-01

    X-ray pulsars are neutron stars in which magnetic forces dominate accretion within the magnetosphere. These systems offer unique laboratories to study magnetic accretion and the behavior of matter under extreme densities, magnetic fields, and gravitational forces. Using joint observations with NuSTAR and XMM-Newton, we observe the complete precession of the warped accretion disk around the X-ray pulsar LMC X-4, and measure the relative phase between the pulsar beam and the softer X-ray photons reprocessed by the disk. This allows us to perform tomography to explore the inner magnetized accretion flow. Additionally, we investigate the unusual flaring events observed from LMC X-4 during October and November of 2015.

  10. Electronic Structure of Doped Lanthanum Cuprates Studied with Resonant Inelastic X-Ray Scattering

    SciTech Connect

    Hill, J.P.; Ellis, D.S.; Kim, J.; Zhang, H.; Gu, G.; Komiya, S.; Ando, Y.; Casa, D.; Gog, T.; Kim, Y.-J.

    2011-02-24

    We report a comprehensive Cu K-edge resonant inelastic x-ray scattering (RIXS) investigation of La{sub 2-x}Sr{sub x}CuO{sub 4} (LSCO) for 0 {le} x {le} 0.35, stripe-ordered La{sub 1.875}Ba{sub 0.125}CuO{sub 4} (LBCO), and La{sub 2}Cu{sub 0.96}Ni{sub 0.04}O{sub 4} (LCNO) crystals. The RIXS spectra measured at three high-symmetry momentum-transfer (q) positions are compared as a function of doping and for the different dopants. The spectra in the energy range 1-6 eV can be described with three broad peaks, which evolve systematically with increased doping. The most systematic trend was observed for q = ({pi},0) corresponding to the zone boundary. As hole doping increased, the spectral weight transfer from high energies to low energies is nearly linear with x at this q. We interpret the peaks as interband transitions in the context of existing band models for this system, assigning them to Zhang-Rice band {yields} upper Hubbard band, lower-lying band {yields} upper Hubbard band, and lower-lying band {yields} Zhang-Rice band transitions. The spectrum of stripe-ordered LBCO was also measured, and found to be identical to the correspondingly doped LSCO, except for a relative enhancement of the near-infrared peak intensity at {approx}1.5-1.7 eV. The temperature dependence of this near-infrared peak in LBCO was more pronounced than for other parts of the spectrum, continuously decreasing in intensity as the temperature was raised from 25 to 300 K. Finally, we find that 4% Ni substitution in the Cu site has a similar effect on the spectra as does Sr substitution in the La site.

  11. Characterization by X-Ray Absorption, X-Ray Powder Diffraction, and Magnetic Susceptibility of Cu Zn Co Al Containing Hydroxycarbonates, Oxycarbonates, Oxides, and Their Products of Reduction

    NASA Astrophysics Data System (ADS)

    Porta, Piero; Morpurgo, Simone; Pettiti, Ida

    1996-02-01

    Copper-zinc-cobalt-aluminium-containing crystalline hydroxycarbonates having hydrotalcite structure have been prepared by coprecipitation. X-ray powder diffraction (XRPD), magnetic susceptibility, and extended X-ray absorption fine structure (EXAFS) indicate that Cu2+, Zn2+, and Co2+are present in an octahedral environment. Calcination of the hydroxycarbonates at 723 K produces quasi-amorphous oxycarbonates where Cu2+and Co2+still retain octahedral coordination and cobalt is almost completely oxidized to Co3+. The coordination of Zn2+, at this stage, is intermediate between the octahedral one of the precursors and the tetrahedral one of ZnO and Zn-based spinels. Further calcination at 973 K produces a mixture of crystalline oxides such as CuO, ZnO, CuAl2O4, ZnAl2O4, and ZnCo2O4. EXAFS analysis of these samples indicates that copper is mainly in a fourfold coordination (although two longer Cu-O distances are also detected), zinc is tetrahedral, and cobalt (as Co3+) is essentially octahedral. EXAFS and XANES investigations performed afterin situreduction (10% H2/N2, at 523 and 623 K) on the oxycarbonates and oxides reveal that the total Cu2+→ Cu0reduction occurs only at 623 K in both series of samples, Co3+is reduced to Co2+only at 623 K in the oxycarbonates, and Zn2+is never reduced.

  12. Local electronic states of Fe{sub 4}N films revealed by x-ray absorption spectroscopy and x-ray magnetic circular dichroism

    SciTech Connect

    Ito, Keita; Toko, Kaoru; Suemasu, Takashi; Takeda, Yukiharu; Saitoh, Yuji; Oguchi, Tamio; Kimura, Akio

    2015-05-21

    We performed x-ray absorption spectroscopy (XAS) and x-ray magnetic circular dichroism (XMCD) measurements at Fe L{sub 2,3} and N K-edges for Fe{sub 4}N epitaxial films grown by molecular beam epitaxy. In order to clarify the element specific local electronic structure of Fe{sub 4}N, we compared experimentally obtained XAS and XMCD spectra with those simulated by a combination of a first-principles calculation and Fermi's golden rule. We revealed that the shoulders observed at Fe L{sub 2,3}-edges in the XAS and XMCD spectra were due to the electric dipole transition from the Fe 2p core-level to the hybridization state generated by σ* anti-bonding between the orbitals of N 2p at the body-centered site and Fe 3d on the face-centered (II) sites. Thus, the observed shoulders were attributed to the local electronic structure of Fe atoms at II sites. As to the N K-edge, the line shape of the obtained spectra was explained by the dipole transition from the N 1s core-level to the hybridization state formed by π* and σ* anti-bondings between the Fe 3d and N 2p orbitals. This hybridization plays an important role in featuring the electronic structures and physical properties of Fe{sub 4}N.

  13. Spectroscopy of strongly correlated systems: Resonant x-ray scattering without energy resolution in the scattered beam

    NASA Astrophysics Data System (ADS)

    Braicovich, L.; Tagliaferri, A.; Annese, E.; Ghiringhelli, G.; Dallera, C.; Fracassi, F.; Palenzona, A.; Brookes, N. B.

    2007-02-01

    The total emission of photons excited by x rays (90° between incident and detected photons) is measured vs the incident photon energy at the CeM4,5 edges in CeIn3 , CeSnIn2 , CeAl2 , CePd3 , and CeRh2 , and at the NiL2,3 edges in NiO. The results show the signature of a second-order process; these experiments must be interpreted as genuine resonant inelastic scattering (though without energy resolution of the emitted photons) and not as absorption spectroscopy measured by the total fluorescence yield. In Ce compounds, information on bulk hybridization can thus be obtained simply and with high sensitivity. The branching ratio between the different scattering channels is also measured. This approach opens innovative perspectives in resonant inelastic x-ray scattering.

  14. Isotope Effects in the Resonant Inelastic Soft X-ray Scattering Maps of Gas-Phase Methanol.

    PubMed

    Benkert, A; Meyer, F; Hauschild, D; Blum, M; Yang, W; Wilks, R G; Bär, M; Reinert, F; Heske, C; Weinhardt, L

    2016-04-14

    The electronic structure of gas-phase methanol molecules (H3COH, H3COD, and D3COD) at atmospheric pressure was investigated using resonant inelastic soft X-ray scattering (RIXS) at the O K and C K edges. We observe strong changes of the relative emission intensities of all valence orbitals as a function of excitation energy, which can be related to the symmetries of the involved orbitals causing an angularly anisotropic RIXS intensity. Furthermore, all observed emission lines are subject to strong spectator shifts of up to -0.9 eV at the O K edge and up to -0.3 eV at the C K edge. At the lowest O K resonance, we find clear evidence for dissociation of the methanol molecule on the time scale of the RIXS process, which is illustrated by comparing X-ray emission spectra of regular and deuterated methanol. PMID:27003748

  15. Resonant anomalous x-ray reflectivity as a probe of ion adsorption at solid-liquid interfaces.

    SciTech Connect

    Fenter, P.; Park, C.; Nagy, K. L.; Sturchio, N. C.; Chemistry; Univ. of Illinois at Chicago

    2007-05-23

    We discuss new opportunities to understand processes at the solid-liquid interface using resonant anomalous X-ray reflectivity (RAXR). This approach is illustrated by determination of element-specific density profiles at mica surfaces in aqueous electrolyte solutions containing Rb{sup +} and Sr{sup 2+}. The total interfacial electron density profile is determined by specular reflectivity (i.e., reflected intensity vs. momentum transfer, q, at an energy, E, far from any characteristic absorption edge). RAXR spectra (i.e., intensity vs. E at fixed q) reveal element-specific ion distributions. Key differences in the interaction of Rb{sup +} and Sr{sup 2+} with mica are observed using resonant anomalous X-ray reflectivity: Rb{sup +} adsorbs in a partially hydrated state, but Sr{sup 2+} adsorbs in both fully and partially hydrated states.

  16. Evidence that the X-Ray Plasma in Microflares is in a Sequence of Subresolution Magnetic Tubes

    NASA Technical Reports Server (NTRS)

    Moore, Ronald L.; Falconer, D. A.; Porter, Jason G.

    1998-01-01

    We analyze the cooling of the X-ray emitting thermal plasma in microflares observed in active regions by the Yohkoh Soft X-ray Telescope. A typical microflare appears to be a transient brightening of an entire small magnetic loop, often having a diameter near the limit of resolution (approximately 2 x 10(exp 8) cm) (Shimizu 1995, PASJ, 47, 251). The X-ray plasma in the loop cools by emission of XUV radiation and by heat conduction to the cooler plasma at the feet of the loop. The cooling rate is determined by the plasma temperature and density and the loop length. The plasma density is determined from the observed X-ray brightness of the loop in combination with the temperature, the loop diameter, and the filling factor. The filling factor is the volume fraction of the loop occupied by the subset of magnetic tubes that is filled by the X-ray plasma and that contains practically all of the X-ray plasma present in the microflare loop. Taking typical values from the hundreds of microflares measured by Shimizu (1995) (X-ray brightness through the thin aluminum filter approximately 4 x 10(exp 3) DN/s/pixel, lifetime approximately 5 min, temperature approximately 6 x 10(exp 6) K, loop length approximately 10(exp 9) cm, loop diameter approximately 3 x 10(exp 8) cm), we find that for filling factors greater than approximately 1% (1) the cooling time is much shorter than the duration of the microflare, and (2) conductive cooling strongly dominates over radiative cooling. Because the cooling time is so short and because the conductive heat flux goes mainly into increasing the plasma density via chromospheric evaporation, we are compelled to conclude that (1) heating to X-ray temperatures continues through nearly the entire life of a microflare, (2) the heating keeps changing to different field lines, so that any one magnetic tube in the sequence of heated tubes emits X-rays only briefly in the life of the microflare, and (3) at any instant during the microflare the tubes

  17. X-ray irradiation of soda-lime glasses studied in situ with surface plasmon resonance spectroscopy

    NASA Astrophysics Data System (ADS)

    Serrano, A.; Gálvez, F.; Rodríguez de la Fuente, O.; García, M. A.

    2013-03-01

    We present here a study of hard X-ray irradiation of soda-lime glasses performed in situ and in real time. For this purpose, we have used a Au thin film grown on glass and studied the excitation of its surface plasmon resonance (SPR) while irradiating the sample with X-rays, using a recently developed experimental setup at a synchrotron beamline [Serrano et al., Rev. Sci. Instrum. 83, 083101 (2012)]. The extreme sensitivity of the SPR to the features of the glass substrate allows probing the modifications caused by the X-rays. Irradiation induces color centers in the soda-lime glass, modifying its refractive index. Comparison of the experimental results with simulated data shows that both, the real and the imaginary parts of the refractive index of soda-lime glasses, change upon irradiation in time intervals of a few minutes. After X-ray irradiation, the effects are partially reversible. The defects responsible for these modifications are identified as non-bridging oxygen hole centers, which fade by recombination with electrons after irradiation. The kinetics of the defect formation and fading process are also studied in real time.

  18. X-ray irradiation of soda-lime glasses studied in situ with surface plasmon resonance spectroscopy

    SciTech Connect

    Serrano, A.; Galvez, F.; Rodriguez de la Fuente, O.; Garcia, M. A.

    2013-03-21

    We present here a study of hard X-ray irradiation of soda-lime glasses performed in situ and in real time. For this purpose, we have used a Au thin film grown on glass and studied the excitation of its surface plasmon resonance (SPR) while irradiating the sample with X-rays, using a recently developed experimental setup at a synchrotron beamline [Serrano et al., Rev. Sci. Instrum. 83, 083101 (2012)]. The extreme sensitivity of the SPR to the features of the glass substrate allows probing the modifications caused by the X-rays. Irradiation induces color centers in the soda-lime glass, modifying its refractive index. Comparison of the experimental results with simulated data shows that both, the real and the imaginary parts of the refractive index of soda-lime glasses, change upon irradiation in time intervals of a few minutes. After X-ray irradiation, the effects are partially reversible. The defects responsible for these modifications are identified as non-bridging oxygen hole centers, which fade by recombination with electrons after irradiation. The kinetics of the defect formation and fading process are also studied in real time.

  19. An ultrahigh-vacuum apparatus for resonant diffraction experiments using soft x rays (hnu=300-2000 eV).

    PubMed

    Takeuchi, T; Chainani, A; Takata, Y; Tanaka, Y; Oura, M; Tsubota, M; Senba, Y; Ohashi, H; Mochiku, T; Hirata, K; Shin, S

    2009-02-01

    We have developed an ultrahigh-vacuum instrument for resonant diffraction experiments using polarized soft x rays in the energy range of hnu=300-2000 eV at beamline BL17SU of SPring-8. The diffractometer consists of modified differentially pumped rotary feedthroughs for theta-2theta stages, a sample manipulator with motor-controlled x-y-z-, tilt (chi)-, and azimuth (phi)-axes, and a liquid helium flow-type cryostat for temperature dependent measurements between 30 and 300 K. Test results indicate that the diffractometer exhibits high reproducibility (better than 0.001 degrees ) for a Bragg reflection of alpha-quartz 100 at a photon energy of hnu=1950 eV. Typical off- and on-resonance Bragg reflections in the energy range of 530-1950 eV could be measured using the apparatus. The results show that x-ray diffraction experiments with energy-, azimuth-, and incident photon polarization-dependence can be reliably measured using soft x rays in the energy range of approximately 300-2000 eV. The facility can be used for resonant diffraction experiments across the L-edge of transition metals, M-edge of lanthanides, and up to the Si K-edge of materials. PMID:19256660

  20. Closed bore XMR (CBXMR) systems for aortic valve replacement: active magnetic shielding of x-ray tubes.

    PubMed

    Bracken, John A; DeCrescenzo, Giovanni; Komljenovic, Philip; Lillaney, Prasheel V; Fahrig, Rebecca; Rowlands, J A

    2009-05-01

    Hybrid closed bore x-ray/MRI systems are being developed to improve the safety and efficacy of percutaneous aortic valve replacement procedures by harnessing the complementary strengths of the x-ray and MRI modalities in a single interventional suite without requiring patient transfer between two rooms. These systems are composed of an x-ray C-arm in close proximity (approximately 1 m) to an MRI scanner. The MRI magnetic fringe field can cause the electron beam in the x-ray tube to deflect. The deflection causes the x-ray field of view to shift position on the detector receptacle. This could result in unnecessary radiation exposure to the patient and the staff in the cardiac catheterization laboratory. Therefore, the electron beam deflection must be corrected. The authors developed an active magnetic shielding system that can correct for electron beam deflection to within an accuracy of 5% without truncating the field of view or increasing exposure to the patient. This system was able to automatically adjust to different field strengths as the external magnetic field acting on the x-ray tube was changed. Although a small torque was observed on the shielding coils of the active shielding system when they were placed in a magnetic field, this torque will not impact their performance if they are securely mounted on the x-ray tube and the C-arm. The heating of the coils of the shielding system for use in the clinic caused by electric current was found to be slow enough not to require a dedicated cooling system for one percutaneous aortic valve replacement procedure. However, a cooling system will be required if multiple procedures are performed in one session. PMID:19544789

  1. Hard X-ray polarizer to enable simultaneous three-dimensional nanoscale imaging of magnetic structure and lattice strain.

    PubMed

    Logan, Jonathan; Harder, Ross; Li, Luxi; Haskel, Daniel; Chen, Pice; Winarski, Robert; Fuesz, Peter; Schlagel, Deborah; Vine, David; Benson, Christa; McNulty, Ian

    2016-09-01

    Recent progress in the development of dichroic Bragg coherent diffractive imaging, a new technique for simultaneous three-dimensional imaging of strain and magnetization at the nanoscale, is reported. This progress includes the installation of a diamond X-ray phase retarder at beamline 34-ID-C of the Advanced Photon Source. The performance of the phase retarder for tuning X-ray polarization is demonstrated with temperature-dependent X-ray magnetic circular dichroism measurements on a gadolinium foil in transmission and on a Gd5Si2Ge2 crystal in diffraction geometry with a partially coherent, focused X-ray beam. Feasibility tests for dichroic Bragg coherent diffractive imaging are presented. These tests include (1) using conventional Bragg coherent diffractive imaging to determine whether the phase retarder introduces aberrations using a nonmagnetic gold nanocrystal as a control sample, and (2) collecting coherent diffraction patterns of a magnetic Gd5Si2Ge2 nanocrystal with left- and right-circularly polarized X-rays. Future applications of dichroic Bragg coherent diffractive imaging for the correlation of strain and lattice defects with magnetic ordering and inhomogeneities are considered. PMID:27577777

  2. Hard X-ray polarizer to enable simultaneous three-dimensional nanoscale imaging of magnetic structure and lattice strain

    PubMed Central

    Logan, Jonathan; Harder, Ross; Li, Luxi; Haskel, Daniel; Chen, Pice; Winarski, Robert; Fuesz, Peter; Schlagel, Deborah; Vine, David; Benson, Christa; McNulty, Ian

    2016-01-01

    Recent progress in the development of dichroic Bragg coherent diffractive imaging, a new technique for simultaneous three-dimensional imaging of strain and magnetization at the nanoscale, is reported. This progress includes the installation of a diamond X-ray phase retarder at beamline 34-ID-C of the Advanced Photon Source. The performance of the phase retarder for tuning X-ray polarization is demonstrated with temperature-dependent X-ray magnetic circular dichroism measurements on a gadolinium foil in transmission and on a Gd5Si2Ge2 crystal in diffraction geometry with a partially coherent, focused X-ray beam. Feasibility tests for dichroic Bragg coherent diffractive imaging are presented. These tests include (1) using conventional Bragg coherent diffractive imaging to determine whether the phase retarder introduces aberrations using a nonmagnetic gold nanocrystal as a control sample, and (2) collecting coherent diffraction patterns of a magnetic Gd5Si2Ge2 nanocrystal with left- and right-circularly polarized X-rays. Future applications of dichroic Bragg coherent diffractive imaging for the correlation of strain and lattice defects with magnetic ordering and inhomogeneities are considered. PMID:27577777

  3. Magnetostatic focal spot correction for x-ray tubes operating in strong magnetic fields using iterative optimization

    PubMed Central

    Lillaney, Prasheel; Shin, Mihye; Conolly, Steven M.; Fahrig, Rebecca

    2012-01-01

    Purpose: Combining x-ray fluoroscopy and MR imaging systems for guidance of interventional procedures has become more commonplace. By designing an x-ray tube that is immune to the magnetic fields outside of the MR bore, the two systems can be placed in close proximity to each other. A major obstacle to robust x-ray tube design is correcting for the effects of the magnetic fields on the x-ray tube focal spot. A potential solution is to design active shielding that locally cancels the magnetic fields near the focal spot. Methods: An iterative optimization algorithm is implemented to design resistive active shielding coils that will be placed outside the x-ray tube insert. The optimization procedure attempts to minimize the power consumption of the shielding coils while satisfying magnetic field homogeneity constraints. The algorithm is composed of a linear programming step and a nonlinear programming step that are interleaved with each other. The coil results are verified using a finite element space charge simulation of the electron beam inside the x-ray tube. To alleviate heating concerns an optimized coil solution is derived that includes a neodymium permanent magnet. Any demagnetization of the permanent magnet is calculated prior to solving for the optimized coils. The temperature dynamics of the coil solutions are calculated using a lumped parameter model, which is used to estimate operation times of the coils before temperature failure. Results: For a magnetic field strength of 88 mT, the algorithm solves for coils that consume 588 A/cm2. This specific coil geometry can operate for 15 min continuously before reaching temperature failure. By including a neodymium magnet in the design the current density drops to 337 A/cm2, which increases the operation time to 59 min. Space charge simulations verify that the coil designs are effective, but for oblique x-ray tube geometries there is still distortion of the focal spot shape along with deflections of approximately

  4. Magnetic field amplification in the thin X-ray rims of SN 1006

    SciTech Connect

    Ressler, Sean M.; Katsuda, Satoru; Reynolds, Stephen P.; Long, Knox S.; Petre, Robert; Williams, Brian J.; Winkler, P. Frank

    2014-08-01

    Several young supernova remnants, including SN 1006, emit synchrotron X-rays in narrow filaments, hereafter thin rims, along their periphery. The widths of these rims imply 50-100 μG fields in the region immediately behind the shock, far larger than expected for the interstellar medium compressed by unmodified shocks, assuming electron radiative losses limit rim widths. However, magnetic field damping could also produce thin rims. Here we review the literature on rim width calculations, summarizing the case for magnetic field amplification. We extend these calculations to include an arbitrary power-law dependence of the diffusion coefficient on energy, D∝E {sup μ}. Loss-limited rim widths should shrink with increasing photon energy, while magnetic-damping models predict widths almost independent of photon energy. We use these results to analyze Chandra observations of SN 1006, in particular the southwest limb. We parameterize the FWHM in terms of energy as FWHM ∝E{sub γ}{sup m{sub E}}. Filament widths in SN 1006 decrease with energy; m{sub E} ∼ –0.3 to –0.8, implying magnetic field amplification by factors of 10-50, above the factor of four expected in strong unmodified shocks. For SN 1006, the rapid shrinkage rules out magnetic damping models. It also favors short mean free paths (small diffusion coefficients) and strong dependence of D on energy (μ ≥ 1).

  5. Development of Position-Sensitive Magnetic Calorimeters for X-Ray Astronomy

    NASA Technical Reports Server (NTRS)

    Bandler, SImon; Stevenson, Thomas; Hsieh, Wen-Ting

    2011-01-01

    Metallic magnetic calorimeters (MMC) are one of the most promising devices to provide very high energy resolution needed for future astronomical x-ray spectroscopy. MMC detectors can be built to large detector arrays having thousands of pixels. Position-sensitive magnetic (PoSM) microcalorimeters consist of multiple absorbers thermally coupled to one magnetic micro calorimeter. Each absorber element has a different thermal coupling to the MMC, resulting in a distribution of different pulse shapes and enabling position discrimination between the absorber elements. PoSMs therefore achieve the large focal plane area with fewer number of readout channels without compromising spatial sampling. Excellent performance of PoSMs was achieved by optimizing the designs of key parameters such as the thermal conductance among the absorbers, magnetic sensor, and heat sink, as well as the absorber heat capacities. Micro fab ri - cation techniques were developed to construct four-absorber PoSMs, in which each absorber consists of a two-layer composite of bismuth and gold. The energy resolution (FWHM full width at half maximum) was measured to be better than 5 eV at 6 keV x-rays for all four absorbers. Position determination was demonstrated with pulse-shape discrimination, as well as with pulse rise time. X-ray microcalorimeters are usually designed to thermalize as quickly as possible to avoid degradation in energy resolution from position dependence to the pulse shapes. Each pixel consists of an absorber and a temperature sensor, both decoupled from the cold bath through a weak thermal link. Each pixel requires a separate readout channel; for instance, with a SQUID (superconducting quantum interference device). For future astronomy missions where thousands to millions of resolution elements are required, having an individual SQUID readout channel for each pixel becomes difficult. One route to attaining these goals is a position-sensitive detector in which a large continuous or

  6. Scaling of the L{sub 2,3} circular magnetic x-ray dichroism of Fe nitrides

    SciTech Connect

    Alouani, M. |; Wills, J.M.; Wilkins, J.W.

    1998-04-01

    We have implemented the calculation of the x-ray-absorption cross section for left- and right-circularly polarized x-ray beams within the local-density approximation by means of our all-electron full-relativistic and spin-polarized full-potential linear muffin-tin orbital method. We show that the L{sub 2,3} circular magnetic x-ray dichroism of Fe, Fe{sub 3}N, and Fe{sub 4}N compounds scales to a single curve when divided by the local magnetic moment. Sum rules determine the spin and orbital magnetic moment of iron atoms in these ordered iron nitrides. {copyright} {ital 1998} {ital The American Physical Society}

  7. Electronic structure, noncollinear magnetism, and x-ray magnetic circular dichroism in the Mn3ZnC perovskite

    NASA Astrophysics Data System (ADS)

    Antonov, V. N.; Harmon, B. N.; Yaresko, A. N.; Shpak, A. P.

    2007-04-01

    Mn3ZnC possesses a magnetic phase transition at Tt=233K from a ferromagnetic phase to a ferrimagnetic one with a noncollinear magnetic structure. The transition is accompanied by a structural change from cubic to tetragonal. The experimentally measured x-ray magnetic circular dichroism (XMCD) at the MnK edge shows a drastic change at the magnetic phase transition, which is associated with the appearance of the noncollinear magnetic structure. The electronic structure and XMCD spectra of the Mn3ZnC were investigated theoretically from first principles, using the fully relativistic Dirac linear muffin-tin orbital band-structure method for both the high-temperature cubic and low-temperature tetragonal noncollinear phases. Densities of valence states, spin, and orbital magnetic moments are analyzed and discussed. The origin of the XMCD spectra in the Mn3ZnC compound is examined. The calculated results are compared with the experimental data.

  8. Analytical modelling and x-ray imaging of oscillations of a single magnetic domain wall

    SciTech Connect

    Bocklage, Lars; Kruger, Benjamin; Fischer, Peter; Meier, Guido

    2009-07-10

    Domain-wall oscillation in a pinnig potential is described analytically in a one dimensional model for the feld-driven case. For a proper description the pinning potential has to be extended by nonharmonic contributions. Oscillations of a domain wall are observed on its genuine time scale by magnetic X-ray microscopy. It is shown that the nonharmonic terms are present in real samples with a strong restoring potential. In the framework of our model we gain deep insight into the domain-wall motion by looking at different phase spaces. The corrections of the harmonic potential can change the motion of the domain wall significantly. The damping parameter of permalloy is determined via the direct imaging technique.

  9. Two-dimensional stimulated resonance Raman spectroscopy of molecules with broadband x-ray pulses

    PubMed Central

    Biggs, Jason D.; Zhang, Yu; Healion, Daniel; Mukamel, Shaul

    2012-01-01

    Expressions for the two-dimensional stimulated x-ray Raman spectroscopy (2D-SXRS) signal obtained using attosecond x-ray pulses are derived. The 1D- and 2D-SXRS signals are calculated for trans-N-methyl acetamide (NMA) with broad bandwidth (181 as, 14.2 eV FWHM) pulses tuned to the oxygen and nitrogen K-edges. Crosspeaks in 2D signals reveal electronic Franck-Condon overlaps between valence orbitals and relaxed orbitals in the presence of the core-hole. PMID:22583220

  10. Momentum-resolved resonant and nonresonant inelastic x-ray scattering at the Advanced Photon Source.

    SciTech Connect

    Gog, T.; Seidler, G. T.; Casa, D. M.; Upton, M. H.; Kim, J.; Shvydko, Y.; Stoupin, S.; Nagle, K. P.; Balasubramanian, M.; Gordon, R. A.; Fister, T. T.; Heald, S. M.; Toellner, T.; Hill, J. P.; Coburn, D. S.; Kim, Y. J.; Said, A. H.; Alp, E. E.; Sturhahn, W.; Yavas, H.; Burns, C. A.; Sinn, H.

    2009-11-01

    The study of electronic excitations by inelastic X-ray scattering (IXS) has a rich history. Very early IXS work, for example, provided seminal demonstrations of the validity of relativistic kinematics and the quantum hypothesis and of Fermi-Dirac statistics. While there have been many important results in the interim, it has been the development of the third generation light sources together with continuing innovations in the manufacture and implementation of dispersive X-ray optics that has led to the rapid growth of IXS studies of electronic excitations.

  11. Study of Increased Radiation When an X-ray Tube is Placed in a Strong Magnetic Field

    SciTech Connect

    Wen, Z.F.; Pelc, N.J.; Nelson, W.R.; Fahrig, R.; /Stanford U., Dept. Radiol.

    2007-01-12

    When a fixed anode x-ray tube is placed in a magnetic field (B) that is parallel to the anode-cathode axis, the x-ray exposure increases with increasing B. It was hypothesized that the increase was caused by backscattered electrons which were constrained by B and reaccelerated by the electric field onto the x-ray tube target. We performed computer simulations and physical experiments to study the behavior of the backscattered electrons in a magnetic field, and their effects on the radiation output, x-ray spectrum, and off-focal radiation. A Monte Carlo program (EGS4) was used to generate the combined energy and angular distribution of the backscattered electrons. The electron trajectories were traced and their landing locations back on the anode were calculated. Radiation emission from each point was modeled with published data (IPEM Report 78), and thus the exposure rate and x-ray spectrum with the contribution of backscattered electrons could be predicted. The point spread function for a pencil beam of electrons was generated and then convolved with the density map of primary electrons incident on the anode as simulated with a finite element program (Opera-3d, Vector Fields, UK). The total spatial distribution of x-ray emission could then be calculated. Simulations showed that for an x-ray tube working at 65 kV, about 54% of the electrons incident on the target were backscattered. In a magnetic field of 0.5 T, although the exposure would be increased by 33%, only a small fraction of the backscattered electrons landed within the focal spot area. The x-ray spectrum was slightly shifted to lower energies and the half value layer (HVL) was reduced by about 6%. Measurements of the exposure rate, half value layer and focal spot distribution were acquired as functions of B. Good agreement was observed between experimental data and simulation results. The wide spatial distribution of secondary x-ray emission can degrade the MTF of the x-ray system at low spatial

  12. A unique 30 Tesla single-solenoid pulsed magnet instrument for x-ray studies

    NASA Astrophysics Data System (ADS)

    Islam, Zahirul; Capatina, Dana; Ruff, Jacob; Das, Ritesh; Nojiri, Hiroyuki; Narumi, Yasuo

    2011-03-01

    We present a dual-cryostat pulsed-magnet instrument at the Advanced Photon Source (APS) with unique capabilities. The dual-cryostat independently cools the solenoid (Tohoku design) using liquid nitrogen and the sample using a closed-cycle refrigerator, respectively. Liquid nitrogen (LN) cooling allows a repetition rate of seven minutes for peak fields of 30 Tesla. The system is unique in that the LN cryostat incorporates a double-funnel vacuum tube passing through the solenoid's bore preserving the entire angular range allowed by the magnet. This scheme is advantageous in that it allows the applied magnetic field to be parallel to the scattering plane complementing typical split-pair magnets with fields normal to the scattering plane. Performance of the coils along with preliminary x-ray diffraction and spectroscopic studies will be presented. Use of the APS is supported by the U. S. DOE, Office of Science, under Contract No. DE-AC02-06CH11357. The work was supported in part by ICC-IMR, Tohoku University.

  13. Resonant x-ray emission spectroscopy of liquid water: novel instrumentation, high resolution, and the"map" approach

    SciTech Connect

    Weinhardt, L.; Fuchs, O.; Blum, M.; Bär, M.; Weigand, M.; Denlinger, J.D.; Zubavichus, Y.; Zharnikov, M.; Grunze, M.; Heske, C.; Umbach, E.

    2008-06-17

    Techniques to study the electronic structure of liquids are rare. Most recently, resonant x-ray emission spectroscopy (XES) has been shown to be an extremely versatile spectroscopy to study both occupied and unoccupied electronic states for liquids in thermodynamic equilibrium. However, XES requires high-brilliance soft x-ray synchrotron radiation and poses significant technical challenges to maintain a liquid sample in an ultra-high vacuum environment. Our group has therefore developed and constructed a novel experimental setup for the study of liquids, with the long-term goal of investigating the electronic structure of biological systems in aqueous environments. We have developed a flow-through liquid cell in which the liquid is separated from vacuum by a thin Si3N4 or SiC window and which allows a precise control of temperature. This approach has significant advantages compared to static liquids cells used in the past. Furthermore, we have designed a dedicated high-transmission, high-resolution soft x-ray spectrometer. The high transmission makes it possible to measure complete resonant XES"maps" in less than an hour, giving unprecedented detailed insight into the electronic structure of the investigated sample. Using this new equipment we have investigated the electronic structure of liquid water. Furthermore, our XES spectra and maps give information about ultra-fast dissociation on the timescale of the O 1s core hole lifetime, which is strongly affected by the initial state hydrogen bonding configuration.

  14. Analysis of Order Formation in Block Copolymer Thin Films UsingResonant Soft X-Ray Scattering

    SciTech Connect

    Virgili, Justin M.; Tao, Yuefei; Kortright, Jeffrey B.; Balsara,Nitash P.; Segalman, Rachel A.

    2006-11-27

    The lateral order of poly(styrene-block-isoprene) copolymer(PS-b-PI) thin films is characterized by the emerging technique ofresonant soft X-ray scattering (RSOXS) at the carbon K edge and comparedto ordering in bulk samples of the same materials measured usingconventional small-angle X-ray scattering. We show resonance using theoryand experiment that the loss of scattering intensity expected with adecrease in sample volume in the case of thin films can be overcome bytuning X-rays to the pi* resonance of PS or PI. Using RSOXS, we study themicrophase ordering of cylinder- and phere-forming PS-b-PI thin films andcompare these results to position space data obtained by atomic forcemicroscopy. Our ability to examine large sample areas (~;9000 mu m2) byRSOXS enables unambiguous identification of the lateral lattice structurein the thin films. In the case of the sphere-forming copolymer thin film,where the spheres are hexagonally arranged, the average sphere-to-spherespacing is between the bulk (body-centered cubic) nearest neighbor andbulk unit cell spacings. In the case of the cylinder-forming copolymerthin film, the cylinder-to-cylinder spacing is within experimental errorof that obtained in the bulk.

  15. Resonance Scattering of Fe XVII X-Ray and EUV Lines

    NASA Technical Reports Server (NTRS)

    Bhatia, A. K.; Saba, J. L. R.; Fisher, Richard R. (Technical Monitor)

    2001-01-01

    Over the years a number of calculations have been carried out to derive intensities of various X-ray and EUV lines in Fe XVII to compare with observed spectra. The predicted intensities have not agreed with solar observations, particularly for the line at 15.02 Angstroms; resonance scattering has been suggested as the source for much of the disagreement. The atomic data calculated earlier used seven configurations, 2s(sup 2) 2p(sup 6),2s(sup 2) 2p(sup 5)3s, 2s(sup 2) 2p(sup 5)3p, 2s(sup 2)2p(sup 5)3d, 2s2 p(sup 6)3s, 2s2p(sup 6)3p, and 2s2p(sup 6)3d, having n=3 orbitals and the scattering calculations in the distorted wave approximation were carried out only for incident energies above the threshold of the highest fine-structure level. These calculations have now been extended to thirteen configurations by adding six more configurations having n=4 orbitals, namely 2s(sup 2) 2p(sup 5)4s, 2s(sup 2) 2p(sup 5)4p, 2s(sup 2) 2p(sup 5)4d, 2s2p(sup 6)4s, 2s2p(sup 6)4p, and 2s2p(sup 6)4d, giving rise to 73 fine structure levels. The scattering calculations are carried out below as well as above the threshold of the highest fine-structure level. The incident energies below the threshold are 55.8, 65, 70, and 76 Ry and those above are 85, 127.5, 170, 212.5, 255, 340, and 425 Ry. The collision strengths are calculated up to total angular momentum L(sup T) = 33. Level populations and intensity ratios are calculated at various electron temperatures and densities. It is not possible to predict how the ratios would change when configurations with n=5 and 6 orbitals are added but some estimates have been made for a few transitions by Liedhal, who indicates an asymptotic convergence when n=5 and 6 orbitals are added. These improved calculations of Fe XVII change the intensity ratios compared to those obtained earlier, bringing the optically thin F(15.02)/F(16.78) ratio and several other ratios closer to the observed values: However, some disagreement with the solar observations

  16. Time-resolved soft X-ray microscopy of magnetic nanostructures at the P04 beamline at PETRA III

    NASA Astrophysics Data System (ADS)

    Wessels, P.; Ewald, J.; Wieland, M.; Nisius, T.; Abbati, G.; Baumbach, S.; Overbuschmann, J.; Vogel, A.; Neumann, A.; Viefhaus, J.; Oepen, H. P.; Meier, G.; Wilhein, T.; Drescher, M.

    2014-04-01

    We present first time-resolved measurements of a new mobile full-field transmission microscope [1] obtained at the soft X-ray beamline P04 at the high brilliance synchrotron radiation source PETRA III. A nanostructured magnetic permalloy (Ni80Fe20) sample can be excited by the magnetic field of a 400 ps full width at half maximum (FWHM) long electric current pulse in a coplanar waveguide. The full-field soft X-ray microscope successively probes the time evolution of the sample magnetization via X-ray magnetic circular dichroism (XMCD) [2] spectromicroscopy in a pump-probe scheme by varying the delay between pump and probe pulses electronically. Static and transient magnetic fields of a permanent magnet and a coil are available in the sample plane to reset the system and to provide external offset fields. The microscope generates a flat-top illumination field of 20 μm diameter by using a grating condenser [3] and the sample plane is directly imaged by a micro zone plate with 60 nm resolution onto a 2D gateable X-ray detector to select the particular bunch in the storage ring that contains the dynamic information. The setup is built into a mobile endstation vacuum system with in-house developed three-axis piezo motorized stages for high accuracy positioning of all microscopy-components inside the chambers.

  17. Study of magnetic field effects for accretions with highly magnetized neutron stars in low mass X-ray binaries

    NASA Astrophysics Data System (ADS)

    Sasano, Makoto; Enoto, Teruaki; Makishima, Kazuo; Sakurai, Soki

    Neutron stars (NSs) in high-mass X-ray binaries (HMXBs), namely those with massive privary stars, generally have strong magnetic fields (˜10 (12) G). In contrast, those in typical low mass binary systems (LMXBs) are weakly magnetized (˜10 (9-10) G). This clear difference in the magnetic field strength is considered to be primarily responsible for the systematic differences in X-ray properties between NSs in HMXBs and those in LMXBs. However, these can also be possible contributions from their accretion-scheme differences, i.e., wind capture in HMXBs and disk accretion in LMXBs. To separate these two effects, we may utilize a few highly-magnetized NSs in LMXBs, including Her X-1, GX 1+4, 4U 1626-67, and a recently recognized object 4U 1822-37 (Sasano et al. PASJ in press, arXiv:1311.4618). In this study, we compare spectral and timing properties of these exceptional strong-field NSs, with those of more typical objects in LMXBs an HMXBs. Their properties that are common with typical HMXBs can be regarded as a signature of strong magnetic fields while those shared by typical LMXBs can be attributed to the disk-fed accretion geometry.

  18. A new bend magnet beam line for scanning transmission x-ray microscopy at the Advanced Light Source

    SciTech Connect

    Warwick, Tony; Ade, Harald; Kilcoyne, A.L. David; Kritscher, Michael; Tylisczcak, Tolek; Fakra, Sirine; Hitchcock, Adam P.; Hitchcock, Peter; Padmore, Howard A.

    2001-12-12

    The high brightness of the bend magnets at the Advanced Light Source has been exploited to illuminate a Scanning Transmission X-ray Microscope (STXM). This is the first diffraction-limited scanning x-ray microscope to operate with useful count rate on a synchrotron bend magnet source. A simple, dedicated beam line has been built covering the range of photon energy from 250 eV to 600 eV. Ease of use and operational availability are radically improved compared to previous installations using undulator beams. This facility provides radiation for C 1s, N 1s and O 1s near edge x-ray absorption spectro-microscopy with a spectral resolution up to about 1:5000 and with STXM count rates in excess of 1 MHz.

  19. Burn out or fade away? On the X-ray and magnetic death of intermediate mass stars

    SciTech Connect

    Drake, Jeremy J.; Kashyap, Vinay; Günther, H. Moritz; Wright, Nicholas J.; Braithwaite, Jonathan

    2014-05-10

    The nature of the mechanisms apparently driving X-rays from intermediate mass stars lacking strong convection zones or massive winds remains poorly understood, and the possible role of hidden, lower mass close companions is still unclear. A 20 ks Chandra HRC-I observation of HR 4796A, an 8 Myr old main sequence A0 star devoid of close stellar companions, has been used to search for a signature or remnant of magnetic activity from the Herbig Ae phase. X-rays were not detected and the X-ray luminosity upper limit was L{sub X} ≤ 1.3 × 10{sup 27} erg s{sup –1}. The result is discussed in the context of various scenarios for generating magnetic activity, including rotational shear and subsurface convection. A dynamo driven by natal differential rotation is unlikely to produce observable X rays, chiefly because of the difficulty in getting the dissipated energy up to the surface of the star. A subsurface convection layer produced by the ionization of helium could host a dynamo that should be effective throughout the main sequence but can only produce X-ray luminosities of the order 10{sup 25} erg s{sup –1}. This luminosity lies only moderately below the current detection limit for Vega. Our study supports the idea that X-ray production in Herbig Ae/Be stars is linked largely to the accretion process rather than the properties of the underlying star, and that early A stars generally decline in X-ray luminosity at least 100,000 fold in only a few million years.

  20. Magnetically Assisted Remote-controlled Endovascular Catheter for Interventional MR Imaging: In Vitro Navigation at 1.5 T versus X-ray Fluoroscopy

    PubMed Central

    Losey, Aaron D.; Lillaney, Prasheel; Martin, Alastair J.; Cooke, Daniel L.; Wilson, Mark W.; Thorne, Bradford R. H.; Sincic, Ryan S.; Arenson, Ronald L.; Saeed, Maythem

    2014-01-01

    Purpose To compare in vitro navigation of a magnetically assisted remote-controlled (MARC) catheter under real-time magnetic resonance (MR) imaging with manual navigation under MR imaging and standard x-ray guidance in endovascular catheterization procedures in an abdominal aortic phantom. Materials and Methods The 2-mm-diameter custom clinical-grade microcatheter prototype with a solenoid coil at the distal tip was deflected with a foot pedal actuator used to deliver 300 mA of positive or negative current. Investigators navigated the catheter into branch vessels in a custom cryogel abdominal aortic phantom. This was repeated under MR imaging guidance without magnetic assistance and under conventional x-ray fluoroscopy. MR experiments were performed at 1.5 T by using a balanced steady-state free precession sequence. The mean procedure times and percentage success data were determined and analyzed with a linear mixed-effects regression analysis. Results The catheter was clearly visible under real-time MR imaging. One hundred ninety-two (80%) of 240 turns were successfully completed with magnetically assisted guidance versus 144 (60%) of 240 turns with nonassisted guidance (P < .001) and 119 (74%) of 160 turns with standard x-ray guidance (P = .028). Overall mean procedure time was shorter with magnetically assisted than with nonassisted guidance under MR imaging (37 seconds ± 6 [standard error of the mean] vs 55 seconds ± 3, P < .001), and time was comparable between magnetically assisted and standard x-ray guidance (37 seconds ± 6 vs 44 seconds ± 3, P = .045). When stratified by angle of branch vessel, magnetic assistance was faster than nonassisted MR guidance at turns of 45°, 60°, and 75°. Conclusion In this study, a MARC catheter for endovascular navigation under real-time MR imaging guidance was developed and tested. For catheterization of branch vessels arising at large angles, magnetically assisted catheterization was faster than manual catheterization