[en] An exchange-biased Co/NiO bilayer was studied by measuring element specific hysteresis loops. A phase-sensitive detection scheme based on fast switching of the polarization of the X-rays was developed for this measurement. Uncompensated Ni²⁺ spins at the Co/NiO interface were observed for the first time. In addition, part of the Ni²⁺ spins were found to switch with the Co layer

[en] The use of inline insertion devices at third-generation synchrotron radiation sources can result in destructive interference effects if the relative phase between the devices is not properly adjusted. The destructive interference can strongly affect the emission spectrum and coherent wavefront of a compound insertion device. We simulate the photon source generated by a dual-inline elliptically polarizing undulator (EPU) situated in a low-β straight section of the planned NSLS-II storage ring and show that a magnetic chicane with adjustable field integral can be used to phase-match the devices. Furthermore, we show that the maximum coherent intensity is delivered by a focusing x-ray beamline if the chicane is adjusted to phase-match the off-axis and red-shifted radiation. Such a system will be installed at the coherent soft x-ray (CSX) beamline of the NSLS-II in order to provide the highest possible coherent flux for coherent soft x-ray scattering experiments.

[en] The coherent soft x-ray and full polarization control (CSX) beamline at the National Synchrotron Light Source - II (NSLS-II) will deliver 1013 coherent photons per second in the energy range of 0.2-2 keV with a resolving power of 2000. The source, a dual elliptically polarizing undulator (EPU), and beamline optics should be optimized to deliver the highest possible coherent flux in a 10-30 (micro)m spot for use in coherent scattering experiments. Using the computer code Synchrotron Radiation Workshop (SRW), we simulate the photon source and focusing optics in order to investigate the conditions which provide the highest usable coherent intensity on the sample. In particular, we find that an intermediate phasing magnet is needed to correct for the relative phase between the two EPUs and that the optimum phase setting produces a spectrum in which the desired wavelength is slightly red-shifted thus requiring a larger aperture than originally anticipated. This setting is distinct from that which produces an on-axis spectrum similar to a single long undulator. Furthermore, partial coherence calculations, utilizing a multiple electron approach, indicate that a high degree of spatial coherence is still obtained at the sample location when such an aperture is used. The aperture size which maximizes the signal-to-noise ratio of a double-slit experiment is explored. This combination of high coherence and intensity is ideally suited for x-ray ptychography experiments which reconstruct the scattering density from micro-diffraction patterns. This technique is briefly reviewed and the effects on the image quality of proximity to the beamline focus are explored.

No abstract available

[en] The first XUV beamline (200-2000 eV) at NSLS-II will have two branches, one optimized for photon hungry experiments requiring high coherent flux and one optimized for studies of polarization sensitive materials and interfaces based on fast polarization switching. We describe here the branch designed for fast polarization switching with frequencies up to 1 kHz, high photon flux, and good energy resolution. The beamline will be served by two canted undulators and is based on the focusing variable line spacing grating monochromator. The two beams will be focused at the same spot of approximately 80x10 μm (hor.xver.). The expected circular polarized flux at the sample from each device up to 1.4 keV will be higher than 10¹² photons/s at a resolving power better than 10⁴. An additional KB focusing system will deliver the two beams to a spot in the μm range.

[en] The use of inline insertion devices at third-generation synchrotron radiation sources can result in destructive interference effects if the relative phase between the devices is not properly adjusted. The destructive interference can strongly affect the emission spectrum and coherent wavefront of a compound insertion device. We simulate the photon source generated by a dual-inline elliptically polarizing undulator (EPU) situated in a low-β straight section of the planned NSLS-II storage ring and show that a magnetic chicane with adjustable field integral can be used to phase-match the devices. Furthermore, we show that the maximum coherent intensity is delivered by a focusing x-ray beamline if the chicane is adjusted to phase-match the off-axis and red-shifted radiation. Such a system will be installed at the coherent soft x-ray (CSX) beamline of the NSLS-II in order to provide the highest possible coherent flux for coherent soft x-ray scattering experiments.

[en] We present a multitechnique approach to study the detailed chemical and magnetic structure of uranium/gadolinium multilayers. At low temperature the saturation magnetization is found to be ∼60% of that of bulk gadolinium. We address this problem, which is found in many other multilayers and suggest a model that may have wider applications. Transmission electron microscopy images indicate a microstructure, consistent with a columnar growth of Gd with crystallites of the order 20 → 100(angstrom). Off-specular neutron scattering is most strongly visible at saturation field, indicating that Gd moments are not aligned with the applied field. X-ray resonant magnetic scattering provides proof of coupled in-plane length scales for both the structural and the magnetic roughness. A detailed x-ray scattering study of both the specular and off-specular reflectivities has been used to investigate the in-plane structure of the multilayers. We calculate the roughness and transverse correlation cut-off length, ζ_x = 120 ± 30(angstrom), and present a simple model to determine an average column size of 27 ± 6(angstrom) and a reduction in the magnetic saturation of ∼40%.

[en] We report the development of a novel experimental chamber for experiments in soft x-ray diffraction tomography, diffraction imaging of single biological objects, and magnetic speckle imaging. The chamber will allow for acquisition of nearly full three-dimensional diffraction data sets as well as high magnification zone plate images of holograms for the diffraction tomography experiment. (authors)

[en] A mutual ferromagnetic and ferroelectric coupling (multiferroic behavior) in Cu-doped ZnO is demonstrated via deterministic control of Cu doping and defect engineering. The coexistence of multivalence Cu ions and oxygen vacancies is important to multiferroic behaviors in ZnO:Cu. The samples show clear ferroelectric and ferromagnetic domain patterns. These domain structures may be written reversibly via electric and magnetic bias.

No abstract available