A new LaCo0.71(1)V0.29(1)O2.97(3) perovskite containing vanadium in octahedral sites: synthesis and structural and magnetic characterization.

In the course of an investigation to prepare the hypothetic new double perovskite La(3)Co(2)VO(9) with Co(2+) and V(5+) in octahedral sites, we obtained the new simple perovskite LaCo(0.71(1))V(0.29(1))O(2.97(3)) as the main phase. The pure compound was then synthesized by the citrate decomposition method. The crystal structure was studied by X-ray (PXRD) and powder neutron diffraction (PND). Physical properties were characterized by X-ray absorption spectroscopy (XAS), X-ray emission spectroscopy (XES) and thermogravimetric analysis (TGA). Rietveld refinements were performed in the orthorhombic space group Pnma (#62). Refined cell parameters were a = 5.4762(2) Å, b = 7.7609(2) Å and c = 5.5122(1) Å. Magnetization measurements showed that this perovskite is an antiferromagnet with a Neel temperature of 15 K. At high T the magnetization follows the Curie-Weiss law corrected by temperature independent paramagnetism (TIP) showing an effective magnetic moment of 3.03µ(B) well described by the contribution of Co(2+) (HS), Co(3+) (IS), V(3+) and V(4+) ions. The crystallographic formula was refined by PND and oxidation state distribution was determined by the combination of PND, XAS, TGA and magnetic measurements.

Diffraction-enhanced imaging microradiography applied in breast samples.

The diffraction-enhanced imaging (DEI) is a powerful tool to observe tumors and other diseases in breast tissue and provide more precise diagnostics. In this work DEI was used to analyze breast tissues details that have poor attenuation contrast. An X-ray imaging system with DEI techniques was developed using synchrotron radiation. The DEI experiment was performed in D10A-XRD2 beamline at the Brazilian Synchrotron--LNLS. The pre-monochromator, upstream of the beamline was adjusted to 10.7 keV. The samples were positioned between two channel-cut Si(333) in non-dispersive geometry mounted in a double axes diffractometer. A direct conversion water-cooled CCD camera of 1242 pixel x 1152 pixel of 25 microm x 25 microm each was used as a two-dimensional detector in scanning mode. The DEI system could show details in low attenuation tissues based on the contrast imaging obtained by attenuation, refraction gradient and ultra-small angle scatter characteristics. In this work the capacity to observe different types of structures and details in breast tissues were investigated.

An inelastic X-ray scattering spectrometer at LNLS.

A high-resolution spectrometer aimed at performing experiments of inelastic X-ray scattering by electronic excitations is described. The spectrometer has been installed at the D12A-XRD1 beamline of the National Synchrotron Light Laboratory (LNLS), in Campinas, Brazil. Synchrotron radiation is monochromated to about 6 keV and focused horizontally onto the sample by a sagittally focusing Si(111) double-crystal monochromator in non-dispersive setting. The spectrometer operates in Rowland circle geometry and is based on a focusing Si(333) analyser in near-backdiffraction geometry for energy analysis of inelastically scattered photons. The analyser works at a fixed Bragg angle, so energy transfers are obtained by varying the incident photon energy. A relative energy resolution of the whole spectrometer of approximately 1.5 x 10(-4) at 5.93 keV has been achieved. As an example of application, inelastic X-ray scattering by plasmon excitation in polycrystalline Be was measured. Test results demonstrate that inelastic X-ray scattering experiments with eV energy resolution and an acceptable counting rate are feasible at the LNLS when focused on plasmon and particle-hole excitations.