Phases found at grain boundary of YBa2Cu3O7-d 50 nm films on SrTiO3 by enhanced anomalous scattering at O:K, Cu:L2,3 and Ba:M4,5 edges

A new phase is detected within 100micrometers of 24 DEG ab grain boundary (GB) in YBa2Cu3O7-d 50 nm films on SrTiO3 by enhanced (001) anomalous scattering. Site identification and temperature dependence is interpreted using crystallographic weights to distinguish enhanced scattering from total electron yield and fluorescence spectra. The c-axis, c0 indicates that only ortho-I phase is present far from GB, both ortho-I and II phases are present near GB. The phase c0 is constant versus temperature across the transition to superconductivity.Comment: 3 pages and 5 figur

NMR measurements on intercalated 3R-TaS2.Ix (I=NH3 and N2H4)

Proton nuclear magnetic resonance was used to probe the environment of the intercalant molecule in low dimensional (aeolotropic) solids 3RI-TaS2(NH3)2/3 and 3RII-TaS2(N2H4)4/3, and, specifically to look for phase transitions associated with changes in superlattice geometry. The proton resonance frequency for the intercalated molecules in the temperature interval 200 to 300K indicates that there are different magnetic environments in three temperature domains. (i) There is only one resonance field for molecules in isotropic magnetic environments. (ii) The high- and low-temperature domains (I and III) have molecules in only two different environments, whereas in the middle temperature domain (II) there are at least four different magnetic environments. (iii) The different magnetic environments measured by the ratio of anisotropic to isotropic resonance absorption intensity (rai) indicate that the ratios rai are constants of the sample in domains I and II. (iv) At low temperatures (domain III), rai depends on magnetic field polarisation effects and the temperature treatment of the sample. The authors conclude that the different magnetic environments observed for ammonia and hydrazine appear to be determined by the host, octahedrally coordinate TaS2

Enhanced anomalous scattering by superconducting nanofilms vs T at O:K, Cu:L2,3, Ba:M4,5

Enhanced (001) anomalous scattering by YBa2Cu3O7-d 50 nm films on SrTiO3 substrates with and without a grain boundary versus temperature is interpreted using crystallographic weights to distinguish it from total electron yield and fluorescence spectra. The power of diffraction enhancement is to ascertain the film oxygen composition from the changes in the c-axis, c0 as the film surface is scanned across the grain boundary, and to determine that c0 is constant versus temperature across the superconducting phase transition.Comment: 4 pages, 6 figure

Investigation of the anisotropy of dissipation processes in single crystal of Yba2Cu3O7-d system

By means of contactless mechanical method of the measurement of energy losses in superconductors, the anisotropy of dissipation processes has been studied in single crystal high-temperature layered superconductors of Yba2Cu3O7-d system, being in mixed state. The observed anisotropy of energy losses indicates the possibility of the existence of the symmetry of order parameter of dx2-y2 type in these single crystals.Comment: 4 pages, 3 figure

Measurement of Synchrotron x-ray energies and line shapes using diffraction markers

Standard reference markers for accurate, reproducible synchrotron x-ray energies are obtained using a three Si crystal spectrometer. The first two crystals are in the monochromator and the third is used to obtain diffraction markers which monitor the energy. Then for any value of the glancing angle on the reference Si crystal the energy for the (333) diffraction must occur at 3/4 that of the (444) and 3/5 of that for the (555). This establishes for the first time an absolute synchrotron energy scale. Higher-order diffractions are used to determine excitation line profiles. We conclude that the use of reference diffractions is necessary to measure reproducible x-ray energies and to analyze the incident photons\u27 line profile. The detection of diffractions near the edge of measurement and near the Cu edge will provide a fast secondary standard which will allow comparison of edge data between different laboratories. The diffraction profiles will allow the proper analysis of spectral line widths

Properties of Intercalated 2H-NbSe2, 4Hb-TaS2 and 1T-TaS2

The layered compounds 2H-NbSe, 24Hb-TaS, 2and 1T-TaS2 have been intercalated with organic molecules; and the resulting crystal structure, heat capacity, conductivity, and superconductivity have been studied. The coordination in the disulfide layers was found to be unchanged in the product phase. Resistance minima appear and the superconducting transition temperature is reduced in the NbSe2 complex. Conversely, superconductivity is induced in the 4Hb-TaS2 complex. Corresponding evidence of a large change of the density of states, negative for 2H-NbSe2 and positive for 4Hb-TaS2, was also observed upon intercalation. The transport properties of all the intercalation complexes show a pronounced dependence upon the coordination of the transition metal

Temperature dependence investigation of dissipation processes in strongly anisotropic high-temperature superconductors of Bi-Pb-Sr-Ca-Cu-O system synthesized using solar energy

The investigation of temperature dependence of damping and period of vibrations of HTSC superconductive cylinder of Bi-Pb-Sr-Ca-Cu-O system suspended by a thin elastic thread and performing axial-torsional vibrations in a magnetic field at temperatures above the critical one for the main phase Tc=107 K were carried out. It was observed some "chaos" temperature region in the temperature interval 107-138 K, where it is seen separate ripples of dissipation and oscillation frequency. It is assumed that the "chaos" region could point to a possibility of existence of other magnetic and more high-temperature phases as single islands in a normal materials matrix.Comment: 10 pages, 0 figure