9 research outputs found
A New Iron Pnictide Oxide (Fe2As2)(Ca5(Mg,Ti)4Oy) and a New Phase in Fe-As-Ca-Mg-Ti-O system
A new layered iron arsenide oxide (Fe2As2)(Ca5(Mg,Ti)4Oy) and its structural
derivative were found in the Fe-As-Ca-Mg-Ti-O system. The crystal structure of
(Fe2As2)(Ca5(Mg,Ti)4Oy) is identical to that of (Fe2As2)(Ca5(Sc,Ti)4Oy), which
was reported in our previous study. The lattice constants of this compound are
a = 3.86(4) A and c = 41.05(2) A. In addition, another phase with a thicker
blocking layer was found. The structure of the compound and its derivative was
tentatively assigned through STEM observation as (Fe2As2)(Ca8(Mg,Ti)6Oy) with
sextuple perovskite-type sheets divided by a rock salt layer. The interlayer
Fe-Fe distance of this compound is ~30 A. The compound and its derivative
exhibited bulk superconductivity, as found from magnetization and resistivity
measurements.Comment: 9 pages, 7 figure
Fermi surfaces and quasi-particle band dispersions of the iron pnictides superconductor KFe2As2 observed by angle-resolved photoemission spectroscopy
We have performed an angle-resolved photoemission study of the iron pnictide
superconductor KFe2As2 with Tc 4 K. Most of the observed Fermi surfaces show
almost two-dimensional shapes, while one of the quasi-particle bands near the
Fermi level has a strong dispersion along the kz direction, consistent with the
result of a band-structure calculation. However, hole Fermi surfaces \alpha and
\zeta are smaller than those predicted by the calculation while other Fermi
surfaces are larger. These observations are consistent with the result of a de
Haas-van Alphen study and a theoretical prediction on inter-band scattering,
possibly indicating many body effects on the electronic structure.Comment: 4 pages, 5 figures. Proceeding of the 9th International Conference on
Spectroscopies in Novel Superconductors (SNS2010
Room Temperature Electrochemical Synthesis of Hg-1212 Superconducting Thin Films
In the present investigation, the novel two-step electrochemical process of
room temperature synthesis of Hg-1212 superconducting films has been developed
and reported first time. Electrochemical parameters were optimized by studying
cyclic voltammetry (CV), linear sweep voltammetry (LSV) and chronoamperometry
(CA) for the deposition of Hg-Ba-Ca-Cu alloy at room temperature. Current time
transient showed progressive growth with hemispheriodal granules, which were
then revealed by scanning electron microscopy (SEM). Stoichiometric
electrocrystallization to get Hg1Ba2Ca1Cu2O6+x (Hg-1212) was completed by
electrochemically intercalating oxygen species into Hg-Ba-Ca-Cu alloy at room
temperature. The oxygen content in the samples was varied by varying the
electrochemical oxidation period and the changes in the crystal structure,
microstructure, and superconducting transition temperature (Tc) and critical
current density (Jc) were recorded. The films oxidized for 28 min showed Tc =
104.7 K with Jc = 1.437 x 103 A/cm2. The dependence of superconducting
parameters on oxygen content is correlated with structure property relations
and reported in this paper.Comment: 39 pages, 17 figures. Submitted to Physica