High Critical Current Density in the Heavily Pb-Doped Bi2Sr2CaCu2O6+d Superconductor: Generation of Novel Pinning Centers (SOLID STATE CHEMISTRY-Multicomponent Materials)

Critical current density (Jc) is a parameter of primary importance for potential applications of high temperature copper oxide superconductors (HTSCs). It is principally limited by the breakdown of zeroresistive current due to thermally activated flux flow at high temperatures and high magnetic fields. Here we report a dramatic increase in Jc in Bi2Sr2CaCu2O6+d (Bi-2212) single crystals doped with a large amount of Pb

Single Crystal Growth at High Pressure (SOLID STATE CHEMISTRY-Multicomponent Materials)

Single crystals of a spin-1/2 Heisenberg alternating chain compound, high pressure phase of (VO)2P2O7 , was grown by slowly cooling the melt at 3 GPa. Powder XRD study at high pressure using synchrotron radiation was performed in advance to observe the formation and the melting of this compound

Magnetically Superior and Easy to Handle L10-FePt Nanocrystals

We report a successful synthesis of monodisperse L10-FePt nanocrystals which are not only superior in magnetism but also easy to handle through being dispersible in solvents. Thanks to a thick SiO2-coating, the thermal treatment needed to form the L10 structure can be done even at 900 oC without inducing coalescence and coarsening. The protecting shell was thereafter removed in a specific way that enabled us to recover the L10-FePt nanocrystals in a water-dispersion. The SiO2-coated nanocrystals show a high coercivity of 18.5 kOe at room temperature in spite of their core size of only 6.5 nm in diameter, and the hysteresis loop of the water-dispersed nanocrystals, which were frozen under an external field, was almost rectangular indicating that their magnetic and structural orientation could be attained.Comment: 14 pages, 5 figure

4-Nitro-6-[(8-quinolyl­amino)­methyl­idene]cyclo­hexa-2,4-dien-1-one

The mol­ecule of the title compound, C16H11N3O3, exists in the keto form and the C=O and N—H bonds are mutually cis in the crystal structure. There are two crystallographically independent mol­ecules per asymmetric unit with broadly similar structural data. The only noticeable difference between the two is the dihedral angles between the benzene and the quinoline rings: 1.04 (4) and 3.07 (4)°. In the structure, intra­molecular N—H⋯O(carbon­yl) and N—H⋯N(pyridine) hydrogen bonds exist but there is no evidence of formal inter­molecular hydrogen-bonding associations

Phonon anomalies and lattice dynamics in superconducting oxychlorides Ca2−x_{2-x}CuO2_2Cl

We present a comprehensive study of the phonon dispersion in an underdoped, superconducting Ca$_{2-x}$CuO$_2$Cl$_2$ crystal. We interpret the results using lattice dynamical calculations based on a shell model, and we compare the results, to other hole-doped cuprates, in particular to the ones isomorphic to La$_{2-x}$Sr$_x$CuO$_4$ (LSCO). We found that an anomalous dip in the Cu-O bond stretching dispersion develops in oxychlorides with a simultaneous marked broadening of the mode. The broadening is maximum at $\approx (\pi / (2a) ~ 0 ~ 0)$ that corresponds to the charge-modulations propagation vector. Our analysis also suggests that screening effects in calculations may cause an apparent cosine-shaped bending of the Cu-O bond-stretching dispersion along both the ($q$ 0 0) and ($q$ $q$ 0) directions, that is not observed on the data close to optimal doping. This observation suggests that the discrepancy between experimental data and \textit{ab-initio} calculations on this mode originates from an overestimation of the doping effects on the mode

Understanding the Unique Structural and Electronic Properties of SrFeO2

We report a first-principles study of SrFeO$_2$, an infinite-layer oxide with Fe atoms in a perfect square-planar coordination down to essentially 0 K. Our results reveal this striking behavior relies on the double occupation of the 3$d_{z^2}$ orbitals of high-spin Fe$^{2+}$. Such an electronic state results from the hybridization of iron's 3$d_{z^2}$ and 4$s$ orbitals, which enables a large reduction of the intra-atomic exchange splitting of the $z^2$ electrons. The generality of the phenomenon is discussed.Comment: 4 pages with 3 figures embedded. More information at http://www.icmab.es/dmmis/leem/jorg