T. Masui

Growth, Structure Analysis and Anisotropic Superconducting Properties of MgB2 Single Crystals

Here we report the growth of sub-millimeter MgB 2 single crystals of various shapes under high pressure in Mg–B–N system. Structure refinement using a single-crystal X-ray diffraction analysis gives lattice parameters a =3.0851(5) A and c =3.5201(5) A with small reliability factors ( R w =0.025, R =0.018), which enables us to analyze the Fourier and Fourier difference maps. The maps clearly show the B sp 2 orbitals and covalency of the B–B bonds. The sharp superconducting transitions at T c =38.1–38.3 K were obtained in both magnetization (Δ T c =0.6 K) and resistivity (Δ T c <0.3 K) measurements. Resistivity measurements with magnetic fields applied parallel and perpendicular to the Mg and B sheets reveal the anisotropic nature of this compound, with upper critical field anisotropy ratio of about 2.7.

Carbon-substitution effect on the electronic properties ofMgB2single crystals

The electronic properties of the carbon substituted MgB

High-pressure synthesis of superconducting Nb1−xB2 (x=0–0.48) with the maximum Tc=9.2 K

_2

Multiple Gap Symmetries for the Order Parameter of Cuprate Superconductors from Penetration Depth Measurements

single crystals are reported. The carbon substitution drops T

Dispersion of magnetic excitations in optimally doped superconducting YBa2Cu3O6.95

_c

Oxygen phonon branches in YBa2Cu3O7

below 2 K. In-plane resistivity shows a remarkable increase in residual resistivity by C-substitution, while the change of in-plane/out-of-plane Hall coefficients is rather small. Raman scattering spectra indicate that the E

Enhancement of Irreversibility Field in Carbon-substituted MgB2 Single Crystals

_{2g}

Crystal growth and characterization of MgB2: the relation between structural and superconducting properties

-phonon frequency radically hardens with increasing the carbon-content, suggesting the weakening of electron-phonon coupling. Another striking C-effect is the increases of the second critical fields in both in-plane and out-of-plane directions, accompanied by a reduction in the anisotropy ratio. The possible changes in the electronic state and the origin of T

Persistence of the superconducting condensate far above the critical temperature of YBa2(Cu,Zn)3O(y) revealed by c-axis optical conductivity measurements for several Zn concentrations and carrier doping levels.

_c

Mott gap excitations in twin-free YBa2Cu3O7-delta (Tc=93 K) studied by resonant inelastic x-ray scattering.

-suppression by C-substitution are discussed.