Superconductivity Transition and Crystal Structure of the High-Tc and High-Hc2 Superconductor DyBa2Cu3O7-δ

Superconductivity transitions of DyBa₂Cu₃O_7-δ in the magnetic field up to 9 T are described together with the crystal structure analysis of the same samples by X-ray powder diffraction combined with Rietveld analysis. A very sharp transition at 93 K with the transition width of 1.2 K in zero magnetic field is observed and the width is still small even in the magnetic field. The upper critical field H_c2 near T_c is very large; the offset field H_c2^off defined at 1% points is 10 T even at 80 K and the slope (-dH_c2/dT) for midpoint is 5.5 T/K. According to the structure analysis, single phase with orthorhombic structure is responsible for the high-T_c and high-H_c2 superconductivity in DyBa₂Cu₃O_7-δ as in YBa₂Cu₃O_7-δ and RBa₂Cu₃O_7-δ (R=Ho or Er).