Crystal Research and Technology
Cryst. Res. Technol. 39, 926 (2004) - Abstract -

Growth, structure, and superconducting properties of Bi2Sr2Ca2Cu3O10 and (Bi,Pb)2Sr2Ca2Cu3O10-y crystals

E. Giannini, V. Garnier, N. Clayton, N. Musolino, R. Gladyshevskii*, and R. Flükiger

DPMC, University of Geneva, 24, quai E.-Ansermet, CH-1211 Geneva 4, Switzerland
*Dept. Inorg. Chem., Ivan Franko National University of L'viv, Kyryla i Metodiya str. 6, UA 79005 L'viv, Ukraine

Keywords crystal growth, Bi-2223, high Tc superconductivity
PACS 74.72.H, 81.10.Fq
DOI 10.1002/crat.200410278

Large and high-quality single crystals of both Pb-free and Pb-doped high temperature superconducting compounds (Bi1-xPbx)2Sr2Ca2Cu3O10-y (x = 0 and 0.3) were grown by means of a newly developed "Vapour-Assisted Travelling Floating Zone" technique (VA-TSFZ). This modified zone-melting technique was realised in an image furnace and allowed for the first time to grow Pb-doped crystals by compensating for the Pb losses occurring at high temperature. Crystals up to 3x2x0.1 mm3 were successfully grown. Post-annealing under high pressure of O2 (up to 10 MPa at T = 500°C) was undertaken to enhance Tc and improve the homogeneity of the crystals. Structural characterisation was performed by single-crystal X-ray diffraction (XRD) and the structure of the 3-layer Bi-based superconducting compound was refined for the first time. Structure refinement showed an incommensurate superlattice in the Pb-free crystals. The space group is orthorhombic, A2aa, with cell parameters a = 27.105(4) Å, b = 5.4133(6) Å and c = 37.009(7) Å. Superconducting studies were carried out by A.C. and D.C. magnetic measurements. Very sharp superconducting transitions were obtained in both kinds of crystals (Δ Tc <= 1 K). In optimally doped Pb-free crystals, critical temperatures up to 111 K were measured. Magnetic critical current densities of 2x105 A/cm2 were measured at T = 30 K and μ0H = 0 T. A weak second peak in the magnetisation loops was observed in the temperature range 40-50 K above which the vortex lattice becomes entangled. We have measured a portion of the irreversibility line (0.1-5 Tesla) and fitted the expression for the melting of a vortex glass in a 2D fluctuation regime to the experimental data. Measurements of the lower critical field allowed to obtain the dependence of the penetration depth on temperature: the linear dependence of λ(T) for T < 30 K is consistent with d wave superconductivity in Bi-2223.




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