Superconductivity in YBa₂Cu₃O₇ single crystals

Abstract

Increased understanding of fundamental properties of the new cuprate superconductors depends on advances in the preparation of quality materials for study. Early work focused on the study of sintered polycrystalline samples. In some cases, grain growth during sintering yielded individual grains large enough (˜80 μm) for single crystal X-ray determination¹. Larger single crystals allow measurements of physical properties including measurements of anisotropic behaviour. The anisotropy of upper critical fields in YBa₂Cu₃O₇ single crystals has been reported by lye et al.² who found critical fields characteristic of a quasi-two-dimensional superconductor, which are highest when the field is orientated perpendicular to the c-axis. Dinger et al.³ have measured critical fields and critical currents of single crystals and find anisotropies of 10 and greater³. These studies contain little detail on the crystal growth of YBa₂Cu₃O₇. Here we report the growth of single crystals as large as 4 mm of YBa₂Cu₃O₇ and DyBa₂Cu₃O₇ and confirm superconductivity in them by magnetic and electrical measurements. Single crystals of other rare earth barium cuprates are also obtained although we have yet to optimize growth conditions for these phases.