Superconductivity in PrBa 2Cu 3O 7− δ single crystals after high-temperature thermal treatment

Maciej Łuszczek; Wojciech Sadowski; Tomasz Klimczuk; Jan Olchowik; Bronisław Susła; Ryszard Czajka

doi:10.1016/s0921-4534(99)00412-8

Superconductivity in PrBa 2Cu 3O 7− δ single crystals after high-temperature thermal treatment

Abstract

The influence of post-growth treatment, consisting of high-temperature reduction, quench and oxidation, on the structural, electrical and magnetic properties of PrBa2Cu3O7−δ single crystals, obtained in Al2O3 and ZrO2 crucibles by the self-flux method, was examined. We report on the observation of inhomogeneous superconductivity in several Al-doped crystals from the ac magnetic susceptibility and resistivity measurements. Superconducting crystals were characterised by X-ray diffraction technique (XRD), scanning electron microscopy (SEM) and electron probe microanalysis (EPMA). Room-temperature scanning tunnelling microscopy (STM) was used to study the topography and local electric conductivity of the crystal surface after thermal treatment. We attribute the onset of the superconductivity in our samples to the structural changes after high-temperature reduction in argon atmosphere providing the decrease in number of Pr on Ba site defects and enhanced by the existence of Al-rich clusters in the material.