Superconducting state parameters, pinning centres and their effectiveness for Y1-xPrxBa2Cu3O7-δ single crystals with low Pr contents

Magnetic measurements on optimally doped and overdoped Y1-xPrxBa2Cu3O7-δ single crystals, with x varying from 0 to 0.024, were made over a wide temperature range up to 0.99Tc. We concentrate on the effect of inhomogeneity introduced by both the Pr substitution and the oxygen deficiency on the intrinsic and extrinsic properties of Y1-xPrxBa2Cu3O7-δ. The superconducting state parameters were determined and the vortex pinning behaviour was analysed using a rigorous treatment for the magnetization behaviour, which includes explicit expressions for the equilibrium B(H), based on the Ginzburg-Landau theory, and for the critical current density, Jc(B). The results obtained for Pr-substituted crystals show a higher characteristic temperature for flux flow activation than for pure YBa2Cu3O7-δ. The extent to which the oxygen content in overdoped YBa2Cu3O7-δ leads to an increase of both the superconducting carrier density, ns, and the thermodynamic critical field, Hc, and shifts the irreversibility line to higher fields was investigated. Simultaneously, a decrease of the critical current density was observed at intermediate magnetic field. This effect is found to be overcompensated by Pr substitution at the Y position in almost fully oxygenated YBa2Cu3O7-δ, since Pr substitution at the Y site introduces effective pinning centres, leading to an increase of the critical current density.