Abstract
Effects of Pr doping on the superconductivity and CuO 2 interlayer coupling of the Bi2212 system were studied carefully for Bi 2 Sr 2 Ca 1-x Pr x Cu 2 O y (x=0-0.78) single crystals. T c was suppressed gradually upon Pr substitution, which cannot be explained in Abrikosov-Gor'kov pair-breaking theory. Instead, the variations of T c with Pr content, for both as-grown and air-annealed crystals, can be well described by a universal parabolic relation T c /T max =1-82.6(n-0.16) 2 . The carrier concentration n was proved to decrease linearly with x, which confirms that hole filling is the main reason for T c suppression. The superconducting volume faction also decreases with Pr content and is proportional to 1-βx 2 . This behavior was attributed to the loss of local superconductivity and weakening of CuO 2 interlayer coupling due to Pr substitution. The second peak in the magnetization curves of Bi 2 Sr 2 Ca 1-x Pr x Cu 2 O y crystals B sp was found to decrease with Pr content and is described by B sp = φ 0 /(s γ) 2 with anisotropy factor γ= γ 0 /(1-Ax) in terms of the dimensional crossover from three-dimensional (3D) flux lines to 2D pancake vortices. The increase of γ with x further demonstrates the destruction of CuO 2 interlayer coupling by Pr substitution. © 1999 The American Physical Society.