Abstract
Magnetic hysteresis measurements on Pr-doped single crystal Bi 2 Sr 2 Ca 0.89 Pr 0.11 Cu 2 O 8+δ show a dimensional crossover from the three-dimensional (3D) vortex glass to the two-dimensional (2D) pancake of vortices. The observed crossover field H 2D for field applied parallel to the c-axis decreases from 6 kG at 5 K to 410 G at 25 K and 120 G at 45 K. The substitution of 11% of magnetic Pr 3- ions for Ca 2- ions effectively decreases the hole concentration on the CuO 2 bi-layers but pushes the superconducting state from the overdoped region to the optimum composition with a superconducting transition temperature T c . of 88 K. The lower crossover field H 2D values of the Pr-doped sample as compared with the undoped Bi 2 Sr 2 CaCu 2 O 8+δ imply that the Josephson coupling between the two superconducting regions of adjacent CuO 2 bi-layers can be reduced by the presence of Pr. © 1999 Elsevier Science B.V. All rights reserved.