Magnetic dimensional crossover in Pr-doped single crystal Bi₂Sr₂Ca_0.89Pr_0.11Cu ₂O_8+δ

Magnetic hysteresis measurements on Pr-doped single crystal Bi₂Sr₂Ca_0.89Pr_0.11Cu ₂O_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 CuO₂ 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 Bi₂Sr₂CaCu₂O_8+δ imply that the Josephson coupling between the two superconducting regions of adjacent CuO₂ bi-layers can be reduced by the presence of Pr.