Magnetic dimensional crossover in pr-doped single crystal Bi_2Sr_2Ca_(0.89)Pr_(0.11)Cu_2O_(8+#delta#)

摘要

Magnetic hysteresis measurements on Pr-doped single crystal Bi_2Sr_2Ca_(0.89)Pr_(0.11)Cu_2O_(8+#delta#) 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 fieldapplied 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_2Sr_2CaCu_2O_(8+#delta#) imply that the Josephson coupling between the two superconducting regions of adjacent CuO_2 bi-layers can be reduced by the presence of Pr.