DIMENSIONAL CROSSOVER AND PEAK EFFECT IN A SUPERCONDUCTING PR1.85CE0.15CUO4-Y SINGLE-CRYSTAL

Magnetic measurements were performed on a Pr1.85Ce0.15CuO4-y single cr ystal with T-c approximate to 22.5 K in magnetic fields H applied para llel to the tetragonal c-axis (H parallel to c). An anomaly in the mag netic hysteresis loop that is reminiscent of a peak effect is observed . The anomaly occurs at a nearly temperature independent crossover fie ld N-cr = 230 Oe in the reduced temperature t = T/T-c region 0.75 less than or equal to t less than or equal to 0.9 and completely disappear s for t less than or equal to 0.75. The irreversibility line follows a power law of the form H-i pi(T)alpha(1-t)(2) in the regime 0.1 less t han or equal to t less than or equal to 0.9. The lower critical magnet ic field H-cl,H-c(T) was estimated from the first penetration of flux at the border between the Meissner state and the mixed state. A quanti tative low temperature magnetic phase diagram based upon these measure ments is presented.