Dimensional crossover and peak effect in a superconducting Pr 1.85Ce 0.15CuO 4- y single crystal

Abstract

Magnetic measurements were performed on a Pr 1.85Ce 0.15CuO 4- y single crystal with T c ≅ 22.5 K in magnetic fields H applied parallel to the tetragonal c-axis ( H‖ c). An anomaly in the magnetic hysteresis loop that is reminiscent of a peak effect is observed. The anomaly occurs at a nearly temperature independent crossover field H cr = 230 Oe in the reduced temperature t = T/ T c region 0.75 ≤ t ≤ 0.9 and completely disappears for t ≤ 0.75. The irreversibility line follows a power law of the form H irr( T) α (1- t) 2 in the regime 0.1 ≤ t ≤ 0.9. The lower critical magnetic field H c1,c( T) was estimated from the first penetration of flux at the border between the Meissner state and the mixed state. A quantitative low temperature magnetic phase diagram based upon these measurements is presented.