Peak effect of a La0.9Pr0.1Ba2Cu2.62Al0.38O7-y single crystal

Superconductivity and an anomalous magnetization peak of a heavily overdoped La0.9Pr0.1Ba2Cu2.62Al0.38O7-y single crystal grown by the self-flux method are investigated by means of magnetization measurements with the magnetic field parallel to the c-axis. The lower critical field Hc1(T) and irreversibility line Hirr(T) have been carefully measured. Both the second magnetization peak H2p(T) and onset field Hon exhibit strong and meaningful temperature dependence in a wide temperature range from 10 K to 35 K (0.25Tc-0.85Tc). The theoretical fitting of the temperature variation indicates that Hon(T) is related to the melting of the flux line lattice, which suggests the similarity of the mechanisms underlying both the fishtail and peak effect. H2p(T) seems to be related to the thermal-disorder-induced vortex pancake decoupling transition. (author)