Improved flux pinning and anomalous magnetization peak in heavily overdoped Bi[sub 2-x]Pb[sub x]Sr[sub 2]CaCu[sub 2-y]Cr[sub y]O[sub 8+δ] single crystals.

Flux pinning and anomalous magnetization peak of heavily overdoped Bi[sub 2-x]Pb[sub x]Sr[sub 2]CaCu[sub 2-y]Cr[sub y]O[sub 8+δ] [Cr-doping (Bi, Pb)-2212] single crystals are investigated by means of magnetization measurements with the magnetic field parallel to the c axis. Compared with undoped Bi[sub 2]Sr[sub 2]CaCu[sub 2]O[sub 8+δ] (Bi-2212) and Pb-doping Bi[sub 2-x]Pb[sub x]Sr[sub 2]CaCu[sub 2]O[sub 8+δ] [(Bi, Pb)-2212] single crystals, the irreversibility line of Cr-doping (Bi, Pb)-2212 single crystals is pronouncedly shifted to high temperatures. The anomalous magnetization peak H[sub 2p] with maximum peak field near 8000 G is observed. The H[sub 2p] exhibits strong temperature dependence from 0.19 to 0.93T[sub c]. The temperature dependence of H[sub 2p] can be explained according to vortex decoupling theory. The improved flux pinning may originate from reduced anisotropy due to Pb doping and a sufficient number of effective pinning centers due to the random Cr substitution on the Cu site. © 2000 American Institute of Physics. [ABSTRACT FROM AUTHOR]