Magnetic studies on the field-driven transition from decoupled to coupled pancake vortex phase in Bi2Sr2CaCu2O8+delta with columnar defects

摘要

The reversible (M-rev) and the irreversible magnetization of Bi2Sr2CaCu2O8+delta single crystals with columnar defects were measured as a function of field and temperature. In contrast to the conventional InB dependence of M-rev observed in the unirradiated sample, the field dependence of M-rev for the irradiated samples exhibits an anomalous dip, corresponding to the expulsion of vortices from the sample. We show,that the coupling transition, which, to our knowledge;. has not been considered previously in analyzing the magnetization data, is : very important to understand the anomalous behavior of M-rev. From the measurement, ae obtain the almost temperature-independent transition line B-cp(T)similar to B-Phi/3, where B-Phi is a matching field. This is in good accordance with the recent computer simulation. The anomalous peak effect is observed at the same field, B similar to B-Phi/3, in Bose-glass (BG) regime, which accompanies the reentrant behavior of BG melting line. [References: 23]