Vortex matter transition in Bi₂Sr₂CaCu₂O_8+y under tilted fields

Abstract

Vortex phase diagram under tilted fields from the c axis in Bi2Sr2CaCu2O8+y is studied by local magnetization hysteresis measurements using Hall probes. When the field is applied at large angles from the c axis, an anomaly (H*p) other than the well-known peak effect (Hp) is found at fields below H*p is nonmonotonic and clearly different from that of Hp and depends on the oxygen content of the crystal. The results suggest existence of a vortex matter transition under tilted fields. Possible mechanisms of the transition are discussed. © 2001 American Physical Society.