Vortex matter phase transitions under tilted fields in pristine and Pb-substituted Bi2Sr2CaCu2O8+y

Vortex matter phase transitions in Bi2Sr2CaCu2O8+gamma (BSCCO) under fields tilted from the c-axis is studied by using Hall probes. Vortex lattice mel ting (H-m(theta)) and peak effect (H-p(theta)) are found to follow a novel angular scaling; transition fields linearly depends on the in-plane compone nt of the field. The novel scaling is valid in the vortex solid phase up to doping-level-dependent angle, theta*. New anomalies in the magnetization h ysteresis curve, H-p* and H-cp*, appear only at large tilting angles. Above theta*, the angular dependence of H-p, H-p*, and H-cp* changes drastically , suggesting the presence of Vortex phase transition at this angle.