ANGULAR-DEPENDENCE OF THE FIRST-ORDER VORTEX-LATTICE PHASE-TRANSITIONIN BI2SR2CACU2O8

The paramagnetic peak in the local ac susceptibility chi' is used to i dentify the first-order vortex-lattice phase transition in Bi2Sr2CaCu2 O8 at various tilt angles theta of the de magnetic field with respect to the c-axis. The transition field H-m follows roughly the 2D scaling function H-dc cos(theta). The amplitude of the paramagnetic peak, and thus the jump in magnetization Delta B, do not depend on the tilt ang le which demonstrates that the entropy jump at the transition, Delta S , is insensitive to the presence of the in-plane field.