Abstract:

The vortex matter phase diagram for H parallel to c of the thallium-based cuprate with formula Tl2Ba2CaCu2O8 (Tl-2212) has been studied using magnetization measurements. We observed a second magnetization peak monotonically decreasing with temperature in the temperature interval 20 K < T < 40 K. At 40 K the second peak splits into two peaks. The field location of the lower part of the second peak decreases with temperature and for 80 K <= T <= T-c it is transformed to a sudden drop. The corresponding upper part of the second peak forms a broad maximum and subsequently develops a negative curvature as it approaches the melting line. In the magnetic field interval [H-LCP,H-UCP] we observed a first-order melting transition (FOT) of the vortex lattice. (c) 2006 Elsevier B.V. All rights reserved.