Abstract:

Local Hall dc-susceptibility and global dc-magnetization measurements are used in order to construct the vortex matter phase diagram for a HgBa2CuO4+x single crystal with T similar to 89.9 K. For T > T* = 82 K, the points where the step in rile local ac-susceptibility measurements and the anomaly in the de magnetization measurements occur fall on the same curve, indicating that the same phenomenon is observed in both cases. We modeled these points by a power law H-m(T) = H-o(1-T/T-c)(a), with a = 2.4 +/- 0.1 and H-o = 267 +/- 125 kOe. The local Nail ac-susceptibility data, below the "step" temperature, show a behavior which can be explained if we suppose that at the vicinity of the step a local peak in the J(c)(T) curve exists (so-called peak effect). (C) 2000 Elsevier Science B.V. All rights reserved.