Local Hall probe ac-susceptibility and global dc magnetization measurements in HgBa 2CuO 4+ x single crystal

Abstract

Local Hall ac-susceptibility and global dc-magnetization measurements are used in order to construct the vortex matter phase diagram for a HgBa 2CuO 4+ x single crystal with T∼89.9 K. For T> T*=82 K, the points where the step in the local ac-susceptibility measurements and the anomaly in the dc 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 Hall 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).