Thermally assisted flux flow character of MgB2

As a new superconductor, MgB2 has many different characteristic features in contrast to the traditional HTSC. The investigation of these features is important both for theoretical study and application of this material. Several groups reported that from the vortex phase diagram of MgB2, 3D vortex glass phase and vortex liquid phase are found. But the flux dynamic mechanism held by this new superconductor could not be considered as a merely a copy of those of the HTSC. While the former is a s-wave superconductor, the latter is d-wave superconductor. In the present article, we present an extensive investigation on the flux mechanism in MgB2 by transport measurement from 5 K to T-c of the sample at magnetic fields up to 7 T, and deal with the experimental data with the linear simulation method within framework of the thermally assisted flux flow theory, which was first proposed by Kes et at. Finally, we obtained an exact expression of the pinning barrier U-0 in the liquid phase of vortex matter of MgB2. (C) 2002 Elsevier Science B.V. All rights reserved.