Full-penetration temperature and magnetic relaxation in a single crystal of ${\mathrm{Bi}}_2$${\mathrm{Sr}}_2$${\mathrm{CaCu}}_2$${\mathrm{O}}_{\mathit{x}}$

We have developed the concept of a characteristic temperature ${\mathit{T}}^{\mathrm{*}}$ at which the flux first fully penetrates the sample. Based on this concept, we have interpreted the effects of the temperature on the magnetic relaxation that have been measured in a single crystal of ${\mathrm{Bi}}_2$ ${\mathrm{Sr}}_2$ ${\mathrm{CaCu}}_2$ ${\mathrm{O}}_{\mathit{x}}$ in a broad range of temperature (5–35 K) and applied magnetic field (0.1–4 kG). The magnetic relaxation exhibits a clear peak in the dM/d lnt-versus-temperature plot, and the peak position is highly affected by the applied field. We have also interpreted the peak shift of dM/d lnt with different fields in terms of the flux-creep and the critical-state models.