The magnetization and magnetic relaxation of a PrFeAsO$_{0.60}$F$_{0.12} sueprconductor

The magnetization and magnetic relaxation of the PrFeAsO$_{0.60}$F$_{0.12]$ polycrystalline sample have been measured as functions of temperature and magnetic field ($H$). The intragrain critical current density ($J_c$) derived from the magnetization measurement is large and the $J_c$ versus $H$ curve displays a second peak which shifts towards the high field region with decreasing temperature. The normalized magnetic relaxation rate exhibits a bell-like shape with a broad maximum at around 10 K. The high value of the magnetic relaxation rate indicates large vortex creep and weak pinning of the vortices in this sample. A vortex phase diagram for the present superconductor has been obtained from the magnetization and resistivity data.