Anisotropy of the upper critical field and critical current in single crystal MgB2 -: art. no. 180502

We report on specific-heat, high-magnetic-field transport, and ac-susceptibility measurements on MgB2 single crystals. The upper critical field for magnetic fields perpendicular and parallel to the basal planes is presented in the entire temperature range. A very different temperature dependence has been observed in the two directions, which yields a temperature-dependent anisotropy with Gammasimilar to5 at low temperatures and similar to2 near T-c. A peak effect is observed for mu(0)Hsimilar to2 T parallel to the c axis, and the critical current density presents a sharp maximum for H parallel to the ab plane.