Role of Intrinsic Pinning for Melting Transition of YBa2Cu3O6.93 in the Parallel Field to CuO2 Layers

Abstract

Vortex lattice melting of an untwinned YBa2Cu306.93 single crystal has been investigated by means of the ac susceptibility and the torque. The crystal shows the vortex-lattice-melting transition in Hlle configuration. The first-order-melting transition of vortex lattice occurs in H -ie, too. The anisotropy in the melting fields is consistent with the three-different mass anisotropy parameters. At lower temperatures, the torque curve shows a sharp peak in the irreversible torque at ()e ~ 90° due to intrinsic pinning. However, the melting transition in the H -ie configuration appears at temperatures, where the intrinsic-pinning peak is absent.