Melting transition in single crystals of Bi2Sr2CaCu2O<f>8+δ</f> studied by the c-axis and in-plane resistivity measurements in parallel magnetic fields.

The vortex-lattice melting transition in Bi2Sr2CaCu2O<f>8+δ</f> single crystals is studied by the simultaneous in-plane <f>Rab</f> and out-of-plane <f>Rc</f> resistivity measurements by using the Corbino transformer contact configuration to avoid the surface barrier effects. It is shown that both the in-plane and out-of-plane resistivity measurements give close values of the vortex-lattice melting field in a wide angular range, while the drastical difference of the resistivity onsets of <f>Rab</f> and <f>Rc</f> has been found near the ab-plane. The observed behavior is discussed in the context of the complex vortex-lattice–vortex-smectic–vortex-liquid phase transition or as an alternative by involving the transition from the crossing vortex-lattice to the tilted vortex-lattice near the ab-plane. [Copyright &y& Elsevier]