Thermally assisted flux flow in epitaxial Bi2Sr2Ca2Cu3O10+δ thin films: Estimation of the anisotropy parameter

The thermally activated flux motion in transport-current-carrying epitaxial Bi2Sr2Ca2Cu3O10+δ thin films was investigated by conventional resistive measurements, with the magnetic field B applied parallel to the c-axis and ranging between 10mT and 3T. It was found that the magnetic field and temperature dependence of the activation energy, as well as the form of the irreversibility line in the thermally assisted flux glow regime, change significantly at a field value Bcr∼0.1 T. This behavior is similar to that reported by us in the case of Bi2Sr2CaCu2O8+δ thin films, and was interpreted in terms of the occurrence of a dimensional crossover in the vortex system, due to the increase of the tilt modulus at low fields. We determined an anisotropy factor γ∼140 for our Bi2Sr2Ca2Cu3O10+δ films, which is lower than that observed for the Bi2Sr2CaCu2O8+δ films