Influence of thermal and structural fluctuations on anisotropic resistivity and nonlinear transport properties of ReBa 2Cu 3O 7-δ (Re=Y,Tm) single crystals
The ϱ ab and ϱ c resistivity components of ReBa 2Cu 3O 7-δ ( Re= Y, Tm) single crystals have been studied both above and below T c. All samples have close ϱ ab(T) values in normal state and differ mainly by the transition width. We have found that the superconducting transition region isn't described by the thermal fluctuations only and is influenced by structural fluctuations too. For the best sample the anisotropy of the resistivity is ∼40 and shows weak temperature dependence. This behavior is shown to be “intrinsic” property of ReBa 2Cu 3O 7-δ system. For the less perfect samples the resistivity anisotropy is found to be highly temperature dependent which is connected with the layered structural fluctuations. Below T c the I-V curves show powerlike E∼j n behaviour with sharp n increase between 1 and 3.