In-plane and out-of-plane magnetoresistivity in a MTG Er-doped YBCO crystal

Abstract

We have measured the temperature dependence of top and bottom voltage signals of a Y 0.8 Er 0.2 Ba 2 Cu 3 O 7−δ crystal in magnetic field up to 7.5 T parallel to the c-axis using the pseudo-flux-transformer method. The results show that in a dissipative regime the voltage signal on the side of the applied current contacts is more than that on the opposite side; meanwhile the bottom voltage signal shows a field-dependent peak effect near the critical temperature T c. We calculated the true resistivities ρ ab and ρ c of the crystal within an anisotropic model. The difference between the calculated ρ ab and ρ c and the experimental values ρ st ab and ρ st c is helpful in understanding flux dynamic behaviour. Based on the Yeshurun-Malozemoff model, we have investigated temperature and field dependences of effective activation energy along the ab-plane and c-axis obtained from the ρ ab (T) and ρ c (T), respectively. The temperature dependence of effective activation energy along the c-axis displays a good thermally activated flux flow (TAFF) behaviour. In the TAFF regime the field dependence of effective activation energy follows a power behaviour, U(H) = 4.24 × 10 4 H −1.1. The TAFF regime and the coupling between the layers have been discussed.

Infield response of (Al2O3)x/CuTl-1223 nanoparticles-superconductor composites

“…3. The power law dependence of activation energy has already been observed in different high temperature superconducting families [33][34][35][36]. The overall decrease in activation energy of CuTl-1223 superconducting matrix has been observed after addition of Al 2 O 3 nanoparticles, which may be due to suppression in inter-grains weak-links caused by the dispersion of these nanoparticles over the grain-boundaries.…”

Deviations from plastic barriers inBi2Sr2CaCu2O8+δthin films

“…For high fields, each −∂ ln ρ/∂T −1 monotonously decreases with temperature from low temperature to a local minimum. One may take the data around these minima for U simulation in which a constant β for −∂ ln ρ(T, H)/∂T −1 data may be determined [17,18]. However, taking into account the flux flow condition U ≤ T , this may lead to a wrong result.…”