Browsing by Author "Simon, Ch."
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Item Anisotropic resistivity measurements by a multi-terminal transport method(IOP Publishing, 1997) Aouaroun, T.; Hardy, V.; Goupil, Ch.; Warmont, F.; Villard, G.; Simon, Ch.Item One-dimensional brownian-motion model for transport measurements in high-temperature superconductors(1996) Goupil, Ch.; Aouaroun, T.; Thopart, D.; Hamet, J. F.; Simon, Ch.Using a one-dimensional model of Brownian motion of vortices over pinning wells, we derive a current-voltage equation assuming a distribution of the effective pinning length. The model describes linear and nonlinear regimes of the E(J) curves in a single-particle description. Thermally activated flux flow and flux flow define the two limits of the dissipative process, respectively, at very low and high current. The pinning relief is described by pinning well depth and pinning well gradient, respectively, which can be checked by resistive and current-voltage measurements. The model is then applied to a YBa2Cu3O7−δ thin film. It provides a phenomenological model of the dissipation induced by transport currentItem Pillar defects, a new type of track in Pb-irradiated Bi-2212 thin films : nanostructural study and influence on the irreversibility line(Elsevier, 1998) H ebert, S.; Hervieu, M.; Hardy, V.; Aouaroun, T.; Simon, Ch.; Provost, J.; Milani, E.; Aruta, C.; Balestrino, G.Item Plastic vortex creep in the high-Tc superconductor (T1 2/3 , Bi1/3) Sr2CaCu2Ox(Elsevier, 1998) Aouaroun, T.; Hardy, V.; Simon, Ch.Item Second-peak effect in a superconducting Tl, Bi -1212 single crystal by ac susceptibility : evidence for vortex plastic behavior(American Physical Society, 1998) Aouaroun, T.; Simon, Ch.A second peak effect is observed for a ~Tl, Bi!-1212 single crystal using ac susceptibility measurements. The analysis of the frequency dependence of the second peak position shows that plasticity governs the vortex dynamics on both sides of the second peak line. This suggests that no particular change in the vortex dynamics occurs by crossing this line. We propose that this second peak effect is due to the temperature activated form of the characteristic relaxation times and to the fact that the characteristic activation energy Uc and the critical current density Jc have inverse variations with the magnetic field B ~when one increases with B the other decreases!. We also propose that the time dependence of the second peak field position should indicate the vortex dynamics behavior: an increasing second peak field position with time is a fingerprint of elastic behavior while a decreasing second peak field position with time is a fingerprint of plastic behavior. The latter case agrees well with our experimental resultsItem Vortex dynamics studied over a wide range of time scale in Bi-2212 Crystals(1995) Goupil, Ch.; Ruyter, A.; Provost, J.; Aouaroun, T.; Simon, Ch.