Flux flow noise in high Tc superconductors thin films

We have studied the fraction pinned of vortex in a type II superconductors. The sample used is the YBa2Cu3O7-d thin films. This fraction pinned is determined from the comparison of the experimental results and the theoretical results previously definite. In continuation one will study the variations of this fraction according to the temperature of the applied magnetic field and the electric current crossing the sample.We have studied the fraction pinned of vortex in a type II superconductors. The sample used is the YBa2Cu3O7-d thin films. This fraction pinned is determined from the comparison of the experimental results and the theoretical results previously definite. In continuation one will study the variations of this fraction according to the temperature of the applied magnetic field and the electric current crossing the sample

Pinning of vortices in superconductors at high critical temperature

Due to problem identification and enumeration of defects in HTC superconductors, the correlation between current density and the transition of vortex pinning volume is not completely mastered. However, many theoretical and experimental studies have been developed to better understand the problem of dissipation due to vortices in type II superconductors

The vortex motion and the magnetization study in YBa2Cu3O7-d single crystal

We have investigated the vortex motion and the magnetization of high critical temperature superconductors YBa2Cu3O7-d Measurements were made using a vibrating sample magnetometer technique. Several magnetization hysteresis cycles have been obtained for different angles, θ, between the applied magnetic field, H, and the crystallographic c-axis. For T = 30 K we observed a central peak and for T = 80 K we observed a second peak or "fishtail".We have investigated the vortex motion and the magnetization of high critical temperature superconductors YBa2Cu3O7-d Measurements were made using a vibrating sample magnetometer technique. Several magnetization hysteresis cycles have been obtained for different angles, θ, between the applied magnetic field, H, and the crystallographic c-axis. For T = 30 K we observed a central peak and for T = 80 K we observed a second peak or "fishtail"

The critical current density and the vortex pinning in high quality YBa2Cu3O7-d thin films

We have measured the critical current density Jc of high quality c-axis oriented YBa2Cu3O7-d thin films. Measurements were performed for various magnetic field and temperature values, and as a function of the angle q between the c-axis and the applied magnetic field direction. A maximum of the critical current density was obtained when the flux lines are aligned along the CuO planes (q = 90°); another maximum in Jc was also observed when the magnetic field is adjusted parallel to the c-axis. We attribute these effects to different, intrinsic and extrinsic, pinning mechanisms of vortices in the sample.We have measured the critical current density Jc of high quality c-axis oriented YBa2Cu3O7-d thin films. Measurements were performed for various magnetic field and temperature values, and as a function of the angle q between the c-axis and the applied magnetic field direction. A maximum of the critical current density was obtained when the flux lines are aligned along the CuO planes (q = 90°); another maximum in Jc was also observed when the magnetic field is adjusted parallel to the c-axis. We attribute these effects to different, intrinsic and extrinsic, pinning mechanisms of vortices in the sample

Magnetization study in YBa2_{2}Cu3_{3}O7−δ_{7-\delta} single crystal

We have studied the magnetization of high critical temperature superconductors YBa$_{2}$Cu$_{3}$O$_{7\hbox{-}\delta}$. Measurements were made using a vibrating sample magnetometer technique. Several magnetization hysteresis cycles have been obtained for different angles, $\theta$, between the applied magnetic field, $H$, and the crystallographic $c$-axis. For $T$ = 30 K we observed a central peak and for $T$ = 80 K we observed a second peak or “fishtail”

Anisotropy of the critical current density in YBa2_{2}Cu3_{3}O7-δ_{7\hbox{-}\delta} single crystal

We have investigated the anisotropy of the critical current density in high temperature superconductors YBa$_{2}$Cu$_{3}$O$_{7\hbox{-}\delta}$ single crystal. Vibrating sample magnetometer (V.S.M.) method was used for these measurements. The applied magnetic field dependence of critical current density for two directions, parallel and perpendicular to the crystallographic c-axis, at various temperatures, are derived from the measured magnetization hysteresis cycles curves using the Bean model. The critical current density for these two orientations are very different, the pinning mechanism can explain this anisotropy

Origin of the noise in the high-Tc_{\bf c} superconducting YBa2_{2}Cu3_{3}O7−δ_{7-\delta} thin films

In the mixed state of high-T$_{\rm c}$ superconductors, the magnetic flux can penetrate the superconducting state in the form of vortices. Moving vortices create resistance, so they must be pinned to permit dissipationless current flow. This is particularly important issue for high-transition-temperature superconductors, in which the vortices move very easily.
We studied the behavior of the characteristic noise of high-T$_{\rm c}$ superconductors near the transition conductor-superconductor region in YBa$_{2}$Cu$_{3}$O$_{7\hbox{-}\delta}$ thin films as a function of the temperature and of the applied magnetic field. Our results show that when the temperature increases near the superconducting transition region, the amplitude of the voltage noise increases. And this amplitude depends strongly on the electrical current crossing the sample