摘要
In high Tc YBa2Cu3O7(Y123) superconductors, by substituting Y with some rare earth elements RE, a stress field surrounding these dopants will be generated due to the lattice mismatch. Based on the effective defect model, the interaction energy and the maximum elementary interaction force (/? between a fluxoid and a stress center are calculated. It is shown that the calculated values for fp can well interpret the data of the enhancement of measured critical current density j's for the substitution of Y with different rare earth elements. Furthermore, by substituting the Gd with Y in the GdBa2Cu3O7_s thin films, the measured critical current density (js) is increased, while the relaxation rate (S) is clearly lowered, which can be attributed to the presence of extra pinning centers. The temperature dependence of the true critical current density jc(T) and the pinning potential UC(T) were determined from the experiment data for both the pure and the substituted thin films. It is found that the experiment results for the pure film are close to the predictions of -pinning model, while those for the substituted thin film follow the theoretical expressions derived from the single vortex collective pinning model with the small size stress-field pinning centers, which strongly supports the idea that the enhancement of j, by the substitution resulted from the stress induced flux pinning rather than the magnetic pinning.
In high Tc YBa2Cu3O7(Y123) superconductors, by substituting Y with some rare earth elements RE, a stress field surrounding these dopants will be generated due to the lattice mismatch. Based on the effective defect model, the interaction energy and the maximum elementary interaction force (/? between a fluxoid and a stress center are calculated. It is shown that the calculated values for fp can well interpret the data of the enhancement of measured critical current density j’s for the substitution of Y with different rare earth elements. Furthermore, by substituting the Gd with Y in the GdBa2Cu3O7_s thin films, the measured critical current density (js) is increased, while the relaxation rate (S) is clearly lowered, which can be attributed to the presence of extra pinning centers. The temperature dependence of the true critical current density jc(T) and the pinning potential UC(T) were determined from the experiment data for both the pure and the substituted thin films. It is found that the experiment
基金
Project supported by the Education Foundation of the Chinese National Education Commission and the National Center for R and D on Superconductivity.
