Critical current and flux pinning characteristics in Sr_(0.6)K_(0.4)Fe_2As_2 superconducting tapes

摘要

Recently, we successfully developed the Fe-sheathed superconducting Sr_(0.6)K_(0.4)Fe_2As_2 tape with the critical temperature of 32.5 K and fairly high critical current density of 1.5×10~8 A/m~2 at 10 T and 4.2 K.[l] The critical current characteristic is considered as one of the most important factors for the applications of superconducting materials. Therefore, precise estimation of temperature and magnetic field dependence of critical current density (J_c) is necessary. In this study, the J_c in the temperature range of 20 K to 30 K and in the magnetic field of up to 7 T were measured by using an inductive method (Campbell's method). Furthermore, basing on the experimental results of the penetrating ac magnetic flux profile and the feature of ac magnetic field dependence of penetration depth, the flux pinning mechanism of the sample within 20 K and 30 K was discussed.