Critical Current and Flux Pinning Characteristics in Sr0.6K0.4Fe2As2 Superconducting Tapes

Since novel iron-based pnictide of Sr
_0.6
K
_0.4
Fe
₂
As
₂
superconductor was discovered, the applications on high magnetic field and large current transportation are highly expected due to its low cost and unique superconductivity such as low anisotropy, relatively high critical current density, and critical temperature. Recently, we have successfully developed the Fe-clad superconducting Sr
_0.6
K
_0.4
Fe
₂
As
₂
tape with the critical temperature of 32.5 K and fairly high critical current density of
$1.5\times 10^{8}\ \text{A/m}^{2}$
at 10 T and 4.2 K. Since the critical current density is considered as one of the most important factors for applications of superconducting materials, detailed investigation on the critical current characteristic and flux pinning mechanism in the supposed operation temperature range is necessary. In this paper, the critical current densities in the temperature range of about 20 K–30 K and at the magnetic field of up to 7 T were measured by using an inductive method (Campbell's method). It turned out that the critical current density of the tape is fairly high around 20 K. In this paper, 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 was discussed.