Sr _0.6 K _0.4 Fe ₂ As ₂ The Critical Current Characteristics Of Iron-based Superconducting Tapes Analysis Of Bar Mechanism

Since novel iron-based pnictide of Sr0.6K0.4Fe2As2 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, comparatively high upper critical magnetic field, relatively high critical current density and critical temperature. Recently, the Fe-clad superconducting Sro.6Ko.4Fe2As2 tape with the critical temperature of 32.5 K and fairly high critical current density of 1.5×108 A/m2 at 10 T and 4.2 K was developed by Institute of Electrical Engineering in Chinese Academy of Sciences.Taking the critical temperature of Sr0.6K0.4Fe2As2 tape into consideration, it was presumed that operating temperature of this tape is 20 K (boiling point of hydrogen) to 30 K. In order to investigate the applicability of this tape, the superconducting characteristics of it in the temperature range of about 20 K to 30 K and at the magnetic field of up to 7 T was studied.Since the critical current density is considered as one of the most important factors for application of superconducting materials, the detail investigation on the critical current characteristic and flux pinning mechanism in the supposed operation temperature and magnetic field range is necessary. Four-probe method and Campbell’s method were used to measure the critical current density of this tape.Critical current density of the sample decreases with the rising of temperature and increases with the reduction of magnetic field. Critical current density of the Fe-clad superconducting Sro.6Ko.4Fe2As2 tapes is proved fairly high at about 20 K. At 19.5 K, critical current density reaches 1.5×108 A/m2 at 0.1 T and 5.1×107 A/m2 at 7 T. Even measuring at 24.4 K, critical current density values is over 2.7×107 A/m2 at 0.1 T. Also, variation of critical current density at about 20 K is comparatively small. It proves that application of Sr0.6K0.4Fe2As2 tape at about 20 K is very hopeful. Furthermore, the result that αL and di fit with the law in traditional metal-superconductor provides an evidence that the flux pinning behavior in the sample can be explained with conventional flux pinning theory.