Upper critical fields and critical current density of BaFe _2(As_(0.68)P_(0.32))_2 single crystal

摘要

The transport properties, upper critical fields, superconducting anisotropy, and critical current density of an iso-valent phosphorus-doped BaFe_2As_2 single crystal close to optimum doping are investigated in this report. Temperature dependent resistivity and susceptibility show a superconducting transition temperature, T_c, just below 31 K both with sharp transitions. The upper critical field parallel to the ab-plane, H_(c2)~(ab), is above 77 T while that along the c-axis direction, H_(c2)~c, is just above 36 T, yielding a low superconducting anisotropy ratio ～ 2. The estimated inter-plane coherence length based on the Ginzburg-Landau (G-L) theory indicates BaFe _2(As_(0.68)P_(0.32))_2 is still above the point for a dimensional crossover inferring the superconducting layers are not weakly-coupled in this system. The critical current density at 5 K obtained from magnetization loops measurement show a modest J_c as high as 10 ~5 A/cm~2.