Author(s)

C. Q. Qu, Z. Y Liu, Y. M Lu, C. Z Chen, C. B Cai, A. H Fang, F. Q Huang, M. F Wang, X. M Xie

.

Binary doping effect is studied for the Fe-based superconductors of Nd_1-xBa_xFeAsO_1-2xF_2x(x = 0.02, 0.05, 0.1, 0.15, 0.2). The X-ray diffractions show that the c-axis lattice constant decreases monotonously with the doping content, in contrast to the little change in the a-axis. Temperature dependences of electric resistivity and magnetic susceptibility reveal that the superconductivity for the studied system emerges at x = 0.1, and enhances together with H_c2(0) as the doping content x increases further. In case of x = 0.2, the superconducting critical temperature reaches as high as 50 K, which is the first demonstration of superconductivity with a high fluorine-doping induced by both electron and hole doping in this family. Negative Hall coefficient (R_H) indicates that electron-type carriers are dominated in the present samples. The complicated temperature dependence of R_H, is believed to arise from a multiband effect together with a complicated scattering, especially at the tem-perature near the T_C.

Binary Doping, Iron-Based Superconductor, Flux Pinning, Scattering

C. Qu, Z. Liu, Y. Lu, C. Chen, C. Cai, A. Fang, F. Huang, M. Wang and X. Xie, "Superconductivity Modulated by Binary Doping in Nd_1-xBa_xFeAsO_1-2xF_2x," Journal of Modern Physics, Vol. 2 No. 6, 2011, pp. 463-471. doi: 10.4236/jmp.2011.26056.