Selective-over-doping in Cu-1234 (CuBa2Ca3Cu4O12-y) system with high T-c >116 K and low superconducting anisotropy 1.6

Thr coexistence of high-T-c (> 116 K) and high carrier concentration (> 0.6 /CuO2) has been achieved in low-anisotropic superconductor Cu-1234 (CuBa2 C a-3 Cu-4 O12-y) system by selective-over-doping effect. The effect has been discovered for the first time in the Cu-1234 system from Hall-coefficient and NMR measurements. This mechanism is interpreted on the basis of the ele ctronic structure from the FLAPW band calculation. These results give a gre at advantage to the Cu-1234 system with a low superconducting anisotropy (g amma = xi(ab)/xi(c) = 1.4 similar to 1.6) for the achievement of high-perfo rmance superconductivity with high J(c) and high H-irr at 77 K. (C) 2000 El sevier Science B.V. All rights reserved.