Upper critical fields and anisotropy limits of high-T/sub c/ superconductors R1Ba2Cu3O/sub 7-//sub y/, where R = Nd, Eu, Gd, Dy, Ho, Er, and Tm, and

The upper critical fields B/sub c/2(T) were measured up to 28 T for R1Ba2Cu3O/sub 7-//sub y/ where R = Nd, Eu, Gd, Dy, Ho, Er, and Tm, and for YBa2Cu3O/sub 7-//sub y/. The midpoints (dB/sub c/2/dT)/sub T //sub = //sub =/ cluster about (2.8 +- 0.2)T/K, the T/sub c/'s = (93 +- 2) K show a slight systematic decrease from Nd to Tm, and the extrapolated values of B/sub c/2(0) cluster about (160 +- 20) T. The wide range of normal-state resistivities indicates that they are not intrinsic to the superconductor. The anisotropy A = B/sub c/2/sub X//B/sub c2/ is estimated to be less than 12 based on the data for the resistive transition. Criteria for the midpoint resistive transition are also reexamined