EFFECT OF IMPURITY ON ANISOTROPY OF HIGH-TC SUPERCONDUCTIVITY IN YBA2(CU1-XZNX)3O7-DELTA SINGLE-CRYSTALS

The effect of Zn doping on anisotropy of high-T(C) superconductivity i s studied in single-crystal YBa2(Cu1-xZnx)3O7-delta (YBCZO) within the range 0<x<0.03. The resistive transition curves under a magnetic fiel d for these impurity-containing systems axe successfully described for the first time by the renormalized fluctuation theory including psi4 term. The derived coherence length ratio xi(ab)/xi(c), which indicates anisotropy in superconductivity, decreases as the impurity concentrat ion increases. However, both rho(c) and the normal state anisotropy rh o(c)/rho(ab) increase. This situation is not consistent with the Lawre nce-Doniach (LD) model. The anisotropic 3-D metal model seems to be ap propriate for the YBCZO system. This result excludes certain types of high-T(c) theories which assume strict two dimensionality of the elect ronic system.