INTERPLANE CHARGE-TRANSPORT IN YBA2CU3O7-Y - SPIN-GAP EFFECT ON INPLANE AND OUT-OF-PLANE RESISTIVITY

We have investigated the anisotropic resistivities of YBa2Cu3O7-y using detwinned crystals with various oxygen contents (6.68 less-than-or-equal-to 7 - y less-than-or-equal-to 6.93). The out-of-plane resistivity rho(c) shows a crossover from high-T metallic to low-T semiconducting behavior while the in-plane resistivity rho(a) deviates in the low-T region from T-linear dependence. We find that the crossover in rho(c) is linked with the onset of nonlinearity in rho(a), which seems to be associated with the ''spin gap'' suggested by neutron and NMR studies.