THEORY OF NEGATIVE MAGNETORESISTANCE IN THE C-AXIS RESISTIVITY OF HIGH-T-C CUPRATES

In order to explain the negative magnetoresistance (MR) in the c-axis resistivity in Bi2Sr2CaCu2O8+delta and YBa2Cu3O6+x, the tunneling cond uctivity has been calculated based on the inter-layer tunneling mechan ism and the Kubo linear-response theory for the electric conductivity. The calculations show that the MR is negative and proportional to B-2 at lower temperature while the MR is positive at higher temperature. The T dependence of MR is also shown to be related to the sign change of d rho(c)/dT. These results are mainly in accordance with the recent experiment.