NEGATIVE MAGNETORESISTANCE OBSERVED IN C-AXIS CONDUCTION IN BI2SR2CACU2O8+DELTA

The magnetoresistance for charge transport along the c-axis is negativ e in Bi2Sr2CaCu2O8+delta, unlike the in-plane transport. We show that Delta rho(c)/rho(c), is thermally activated with a gap Delta that vari es from 520 K to 997 K as the doping proceeds from under- to over-dope d. We suggest that the applied field lowers the barrier impeding c-axi s charge transport, by coupling to the Zeeman energy.