The anomalous thermoelectric power of the La doped Bi-2201 phase

Samples of the Bi_1.9Sr_1.6La_0.4CuO_y system with different oxygen contents have Obtained by annealing the as-grown samples at different and oxygen partial pressures. The results of resistivity and thermoelectric power (TEP) measurements of these samples are reported here. Some anomalous phenomena in transport for the underdoped samples of Bi_1.9Sr_1.6La_0.4CuO_y were observed, i.e., below a characteristic temperature, the TEP exhibits a significant enhancement and the temperature dependence of the resistivity deviates downward from linearity. These results imply that a ,pu. gap exists in the La doped Bi-2201 system By comparison with the results reported previously, we suggest that the microstructural characteristics are another important factor in determining the spin excitation spectrum.