Giant Nernst effect in La0.88MnO3 and La0.7Ca0.3MnO3

Nernst coefficient measurements of La0.88MnO3 (T-c similar to 265 K) and La 0.7Ca0.3MnO3 (T-c similar to 265 K) are reported as a function of temperatu re (100-320 K) in moderate applied magnetic fields (0.38 < H < 1.8 T). For T > T-c, our data can be accounted for by the transport behaviour of small polarons. We find the semiconductor-metal transition is dominated by an inc rease in the hole density. For T less than or equal to T-c, an anomalous su ppression of the Nernst coefficient was observed when the field increased f rom 0.38 to 1.8 T. The colossal magnetoresistance effect is attributed to a field-induced increase in the mobility of the charge carriers. (C) 2000 El sevier Science B.V. All rights reserved.