THERMOPOWER OF GIANT MAGNETORESISTIVE OXIDE SYSTEM LA1-XCUXMNO3 LESS-THAN-OR-EQUAL-TO-X-LESS-THAN-OR-EQUAL-TO-0.4)

The thermopower (Seebeck coefficient, S) of the perovskite oxide syste m La1-xCaxMnO3 for compositions 0.1 less than or equal to x less than or equal to 0.4 has been measured for 4.5 K less than or equal to T le ss than or equal to 360 K. The observed S is rather complex and points to a number of processes occuring in these materials. We suggest a sc heme to analyze the data. S depends on the Mn4+ content and shows a sy stematic change to more negative value as x (i.e, Mn4+ content) increa ses. A large negative peak in S at around 25 K has been observed sugge sting the existance of a strong inelastic scattering mechanism hithert o not seen in this material.