Spin-entropy origin and scaling behaviour of thermopower in LaBaCoO system*

We report a detailed investigation of thermopower and magnetic properties for La$_{1-x}$Ba$_x$CoO$_3$. A large negative magnetothempower is found to scale with both magnetic field and temperature, indicating that a spin entropy contribution to thermompower. We have formulated a new and general expression to describe the thermopower from spin entropy with spin-interaction considered. Our formula can fit the scaling behavior quite well and provides a satisfactory description to the observed data. The magnetic results further consolidate our claim. This investigation suggests that spin entropy plays a substantial role in the enhanced thermopower in this cobaltite system.