Seebeck and Nernst effect in the mixed state of slightly oxygen deficient YBaCuO

For an epitaxial c-axis oriented slightly oxygen deficient YBaCuO film, showing a positive Seebeck coefficient around 100 K, the Nernst effect has been measured in the mixed state for magnetic fields up to 9 T. The transport entropy calculated in the usual way is about an order of magnitude smaller than for a similar but fully oxygenated film with a negative Seebeck coefficient near 100 K. This can be explained by the enhanced decoupling of the CuO2 planes in the slightly oxygen deficient material, resulting in a strong departure of the vortices ("pancake vortices") from the standard Abrikosov type. © 1991.