Thermomagnetic transport properties of Nd1.85Ce0.15CuO4+delta films: Evidence for two types of charge carriers

We report measurements of the thermomagnetic properties of Nd1.85Ce0.15CuO4+/-delta thin films as a function of oxygen content. The variation of the Nernst coefficient with carrier doping-and its large magnitude-cannot be explained by a conventional single-carrier model. These measurements along with the variation of the Hall coefficient and the thermoelectric power with oxygen doping suggest that a two-carrier model might be suitable to describe the transport properties of these electron-doped cuprate superconductors. The ratio of the electrical and thermal Hall mobilities is presented as further evidence for the applicability of a two-carrier model. We finally show the correlation between the doping dependence of the Nernst coefficient and the magnetoresistance.