Transport entropy in ${\mathrm{YBa}}_2$${\mathrm{Cu}}_3$${\mathrm{O}}_7$: A comparison between epitaxial and polycrystalline thin films

The dissipative behavior in thin films of ${\mathrm{YBa}}_2$ ${\mathrm{Cu}}_3$ ${\mathrm{O}}_{7\mathrm{-}\mathrm{\delta }}$ has been investigated under the influence of a temperature gradient. By using the sample configuration itself as a thermometer, a method has been developed for the study of flux dynamics in the presence of a temperature gradient. The temperature and magnetic-field dependence of the transport entropy was measured, and the influence of grain boundaries on this quantity was investigated. For an epitaxial ${\mathrm{YBa}}_2$ ${\mathrm{Cu}}_3$ ${\mathrm{O}}_{7\mathrm{-}\mathrm{\delta }}$ film near ${\mathit{T}}_{\mathit{c}}$, we obtain the value -${\mathit{dH}}_{\mathit{c}2}$/dT=2±0.5 T/K and the Ginzburg-Landau parameter ${\mathrm{\kappa }}_{\mathrm{GL}}$=80±10.