PINNING AND THE MIXED-STATE THERMOMAGNETIC TRANSPORT-PROPERTIES OF YBA2CU3O7-DELTA

We have studied the role of pinning in the mixed-state thermomagnetic transport properties of YBa(2)Cu3O(7-delta). We demonstrate the pinnin g independence of the transport entropy S-phi, and its consequent scal ing within an anisotropic mass model. Due to the anisotropy of YBa2Cu3 O7-delta the extrinsic pinning strength effectively decreases as we ro tate the magnetic field into the ab plane, The Nernst (E(y)/del(x)T) a nd Seebeck (E(x)/del(x)T) effects are enhanced as we reduce the effect ive pinning, yet the transport entropy S(phi)proportional to(E(y)/del( x)T)/rho(xx), the ratio of the Nernst and Seebeck signals, and the rat io of Seebeck and longitudinal resistivity rho(xx) are unchanged, simi lar to the pinning independence observed for the Hall conductivity sig ma(xy). These results can be explained within a simple phenomenologica l model of vortex dynamics.