THERMOELECTRIC AND THERMOMAGNETIC EFFECTS IN THE MIXED-STATE - ANALYSIS OF THE THERMAL ANGLE

In this paper thermoelectric and thermomagnetic coefficients in the mixed state are discussed. Besides the contribution of the Abrikosov vortices, also the role of the vortex-antivortex pairs and of the quasi-particles unbounded and localized in the vortex core is considered. The vortex-antivortex contribution to the Seebeck and Nernst effects is calculated in detail. To study the role of normal excitation we propose to measure the thermal angle, alpha(th) that represents the direction of the vortex velocity. In fact, taking the unbounded quasiparticles into account, or not, as the temperature varies, alpha(th) shows an important difference in behavior, easy to detect experimentally. Measurements of the Seebeck effect and Nernst effect on a Bi(2223) tape are presented and the thermal-angle behavior is discussed. The experimental data are in agreement with the models that consider the unbounded quasiparticles contribution, but some caution must be taken as to the role of the Josephson vortices.