Thermomagnetic Effects in Superconductors

Abstract

Transport properties of superconductors in the mixed state and the intermediate state are discussed. The paper outlines a phenomenological model for the thermomagnetic effects occurring when vortices are free to move. These effects involve the entropy transported by moving vortices. We have described the measurement of two effects which are abnormally large in a superconductor, the Ettingshausen effect and the Nernst effect. Both effects have been measured as functions of magnetic field and temperature in a type-II alloy (In+40 at.% Pb), and the Ettingshausen effect has been measured in a type-I alloy (Sn+ 0.05 at.% In). The values of transported entropy per cm of flux line per flux quantum computed from these measurements are compared with existing theories. For both type-I and type-II superconductors, the theories agree roughly with the measurements at low temperatures but fail to agree near $T_c$.