Analysis of Phonon-Drag Thermomagnetic Effects in n-Type Germanium

In a recent paper 1 we have presented measurements of the Nernst effect and the change of thermoelectric power in a magnetic field for n-type germanium of high purity. These two effects were shown to be * T h i s p a p e r , t h o u g h complete in itself, c o n s t i t u t e s p a r t II of a s t u d y , p a r t I of which was presented in Ref. 1. In addition to describing t h e phenomena and t h e physical principles underlying t h e m , Ref. 1 develops t h e background of t h e p r e s e n t s t u d y and gives details of t h e measuring techniques. 657 736 TIIE BELL SYSTEM T E C H N I C A L J O U R N A L , MAY 1 9 5 9 compounded out of electron-diffusion and phonon-drag contributions, the latter being the predominant one in the range near liquid-air temperature. Now the phonon-drag phenomenon 2 -- the pushing of charge carriers from hot to cold by the asymmetric phonon distribution which a thermal gradient produces -- depends on the details of both the electron-phonon interaction and the processes which scatter phonons. The anisotropies of these interactions and their dependences on wave number enter in different ways into the several thermomagnetic quantities which one can measure. Thus, an analysis of thermomagnetic data should make it possible to sort out the different factors involved in phonon drag, and to obtain information not previously available about electronphonon and phonon-phonon interactions. In our first paper we used qualitative arguments to draw a number of semiquantitative conclusions about these interactions.