Electrical and thermal phenomena occurring when a conductor or semiconductor which is carrying a thermal current (that is, is in a temperature gradient) is placed in a magnetic field. See Semiconductor
Let the temperature gradient be transverse to the magnetic field Hz, for example, along x. Then the following transverse-transverse effects are observed:
1. Ettingshausen-Nernst effect, an electric field along y.
2. Righi-Leduc effect, a temperature gradient along y.
3. An electric potential change along x, amounting to a change of thermoelectric power.
4. A temperature gradient change along x, amounting to a change of thermal resistance.
Let the temperature gradient be along H. Then changes in thermoelectric power and in thermal conductivity are observed in the direction of H.
a group of effects produced by the influence of a magnetic field on the electric and thermal properties of conductors and semiconductors in which temperature gradients exist. As with galvanomagnetic phenomena, thermomagnetic effects are caused by the action of a magnetic field on moving particles that carry electric charges—that is, electrons in conductors and electrons and holes in semiconductors. A magnetic field bends the trajectory of moving charges; in particular, it deflects both the electric current flowing through the body and the heat flux associated with the transfer of particles. As a result, components of the electric current and heat flux appear that are perpendicular to the magnetic field; other effects are observed as well.
Thermomagnetic effects can be classified by considering the relative arrangement of the following vectors; the magnetic field intensity H, the temperature gradient VT in the conductor, the heat flux density W, and a vector N parallel to the direction in which the effect is measured. Thermomagnetic effects are measured perpendicular or parallel to the initial temperature gradient and are called transverse and longitudinal effects, respectively.
A characteristic example of a thermomagnetic effect is the generation of an electric field E in a semiconductor or metal conductor if the object has a temperature gradient and a superimposed magnetic field H perpendicular to it (the Nernst-Ettingshausen effect). The field E has both longitudinal and transverse components. The Righi-Leduc effect and other phenomena are also related to thermomagnetic effects.
REFERENCESBlatt, F. J. Teoriia podvizhnosti elektronov v tverdykh telakh. Moscow-Leningrad, 1963. (Translated from English.)
Tsidil’kovskii, 1. M. Termomagnilnye iavleniia v poluprovodnikakh. Moscow, 1960.