# Thermomagnetic Effects

## Thermomagnetic effects

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.

For related phenomena See Hall effect, Magnetoresistance

## Thermomagnetic Effects

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.

### REFERENCES

Blatt, F. J. Teoriia podvizhnosti elektronov v tverdykh telakh. Moscow-Leningrad, 1963. (Translated from English.)
Tsidil’kovskii, 1. M. Termomagnilnye iavleniia v poluprovodnikakh. Moscow, 1960.
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