Ettingshausen effect

The Ettingshausen effect , named after Albert von Ettingshausen , describes the occurrence of a temperature difference in a current-carrying conductor that is located in a stationary magnetic field. It belongs to the galvanomagnetic effects .

When a current I flows perpendicular to a magnetic field B , a temperature difference ΔT occurs perpendicular to them .

If a current I _y with the current density j _y flows in one direction (y) and a magnetic field with the flux density B _z acts perpendicular to it (z) , a temperature gradient arises perpendicular to both

${\displaystyle {\frac {{\text{d}}T}{{\text{d}}x}}=P\cdot j_{y}\cdot B_{z}}$.

P is the Ettingshausen coefficient , which has the unit K · m / (A · T) = K · m / (J / m ² ) = K · m ³ / J.

The cause of the effect is the Lorentz force , which increasingly drives the mobile charge carriers (electrons) to one side of the conductor ( Hall effect ). Slow electrons are deflected more strongly than fast electrons. Since they have less energy than fast ones, the side they are directed to is cooler than the other. The effect occurs above all with metals such as bismuth , which are poor conductors of electricity (high heating) and poor conductors of heat (slow compensation of the temperature difference).

The Ettingshausen effect can falsify measurements of the Hall effect because thermoelectric phenomena can occur due to the temperature difference. However, since heat transport is a slow process, this source of error can be eliminated by measuring the Hall effect with alternating current.

The reverse of the Ettingshausen effect is the thermomagnetic Nernst effect , which is also known as the first Ettingshausen-Nernst effect .

Individual evidence

1. ↑ ^{a b} Karlheinz Seeger: Semiconductor Physics, ISBN 978-3-322985538
2. ↑ ^{a b} Hari Singh Nalwa: Handbook of Thin Films, Academic Press, ISBN 978-0-080533247 , page 463
3. ↑ In the literature you can also find a definition with the current strength I instead of the current density j