Néel temperature

The Néel temperature (after Louis Néel, who received the Nobel Prize in Physics for their discovery in 1970) is the temperature above which an antiferromagnetic material becomes paramagnetic; the thermal energy is large enough to destroy the magnetic order of the material in this. The Néel temperature is thus the analogue of the Curie temperature of ferromagnetic materials.

Above applies to the magnetic susceptibility as a function of temperature:

With the material-specific Curie constants

Below takes the susceptibility with decreasing temperature also decreases, ie when it has reached its maximum.

Derivation

The derivation is carried out from the molecular field theory: ie a magnetic moment is considered in the central magnetic field of its neighbors. As a result, applies the law Curiesche:

It is

• The magnetic field constant
• The magnetization
• The replacement area, wherein the coupling controls.

Thus follows:

And can be as identify.