Curie Temperature and Neel Temperature
Curie Temperature
Curie temperature is the temperature at or above which certain materials lose their permanent magnetic properties. This is a sharp change in the magnetic properties of materials. Induced magnetism (arises when we force disordered magnetic moments to align in the presence of a magnetic field) can often replace this lost magnetism.
At or above the Curie temperature, the ordered magnetic moments change into a disordered state, which causes the materials to change from ferromagnetic to paramagnetic and their susceptibility becomes minimum. Therefore, higher temperatures can make magnets weaker. Moreover, spontaneous magnetism arises only below the Curie temperature.
The susceptibility above the Curie temperature i.e., in the paramagnetic phase is described by-
χ = C/(T − TC)
(T > TC)
Neel Temperature
Neel temperature is the temperature above which certain antiferromagnetic materials become paramagnetic and their susceptibility becomes maximum.
Above Neel Temperature, the relationship between magnetization and field intensity is governed by law very similar to Curie Weiss law.
M = C.H/(T + TN)
Where,
M = Magnetisation
C = Curie Constant
H = magnetic field intensity
TN = Neel Temperature
How can temperature affect the magnets?
Low temperatures: If a magnet is at low temperatures the magnetism of the magnet will increase. When materials are in an environment with low temperatures, the magnetic atoms spontaneously realign themselves achieving a revival of ferromagnetism, antiferromagnetism, or ferromagnetism. In the case of minerals, the ability to retain magnetism is below the Curie point.
High temperatures: If the magnet is at high temperatures the magnetism of the magnet will be affected by the strength it possesses. This increase in temperature leads to conversion from ferromagnetism to paramagnetism, creating an increase in temperature, which is known as the Curie temperature.
