Neel temperature
Definition and meaning of Neel temperature in chemistry.
Neel temperature is the critical temperature above which an antiferromagnetic material transitions into a paramagnetic state, causing the material's magnetic moments to become randomly disordered due to thermal agitation. It is named after the French physicist Louis Neel, who discovered this phenomenon.
In more detail
In an antiferromagnetic material below the Neel temperature, the magnetic dipoles of adjacent atoms naturally align in opposite directions, resulting in a net macroscopic magnetization of zero. This highly ordered state is maintained by strong exchange interactions between the atoms. However, as the temperature is raised, thermal energy begins to overcome these organizing forces. Once the Neel temperature is reached, the thermal fluctuations entirely disrupt the antiparallel alignment. The material then behaves as a paramagnet, where the magnetic spins point in random directions but can be temporarily aligned by an external magnetic field.
Key facts
| Field | Physical Chemistry |
|---|---|
| Symbol | TN |
| Transition | Antiferromagnetic to paramagnetic |
Manganese(II) oxide (MnO) is an antiferromagnetic compound with a Neel temperature of approximately 116 Kelvin, above which it becomes paramagnetic.
Frequently asked questions
How is Neel temperature different from Curie temperature?
Curie temperature applies to ferromagnetic materials, while Neel temperature applies to antiferromagnetic materials.
What happens to the net magnetism below the Neel temperature?
The net magnetism is effectively zero due to opposing spin alignments.