I'm wondering whether ferrimagnetic materials have a Néel or Curie temperature (or both) and whether it depends on the material. They would be temperatures at which the material undergoes a magnetic phase transition, from ferrimagnetism to paramagnetism.
From what I gathered, Wikipedia claims
The Néel temperature (…) is the temperature above which an
antiferromagnetic material becomes paramagnetic.
The article on ferrimagnetism talks about a Curie temperature, no mention of a Néel one. However the Oxford dictionary and Wolfram Physics claim
The transition temperature for an antiferromagnetic or ferrimagnetic
substance, above which it is paramagnetic (analogous to the Curie
temperature for ferromagnetics).
and
The temperature at which ferrimagnetic and antiferromagnetic materials
become paramagnetic.
respectively. So they favor the Néel temperature over the Curie one.
The book "Introduction to the theory of ferromagnetism" by Amikam Aharoni, page 29 claims that
(…) Tc is called the ferrimagnetic Curie point.
The Ph.D. thesis (page 21) "The Application of Environmental Magnetism to Archaeological Prospection" by N. T. Linford claims that there are the two temperatures and that they are different:
Above the ferrimagnetic Curie point Tc the magnetisation of each
sublattice will behave as a paramagnet with a separate Curie constant.
However below Tc a ferrimagnetic Néel temperature exists at which
non-zero values of the sublattice magnetisations MA and MB can occur
for zero applied field.
I am therefore left extremely confused. For ferrimagnetic materials, are the Néel and Curie temperatures different? Or are they equivalent and/or equal? If they're different, what is their difference(s)? Is there some "hidden physics" that differentiate them?
Best Answer
In a ferrimagnet, the temperature at which the sublattice magnetizations cancel is generally called the compensation temperature. There is a nice series of these in the rare-earth iron garnets. It is not a phase transition.
I had never seen the term Néel temperature for this before. That is for the phase transition to the paramagnetic state.