In a material with two kinds of magnetic atoms with different magnetic moments, the reciprocal action between them is obtained. Two kinds of magnetic atoms, A and B, can depend on different valence, different chemical type or that they occupy different crystallographic positions. A and B are situated in in two different lattices within each other. It is possible to have three different kinds of reciprocal action between the nearest neighbours; AA, BB and AB. No consideration is taken to reciprocal action for longer distances. With a positive reciprocal action we get ferromagnetism with two different components. If the reciprocal action is negative between AB, the magnetization is directed towards the opposite way. Antiferromagnetism is obtained if the magnetization of both lattices are of the same values and directed the opposite way, thus the spontaneous magnetization are zero in total. If the values are different, ferrimagnetism and a spontanious magnetization of the material is obtained. For a schematic disposition of antiferro and ferrimagnetic materials, see below. Possible occurances of spontaneous magnetizations of the lattices are destroyed at high temperatures. Both A and B appear paramagnetic.
Antiferro magnetism is obtained when the different lattices are similar to each other and possessed with the same ion, i.e. MnO and FeF2.
Figure: Antiferromagnetism and ferrimagnetism,
respectively.
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